Category: Podcast Transcripts

Peter 0:12
Hi, and welcome back to The Gastronauts Podcast. My name is Peter and I’ll be your host. Here at Gastronauts we are committed to exploring communication throughout the body, with a particular focus on the crosstalk between gut and brain. We invite experts in this field to share both their research and their incredible journeys. So come join me as we explore the steps that go into shaping a scientist on the Gastronauts podcast.

Today, we have a double-header, we have two young scientists who are rising stars in their field. First up, we have Dr. Natale Sciolino, who is a postdoctoral fellow at the developmental neurobiology group at the National Institutes of Environmental Health Sciences in Dr. Patricia Jensen’s lab. She completed her PhD in Dr. Phillip Holmes lab at the University of Georgia, where she studied the effects of voluntary exercise in preventing cocaine relapse. She is currently studying the role of norepinephrine neurons in the locus coeruleus. These neurons are traditionally thought to be involved in that fight-or-flight response and related to these stress or panic like situations. But Dr. Sciolino has uncovered some interesting results that they may also play a role in feeding behavior. So could you tell us a little bit more about this project and how you stumbled into this field from going into a research field to begin with?

Dr. Sciolino 1:58
Yeah. So the thing that’s always fascinated me is how does the brain form emotions and then take those complex internal states and integrate them with essential needs like hunger to then drive motivated behavior of an animal. Because all the things that we do are not happening in isolation. All of these internal states work together in concert, and the brain must decide what gets priority. So to me that orchestration is the most interesting. And it turns out, as you said, the neurons that orchestrate the fight-or-flight response, actually do much more in that coordination. They also tap into other internal needs, like relaying information about hunger or feeding. So what I’m talking about is the locus coeruleus. So the locus coeruleus is the largest grouping of norepinephrine containing neurons in the brain. These neurons actively synthesize the neurotransmitter norepinephrine. But they have diverse projections all throughout the brain. And that’s how come the neurons are able to modulate a variety of processes in the brain. So they’re implicated in emotion regulation, stress responses, cognition, arousal, sleep wake, the list goes on and on and on. And we’ve uncovered they also play a role in modulating feeding. So how does this transmitter system do all of these things? And it turns out, it does so many things through circuit-specific projections throughout the brain. And really, what we think the system is doing is turning up the gain and neural networks to say, “okay, this is the priority right now based on my internal state or the environment […] well, I’m full, there’s no predator around. I can work on cognition; I can focus my efforts towards that. So I want to turn up the gain if I’m norepinephrine in cognitive circuits.” Whereas say there was a predator around and you have to run for your life, I want to turn up the gain and my stress responsive centers to get away from that predator. If you were to think of it as a radio dial, right? But you have that radio dial not on one particular channel, but you have this Master Control Center, where you have radio dials on a bunch of stations, and you’re turning up those radio dials to see what kind of signals you want to listen to, on these different channels.

Peter 4:47
So how does the stress feed into this circuit? To my understanding what you’ve described so far is, once you’ve had this stressful state, you can affect the game based off of norepinephrine, but how does the stress get into the circuit to begin with?

Dr. Sciolino 5:00
Yeah, so good question. So I think a lot of it has to do with what the level of activity is in locus coeruleus neurons. So we know stress classically, can cause this robust activation of locus coeruleus neurons. Whereas other things, let’s say appetitive things that are rewarding, unpleasant, like feeding, cause the opposite change, a decrease in locus coeruleus activity. And that magnitude of effect of just endogenous eating is small when you talk about every bite by bite effects. So we have all of these, all of these ways that our behaviors can change locus coeruleus activity.

Peter 5:44
That’s really neat. And do we have an idea of kind of where the locus coeruleus projects to, to control feeding or to control these different responses?

Dr. Sciolino 5:53
Yeah, so we’ve identified a circuit in the brain; probably, there’s many more But there’s a projection from locus release to lateral hypothalamus that suppresses feeding. And it also induces a negative emotional state, so characteristic of an anxiety-like response, if you will. And it’s aversive. So this is just one circuit that we’ve identified, but there may be others.

Peter 6:21
Do you think there’s a way to uncouple the anxiety effect with the feeding behavior? Do you think those two go hand in hand?

Dr. Sciolino 6:27
I think it’s probably projection specific, or if not projection-specific, cell type specific at the target. I think that there probably is a way to uncouple the anxiety and feeding. And the reason why is because a lot of beauty in science comes from just observing. And so one really cool observation that we found is when we just looked at natural endogenous activity of locus coeruleus neurons. When animals are eating, we found that there’s this dynamic change in activity during feeding and local coeruleus activity. So here’s the dynamicness, when you approach food, you have this sharp rise in locus coeruleus activity. And when you consume food, you have a smaller decrease in activity. So you have two different processes that are happening. And both of those processes are modulated by how hungry you are. So if you’re less hungry, both responses are attenuated. And so they’re looking at endogenous activity. And this is just speculation, but if I were to guess, I don’t think that they’re having moment-to-moment instant changes in anxiety. I think probably what’s going on, there are the subtle changes in arousal or salience. And so perhaps, if that’s true, the circuits that are mediating those food related changes in locus coeruleus activity and changes in arousal or salience those may not be anxiety dependent.

Peter 8:01
So that’s how you think about kind of teasing apart the two effects? Really interesting. And then your previous work was on the effects of exercise and preventing relapse from cocaine. How do you see that work related to the work that you’re doing? Now, I know you mentioned you’re very interested in these physiologic states and [during your] postdoctoral training was there something in particular a field in particular or type of environment that you’re looking for in particular, to move you towards this direction?

Dr. Sciolino 8:30
Yeah. So it all falls within the umbrella of what is motivated behavior. So motivated behavior, simply put, is the ability to seek pleasure or to avoid harm. And we have adaptive processes set in place in the brain to allow us to fulfill those two motivated behaviors, right? So to seek pleasure, you know, we seek out food, but there can be maladaptation in those processes, leading to, let’s say, drug addiction. So it’s just I guess, a dysfunction versus an adaptive behavior, but it’s all looking at the same, probably tapping into similar circuitry and mechanisms.

Peter 9:15
Was the locus coeruleus involved at all in the exercise?

Dr. Sciolino 9:18
Yeah, it turns out if you run a lot, you see this up-regulation of a growth factor or a trophic factor called galanin. And it’s only in one brain region. The locus coeruleus is, you don’t see it and other galanin-expressing neurons in the brain. Exercise selectively dramatically up-regulates this trophic factor glanin. The work I did as a PhD student and Phil Holmes lab was really trying to understand what galanin was doing in the locus coeruleus, in terms of how it would affect the function of locos coeruleus in terms of its chemical functions, structural changes, as well as its behavioral effects. And we found out that galanin is necessary and sufficient for promoting resilience to stress. Because when you exercise, you’re very resilient to stress. And those changes are mediated by gallon.

Peter 10:21
And do you feel like galanin will also have any influences on kind of the norepinephrine gating of appetitive behavior?

Dr. Sciolino 10:29
Yeah, that’s a really cool question. I don’t see why not. Yeah, but we haven’t looked at that. Yeah, that’s a really cool question.

Peter 10:38
Well, I’m excited to see what comes out of that. You were recently awarded a K99 from the NIH, and congratulations on that. For those who are not familiar with the term of the K99, it’s a grant that will allow you to transition to starting your own laboratory. Now that you’ve gone through the process, I was wondering if you have any advice for others, looking to apply For this award or something that you felt was really helpful for your application.

Dr. Sciolino 11:06
I’m trying to decide if I want to give the true answer or the polished answer. I’ll first give the polished answer. The polished answer is: submit. Even if you think you’re not ready, because I think that oftentimes we are our own gatekeepers, and we can be the hardest on ourselves. So get over that if that’s something that you’re struggling with. And then number two, have it be as polished as it can be, have multiple people look at your application materials and critique it. I think I spent probably, like literally months on just my specific aims page. And then soon as I figured out what the aims would be, then the rest kind of followed suit, but leave a lot of time to work and edit. My first time, I was reviewed on the first submission and I received an OK score, not fundable. And then the second time I received a perfect score. And I think that has a lot to do with the fact that I revised a lot, and had the opportunity to bounce my ideas off of multiple people. So I think that’s really important. And I tried that, and it’s well, I got I was funded by an institute that only awards 1 K99 a year. So the odds were stacked against me. So maybe for me, it was more important to really have a polished application whereas other institutes that say fund 50%, maybe that’s less important. So inherent in that processes, know your institute and your odds.

Peter 12:44
Was that your polished answer your real answer-

Dr. Sciolino 12:48
The real answer is polish the turd. And that is like: a lot of things in science don’t work out. So how to spin your experience and you know, your failed experiments, and all of these things together as one uniform logical flow. And I think that the answer always is polish the turd.

Peter 13:18
So what was the turd that you’re polishing? I know briefly we have talked about your view of these locus coeruleus neurons, or these norepinephrine neurons within the locus are really just tuning [the gain]. How you go about testing this?

Dr. Sciolino 13:30
Yeah, so for me, it was more, it was a really big challenge to get up fiber photometry in the locus coeruleus. And I thought photometry is so it’s a way to measure endogenous activity of neuronal cell types. And I study a really hard area to target and study in the brain the hindbrain: the locus coeruleus. And so for me, my thing that I had to polish was really gaining access to that cell type in a reliable way so that we could trust the data. And so that took me a really long time to do. And so you know, that first submission, what I had was proof of principle that I could record from that cell type. And you know, that’s good enough. Like it wasn’t the inherent answer to the question. But I overcame that hurdle. And that was what I presented as a strong point. And by the time I had the second revision, I actually had real data to support the underlying hypothesis of my research.

Peter 14:34
Yeah, that’s neat. So then you were able to measure the changes. You mentioned that when these mice moved closer, or when they started approaching food, you saw a spike in these norepinephrine neurons, but then as they started consuming it, they had a decrease in activity and that was measured through this fiber photometry. What do you see this technique being used for expanding upon that research?

Dr. Sciolino 14:59
Basically, fiber photometry is really great for recording from deep brain structures. However, what it is not good at is defining cellular resolution. So what you’re recording is actually a population of neurons. So if, let’s say, the neural signatures that we just described, and the locus coeruleus neurons are only mediated by, I don’t know, a third of the cells, then the response, let’s say, when you record in the population might look entirely different than if you were to record from that third of the population. So I would say that the next steps are getting at subpopulations and really identifying the neural source. And then once we do identify the causality, are they causally linked to the changes in behavior?

Peter 15:52
Do you have aspirations in your lab to potentially silence these specific norepinephrine neurons and look at whether or not you can modulate their stress levels and their consumption?

Dr. Sciolino 16:03
Right, and in a very temporally specific manner.

Peter 16:07
That’s really cool. I can’t wait to see what you find out. I wanted to take kind of a step backwards, even before you started doing this type of research. When you were transitioning from a grad student to a postdoc position, how did you decide to pick the NIH versus any other academic institution?

Dr. Sciolino 16:25
What I really like about being in the intramural program at the NIH, is that we have all kinds of incredible resources. And that resource comes in the flavor of money to buy reagents or equipment, but also people and that’s probably where it shines the most. So we have phenomenal cores and staff scientists and postdocs and post backs, and all are very skilled. And because the PI’s don’t have to write grants, they’re more in the lab and to me I saw that as a huge strength to be a postdoc in that kind of environment. Because you can work one on one with the expert in in whichever be that a PI or the head of a core of an imaging core say, for example, or are really phenomenal neuro-behavioral core

Peter 17:19
And then one last question I wanted to ask was mostly focused on where you see the field moving forward with regards to the involvement of norepinephrine in feeding, or is there even a field for this? Are you pioneering this field to begin with?

Dr. Sciolino 17:35
Yeah, I think what this argues is it supports the work of many people in the field. Basically, newer work is showing that there’s a lot of diversity and the noradrenergic system. Previously, the idea was that the noradrenergic system is just, you know, this pretty homogenous neuromodulatory system that is acting at multiple places all at once. And it’s basically just turning up the gain of function of multiple neural networks. But I think what we’re learning is that there’s a lot of diversity in terms of projection specific functions, or molecular diversity or genetic or developmental diversity in the system. And once we uncover that diversity, we can really link it to complex behaviors. So I think that my research fits within that framework. And that locus coeruleus neurons are doing diverse functions, one of which includes feeding and modulation.

Peter 18:39
Do you feel like […] the fact that current complex behaviors haven’t been modulated specifically by targeting this homogenous population that we haven’t appreciated the diversity for- so ultimately, do you feel that by getting to the crux of the diversity within kind of norepinephrine cells or cells that we’ve classified as a particular subtype we’ll be able to really treat or modulate complex behaviors.

Dr. Sciolino 19:05
Yeah, I think that that’s, that’s one way to get out. And and that’s where the latest advances and tools currently allow us to get out.

Peter 19:15
Yeah, I think like a lot of the technology that we’ve seen has been, at least with the development of technology, we’ve seen more finer and finer kind of granulation of cell types of tissue of anything in general. And do you think there will reach a point where we continue to look at each of these individual cells and then continue to, break them down into smaller and smaller parts- do you think there will be a point where we’re going too deep, and that we won’t be able to see a large behavioral response by targeting kind of a sub population of a sub population of cells?

Dr. Sciolino 19:49
Yeah, I don’t know. I guess it’s all worth studying. And I think I use behavior as that readout of whether something is functionally important, right? So that’s that’s how I see behavior as a way to ground, whatever you’re studying. And its basic relevance, not to say that things that don’t change behavior are not relevant. But of all the things to study and there are so many, that’s just the way that I make my decisions.

Peter 20:19
It’s a very important readout, right? If we see a change in a protein, we don’t know what this affects in the animal or in the human in the long term. Yeah. Well, thank you so much for sharing some of your thoughts and ideas with us.

Dr. Sciolino 20:31
Yeah, thank you for having me. This was fun.

Peter 20:52
We also have Dr. Sophia Axelrod here with us today. She is a postdoctoral researcher at Rockefeller University in Dr. Michael Young’s lab. Her current research focuses on how circadian rhythms work and what physiologic or homeostatic processes are regulated by our circadian rhythms. We were just talking a little bit beforehand and I wanted to ask her a little bit about her career development or career path coming to this postdoctoral position, and trying to find out where she was doing her PhD, but had some difficulty researching this. So I just wanted her to share some of her story.

Dr. Axelrod 21:28
Happy to be here. Thank you. And yeah, I think when I was, you know, an undergrad, I had two main areas of research interests and those were immunology and the nervous system. And I did the immunology part first, but then I wanted to switch to neuroscience and from my PhD, I joined a lab at Rockefeller with Ulrike Gaul and she studied developmental neurogenetics, so how are genes affecting development of the nervous system. And specifically, we were interested in glia. So it was actually glial phagocytosis apoptotic cells that means, how do glia remove dying neurons during development?

Peter 22:15
Because our brain produces an excess of neurons.

Dr. Axelrod 22:18
That’s right. And that was also the connection to the immunology thing I did before, because in my undergrad, I studied how macrophages eat tuberculosis bacteria. So I came from infection biology, where I studied phagocytosis of bacteria. And then I switched to neurodevelopment where I studied how glia eat dying neurons. And then for my postdoctoral work, I wanted to do adult behavior. I had seen a couple of talks where people study behavior in flies, and I thought that was preposterous that you would even you know, consider doing that but you can figure out so many things about it in flies that I thought, “yeah, why not stick with the, with the fly.” Ultimately, all behaviors are, you know, we all have to achieve the same stuff.” Whether we are fruit fly or a person, we have to find the food, we have to avoid dangerous stuff and we have to find a mate. And we don’t know how it works in any organism. So we might as well study it in something simple.

Peter 23:20
So the transition from development to adult behavior, was that kind of an organic process for you? Did you have to tell yourself, oh, I’m not going to be a developmental neuroscientist anymore? Or is that something that you’re still thinking is part of where you want your career moving forward?

Dr. Axelrod 23:37
So there is actually a development aspect in my story here. You know, in my postdoctoral work, it’s just, you know, that there is something like developmental contributions to adult behavior, obviously. And I’m not excluding it for the future. The transition was pretty smooth, because, you know, we’re all such specialists anyway, and the focus really in my lab, like it in Ulrike’s lab is a genetics. And so if you if you think from a genetic perspective, it doesn’t matter what the actual assay is, whether it’s like, looking at macrophages in the embryo or looking at sleep in the adult, you know, you’re knocking out genes in certain cells, and you look at the contribution of these cells to whatever your phenotype is. So it’s not you, of course, you need to understand a lot of new stuff, but it’s not that different to me whether it would be a different topic in developmental biology versus just switching to adult behavior.

Peter 24:30
So just understanding how the genes interplay [and] the programming of the biology in the cell types as opposed to what the readout is. Yeah. Okay. Really interesting. And now your current work really focuses on circadian rhythms. And you mentioned you’re interested in an array of physiological behaviors. Can you tell me what roles the circadian rhythms play in governing different types of behavior?

Dr. Axelrod 24:54
Yes, um, it’s kind of shocking actually. Pretty much anything you can think of is circadianly regulated not just when we sleep, that’s the most obvious thing, right? Like, the timing of sleep is regulated by circadian rhythms, but also things like your body temperature, your bowel movements, but also your mood, alertness. Any hormone you can think of, any physiological parameter that has been tested, almost any logic parameter is circadian regulated. It’s like a bead of strings that exists to optimize processes in our body. And we’re not even aware of it.

Peter 25:33
And other particular behaviors or actions that you’re looking to read out from the circadian rhythms. And let me take a step back- a circadian rhythm is an internal clock within yourself that correct kind of something that has a certain sense of timing throughout the day.

Dr. Axelrod 25:47
Right. So the definition of a circadian rhythm means that it’s a physiological parameter or a behavior that takes about a day- circadia means about a day. And there’s another actually aspect to the definition and that is that it has to be entrainable, entrainable to a so called zeitgeber, a time cue, the most famous zeitgebber is light. But the big focus of the field is right now uncovering other time cues. Like for example, food, food is another zeitgeiber. But all kinds of things can be zeitgebers. In fact, you can think of it as anything you do or don’t do at a certain time of day might be a zeitgeber.

Peter 26:23
So we have these intrinsic clocks that can also be governed by kind of environmental cues such as light or food or whatnot. And if the cues are discordant, say like, you go on a flight, right, and you have jet lag, and your cues are discordant is the one that wins out if your environmental cues are very different than your kind of molecular clocks. How does your body resolve this?

Dr. Axelrod 26:45
Yeah, that’s a good question. So when you go on a trip, and the light input starts conflicting with your inner clock, what happens is that the amplitude of your circadian rhythm just breaks and there is a phase reset going on. And that takes a few days and then you were back on track with the new timezone. If you create a conflict between, for example, different zeitgebers. So you eat out of sync with your food, that’s actually fine. And you will have split rhythms in your body, like your brain can be on one timezone. And your liver can be on another one.

Peter 27:22
What effects will that have if your brain and your liver functioning on different time scales?

Dr. Axelrod 27:27
So that’s actually not a big problem probably as long as it’s regular. So I feel like there’s a big thing in the field right now. It’s called time-restricted eating, or feeding, where you don’t eat at certain times of the day, and then your liver clock is probably going to be entrained to a phase shift to your light input. If you don’t eat, for example, for the first six hours or so of your wake time, but as long as you do this every single day, there are no negative effect. And in fact, we know that time-restricted feeding has a lot of health benefits. So like everything with rhythms, it’s important to repeat it all the time.

Peter 28:02
certainly. And these rhythms govern pretty much all of our biology, and I was wondering, are you focusing on any particular biology in particular? Or do you care about all of these different physiological behaviors that are regulated by the circadian rhythm?

Dr. Axelrod 28:16
So what I wanted to actually work on was sleep when I came to the lab, because sleep independently of rhythms is kind of an enigma. We don’t really understand the function of it still; some people think it’s one of the big frontiers in science. So a lot of basic research is focused in you know, in the field is trying to understand why we sleep, what happens to the cells in our body when we sleep, and why is it so bad if we don’t sleep? And do other animals sleep the same way that humans sleep? No, in fact, our sleep is pretty unusual, and that is so consolidated, most animals nap, including fruit flies. So sleep and most animals have a circadian rhythmicity but it’s still much more fragmented than in humans. Almost no animal sleeps in one block. And also the amount of sleep is vastly different across the animal kingdom. And there are theories about what that means, and how we can use that information to understand what sleep is. But basically what I wanted to know when I came to the lab is how glia affect circadian rhythms and sleep. And what I found was that there is this thing called the blood brain barrier that is basically like a protective membrane or protective layer around the brain to ensure that in the brain, you have very specific, a very specific micro environment, so that neurons can function. And I found out that this barrier is actually not always closed and that that barrier opens and closes and that has something to do asleep. So that’s what I work on. So no, I don’t work at all on all aspects of circadian biology. I try to say it’s a huge, huge field.

Peter 29:55
Interesting. Could you tell us a little bit more about this blood brain barrier membrane changing with regards to sleep. Are you saying that if you sleep more, is there a a stronger membrane or a stronger barrier? Is it the fact that the barrier changes its integrity? Or is it the fact that the barrier kind of moves?

Dr. Axelrod 30:14
So yeah, that’s exactly what I found. I found that if you don’t sleep, the BBB, the blood brain barrier, it kind of breaks down and it’s, it’s the tight junctions, it’s the the proteins that are between the cells that form the barrier. It’s like a diffusion barrier. It doesn’t let anything through. It’s like it looks on the electron-microscopy looks like a ladder. And this ladder protects the brain because stuff just can’t get through. But when you don’t sleep, the ladder breaks a little bit. And when you then catch up on sleep, it closes again. That’s what it found. And that’s kind of unusual. I mean, it’s kind of unexpected, because we thought the BBB is static. We thought it just has to be made and it has to stay in place. And that’s that and I don’t think that’s the case. And that has all kinds of interesting implications.

Peter 31:02
Yeah, that’s really neat. I was wondering, why do you think the blood brain barrier changes with regards to lack of sleep? Do you think it’s perhaps because you’re not getting enough sleep? Your brain thinks that, oh, maybe I need to grab something else from the bloodstream?

Dr. Axelrod 31:15
Yeah, that’s the million dollar question, at least in my mind: what is actually going through? And what is the body trying to achieve? I do think that it is trying to do something, I think this isn’t some kind of adaptive response. I don’t think it’s actually breaking because I know that it closes really quickly again. So I think it’s trying to accomplish something, either letting something get out or letting something get in. And I don’t know what that is. But of course, I thought about what it could be. And there is, of course, a number of things that are asymmetrically distributed across the blood brain barrier. That is why we have it in the first place, right? And one of the most basic things that is that has a differential is our ions, the ion concentration, for example, potassium is very different in the blood than from the brain and you could actually say that opening the BBB just a little bit would allow ions to flow according to their concentration gradient. And then you could imagine how that could affect globally neuronal excitability in the brain. In fact, that has been shown in, in […] lab a few years ago there across the wake states, you see changes in ionic concentrations outside of neurons, but they don’t know where that comes from. So I still don’t know where it comes from. But it could be the BBB that allows those changes. And then that could be a mechanism to quickly switch from asleep into an awake brain. Because that’s what we experience right when we fall asleep, our arousal threshold is higher, clearly something changes in a pretty profound level about the way you know how arousal the whole brain is. So you know, this could be how-

Peter 32:49
Sorry I must have missed something. Did you say that when you’re going from a sleep state to waking up your blood brain barrier changes as well or is that only over time, in a sleep deprived state.

Dr. Axelrod 33:02
So I’ve done both experiments. I’ve just, I’ve just looked at the blood brain barrier in its natural state. And what I’ve done over over 24 hours, and I see that there is a change in the permeability of the blood brain barrier. And that change is very subtle. It took me years to figure out that it actually happens. But when you then sleep deprived an animal, then there is a big change, and it really breaks down.

Peter 33:26
That’s really interesting. What comes to my mind is whether or not there’s a circadian factor or some. So we talk about these light entrainment cues, whether or not there’s a cue within the bloodstream that helps to regulate your circadian rhythms.

Dr. Axelrod 33:38
Yeah, that’s an interesting question, because I actually have a second project that is about this time restricted feeding that I mentioned before, and there you definitely are taking up stuff, right, taking up food at different times a day or not. And what we tried to understand is whether this helps the animal’s health. So we know already that time restricted feeding is really beneficial, but we wanted to know the ultimate question: does it help you live longer and it is it actually dependent on a functioning circadian clock. So if you are arhythmic and you don’t know what time of day it is because you have you know, mutations in and clock genes, then it’s not beneficial which suggests that it acts like a like a time cue at certain times of day that really helps you have a really good rhythm and at other times of the day you don’t eat your body maybe can do other stuff. For example, repair itself versus if you eat all the time. You’re just in this constant state of digestion, which is not good. And here what I also saw that the BBB is actually normally degrades over time and is actually not degrading as much when you have this time restricted feeding that helps you with your longevity.

Peter 34:41
So how long over the course of time does your blood brain barrier degrade? Is it over the course of months, years?

Dr. Axelrod 34:50
So for flies, they live only about three months which is why we can do this these longevity experiments directly. In there, you can see that in old flies, the BBB gets leakier, so it means about like halfway through their lifespan. In humans, it’s different and actually blood brain barrier degeneration is a hallmark of almost all neurodegenerative disorders. But nobody really understands what that means is that cause or effect. And I should mention that many of these [individuals] also have sleep problems. So there are these three areas: age, neurodegeneration, blood brain barrier and sleep problems. And if my findings from flies are true in humans, then they might not just be correlated, but actually causally linked to each other.

Peter 35:35
Yeah, that’s really neat. When you’re talking about extending the lifespan width time restricted feeding, one of the other studies that I know that has been done to really understand kind of dietary interventions to extend lifespan is caloric restriction. Do you think there’s any interplay between the time restricted feeding and the caloric restriction feeding?

Dr. Axelrod 35:54
So that was a major question. Of course we had, are we […] just doing caloric restriction? So we did assays where we watch how much they eat, and they actually eat more in those 12 hours than the animals that eat for 24 hours. So it’s not that, which is good, because it means it’s a distinct mechanism from caloric restriction.

Peter 36:15
So if you could calorically restrict and time restrict, would that extend lifespan even further?

Dr. Axelrod 36:20
So we did that too. And it seems like there’s an additive effect, which also speaks to the fact that those effects are different. And, yeah, it’s pretty, it’s pretty strong effects, actually, in those flies. And they were actually so strong that I started doing it myself, time restricted feeding.

Peter 36:40
It’s very popular, very popular, and-

Dr. Axelrod 36:41
it’s really easy for me, I always skip breakfast. So it’s just like, yeah, I’m gonna live longer.

Peter 36:46
It’s really interesting, right? Because people always say, you know, breakfast is the most important meal of the night. True.

Dr. Axelrod 36:52
Yeah, yeah. There’s this concept of like grazing, having like five meals a day. That’s not what we think. We think you really want to partition these activities, so that your body is not constantly burning fuel.

Peter 37:06
I think from an evolutionary perspective, right, because of the abundance of food now, it’s very easy. But if you thought about like when we were kind of a hunter/gatherer society and we had to go hunt for food, I don’t think we would eat or have these grazing properties. And I wonder whether or not our circadian rhythms are more in tune back then than they are now.

Dr. Axelrod 37:24
Yeah, there is also just the light. You know, people used to spend a lot of time outside and we don’t know we have lighting inside, but the light outside is way, way stronger. And we just don’t sense it. And because we don’t sense it, we don’t think it’s important. But our circadian system senses it very well. You know, the cells in the back of our eyes that react to the blue light, which resets our circadian clock. They respond to light exactly in the in the intensity that it is presented to our eyes. And so by being indoors a lot, our circadian rhythm is dampened a lot. There are studies that show that just a weekend Camping really boosts your melatonin rhythm, which helps you sleep.

Peter 38:06
Yeah, that’s really interesting, because we talked about all this time restricted feeding on extending lifespan. But what about kind of governing the light that you get every day and whether or not that has an impact on your overall lifespan? So making sure that[we] don’t get too much artificial light, is that been shown as to have an effect on lifespan as well?

Dr. Axelrod 38:26
Yeah. So there’s this cool question about why have circadian rhythms at all. And some of the experiments that have been done are, for example, constantly shifting your light/dark schedule, or having you in constant conditions and constant light conditions, which fruit flies, for example, and that definitely shortens your lifespan.

Peter 38:46
So there’s like an ideal amount of light and an ideal time to eat and there’s all of this will help to kind of cue our body to the best physiological state. Yeah, it’s really interesting. I want to transition a little bit to kind of the fact that you have (or) are in the process of publishing a book?

Dr. Axelrod 39:02
Yeah, it’s actually available for pre ordering. And it comes out in bookstores in May.

Peter 39:07
Amazing. And the book is on how babies sleep. And I was wondering, a why publish a book and then, what was kind of the motivation behind that, as we typically want to publish articles? What made you decide to go ahead and publish a book for general public?

Dr. Axelrod 39:24
Yeah, it’s a good question because I was actually always someone who really did not was not interested in translational things at all. I was always someone who almost prided myself in thinking I want to understand like basic principles of biology, I don’t care if there’s any applications to human health. But I just landed in the lab where, you know, it’s kind of unusual for a field like circadian biology is that it goes from you know, molecular genetics and fruit flies to human health, literally in one step. That’s that’s very unusual. And so when when you don’t want your mice to To wake up you have these special red filters in the in the door and you have this red light if you have to open the incubator at night. We have the same thing for our fruit flies. We have these dark incubators and if we have to handle the flies, we have red torches. So when my first baby was born, I was like, why I remember not using red light bulbs at night because you know when I have to go and feed her or when I have to change her diaper. I know that any light but red light will affect her melatonin, her sleep, everything.

Peter 40:30
We do that for our experiments.

Dr. Axelrod 40:31
Why not do it for our babies? So I exchanged all the lightbulbs to red bulbs. So of course it works, it’s known that this is our biology. And then there’s other things. What else do I know to help my baby sleep? I use to be a bad sleeper, so for me the biggest biggest fear was that when I have kids, I’ll never get sleep again. So I used everything that I had to help them sleep at night and then it all kind of works, which is in a way it’s not that surprising. And I need to write it down, so I remember just for myself, so I remember what I did exactly if I have another kid, I know what worked. And then it just became more and more and eventually became a book and I thought, it’ll be a book that I’ll self-publish or whatever, and I talked to a couple people and there was a lot of interest and here we are.

Peter 41:25
That’s really cool. Something that I realized was that I’m very early in my graduate career, but the things that we do in science definitely have an impact on our daily life. I’m currently doing research on how amino acids are sensed in the gut and I’m definitely thinking about how many amino acids that I’m taking in and what is the food composition. It’s really nice to see that you’ve taken the information you’ve felt you’ve gotten from your day to day research and shared that with other people and I think that’s really neat. I think that should be more in science. I’m sure there are people who are making discoveries and implementing them, maybe not to the degree that you are with circadian rhythms, but at least impacting how they make life decisions on a day-to-day basis.

Dr. Axelrod 42:02
Yeah, you should write a book.

Peter 42:04
I don’t know if I’m there yet, but definitely something to consider. I was wondering now that you have this really good understanding of circadian rhythms and how they can be applied to modifying our sleep and extending our lifespan. Where do you see your research moving forward from this as you plan to potentially start your own lab?

Dr. Axelrod 42:29
I’ve thought about this a lot this year as I was writing research statements and I tried to think where I want to take all of this. I’m lucky because this whole blood brain barrier can go in many different directions as well as time restricted feeding and there’s also intersections between these projects. But one thing I was interested in, apart from the very hard question of how it actually works or what is exchanged? We touched on each of these things as a graduate student working on their post-doc. But something I was also interested in is, is this true in mice and mammmals? If it’s true, maybe our blood brain barrier also not static? I started collaborating with mouse researchers and there seems to be indications that this is true as well. So something that I’m trying to decide is if I want to, in the future, do I want a lab that also does mouse work, because it’d be fun to bridge those two model systems.

Peter 43:26
I think that’d be really exciting and I can’t wait to see what you come up with.

Dr. Axelrod 43:30
Thank you.

Peter 43:31
I want to thank you so much for your time.

Peter 43:42
Dr. Sciolino and Dr. Axelrod shared with us two different paths to being a successful researcher. What I really want to emphasize is the importance of taking that first step. Don’t take too much time deliberating your ideas. Go ahead and write it down, pitch it to others, and polish it. If there’s something you don’t quite understand something about your daily routine, think about why. Don’t brush the thought aside and see if you can integrate this thought into a research question. The first step is often very daunting, but constantly pushing ourselves to put our foot down is the quickest way to progress forward in science. I want to thank you all so much for listening, and we’ll see you next time. For more of our content, you can follow us on Twitter @gutbrains or visit our website at thinkgastronauts.com. The Gastronauts Podcast would be impossible without the incredible team that we have here. Meredith Schmehl is our producer and theme music composer. And special thanks to the founders of Gastronauts, Dr. Diego Bohórquez, and the Bohórquez laboratory.

Peter  0:00 

What are you feeling right now?

Dr. Schwartz  0:02 

Well, I’m really bad at identifying the flavors. I mean, it tastes like some kind of sandwich, some onion flavor. And maybe something like avocado. Maybe have some chicken in it. Some kind of like chicken fajita-y kind of taste.

Peter  0:21 

Sure you can open up your eyes and take a look. So this is an arepa, it is from a Venezuelan restaurant called Guasaca. I realized you probably don’t have time to go grab food before your flight.

Hi, and welcome back to The Gastronauts Podcast. My name is Peter and I’ll be your host. Here at Gastronauts we are committed to exploring communication throughout the body, with a particular focus on the crosstalk between gut and brain. We invite experts in this field to share both their research and their incredible journeys. So come join me as we explore the steps that go into shaping a scientist on The Gastronauts Podcast.

Today, we have Dr. Gary Schwartz, a Professor in The Departments of Medicine, Neuroscience, and Psychiatry and Behavioral Sciences at Albert Einstein College of Medicine. Dr. Schwartz completed his Ph.D. in physiological psychology from the University of Pennsylvania, his post-doctoral fellowship in neurophysiology at the Monell Chemical Senses Center. He received his first faculty appointment at Johns Hopkins and since 2004 has been at Albert Einstein. His research focuses on communication between the gut and brain and how this circuitry and in particular the vagus nerve regulates food intake and energy balance. So I want to start with the fact that you now serve on the International Advisory Council at Monell Center, which must be a nice coming full circle for you allowing you to advise for the institution which you trained at. Could you tell me some more about this?

Dr. Schwartz  2:17 

Sure. Monell is a very unique institution in the United States that has had a history of both academic and commercial support, sponsorship and interaction. And it’s a basic research institute that is focused on identifying things that were very important to me in my career, and that is the neurobiological basis and the chemical basis for chemical senses smell and taste. So it has collaborations with investigators around the world, and in particular University of Pennsylvania. And as a postdoctoral trainee there I was interested in moving from the study of eating behavior and how taste and taste nerves affected eating behavior to actually try to identify how the brain encoded the sense of taste that was important to control eating. So, my PhD had been in really the very fine grain analysis of actual eating, behavior, licking, chewing, etc. and the roles of the nerves that supply the tongue. So I would interact by transacting those nerves and seeing the effects on actual eating and licking behavior. And while that was very intriguing, it got me to thinking about what types of signals were actually available in those nerves that I was interrupting or what types of signals actually arose from the tongue when we eat, and where and how were they transmitted to the brain and how did the brain respond to those. And so I really wanted to move on to what I thought was at the time, harder science, which was actual neurophysiology or how nerve cells respond. And at the time, Eva Kosar was studying the neurophysiological responses of taste stimulated cells in the brain in particularly in cortex. And she had really pioneered the identification of a region of the brain that received input directly from the tongue. And so when we think about how the body is represented in the brain, we think of a map of the body surface along the brain. And what Eva Kosar had done was to map how taste is identified in the brain, not just the tongue, but taste in particular. And so my postdoctoral experience there was perfect for me because I learned how to identify the regions in the brain that were sensitive to tastes on the tongue. And I already knew how those tastes would affect eating behavior. So I felt that I was getting insight into how we actually processed taste and how taste could reach the level of the brain where we could be conscious of it, we could learn from it and we could act on it so I thought I was getting at the wet biology of taste.

Peter  5:01 

Really interesting. So from taste and our understanding of taste in the brain were you looking at particularly the circuitry that links these taste buds to regions in our brain? Or were you looking at particular signaling molecules? How exactly is that information conveyed?

Dr. Schwartz  5:16 

The types of studies that we were doing were to try to, we’re based on again, the behavior- […] my perspective was formed from my behavioral studies that showed that the different basic qualities of tastes that we now consider to be not only solved sour, bitter and sweet but also umami, or the amino acid or protein taste. It […] was early in those times, but people were beginning to study the molecules that were in the taste cells on the tongue that were responsible for the generation of signals at the tongue, but we didn’t know how those types those five basic types could represented in the brain, whether they were in a mixture of cells that were all mixed together, or whether like the visual system, perhaps there were particular columns of cells that mapped particular taste qualities, or there was another mapping possible that had to do food, how I interpreted my behavioral studies. And that was, the oral cavity, in general, has multiple taste nerves, one for the front of the tongue, one for the back of the tongue and one for the palate. And so another possible organizing strategy, or organizing framework could be that each nerve projected to a particular region of the brain so that there’d be a map of the different taste nerves and thereby a map of the front of the tongue versus the back of the tongue versus the palate. And as we started to place so it was a circuit perspective, but it was also sort of a mapping perspective or a mapping outlook that is based on the map of the tongue and its sensitivity. How was that map repeated or represented in the brain that we see a remapping of the tongue in the brain, according to the nerves, or according to the tastes. So the experiments were really designed to try a variety of tastes in a very systematic order in the front of the tongue, in the back of the tongue, and on the palate, with or without the nerve […] so that we could distinguish between those two possibilities. And what we found is that, in fact, there’s both kinds of maps […] And so different tastes stimulate different populations of neurons in the taste cortex, and as well as the different nerves corresponded to slightly different regions of the map. So the segregation of the information arising from a particular place on the tongue, and a particular chemical on the tongue was preserved. So there was sort of a high fidelity mapping of the oral expression variance at the highest level of the taste brain in the cortex.

Peter  8:04

Cool. That’s really interesting. Yeah, I had not known specifically about that. I think I hear colloquially a lot about tastes and like, Oh, I really like this because of how it tastes, but not really understanding how that reaches certain circuits within our brain.

Dr. Schwartz  8:18 

And in in the brain as it reaches it. This region of the cortex is the earliest processing in the cortex. There are other regions of the brain that tastes reach that are important for choice and are important for effects that are important for our emotional responses to taste for animal models of understanding taste behavior, you know, We can’t use verbal communication, so we have to use tests of animals willingness to continue to eat or to reject. And those responses happen. Typically they happen very quickly. Sometimes they happen by reflexes that happen in the brainstem. So very early on in the brainstem. The first place […] where taste information comes in. And that information has access to motor neuron neurons or motor nerve cells that actually control our jaws, and our tongue and our swallowing muscles. It’s important for species especially like rodents who don’t have emesis, they’re not able to expel or vomit. So[…] the oral decision to continue to ingest or to spit out can be life determining, right, because they only have one chance- if they ingest a toxin then they have to face the consequences of that toxin. So it’s very important to have some very hard-wired early detection mechanisms for the sensation of something that’s potentially good versus potentially bad. So that[…] the organism has the ability to either ingest or reject, so that it doesn’t have to survive bad consequences. And so that mapping is also present at the level of brainstem, but then for higher species with more cortex and other, more developed central nervous systems that have more capability for learning, that have more capability for choice and that have different kinds of effect, it’s important to have that information represented at other higher levels of the central nervous system such as the cortex. So it has both a sort of a cognitive mapping, if you will, a sensory mapping as well as a hedonic affective map.

Peter  10:24 

Cool. So then from there, you moved further down the alimentary tract, and then you started studying the gut. What was going through your head when you were thinking, at least from your graduate work, studying tastes to moving kind of to post-ingestive sensing. Why did you make this switch?

Dr. Schwartz  10:39 

I think that’s a really interesting question. To answer it, I want to take a step back as an undergraduate at Hopkins, I had the opportunity to be in work study and I knew I wanted to work in a laboratory, and I was interested in behavior in general and the laboratory that I found was with Elliott Blass. And in fact, Tina Williams, and they were involved in understanding how we develop the control of eating. Eating in mammals [and] especially in humans, there’s a critical phase because human infants are altricial. You know, they rely on the mom. And so rodent models are appropriate to study the beginnings of feeding, the development of feeding and what controls it. And I was really fascinated by the idea that, you know, smell became very important for these young rodents who were born hairless and blind and couldn’t thermoregulate well. Smell was an important sensory control. And then, other studies were underway where the oral cavity was stimulated with nutrients and that could control eating as well. So those early undergraduate experiences really made me interested in how food can drive sensation per se. And so in my undergrad and my graduate school work I then studied specifically in the oral cavity. But it became clear that the oral cavity is really only the beginning of our interaction between the external environment and our inside-most intimate selves, the internal mileu. And what became clear was that, sure, the acceptance or rejection of food is important, but then what becomes very important are the consequences of that food for nutrition for our basic biology. So it made sense to start to look at conservation of mechanism, the oral cavity is important to accept or reject, and the post oral area of the elementary tract is important to absorb and digest, then there must also be some important chemosensation there. And we also know from a variety of studies that have been done well before that, you know, that there are certain sensations that we Have from the gastrointestinal tract that help determine our feeding. So it was a natural segue for me. And for me, it was sort of it was my move to something more novel at that time, because people really weren’t working on those types of signals in that way from the perspective of how chemosensation drives feeding and how, when, what the neural circuits that mediate that controller. Yeah, now it’s really hot area.

Peter  13:26 

Understanding gut sensing is very popular. Do we have a good understanding of if something is palatable or tastes good, but in our gut, we have some sense of the fact that this is a non-nutritive material or something that is non-rewarding with regards to gut sensation. How are those two lines of information conveyed? Or is there a way to compute both of those?

Dr. Schwartz  13:49 

[…] I think the short answer is we don’t know. There’s several lines of evidence. First of all, this is a very hot area of investigation. For a couple of obvious reasons. Our body’s able to discriminate between things that are nutritionally good for us and nutritionally not good for us. And yet we eat them anyway and and our food sources designed to […] bypass our normal biological controls and precipitate overeating for example. And so, you know, one can imagine from a health perspective with overeating and obesity or serious epidemic problems, especially in childhood. Now, it becomes really important to appreciate how our guts are or are not sensitive to either naturally occurring nutritional sources or unnatural non-nutritional sources. So, we know first of all that there are tastes like cells not only in the oral cavity, but also in the gastrointestinal tract. And in fact that when nutrients or even these non-nutrient artificial sweetener-like molecules are placed directly into the intestines, they can actually affect food in similar ways, suggesting that they we can fool our natural detectors by synthetic compounds. And some of the consequences of that could be to overeat […] It also turns out that some of the artificial sweeteners and some of the sensors that we have in our gut may be enough- the artificial sweeteners may be enough to drive the secretion of factors that can precipitate diabetes, for example, so that […] the artificial sweeteners might act on Beta cells to drive insulin release. And you don’t want that unless you really have nutrition available for the insulin to have its effects on glucose absorption, so that could drive insulin insensitivity. So it becomes from a practical day-to-day health perspective, very important to understand the degree to which our gut actually does sense nutrients and how well it discriminates among those nutrients and how it can or can’t be fooled by artificial sweeteners. And if so, what are the molecules that are responsible for transmitting that signal from the sweetener, the artificial or real to the brain?

Peter 16:09

So some of these signaling molecules or the way that our gut senses different macronutrients have some overlap, right? In the sense that some enteroendocrine cells or some of the cells in our gut that sense nutrients or any stimuli within the gut are able to convey this information to our brain through different signaling molecules. I was wondering, we think traditionally of this is a satiating food, or this is a food that decreases the amount of my appetite. But do you think there is finer resolution of information? How is that more detailed information encoded to the brain?

Dr. Schwartz  16:45 

The answer to that is I’m really not sure. What we do know from studies of the sensors of the gut is two classes of information: one, the actual sensors that are responsible for detecting lipids or detecting carbohydrates or detecting amino acids in generating a neural response in the gut sensory nerves are not well known. Some taste cell elements are present, and those are for sweeteners. Some sodium-like elements are present, but sodium chloride is not really an important constituent in terms of nutrient absorption. So, the actual sensors, the molecular characterization of those sensors is really still in its infancy and we can’t make a mapping or a one to one correspondence of which transducers are for which nutrients. Also, it’s important to remember that when we eat food, it’s not just the nutrient that’s in that food, that food has physical and chemical properties in addition to the nutrient itself. And because there are endocrine cells in the gut the nutrients also have the ability to drive secretions of hormonal or paracrine hemical factors that themselves can activate nerves. So we can think about it maximally as the simple something as simple as a nutrient in the gut really has a mechanical properties that occupies space, it can stretch etc. It can have pH properties that are relevant. It could as osmotic or viscosity properties that are relevant, even if it’s diluted, it has the nutrient and it has the ability to secrete factors that can act on the nerves so […] even when it gets passed from the stomach to the duodenum, it’s a very complex stimulus, and the nerves have the capability to respond to multiple dimensions of those. Having said that, I think that it is very unlikely and one can make the analogy of sort of two point discrimination. You know, we know from a skin sensitivity perspective that our fingertips are very sensitive to the distance between two sharp points, but if we put those two points on our back, we can’t tell There are two we feel it as one object. And I think that certain types of feedback from the gut about food are like that, that we just really need to know we certainly need to know something about caloric density and that we do know that because gastric emptying and the delivery of nutrients is directly proportional to how many calories per per unit volume of food we have. So calories are sensed somehow. But other than that, we really have a sense of food, and that food can either be more or less satiating, depending on a variety of things. How calorically dense it is, how many endocrine factors are releases over what timeframe and how fast or slow it tends to empty which correlates with the calories again. And people’s ability importantly for the real gist of your question, behaviorally people’s ability to discriminate how they feel in their guts is notoriously poor. We’re not really tuned into exactly how our guts feel. And in fact, one could make the argument that with the plethora of sensory stimulation that we get from the outside world, every day, we become even less sensitive, you know, we become more inured. And you know, there’s many reasons to eat and to continue eating. So we have 24-7 access to food, if not food, then pictures of food on television. We go to the refrigerator, we go to the convenience store, etc. So the head factors, our head senses, the sight, the sound, the smell, the touch of food, are always being driven, and our behaviors or habits about eating and the consistent availability of food, if anything, promote the acquisition of food, and really, I think can help make us less sensitive to the gut signals. And in fact, along those lines, there’s evidence to suggest that the ability of the gastrointestinal tract and neurons in the gastrointestinal tract to dictate certain features of foods actually gets dampened during obesity. So carrying around excess adipose tissue or having too much energy stored on board in the form of fat causes the release of factors that contribute to a dampening of the neural signals both in the central nervous system and even in the gut in terms of gut sensing. So it’s really sort of a triple whammy, we have an accentuation of the head factors, the sight, the smell, the constant availability of food and the ease of acquisition of food, our habits of eating that food, the fact that having eaten it, we become less sensitive to the filling effects of food. So those three things really conspire to make us even less sensitive to this kind of rich environment.

I want to mention briefly though, let’s look at the flip side. You know, now in this country, unfortunately, it’s more rare to have normally scheduled meals: morning, afternoon night. Even with the social aspect, everyone’s busy: kids are busy, families busy, so we don’t all sit together at time. And so we lose both the social context and the temporal context that determines nutrient availability. So our stomachs are full all the time, irrespective of the social interaction and irrespective of the time of day. Well, that just wreaks havoc with any kind of biological rhythm of waxing and waning of energy-use, exercise, how tired you are, how awake you are. The reason I bring that up is that when one can establish a social rhythm of eating that is in-sync with the circadian rhythm, those types of social constructs have very beneficial biological consequences, and those been beneficial. So those, we can modify our behavior to have those traditional experiences and that by itself, I think will go a long way to improving the ability of our gut senses to do what they’re supposed to do rather than to act in ignorance of them?

Peter  23:04 

Yeah, there’s so many complex factors, even the surrounding factors, not even the food itself, which is already a very complex particle or a stimulus that we have to ingest or comprehend. Right? And I think a lot of approaches to understanding this is really simplifying it down, right, taking a particular macronutrient or taking a particular composition of the food to study how it is signal to the brain. What is I guess the significance of breaking it down into individual macronutrients? If that is not typically what we ingest or consume?

Dr. Schwartz  23:36 

So that’s, that’s a really great question. And I think part of the answer that question, quite frankly, is that at least Western science tends to approach biological problems in a very reductionistic way, where we use the knowledge that we do have about how the physical and chemical world is organized and apply that directly to biology as if it would be appropriate. However, because even throughout evolution, there are […] animals with very specific appetites […] for different kinds of insects or different kinds of prey, etc. But in general, almost everything that everyone eats is typically has a mixture, or we make mixtures of a variety of macronutrients. And I think part of the rationale for studying individual macronutrients or individual stimuli is that we sort of have to start somewhere and I think that is guided by and it could be you know, insufficient, but is guided by our rudimentary understanding of how biochemistry works between receptors and ligands […] we know that this is how biology is organized to some degree, it is an important organizing principle. And so for the periphery, it makes sense to try to parse that. It does sidestep the question of well, in real life, you’ve got everything happening at once. So, what does it matter? And so now I want to bring in another aspect and that is related to the idea that foods are complex stimuli. And that is that in biology even though we apply the individual tools, we also know that there’s multiple sensitivities. And so we know that in biology for any system that it is very important, like eating, there needs to be redundant mechanisms to get a signal across. So I think that the analytical approach provides the opportunity to see the contribution of each individual and it also provides the opportunity to say, well, does the sum provide a greater signal than the individual parts? And if not, fine, and if so, how did does that work? So I think there is some sort of conceptual benefit to this analytical approach, remembering that it allows recombination and then assessing how the real world phenomenon works when you have the whole food available.

Peter  26:15 

So kind of breaking a complex problem into smaller parts and then seeing whether or not these two these parts together-

Dr. Schwartz  26:21 

Together account for the whole. And if not, that becomes very [nice] and even if so either way, it becomes very interesting.

Peter  26:27 

Certainly, and I think this is a nice segue to asking a bit about one of the grants that you’re funded for. I saw on the NIH reporter that you’re funded for a P30 Grant on animal physiology and animal phenotyping. Could you tell us a little bit more about what this entails?

Dr. Schwartz  26:42 

Sure. So the P30: that’s a code that the National Institutes of Health use for what’s called a center grant. And this in particular, there are two center grants that I’m involved in the New York Obesity Research Center, which is headquartered at Columbia University. And the Albert Einstein-Mount Sinai Diabetes Research Center, which was originally based at Einstein, for the last 30 some years and over the last five years, we’ve joined forces with investigators at Mount Sinai. And these center grants are funded through the National Institutes of Health and particularly the National Institute of Digestive and Kidney Diseases, to bring together investigators with expertise in a variety of approaches both human & animal, not only live animal but also tissue based approaches and molecular and computational approaches. So that one can attack a problem from multiple perspectives. And so that when there are a critical mass of investigators in one of these center granted institutions, then the different investigators bring their own separate research questions and their own research expertise to the forefront. The function of the animal physiology cores that I run is to help investigators understand the whole landscape of energy balance in the animal models or in the human conditions under investigation. So let’s say someone finds a new mouse genetic strain that exhibits overeating and obesity in development. And they want to understand how that happens. So the function of the grant, the part of the core that I serve as director of is to help them break that down. It’s like, well, what part of their phenotype is due to overeating? And do they overeat only certain nutrients? What is their local motor response like and what is their basal energy expenditure, their basal metabolic rate like and are they very susceptible to exercise? What is their hormonal profile like? So in order to really understand the multiple causes of obesity or diabetes, one needs to have a systematic way of examining contribution of behavior and metabolic physiology and organ physiology and molecular biology. That’s what this core does in sort of multi-level, multi-disciplinary, taking apart the energy balance equation, energy intake and energy expenditure, energy availability and energy expenditure and how it happens. And then we work with the investigator to understand what is it about the phenotype of that animal? What is it about the gene expression of that animal that can lead to these different behavioral and metabolic changes? So we try to take either natural experiments that result in obesity or diabetes, or targeted experiments where genetic susceptibility to obesity or diabetes has been identified in humans and to try to develop animal models, which will then allow us to probe how will this genetic change manifest itself in either the behavior of theology and that’s what we do.

Peter  29:58 

At what stage in your career did you think that this was, oh gee, I think I would love to be a director of an animal core?

Dr. Schwartz  30:04 

So this was something that I fell into. I mean, I was recruited because I have my own R01s: regular grants from a principal investigator that where I study gut-brain communication and nutrient detection, etc. And I was recruited to the Diabetes Center because they were interested in the way that the brain communicated with the peripheral organs to control metabolism, which 15 years ago was a newer idea in the field. We knew about gut-brain for feeding, but people hadn’t been looking at the role of the brain as much in terms of the control of metabolism. And so for me, it provided an opportunity to learn about metabolism. And as a result, it became clear that there were certain capabilities that I used in my own research that were amenable to the Diabetes Research Center group at large. And so it was at a realization on your end or other people or sort of both. So because I sometimes get bored easily or I’m very interested in learning other things, I became interested in moving outside of feeding behavior and into neural control of metabolism. And at the same time, the field was moving in a direction of neuro-control metabolism. So other investigators at Einstein & Sinai had been becoming very interested in this, and I was the one who had actually developed sort of the range of tests that could directly be applied to those so it became sort of a natural fit.

Peter  31:32 

This is something that I have not thought much about. As early in my career, how to become more involved in overseeing larger projects or larger opportunities. Is there some way that you would recommend a younger trainee or someone earlier in their graduate career going out and interacting with other professionals? Is there a way that you approach this?

Dr. Schwartz  31:52 

It’s interesting, because this core directorship business, you know, it’s not something that you want to necessarily pursue as you become a senior investigator. Because you have your own projects that you’re really running and your other grants and other interests, but it is a great career development tool for young investigators these days in the field. So in the feeding and metabolism, there are so many good meetings. And so many approaches that are being used that the younger investigator can really take advantage of expertise from people with very specialized interests and specialized approaches. And by going to meetings, they can start to really identify the outlines of their interests and what things fit into their interests. And as they do so, they will gain […] expertise in the techniques that are required to really address their problem. I guess the point I’m getting at is, as a junior investigator, you have a problem that you think you’re interested but you don’t really necessarily yet understand the full ramifications of that problem or how many ways into that problem. There are how many experimental ways into that problem. And as you mature and as you encounter other research programs, hopefully you maintain your interest in your core problem that you began with, then you’ll naturally start to find yourself interested in other ways that people have of tapping into that problem. And that may express itself in Oh, well, I really need to incorporate this kind of measurement into the way I’m doing experiments and into the way I’m thinking about the problem, because the problem is maybe a little bigger than I thought it was. Or there’s other ways and those ways require some technical and conceptual advance. And so your stick-to-itiveness about your initial problem as a junior investigator, and your curiosity will help feed your growing knowledge base of finding out who’s doing similar work, and are they approaching it the same way and if not, oh, well, that might open a new perspective for you that you can incorporate into your own. I think one of the guiding features of successful career development is how, as people mature intellectually, they gain a greater perspective by appreciating what other people’s work can bring to their own. Both technically and conceptually. And that’s how you grow intellectually. And that’s how you become authoritative. And that compels you to become more thoughtful. And the more thoughtful you are, the more you read and the more you meet and incorporate other people’s ideas. The core answer to your question about, you know, well, how would you advise a, you know, a junior investigator to consider, you know, directing a core or being involved in these multiple kinds of projects? Part of the core of the answer is that I think I was trained this way. I feel fortunate to have been trained this way that science is, in essence, a very human endeavor, a social human endeavor. We do hear of people working away in a basement lab by themselves coming up with some amazing discovery, but those days are mostly gone. And in fact, you know, a lot of high profile work, it’s no exaggeration to stand that, to say that, you know, people stand on the shoulders of giants that they really do represent collaborations in real time but also collaboration of historical growth from concepts and incorporating concepts and techniques that others have developed. And junior investigators, I think successful junior investigators learn how to effectively communicate and draw from other people bounce challenge their own ideas with other people or against other people and take from that, how they can really synthesize and incorporate and advance their problem. So I think that the key to the successful trajectory is identifying what you think you’re interested in, testing the strength of your interest by challenging it with other people. And as a result of that incorporating their sense of the problem. And finding out however you can, how to approach it by any means necessary and making it part of yourself. That’s really what I think.

Peter  36:28

Wow, that’s really powerful. Knowing that you’ve served on several study sections and you’ve reviewed many grants, do you think this is actually a weakness of a lot of young investigators coming in who are approaching it with more of, I guess, a siloed approach from writing a proposal? Does the fact that this kind of lack of desire to challenge their approaches with other faculty or leaning on more experienced members, and limit kind of their ability to see alternative approaches, potential pitfalls. Are these things that you see as common weakness in early grants?

Dr. Schwartz  37:02 

I think a couple of things. One, while the electronic data age and you know, PubMed are great, amazing tools. I think that many junior investigators, through no fault of their own have developed their mentality about science or their mentality about their specialty area of interest from reading abstracts on PubMed. I don’t think that’s really an over-exaggeration. You know, papers have become larger and larger, more complex, but there’s large bodies of literature, older literature where the papers are smaller and simpler, but junior investigators typically have not had as part of their graduate education, the discipline to really read through the actual corpus of how science progressed to the point where there and I don’t mean going back 100 years, although sometimes it might take that, but I do mean the actual discipline of going to the trouble to find out the sources and really read them so that you have the ability puzzle over them. And I think that comes across in grant writing in grantsmanship. Because your ability to conceptualize a problem and justify what you think is important about it typically is too shallow, because there are typically many other findings that one could reference that actually have the thread of the thought that provide a very strong rationale. And in the culture where the background and significance or rationale sections are just done by pegging citations from a few paragraphs, it’s short sells the significance of a grant, so that the significance sections and the rationales are either very self contained. Look, I did all these experiments, I have 48 preliminary figures, in complete ignorance of the fact that a field had developed of this several times with, you know, large findings, or at least a lot of the major concepts already laid out. So it’s not that the person’s rationale or experiments aren’t interesting or potentially important. It’s that they could be even more so had they taken into account a consideration of the idea of body hosting that had occurred before. I think that’s a major issue. The other side of that from a study section perspective, is that so you know, people get older, they get more senior they rotate off study section, and the NIH has guidelines dictate that people who do have R01 you know, the primary Principal Investigator Grants are the ones who are now reviewing others. And if they themselves have this rather formulaic, superficial approach to okay, well, here’s how I took in my grantsmanship course: I have to have a background significance. I have to have certain preliminary data and this should sell and they use those criteria to evaluate a proposal, then that perpetuates this cycle. In addition, those younger reviewers because they don’t have the background in this way, they’ve been themselves siloed. They don’t really appreciate that, or it’s more difficult to appreciate that study sections function through advocacy, both for and against. And advocacy requires the ability to compellingly convince people about how important the research perspective and how important the research rationale is. Okay? So not only is the pursuit of the scientific experiment a human endeavor, but the evaluation of a scientific research program for the purposes of funding is a very social endeavor and requires advocacy either for or against that where the reviewers actually are able to instill in the other panel members an understanding of the perspective of where that grant is coming from. And if those younger PI’s themselves have never really developed what it means to have that kind of perspective, then they’re not going to be as effective advocates. So both from the applicant and the reviewer perspective, I view the superficiality and the ease of you know, making bullet points and making citations and sort of more confined turf protection, if you will, you know, defending your own turf or your own specialized research area has really significant complications and impediments to the review process for science.

Peter 41:21

If you aren’t an expert in the field of the proposal that you are reviewing, how do you read deeply into that?

Dr . Schwartz 41:28

It depends on who you are, but you learn. You learn how to become a reviewer. It’s on-the-job training and you learn how to learn. Part of going to college and going to graduate school is not to do a project particularly, but it is actually how to learn how to learn, so that when you find out what you’re interested in, you have the intellectual tool kit to do it. The same is true for evaluation of science, you need to learn. Hopefully you’ve learned how to learn and that skill can be applied to disciplines outside of your own. Again, junior investigators have not typically been pushed that way, because it’s very labor intensive to start over. Where do I start? How do I read? Learning how to read. You get better at it with age. You get better at sorting wheat from chaff in terms of the findings and what the significance of the findings and your ability to peg facts if they are hypothetically deductive or if there are logical flaws. You get much better at your critical acumen of whether or not someone has put the pieces of the story together logically, scientifically according to the scientific method or not. You also get better because you do expand your knowledge base just with age if you’re reading at all. There’s an inundating amount of reading to be done, but you do get better with that and as a result, your knowledge base broadens and your knowledge base of other people and their expertise broadens too and so your ability to tap into and at least begin with an intuition of what the problem is helps target your reading. There are people who have come to study section who read every single grant and try to develop the expertise, but that’s not sustainable in any stretch. But more senior people and junior people too, as they read and interact, and as they make doing science their identity for intellectual function, it comes more naturally. But make no mistake, it’s real work and it requires that you immerse yourself in someone else’s intellectual effort. Put yourself in someone else’s head. And that’s a very unique, a little bit scary position to be in and one of great responsibility and so I think that the reviewers have a really great responsibility to the field.

Peter 43:55

Well, I want to thank you for your time Dr. Schwartz.

Peter 44:09

Dr. Schwartz showed us how little we actually understand about a process that we conduct multiple times a day: eating. How unique properties of food are relayed and interpreted in the context of behaviorally complex individuals is a question that has only begun to be answered. In order to get to the crux of some of these challenging, but essential research questions, Dr. Schwartz has taught us to truly put ourselves in the shoes of others. Dig deep into the existing literature, appreciate what other’s research can bring to your own, and continuously teach yourself to learn. In doing so, we can begin to ask more thoughtful and compelling questions that will advance our research. Thank you all so much for listening and we’ll see you on the next episode. For more of our content, you can follow us on twitter @gutbrains or visit our website @thinkgastronauts.com. The Gastronauts podcast would be impossible without our incredible team. Meredith Schmehl is our producer and theme music composer. And special thanks to the founders of Gastraonuts: Dr. Diego Bohórquez and the Bohorquez laboratory.

Peter  0:00 

What are your thoughts? What are you feeling right now?

Dr. Clevers  0:02 

I’m on a tropical island. Sweet, sweet fruits. Very relaxed. Enjoying the sun doing nothing.

Peter  0:12 

So what it was, was a gummy worm. The reason why I picked the gummy worm and I like your interpretation of it. The reason why I picked the gummy worm is because it kind of looks like an intestine with its ridges and I thought that was really interesting that they put the effort into making these ridges into gummy worms. Why not just make a smooth surface …

Dr. Clevers  0:30 

Can I have another one?

Peter  0:44 

Hi, and welcome back to The Gastronauts Podcast. My name is Peter and I’ll be your host. Here at Gastronauts we are committed to exploring communication throughout the body, with a particular focus on the crosstalk between gut and brain. We invite experts in this field to share both their research and their incredible journeys. So come join me as we explore the steps that go into shaping a scientist on the Gastronauts podcast.

Today, we have Dr. Hans Clevers, the director of research at the Princess Máxima Center for pediatric oncology and a professor of molecular genetics at Utrecht University. For those of you who study the gut or use organoids in your research, he needs no introduction. Dr. Clevers was the first to discover stem cells in the intestine and that the disruption of a downstream effector of the Wnt pathway, TCF4 abolishes stem cell crypts. He also showed that activating Wnt mutations underlie the development of colon cancer. He developed the first organoids through culturing living stem cells in the intestinal tract and has been awarded the Louis-Jeantet Prize for Medicine, the Breakthrough Prize in Life Sciences, the Heineken Prize from the Royal Netherlands Academy of the Arts and Sciences to name a few and has authored over 600 publications with over 100,000 citations. We really appreciate you taking the time to be on our podcast, Dr. Clevers.

I want to start by discussing your scientific journey. In hindsight, it is always easier to explain a career decision as planned; however, you have been very open about your initial thoughts on pursuing a career in both medicine and science. Can you take us through a few different big-decision moments in your career and what went through your head and what helped you make those decisions?

Dr. Clevers  2:48 

Yeah, so I’m actually 62 so I’m not the youngest anymore. When I was a young kid, I already knew that I was going to be a scientist. I was interested in biology. I read all the discovery stories of Africa and the bulls. And so when I was 18, in Holland, you go to university at 18. I picked up biology and was actually quite disappointed because it was still […] 19th century science, very descriptive, lots of Latin names, taxonomy, very little [instruments or] tools that you could do much with. Because this was [1975], this was just before molecular biology, DNA technology was just being developed and spread around the world. So I then also went to medical school. I completed two studies in the course of my master’s in biology. I spent some time at NIH; I spent a year in Nairobi, and that’s when I started learning about monoclonal antibodies that had just been developed, and about the first gene cloning experiments and I realized biology is probably going through a revolution now, but I also liked socially the medical environment, […] the clinical environment much more than the lab environment In labs, you’re locked up with a few people that you have selected. It’s much more social- you see the entire population of your city combined, all the young, poor, rich- you have nurses, you have the doctors, you have the students, you have the patients. In a lab, it’s 10 – 15 people, always the same. But so I then got a training position, pediatrics in Utrecht. They asked me, well, because of your double background, why don’t you start some research and you can do a PhD, which we don’t leave University with a PhD, we leave with a masters. So I started some research. And in that year, I realized although socially, it’s not always the simplest environment, really I’m a scientist. I’m not a doctor. And I then gave up that training position, wrote four papers on a project that I designed myself entirely, and didn’t end up in the biggest journals. Also, I was an immunologist. Essentially, I wrote two pairs of papers: on T cells and I repeated the exact same thing on B cells. And that already I think people started looking at me, “how can you be interested in T cells and be interested in B cells- you have to choose.” And that [is] something I I’ve learned that you don’t have to confine yourself to, to a discipline. But then I also realized I had to learn molecular biology from scratch. And I got a postdoc position in Boston in a lab of a Dutch PI, Terhorst. And I learned to clone TCL genes, and I was still a molecular biologist. And that is when I although was a tough time: 4 years. In the end, it worked out well and that’s when I realized this was the right decision for me. I’m a scientist. I find hospitals fantastic places, […] also the patients are better off if I’m in the lab and not with the patients.

Peter  5:47 

Yeah, so you mentioned- I know this is a while back at this point, but you mentioned that other people in the clinic and mentioned maybe you should go into research. Was there any hesitation or reservation thinking that, “oh, if I leave medicine now, I won’t ever come back to it at that time.” I think now you certainly have established yourself as a scientist, but at the time, did you have any concerns?

Dr. Clevers  6:06 

It was a real decision point for many reasons, but one thing is that the medical profession is a hard profession; it’s not easy. You have to be able to work hard. You have to be social. You have to be smart. But what I could see is that most doctors that would bring this with them, have a nice life, they have a good career. They work hard, but everybody understands what they do. There’s not this hierarchy, you have a few top doctors and then all sorts of other levels of doctors. There’s not this constant competition that you have in science. On the other hand, I knew that I am a scientist that says. Im not really sure I’m going to be a successful scientist, but that’s where my passion is. So I actually sat with my father for quite some time and asked him for advice. He said, it’s your decision. That’s if you if that’s where your heart is, go there. But it’s extremely risky because a career in science is very unpredictable […] As a doctor, you know, by the end of your day, you know, whether you have the skills to be a good doctor. As a scientist, even after a PhD or a postdoc, you don’t know whether you have the skills and the luck and persistence to be a PI and everything with it for many, many years because it’s just very hard work.

Peter  7:17

So when do you know that you have the stuff to be a scientist?

Dr. Clevers  7:20

Well when we first started discovering things [that were really just] small but were important. I was probably eight years into being a PI when I realized that we’re now doing things that […] people find interesting. And it was luck. So we’ve apparently made a few choices of where to go with the with the science, but it might also have not happened. And there’s also if you’re too long without a significant new insight, that is the end of your career, even if you’re as good as somebody else who did get an insight and got this boost to the career.

Peter  7:57 

But you mentioned earlier that people were telling you can either be a T cell scientist or a B cell scientist and you saw this not true- you can always pivot your research in the direction that you want it to go. Could you elaborate or unpack a little bit more about that?

Dr. Clevers  8:08 

Yeah, I can maybe describe the trajectory of my lab, which is very abstract. It’s because almost everything we did failed, and I forgot about it, but my [early] people actually know all this, because they went through that. So we started as a lab that wanted to find transcription factors in T cells. And knowing that these genes, although the genome was known in the late 80s, at all was still a decade away. But we knew that transcription factors are very important for cell decisions. And so we cloned a few amongst them, [and one] was a gene called TCF1. And then it took about five to six years until we realized that this was a crucial transcription factor, but not so much for T cells, but for early development in any kind of animal. It’s part of the Wnt pathway. So then I basically changed my lab from a molecular immunology lab. We had fruit flies, we had frogs, all these in collaborations. We have zebrafish, we did lots of mouse genetics. And then we finally hit on this link with the gut. And then I again converted my lab from a developmental model organism lab to a gut lab and we had to get to know somebody who knew histology and paraffin sectioning.

Peter  9:19 

Do you have any hesitation with making that switch?

Dr. Clevers  9:21 

No, it’s part of the personality of me, but also you sense that the lab around you starts to, I don’t know how that works, but has the same personality as yourself. I don’t know whether the lab programs me or I program the lab, so as long as the technologies around it doesn’t really matter if you need DNA sequencing. It doesn’t matter if it’s a zebrafish, or yeast or human cancer, sequencing is sequencing. So we’ve always been going in areas where we at least knew that we have mastered the technology and then the biological questions in the end [everything that] we’ve discovered is always simple. So there’s a few things if I can, if I look back, because I’ve been doing this now for 30 years, that have been very well for us. One is no fear [and] an enormous amount of trust. And that’s what I learned from my PhD advisor. So you can trust other scientists, you can share unpublished information you can, and you always get more bang [for your buck], because if people trust you, they are easy collaborators, they will help you when you need them. And it’s more fun. So there’s a lot of paranoia in science, which I think is sort of self-fulfilling. Because if you’re paranoid about your neighbor, bad things will happen. And if you’re open to your neighbor, that’s one thing. So trust, and courage so you can make a difference in somebody else’s discipline. If you bring in the right technologies and a good way of thinking, you can actually make a discovery. You have to have good collaborators to protect you from stupid mistakes, but also introduce you into that community. We’ve done that a lot. So we’ve written on fruit fly genetics on zebrafish genetics on the highest level journals, but always with a collaborator in that field that had helped us. And then one thing that I’ve often said is, I strongly discouraged my lab to formulate hypotheses. Now this is not how science is supposed to work. So my strong sense is if you enter a field where little there’s known and where you don’t really know the questions, you can ask. So don’t ask strong questions that are looking for strong answers where you already know the answer, because that’s your hypothesis. Just be open-minded, go into experiments, build a robust experimental system, and just watch. Watch and watch and watch. And then the human brain always immediately comes up with solutions, which other hypotheses, but you can sit down with a number of smart people and come up with 1000 solutions to your problems that could all be true. And evolution has picked one randomly. So why would your brain- I think it’s very arrogant to sit down and formulate a hypothesis in a field where you know nothing. And the human brain also works in that way that once you have your hypothesis, you will publish the hypothesis. You’ll find the evidence that it’s true. And that’s I think, where many non-fraudulent but papers are produced that turned out to be wrong, because in that process, you lose your open-mindedness. That’s not how our brains are comfortable to work with. So that’s something that I see a lot in my lab and somebody says, experiment fails, I say, “why? Did you drop it on the ground?” No, no, no, because you know, this is the result I got, and I should have gotten this. This is because you have your hypothesis. Get rid of your hypothesis and look at the results with an open mind […] So I think for discovery science, this is really the way to go. You cannot write grants, you cannot write papers [in which] you refuse to work with hypotheses, but it’s for me at least has been the most productive way of doing this. I guess a more applied science like in clinical science where you have to have a strong question and you have to have a hypothesis and there’s only a few answers: a drug will or will not work. So there it works. But for this open end where, you have no clue what you’re looking at and what the processes are, the hypotheses will blind you rather than help you.

Peter  13:21 

Yeah, one thing that you just said that really resonated with me was the fact that our context really biases our hypotheses. Where we are situated in a particular lab, or where we are in the world biases or informs our decision on how we approach science. And this is why it’s important to have collaborations with people who have different viewpoints than your own. In an era where communication internationally is just a few clicks on your computer away, what do you see the value in, in these large […] scientific organizations or societies that bring people together for an international conference? And if you were in charge of one of these conferences, how would you run it so that you would have effective communication?

Dr. Clevers  13:58 

That is a very good question. So for me, personally, these meetings [where] I’m a speaker, I have good access to the other speakers. So that’s where I get my information from. That’s where I build my, my networks, my collaborators. And that’s where I hear about the newest technologies about who to trust, who not to trust, what works, what doesn’t work. I rarely read papers. So I don’t read- I read Nature and Science but not the second or only the first part about the political things. So because we review a lot of papers so there’s a source of information so […] I would advise anybody you know, [when] you get asked to review, review. Because it gives you connections with journals; you learn a lot you learned before it’s appears half a year later in print. And so that’s for me, and I guess for many people, the face to face is still very important and Skype works well once you know people and you collaborate, so it’s a very good way of collaborating long distance. I guess for young people, it’s these larger meetings really, for me when I was young, you get a very good sense of who’s who in the field, you know what’s happening? What’s the general thinking, you know, what is the argumentation in this field? Or do people like or don’t like? Where are the open questions? On whose toes will I step if I say this? […] so I’m not really sure what I would do if we would organize meetings- I spend lots of time in meetings. I would organize them very differently. I would have more young people into podium. Shorter talks to basically get them exposed to, to communicate to audiences. Yeah, I think they get-togethers like large poster sessions with free beer work fantastically well. But the face to face at least for me, I’m not from the millennial generation, is very important. And many of the papers that that that we’ve written often result from talking to someone, get a good idea together, work it out together and you create a lot of friendships along the way as well.

Peter  16:15 

You talked about […] not stepping on other people’s toes, but the value of a lot of these conferences is to know who’s in the field. I saw recently that you tweeted some classic images from Lieberkühn’s thesis regarding the structure of the gut, and then some of Joseph Paneth’s pictures of the Paneth cells. I was wondering what drew you to these pictures in particular and what about these scientists encourage you to tweet about them?

Dr. Clevers  16:36 

Yeah. Well, so of course, these two have written extensively about guts and Lieberkuhn, who lived in the 1700s was German but worked in Holland did a PhD, which my students were very happy to read that it was only 32 pages. But then I could point out this actually written in Latin, so… well as a as a medical student, I had a very good memory, which isn’t so good anymore. But there’s many structures and diseases and phenomena that have a person’s name attached to it […] and nobody ever knows, you know, [for example], who was Merkel? And so I’ve made it a bit of a hobby to try to figure out, you know, who was this person? Why, and often they’re not the first discoverers, but for some reason they were the most visible person. Actually between Europe and the US, there are differences; like Kahler for us is multiple myeloma. Now I don’t think the US uses Kahler’s disease for this, but it was discovered by a German called Kahler. So I’d like to dig up these […]  just a hobby, and to find something that’s 300 years old, and it would be sitting in a museum and nobody knew what it was. So I found this thesis and then I realized this is really good.

Peter  17:50 

Do you encourage your graduate students to go through and the history of science as well?

Dr. Clevers  17:54 

Not really. So what I do a lot with my graduate students is discuss the process of science, and all the different decisions you take and what information is true, everything published, and doubt what was published. And so that I do a lot. I try to create a culture of interrogation and also try to explain that when you argue with somebody or you criticize or you have remarks about the work of somebody, you’re not criticizing the person, you’re criticizing something that the person says because it feels very personal. When you the paper gets reviewed, you see the review report, it hurts when it’s negative. But the process intended not to hurt you, but actually  say something about the same bit of work that you have. So that’s something is that I do a lot with my students.

Peter  18:45 

If you could travel back in time and have a conversation with any scientist, who would it be in what would you talk about?

Dr. Clevers  18:51 

Yeah, there’s a guy, Leblond, who is my personal hero, who is I think, originally French [and] migrated, because his wife is Jewish, migrated to Montreal in Canada, French Canada, and was still an active scientist at a very high age when he was 94-95, actively engaged, and many of his original discoveries [were] when he worked in the Curie University in Paris where radioactivity was discovered. So he learned how to use radio labels and he started applying them in biological systems. He saw the first label DNA, the first to label protein, the first to label sugars. Essentially, I think, he discovered stem cell hierarchies by showing how labels travel through the skin. For instance, he was the first to show that all cells make protein- quite a quite a spectacular finding because people believed that the liver makes all protein and the rest just take it up from serum. He was the first to show the ER Golgi secretory pathway. So he could have earned three, four Nobel prizes. Those papers are published in journals and were repeated later and several people got Nobel Prizes [for this work]. He’s always a bit a bit neglected. I don’t know why. But also everything we published about the gut stem cells. After the fact I found out that he had published sort of theoretical papers that predicted everything. So this is like a string of maybe 10 Nature, Cell, Science papers, we can now safely say after they have published that they were not original, because actually Leblond, CP Leblond had already published the hypotheses.

Peter  20:27

What would you like to ask him?

Dr. Clevers  20:28

What would have liked to ask him? I think, how his findings relate to disease, the various diseases of the gut. He doesn’t say much about [his views] in his papers. But it’s clear that he was a pathologist. He must have been looking at all of these structures from a pathological point of view.

Peter  20:47 

I think that’s fascinating. And personally, I like to get to know the scientists behind the science and I know a lot of times for people who are key figures in the field, they publish books, and we really like to know what their frame of mind is or what their reference and viewpoints are, but oftentimes when we’re judging the science currently in when we’re reviewing […] some article during a journal club, we […] dissociate the scientists from the science and I was wondering, at what point do you think we should look at the context that the scientist is working in when we’re evaluating their work?

Dr. Clevers  21:20 

I think always. So my thought when I started science was this is this is an extremely rational activity that you know, you sit, you’re smart, you design, you test, that’s how you define hypothesis, you design experiments that would contradict what you’re thinking and you would re-formulate your hypotheses. Over the years, I’ve learned that in experimental biological sciences that’s not how it works. I think 80-90% of what happens leading up to a discovery is random events between people. It’s characters of individuals, and eventually when that turns into a potential discovery, then we go into this mode that people think scientists always do. You become very rational you do your experiments you do your controls and this and that and then you write your paper as if you would always be looking for that particular phenomenon which you basically stumbled across it and you interpreted it well. So I think that first 80% that’s the biggest difference between people who constantly make discoveries and people who are extremely smart and know everything but don’t make discoveries that […] actually in this process of searching, stepping into dark [and] changing opinions, talking to people, hooking up with people, that that is where the discoveries really arise and then once use you see the light then you switch to this mode and that is the second part is you can learn. For a doctor there’s much more of the second part; so if you’re a clinician a lot of what you do once you know, it is this disease then you do this and these are the tests I do this how I follow up. For us is much less so, in basic exploratory science. So the context of a person that contacts you know why this person all of a sudden switch from this model system or that model system? What happened in his life that he meets somebody? Did he do that? That is that is crucial if you want to really, it would be good if you could make the discovery process more efficient, because we waste most experiments, as everybody knows, end up on the floor. And if you could make that process more efficient, that would be fantastic. So I’ve been talking a lot to colleagues knows more senior scientists who have made discoveries and they also don’t know exactly how this works. And it would be great […] but a lot of it is in the social interactions in the unexpected ideas that pop up because somebody says something, you make a link with something you’re thinking and all of a sudden there is an answer.

Peter  23:49 

I think that’s a nice way to paint it because a lot of people who aren’t in the scientific field think it’s a very isolated process. You’re working on a project you’re kind of hitting your head against the wall, kind of racking your brains but you need to reach out to other people and communicate with them to see if they have some other framework for you to think about.

Dr. Clevers. 24:04

Exactly.

Peter  24:06 

I also noticed on the other aspect of your Twitter, you posted a couple of animations or videos. Could you tell me a little bit about what got you into using videos or animations to explain science?

Dr. Clevers  24:18 

Yeah, so I’ve always I used to draw a lot as a kid. I collect art paintings. And so I’ve always been drawn by the visual. So stepping back I learned how to write papers over the years and what I used to do for a long time, so I spend endless amounts of time on the title and the summary. And if the title and the summary don’t draw attention, build up some tension and resolve. The storyline of a scientific paper is extremely important. And if you cannot write up your story in 125 words, which some of these journals [require], then there’s something wrong with the stories. There’s two stories or there’s only three quarters of a story or the order is wrong. If you cannot produce a 100 character title that has the message and draws attention has all the keywords, there’s something wrong with what you’re trying to communicate. So that I knew that for a long time. Then I got into contact with this guy who was, I think a physics PhD student, and he never graduated. He had this extreme talent- I think he uses the Pixar software. And the way we started working together is whenever I thought, we have a really nice discovery, I will do my title, my summary and we then try to write a script, they have a one minute audio, video animation video. And he would look at it, we talk he said, Well, this doesn’t work, and then he would turn it into so he gave a lot of images. Now what does this look like ? And he asked how many cells are there? How fast the move? So really, a lot of this is really correct modeling in these as many 40 or 50 animations now. Then he makes a cartoon of how we think the animation should go. And then we’ll go back and forth. And then I’ll say, well, that’s not what I said. Then read your text. This is what you say. I said, well, I meant something else. Yeah, so text is very ambiguous. And it’s clear that to listen to people talk or to read, particularly to two people talk, you get tired and lecture can last 45 minutes, but then it’s done. So and part of it, I think, because it takes a lot of brainpower to interpret what the person is trying to communicate. So once we figured out, okay, this is what I mean and okay, now I understand it, then he would make this movie and then it will be back and forth. And then when the movie is there, all of a sudden, everybody who watches the movie is effortless. They just look at when I give talks- I have many but often what I used to do is I would first show the experiments and summarize in the video, but I didn’t realize what works much better is if I first showed a video, people know the story and you see it and it’s the moment that it moves, people sit up, and they watch and it’s effortless to enjoy. And it’s artistically well done. And then I just showed the slides that show the evidence for what I just said. So you can say show, much more in 45 minutes you could ever do if you’re just talking and showing static slides. I also see when it’s playing- I speak a lot for lay audience like politicians or an artist [or] journalists, and the moment it moves, everybody pays attention. So the more I have movement on the screen, the easier people find it to just stay with me and I can communicate much, much more information through these visuals and they could ever do. Probably the people who are in in animations probably know this, I just discovered this. And the way they are made […] originally, they were made for scientific audiences. But it turns out that it works [for] any lay person with some education, know what the stomach looks like. You zoom in, they know what they’re looking at. They know more or less what a cell looks like […] so they understand immediately. The enjoy the aesthetics, they would not enjoy the aesthetics of a table. So in papers, I have very few tables or blocks […] You want different kinds of variables in the paper, and definitely colorful ones. You don’t want just numbers or lines.

Peter  28:20 

Do you feel like working on these animations has influenced how you write your papers? And is there kind of now a different type of structure or some principles that you follow when you’re writing?

Dr. Clevers  28:29 

Yeah, so this is writing this script, but it’s a bit like writing a summary but at the same time, you have to it’s not only the summary where you have you know, 10 sentences or so of a paper but you also have all the support that you would have that you use the entire paper for. So animation essentially captures everything that’s in the paper in one minute. And so I must say that I now find myself thinking, is this story ready to be submitted? Is a complete? Is it exciting? Will people like this? What is the real message here? When I think through the eyes of the animator, I get a much better sense of you know, what we need [is] a single message, we don’t need three message. We don’t need […] to prove five times what we know is true. We just show it once. And then we have all the backup evidence if needed. So to make a sort of an abstracted, clean, aesthetically pleasant representation of the work that I think in these animations works best.

Peter  29:27 

Really neat. How do you feel like how you frame a picture has influenced how you think about questions in science, when you’re doing this animation, you need to have this kind of viewpoint or this needs to be zoomed in here. Does that affect how you think about when you’re conversing with other people about their science? Like, oh, should we focus more on this part of the scientific process?

Dr. Clevers  29:47 

Yeah, sort of? Well, there are what you’re asking. There are several questions that have arisen in the process of making these animations because, like where cells come from where do they go and why? Why does this go there. So when you visualize the process you’re looking at you actually, you note the holes in your knowledge? Well, we’re not looking at this at all, but it’s a big issue because we don’t know where the cell will go next, or why it dies here and not there. So I guess it’s formalizes, in a way, a process of asking questions or seeing where the openings still are, or where the research can go, because literally you can see in these animations, we know this, we know this, but we don’t know this. So we just keep it out of the current animation [and it’s where] we should really be moving the [of] in the lab.

Peter  30:41 

I want to ask one quick question about your lab work. I know you have pioneered the field of organoids. And people are using organoids. And they’re using kind of spheroids, tumoroids. They’re developing a lot of different in vitro systems to model […] high throughput personalized screening of therapeutics. Where do you see the field going? And what do you think the current limitations of organoids are.

Dr. Clevers  31:03 

There are two types of organoids. The type that we developed is based on the stem cells or stem cell activities that are present in adults, in born bodies. And so every organ will have its own stem cell function. And then there’s the embryonic stem cell-based organoids that [built] brain that we cannot do or built our kidney or heart. So we basically use stem cells that maintain or repair tissues, [which is a] very different, very different approach. So for our approach, and I won’t speak for the other field, but for our approach, it is, like the best lab models, extremely reductionist, so it is an abstraction of reality. The original mini guts grown from one stem cell was aesthetically very nice because you start from one cell, it builds a gut. It’s very surprising that’s possible at all, and we still don’t understand much of that process. But is a complete gut, it has no immune cells, it has no muscle. It has no nerves, no blood vessels. So I think the big challenge is now is to, and this looks extremely promising, add additional layers. My approach would always be start as reductionist, as simple as you can. Add one variable, figure out how it works, add another variable and slowly build up the system. There’s a strong tendency with many scientists to say well there’s not a real life this is not how it works; it’s much more complex. And then they add everything together, and reviewers will tell us, you have to add this and that, but then I no longer know what I’m looking at. It’s too noisy. But that’s the style of research. So I thought I see now people are adding the microbiome by injecting and scientists many guts people adding organs, nerve cells, muscle cells, co-culturing […] You can you can have a piece of gut and a piece of brain and see how they communicate so that I think the developments that are currently happening in any place is just adding more complexity and getting closer to what a real organ looks like. Having said that, I must say there have been a large number of discoveries made by many labs in these extremely simplified systems that could then be checked in mice or in humans and patients, and confirmed to be true. So I think the power of modern science has been reductionism to a large extent and these organoids are an ideal model for that approach.

Peter  33:25 

Well, thank you so much for your time, Dr. Clevers.

Dr. Clevers  33:27 

Okay, thank you.

Peter  33:39 

Dr. Clevers shared a few of the things that went through his mind over his extensive research career. And one of the things that really stood out to me was the importance in trying to interpret your results without any preconceived notions. Natural processes are incredible, and it is important for scientists to really appreciate all the facets of the process. When you think you have a handle of these biological phenomena try and portray it as a movie. Use your imagination to piece together your observations and direct your future scientific questions by filling in the missing parts. I want to thank you all so much for listening, and we’ll see you on the next episode. For more of our content, you can follow us on Twitter @gutbrains or visit our website at thinkgastronauts.com. The Gastronauts Podcast would be impossible without the incredible team that we have here. Meredith Schmehl is our producer and theme music composer. And special thanks to the founders of Gastronauts, Dr. Diego Bohórquez, and the Bohórquez laboratory.

Dr. Bayrer 0:00 

Tastes like a dark chocolate with cayenne or capsaicin.

Peter 0:08

Perfect. That’s exactly what it was. You do research on enterochromaffin cells and a lot of the things that these enterochromaffin cells sense are irritants; the spiciness in the chocolate was used to mix up with the sweetness of the chocolate that normally is there to give that […] conflicting message to the enterochromaffin cells.

Dr. Bayrer 0:26 

Squirrels and other rodents are smart enough to sample and then avoid these hot peppers, but people were kind of dumb about it. And we’re like, we like that we’re gonna have some more. So that’s what we do.

Peter 0:41 

And that’s why we put it in our chocolate.

Hi, and welcome back to The Gastronauts Podcast. My name is Peter and I’ll be your host. Here at Gastronauts we are committed to exploring communication throughout the body with a focus on the cross-talk between gut and brain. We invite experts in this field to share both their research and their journey. So come join me as we explore the steps that going to shaping the scientist on The Gastronauts Podcast.

Today, we have Dr. James Bayrer, an assistant professor and pediatric gastroenterologist at UCSF. He completed his MD and PhDs at Case Western Reserve University School of Medicine. At Case Western, he studied specific the structure and function of proteins involved in sex determination in the laboratory of Dr. Michael Weiss. Upon finishing his PhD, he traveled out west to California for residency in pediatrics at UCSF. He stayed on to do a fellowship in gastroenterology (where he took care of children with digestive, pancreatic and liver conditions). He worked with Dr. Robert Fletterick and Dr. Holly Ingraham to study factors involved in colon cancer development and has taken advantage of organoids as a model system. These organoids are a really neat system that displays the shape and morphology of your gut, but can be studied in a culture dish! Dr. Bayrer has used organoids to study enterochromaffin, rare 5-HT secreting cells in the epithelial layer of the gut to better understand visceral (or our internal sense of pain).

So I want to start by taking a trip down memory lane with you. When you were at Case Western, what drew you to studying sex determinations in fruit flies? And how did that inform your decision to pursue a residency in pediatrics? They seem a little bit desperate to me, but I was wondering what was going through your head at the time.

Dr. Bayrer [3:03] 

Thanks for having me. So that’s an interesting question. And yeah, the sex determination and crystallography are pretty far removed from what I’ve been doing lately. But what drew me to study this was the idea that the structure of a protein can really dictate its function. And so in Drosophila, sex is determined by this gene I was studying called double sex. And I was curious as to how the structures that the female or the male specific sequences change the function that would give you such dramatically different phenotype and development. So really, it goes back to more of an interest in structure or function and protein biochemistry.

Peter 3:52 

And development as well. Did that have any influence on your decision to pursue a career in pediatrics? Or were the two separate ideas In your head at that time?

Dr. Bayrer 4:00 

The two are separate. So when I was training in the PhD phase of my work, I knew that I was going to sub-specialize into something and what that was going to be, I wasn’t entirely sure. I still had an interest in protein interactions and structural biology, which is pretty general and can be applied across all of the disciplines in medicine. And so what really convinced me to do pediatrics was actually when I went back as a third year medical student and started my clerkship rotations. I started out with pediatrics and I really fell in love with both the patient populations and working with the families and the children but also the relationships that you can develop in the long term care of these families with complex medical issues. I found that to be a very rewarding side of medicine. And the other thing that I thought was really interesting in pediatrics is that somebody could come with you with a certain set of symptoms and depending on the age of the patient, you can have a very, very different differential diagnosis. And so in many ways, it ticked those boxes of clinical thought process and puzzle solving that makes medicine a lot of fun. And it just adds that extra layer of complexity to the process.

Peter 5:18 

Yeah, that’s really neat. Do you feel like your time away from your PhD to when you started doing research again during your fellow years while you were a third and fourth year medical student and while you were pursuing your residency in pediatrics has influenced or framed how you think of research or changed how your thought process and research was?

Dr. Bayrer 5:35 

Yeah, and so the intervening time is really a time that I focused on my clinical skills and to tried to hone those to be the best clinician that I can be. And so I really focused on that. But at the same time, the farther and farther away from the basic research that I can do, the more I really did start to miss it. To be able to ask a fundamental question and to able to answer it. So what I would say is that that clinical time served to help me focus my research questions on work that is more directly applicable to the patients that I care about, that I’m treating. That’s probably the biggest takeaway that I had in terms of my clinical experience in forming the research.

Peter 6:25 

Do you mind telling me a little bit more about your current research efforts?

Dr. Bayrer 6:26 

Yeah, so our lab has mainly two projects with some overlap. One side of that is based around epithelial regeneration and differentiation. And so what programs are there that help control this normal process where the gut intestinal lining is renewed every week or so, and help control the proper distribution of the specialized sensory cells and other cells that compose the lining of the gut. So that’s one side of the lab and then the other side of the lab is a collaborative effort. With a number of really fantastic investigators looking at the signaling side and the signal integration processing. So that’s the sensory visceral pain aspect to the research. So we have one side that’s really organoid and developmental biology focused. And then another side that’s more physiology focus.

Peter 7:20

Do you see kind of the organoid and developmental biology influencing or having an impact on the clinic? What kind of diseases are there that we know of in pediatric populations where there are developmental or programming issues with our intestinal cells?

Dr. Bayrer 7:33

So there are an increasingly recognized number of genes involved in epithelium renewal as well as barrier formation that had been implicated in our very early onset IBD patient population, and IBD stands for inflammatory bowel disease. These patients are diagnosed between zero and five years of age with inflammatory bowel disease. We now have the tools to be able to try and identify genetic causes that we can intervene on specifically. And that’s one major aspect. In terms of organoids, one of the other thing that’s been really interesting is actually cystic fibrosis. We think about cystic fibrosis mainly in terms of pulmonary disease, right? Because that’s what really drives that clinical morbidity and mortality. But when you take a step back and look, you realize that the transmembrane protein that’s mutated in cystic fibrosis is expressed throughout the GI tract as well. And so there’s liver disease, pancreatic disease, as well as intestinal disease. In cystic fibrosis, there have been a number of really game changing medications that have come to market. And when you look at trying to match those drugs with particular type of mutation, going to trials, the drugs are really targeted to a particular mutation. What we don’t know from the clinical trials is if drug x is going to work with mutation y or mutation z if it’s only been studied for mutation a. And what was figured out is that if you make organoids from cystic fibrosis patients, you can stimulate those organoids with forskolin. and functioning CFTR will allow those organoids to swell due to flux of the ion channel.

Peter 9:20 

So this essentially allows a high throughput readout.

Dr. Bayrer 9:23 

That’s right. And then in even more importantly, allows you to do a personalized medicine approach. And so now you can take an organoid from a cystic fibrosis patient, you can expose it to different potential medications and find out very quickly if there particular CF mutation is going to respond to that truck. And so again, that’s really revolutionized the ability to match the right patient with the right drug, which is really that basis of precision medicine.

Peter 9:47 

And I think the field of organoids has really taken off because it is more similar to what we see in our living tissue. What drew you initially to the field of organoids? I noticed you previously kind of did a lot of structural functional relationships but what drew you to the cell culture and organoids in particular?

Dr. Bayrer 10:04 

I became really enamored with a particular nuclear receptor that was expressed in the liver and the pancreas as well as in the intestine. And began to think about that first from structural biology aspects. I was interested in potentially drugging the receptor to tune activity either up or down. And as I was going through the biochemistry of that, I started to become really interested in the underlying biology. So at that point, I realized that I needed to add some skills to my experimental tool kit in order to be able to answer some bigger questions about how the receptors function overall in the tissue- that’s what really led me to being able to do organoids.  had a collaborative research experience with [a] lab at UCSF who had at the time recently brought in the organoids and technology. That enabled me to have support from an established stem cell investigator to teach me the ropes in terms of using this technology to be able to get at those questions about cell renewal and differentiation.

Peter 11:13

Cystic fibrosis is typically looked at as a gene mutation and pathology is typically seen kind of within the lungs are skin as well. Why use an organoid from the intestine as opposed to an organoid from the lung to test this? Is it just because of the ease of grabbing the tissue?

Dr. Bayrer 11:29

So patients with cystic fibrosis do have intestinal dysmotility and it’s thought to be primarily due to problems with secretion. And so there are a number of GI issues that we co-manage with our pediatric pulmonologist. But to directly answer your question, it’s entirely expediency. To do a rectal biopsy to obtain tissue to do an organoid can be done even without sedation is very, very quick. it’s painless procedure. Whereas to take lung tissue is much, much more involved. And so it really just became fundamentally easier and faster.

Peter 12:07 

That’s really neat. The first thing that came to my mind when you’re telling me about inflammatory bowel disease is that we tend to delineate it into two types: Crohn’s disease and ulcerative colitis. As I learned more about the two pathologies, [IBD] most likely lies among the spectrum. Do you feel like this organoid approach will help us better classify different types of inflammatory bowel disease? And do you think ultimately, there will be a treatment that is targeted to specific subsets of these?

Dr. Bayrer 12:32 

Yeah, so certainly, so my feeling is that inflammatory bowel disease is a spectrum of probably 100 or 200 different things that are essentially pheno-copies that we have somewhat artificially sorted into ulcerative colitis, Crohn’s disease, or indeterminant colitis. And it’s been clear from the sequencing approaches that there are mutations associated with disease both in the intestinal epithelium as well as within the immune system. We know also that microbiome can play a part in disease pathogenesis and propagation. I think that it’s vast oversimplification that we’ve done, but at the end of the day, if we ask: for the current treatments that are available to that simplification work now? Well, kind of you. So we, we make a big deal trying to change between Crohn’s disease and ulcerative colitis, and then we end up treating them the same about half the time. So there’s definitely a need to be able to really separate out distinct pathophysiologic mechanisms so that we can like the CF analogy, be able to really target the right medication to the right pathophysiology. I think that organoids will be a part of that, and to some extent, they already are. And so it’s really going to be figuring out where we can use the organoids, where we have to use our other systems. But at the end of the day, I think we’re going to end up with thousands and thousands of patients with IBD from sequencing and then it’s going to be figuring out how can we can separate the signal from the noise and understand what variants we’re seeing are actually disease-related, and how we’re going to address those with medications that puts the disease into remission.

Peter 14:12 

I want to segway little bit into the other aspect of your lab, the visceral sensing component of it. And by visceral sensing, we mean this internal pain that we don’t really classify as the same type of pain that we have when we have like a cut or a wound. This is so different from inflammatory bowel disease where we do have a regimented treatment plan for how we treat [it] compared to irritable bowel syndrome, which is a common syndrome associated with visceral pain. And I was wondering, your thoughts on what our research efforts are, what your research efforts are and what kind of therapeutics do you think we’ll be able to develop for IBS?

Dr. Bayrer 14:51 

So our lab has been really interested in the enterochromaffin cell which is the serotonin producing cell within the lining of the gut. These cells that they represent about 1% of the epithelial cells, but they’re responsible for about 90% of the body serotonin production. These are major neurotransmitter factories throughout the lining of the gut. And we became interested in understanding what makes them tick and how they work. And so we incorporated the organoids to be able to study enterochromaffin in as native an environment as possible, but still accessible for excitation studies and to be able to really understand what types of signals they respond to. And then the next aspect that we’re interested in is what happens to that serotonin and so is this a humoral thing is it paracrine, is it autocrine?

Peter 15:49 

And these are all different ways that serotonin is being secreted either through the blood or to nearby neurons?

Dr. Bayrer 15:54 

Yeah, exactly. We asked where the serotonin receptor expressing neuron lies in relation to the enterochromaffin cell and found that they do traverse right underneath these enterochromaffin cells. And so then that allowed us to ask whether or not these are forming a synapse like connection. And so is this really a direct talking of enterochromaffin cell to the nerve fiber itself.

Peter 16:22 

And these enterochromaffin cells respond to both mechanical and chemical stimuli.

Dr. Bayrer 16:26 

Yeah. And so we’ve looked at the chemical response to this, and show that if you stimulate the enterochromaffin cell, you increase nerve firing immediately and the the associated fiber can be blocked either by using agents that block enterochromaffin cell activity or agents that block the nerve fiber. The Beyder group at Mayo has looked at mechanical sensitivity and looking at Piezo2 expression within enterochromaffin cells, I guess, oversimplify you’re poking it with a stick, but they’re using a really fine technique to apply gradients of mechanical pressure to the enterochromaffin cells, either in isolation or as part of an organoid. And seeing that the mechanical pressure does also cause depolarization and releases serotonin from the cells. And so then you can say that it looks like there’s both mechanical and chemo ensory effects.

Peter 17:20 

For me, it’s easier to intuitively understand the space that mechanical sensation occupies in the sense that you can feel a certain amount of force. But the chemical space is much larger. Do we have any idea of what compounds activate enterochromaffin cells? Do we respond to all types of food [or do] they respond to the bacteria in our gut? Is there any discrimination or has

[there]

been [data] shown that enterochromaffin cells respond to all of these stimuli?

Dr. Bayrer 17:47 

So we found that there are specific receptors for specific targets in enterochromaffin cells and you can kind of lump these things into three main categories and so they respond to irritants, the real pungent substances found in garlic or wasabi triggers them, various short chain fatty acids, which we tend to think of has microbial byproducts. In particular, isovalerate was very strong activator of enterochromaffin cells. And that’s the short chain fatty acid that gives gym socks, or stinky cheese that particular odor. And then catecholamines also activated the cells quite strongly. That was done on a relatively limited survey of things that we thought could potentially be activating the cells. It’s possible that we’ve missed whole categories, but we thought that was pretty good start and when we think about the things that activate the EC cells, and these are all potentially all seem to have the same common theme of you know, maybe there’s danger in this luminal inside gut environment, and given the importance of serotonin and secretion and motility. Maybe it’s a way for the GI tract can protect itself when it senses essential luminal danger.

Peter 19:06

Really neat. And then the other aspect is these are serotonin-secreting cells. And you touched upon this earlier, whether it’s humoral, whether it’s paracrine, do you have kind of a framework or an idea of how you think the serotonin is being transmitted?

Dr. Bayrer 19:21

We’re particularly interested in serotonin release into one of these synaptic connections. You know, what we saw is when we activate the EC cells that we can elicit a mechanical hypersensitivity in the attached afferret nerve fibers. And so what that implies to us is that this may be partially a mechanism to explain increased gut pain in a patient with IBS relative to somebody without. When we think about IBS and enterochromaffin cells, there’s been some prior work looking at the number of enterochromaffin cells, [they] appear to be potentially increased in some patients with IBS suggesting that maybe they have even more of a serotonin input. And there have also been some studies that suggest that during estrous cycle that there’s changes in the amount of serotonin produced in EC cells, or maybe even a change in EC cell number themselves. And when we think about conditions like IBS, there’s a about a three fold increase in females compared to males. So there’s definitely a biological sex based difference here that is reflected in the serotonin and is also reflected in disease pathology. And so the question is, well, is this also related? And so some of the work that we’re doing now is to really try and map out these connections between the enterochromaffin cells and their associated nerve fibers as well has to engineer their activity. So to activate or deactivate enterochromaffin cells, and ask how that affects the perception of visceral pain in our rodent models.

Peter 20:57 

I’m really excited to see some of the work that comes out of your lab to study this, I want to transition a bit to your career. I was talking to a colleague here at Duke previously, and he told me that no stage in his career really prepared him for the next stage of his career. Can you tell me some more about the challenges that you hadn’t anticipated transitioning from a fellow to an assistant professor.

Dr. Bayrer 21:22 

I was really blessed with a very supportive division and supportive mentors. So I think that actually was really nice about my environment, particular where I trained. I think probably one of the biggest difficulties is figuring out how to manage your time. You’re working on your independence for both your research career, but at the same time, now you’re an attending physician and you’re responsible for an awful lot of patient care. It’s trying to being able to balance those two worlds, so that you’re providing optimal care to your patients. And you’re not letting people down. But at the same time, you’re really jealously guarding your time, so that you can be productive in the lab and prepare yourself for the next stage after that, which is the independent investigator stage.

Peter 22:13 

Being a physician is a full-time job being a professor as a full time job as well. And how do you manage to put both of those? Are there some things that you have to compromise on? Or do you feel like, there are some things that you’ve given away a little bit?

Dr. Bayrer 22:26 

Yeah, and so I’ve certainly pulled back from the number of patients that I see, you know, if I’m out traveling, I feel it’s not entirely fair to my patients, for them to not be able to find an appointment for me for like five months; that’s not so good. And so, moving towards systems of working within the pediatric fellowship training program to work in teaching clinic situations, and to have patient care there but also be working with a larger team of physicians. So that if I’m not around somebody else who knows the patient and is involved in the cares around, and so we can always make sure that we’re delivering the care to the patient that we need. That’s probably been the biggest change and the biggest pullback that I’ve had from my regular fellowship years to where I am now.

Peter 23:18 

It’s a dependence on a team. It’s a team effort. And that’s something you’ve reiterated before and something that you continue to impress. You are also the assistant fellowship director at UCSF. What do you feel this role has taught you about yourself and what are you hoping to instill in your trainees or your fellows at this point?

Dr. Bayrer 23:36 

In terms of what is taught about myself, I really reiterated that I very much enjoy teaching and I enjoy working with learners in a complicated academic environment where we can really sit and think about problems, think about solutions for patients if I’m in the patient setting. Or challenging hypotheses or research plans in the basic science setting. That’s been actually been lot of fun working with our fellows as they go through this really intensive period of training. You know, they come in on one side has graduating pediatric residents, and then leave three or four years later as gastroenterology specialists and academicians. And that’s been a very fulfilling part of my job.

Peter 24:31 

And when you are training some of these fellows, do you feel like there are some common mistakes or challenges, or growth opportunities that you notice and I don’t know- when you reflect on your own time as a fellow, are these things that you have also recognized?

Dr. Bayrer 24:44 

I think the biggest thing is just how quickly time goes by and how much of a compressed timeline you’re on has a fellow and especially if you’re interested in developing an academic research career there, if you don’t have as much of a baseline background and doing science, it takes a good effort to really get up to speed. And so it’s really stopping and in thinking coming back, even at the end of your first year, say, all right, so by x many months, we need to be kind of this far along so that you can have an application because that NIH application isn’t going to be renewed or be reviewed for like four months after you put it in and then anticipate another submission. And so all of a sudden, you’re building in a year and a half time before you would know if you’re going to get a grant or not, as a junior faculty. And so the timing is I think one of the biggest surprises in the for fellows.

Peter 25:52 

And do you feel like there is a pressure kind of with regards to time as you’re starting up your own lab. Do you feel this similar time crunch? Or not so much?

Dr. Bayrer 26:04 

Yeah, I think that it’s, it’s fair, I think everybody feels kind of that pressure. There’s always that pressure. Again, I’ve been lucky in that the environment that I’ve been in has been very supportive. And, you know, working with, with David and Holly and Stu on this collaborative environment has also given me access to additional resources that, you know, I didn’t foresee myself having even a few years ago as I was looking more in staying more on the affiliate side of things. So I think that that’s been a real leg up.

Peter 26:42 

Sounds like you’ve had some really great mentors. And I was wondering, as you’re looking to build your team, what are you looking for in mentees?

Dr. Bayrer 26:49 

So I think the biggest thing that I want the that I look for is curiosity and a drive to answer questions. And so to have people that are excited to come in and to think about a problem and to think big about a problem, not being afraid to fail at it. As long as you know, you’re learning a lesson from the work in the process. So that’s one of the big things that I look for. And then the other thing is somebody that works well in a collaborative team environment. In many ways, what I’m looking for in somebody coming into the lab is the same thing that I’m looking for in somebody coming into our fellowship program. We’ve got a lot of folks that we’ve had real success with in training in an active research environment, and with wide, wide variety of backgrounds. Again, I think that those key qualities are ones that they don’t necessarily show up on a research pedigree of you know, I went to Harvard, Yale, Duke, wherever but rather, that they really come across and how that person approaches science.

Peter  27:59 

Do you feel that a lot of the skills to be successful in medicine are the same as the skills that are necessary to be successful in research?

Dr. Bayrer 28:07 

I think so. So a large part of medicine is really about pattern recognition, being able to separate that signal from the noise. And so when you’ve got a panel of lab tests coming back, and somebody who has a whole bunch of different somatic complaints, but figuring out like, what’s really the heart of the matter. That pattern recognition also plays a role in science, right? When you’re looking through your data, and sometimes you just have noise in there. And sometimes you have a real signal to being able to identify that that signal and go with it. And so I think that those are two there are things that are very, very similar. I think, certainly curiosity is important in medicine, and so particularly at large academic centers where people coming in are not necessarily coming in with their garden variety problems to really be able to think like, all right, well, what else is going on in here? And what tests do I need to do? Or what what history questions do I need to ask that will really allow me to get to the to the heart of what’s bothering this patient? Yeah, there’s an awful lot of overlap. At the same time. There’s also a real distinction in the time course of decision making. If you’re thinking about your lab experiment, and you’re trying to get the best controls, because you know, you’re going to send out this $30,000 single cell RNA sequencing data set adventure and like, boy, you better make sure you got everything absolutely correct on that. You know, you’ve got some luxury of time where you can sit and you can think about that for a week or so. You don’t always have that luxury so the PhD year you can gather a lot more information and really feel like you’re making informed decision. In medicine, sometimes you’re operating on imperfect data and you just have to acknowledge all right, this is imperfect data. And I may be wrong, but I have to go with the best guess because we don’t really have a lot of extra time to figure this out.

Peter 30:30 

Speaking of the concept of time, I was wondering, where would you like to see the field of gastroenterology in 10 years?

Dr. Bayrer  30:38 

You know, I think right now we’re really at a golden age of a nexus between being able to have epithelial biology, neuronal, microbiome and immune response systems all coming together and having the tools to be able to dissect and try and understand what the what the inputs and the outputs from each of these systems are and how they work with each other. So in 10 years, you know, I’d like to know that we’ve been able to map out some of the sensory systems and getting a handle on the pathways that are involved in the problems that really affect activities of daily life for people with chronic pain issues. So can we figure out what those with some of these pathways [affected] are so that we can target some treatments. In 10 years, I’d like to be able to say that yeah, we finally have a medication that can help or a therapy plan that can that can really benefit somebody with really severe IBS and get them so that they can pursue the things that they want to do. Really neat.

Peter 31:41 

Well, thank you so much for your time.

Dr. Bayrer 31:43 

Of course. Thank you.

Peter 31:55 

Dr. Bayrer, took us from bench to bedside and really focused on how he sees intestinal organoid models being incorporated in the diagnosis of disease. He underscored the importance of improving our time management during each phase of our career. And that’s something I hope we all take the time to think about. How can we make sure we’re being both rigorous and efficient? I’ll leave you with that. I want to thank you all so much for listening, and we’ll see you on the next episode. If you like what you’ve heard, we’d love it if you could leave us a review. For more of our content, you can follow us on Twitter @Gutbrains or visit our website at thinkgastronauts com. The Gastronauts Podcast would be impossible without the incredible team that we have here. Meredith Schmehl is our producer and theme music composer. And special thanks to the founders of Gastronauts, Dr. Diego Bohórquez, and the Bohórquez laboratory

Peter  0:00 

What are your thoughts?

Dr. Wu  0:01 

You know, I feel like I should know what this is, like got seeds in it […] I don’t think it’s a cherry. I don’t know- I think the closest I can get to it’s a some type of strawberry jam type of thing.

Peter  0:15 

Yeah, that was right on the money […] It was a raspberry covered in strawberry yogurt. I chose the raspberry because I went to the Mayo Clinic website, and I was looking up foods that were high in fiber and I didn’t know this but a cup of raspberries has about eight grams of fiber in it, while an apple which we think of kind of like an apple a day keeps the doctor away as kind of the main fiber fruit which only has about 3.5 grams of fiber in it.

Dr. Wu  0:38 

You know, in our studies a vegan eats about 30 grams of fiber a day. But if you’re in Africa, living in rural Africa, they’ve done these studies [that show that they are] eating greater than 50 grams of fiber a day. That’s a lot of raspberries.

Peter  1:01

Hi, and welcome back to season two of The Gastronauts Podcast. My name is Peter and I’ll be your host. For those who have listened to season one thank you so much, and we hope you’re ready for another great season. If you like what you’ve heard, we’d love it if you could leave a review on whatever platform you listen to us on! For those who are new, thanks for joining us and we’re excited to have you. Here at Gastronauts, we are committed to exploring communication in the body, and in particular, how our gut talks to our brain. We will be inviting leading gut brain scientists to share both their incredible research and their captivating life stories. So come join me as we explore the steps that go into shaping a scientist on The Gastronauts Podcast.

Today we have Dr. Gary Wu. The Ferdinand G Weisbrod Professor in Gastroenterology at the Perelman School of Medicine at the University of Pennsylvania. He is the director and chair of the scientific advisory board for the American Gastroenterological Association Center for Gut Microbiome Research and Education. He is also an elected member of both the American Society for Clinical Investigation and the American Association of Physicians. A bit about Dr. Wu’s career path, he completed medical school at Northwestern, his residency at the University of Minnesota hospital, his fellowship in gastroenterology at the University of Michigan Ann Arbor. And his research really focuses on the interplay between the gut microbiome, or the aggregates of microbes that reside within our intestines, and this gut intestinal tissue. So right off the bat, I want to ask a little bit about the inspiration behind your decision to study the microbiome. When was the first time you heard about this term and when did you realize this is a field you wanted to pursue?

Dr. Wu  3:05 

Well, you know […] there was some serendipity involved in this. We’ve always sort of been interested in microbes in the gut, because I’m a gastroenterologist. And this is something from a practical standpoint that we […] do in my clinical practice. But for a while, we had been interested in how microbes in the gut could change host physiology, meaning gene expression in the intestinal tract. And a long time ago, we had made an observation that there were certain genes in the intestinal tract that were regulated by bacteria. So we actually deleted that gene with the notion that perhaps it might change bacteria in our gut in some way, because this gene led to a secreted product. And because it was in the gut lumen with all the bacteria we thought it might have an effect on bacteria. So we went through very antiquated types of technologies basically to try to visualize a difference in the composition of bacteria in the gut by looking at stool samples. And in mice, we really couldn’t see anything, which was no real surprise [since] by visually inspecting things, you’re just not going to see anything. But that was around the time that high-throughput sequencing technologies were being applied to studying microbial communities […] and it just turned out that there was a scientist, a very good scientist at Penn, Rick Bushman, who’s now the chair of microbiology at the University of Pennsylvania that was actually at the forefront of that technology. So I basically met up with him and and we began a collaboration. And we found some very interesting things with this. And around that time, the NIH had the first call for the Human Microbiome Project grant applications. And so that’s how we got started in the whole area.

Peter 4:59

So yeah, for me, the microbiome has [moved] to the popular press, and it’s a very commonplace topic nowadays. We hear about it in the news. We hear about it in the foods that we eat. So I was wondering, did you have any interest in the microbiome before you decided to pursue a career in gastroenterology or did that happen later?

Dr. Wu 5:15

You know, I think it sort of happened later. As a physician. We see this in clinical practice a lot. We get a lot of questions about probiotics, prebiotics, about fermented food, what’s good, what’s bad. So from a clinical standpoint, it’s actually a very relevant topic that the patients bring up very often. Unfortunately, we don’t have a lot of real strong evidence that our current probiotics have a real strong effect on either preventing and or treating disease. There is a little bit of evidence to suggest maybe they do something. And […] there are individuals that swear they feel better when they take these probiotics, and I can’t deny the fact that it probably on a case by case basis it may provide some type of benefit. But it’s the notion that as a physician, I’ve sort of known about this because I’ve been in training for a very long period of time, before I became a gastroenterologist. And so now that I’m in the GI field, and it just sort of makes sense that it will come back full circle to what I sort of known about in a clinical entity with patients that now we can actually study it scientifically because we have these types of technologies.

Peter  6:27 

Certainly. So I was wondering what sparked your decision to pursue research? Had you always been conducting research while you were a medical student or while you were a resident? Or was there something about the microbiome that really drew you towards that field? And do you feel that your medical training had prepared you to go into the field of research?

Dr. Wu  6:42 

Yeah, it’s a good question. So I did a lot of research when I was an undergraduate at Cornell as a chemistry major, and I really didn’t do a lot of research after that. And in medical school, I knew that I was interested in internal medicine. So I did a residency in internal medicine. I decided to go into the field of gastroenterology more because I liked the clinical practice of gastroenterology. I like doing procedures. I like what gastroenterologists do: make a diagnosis, make interventions. So it’s more from a clinical standpoint that I ended up in gastroenterology. And more by just opportunity, when we train as fellows in a sub specialty, [we] have opportunities to do a research track or a clinical track, [where you] take care of more patients. I just by opportunity [found] a research position that was open at the University of Michigan where I did my fellowship. And that’s just what I’ve been doing ever since. I mean, I really liked clinical medicine. I like taking care of patients. But I like doing basic science research because

[it]

opened my eyes to so many other things that physicians can do. It’s a very rare rewarding experience to take care of patients, as well as think about questions that you might be able to explore in the laboratory that might ultimately have an impact on the types of things and patients that you see every day in the clinical setting.

Peter  8:16 

So now that you are a relatively established physician scientist, what qualities do you feel are important for some younger students who wish to be someone who follows in your path?

Dr. Wu  8:25 

You know, I think it takes a lot of different qualities. It takes a lot of perseverance. It takes resilience. But one of the traits that I find in common with individuals that are successful scientists, is creativity. So when people work with me or I talk to other investigators, it’s those individuals that come into the laboratory- they may not have had a lot of laboratory experience, but [they’re] just full of ideas, full of questions and I think some of the best scientists in the world are just deeply creative people. They can come up with ideas, they can see and envision things that the average person cannot actually see. So I, for example, have a lot of admiration for artists, or painters, for musicians who can create things that other people cannot actually conceive of. And it’s the same thing for a scientist, it’s just a little bit different because you’re using science as sort of an output for your creativity. So it’s not as if you know, people that are not innately as creative would not be successful in science, I think that you can learn to explore questions and open your mind to things. In a broader sense it’s something that you can develop over time. But I think innately, there are just people that that are just sort of hard-wired to be incredibly creative. And I think those types of individuals really push the field forward.

Peter  9:58 

That’s really interesting. Is there a way to foster creativity? Do you kind of encourage art projects in your laboratory to […] stimulate a different part of your mind to be more creative? Or is there an impetus in your laboratory to try and hone in and develop this creative process?

Dr. Wu  10:15 

Yeah, it’s a very interesting question. Part of that is, I think part of being a good mentor. So when people start out in the laboratory, especially if they haven’t done a lot of basic science research, it’s basically you just have to learn these techniques. And so part of the laboratory experience is a two part process. One is technology, you’re going to have to be able to put your hands on and do an experiment because even if you have the best ideas in the world, if you can’t do the experiment, then you really can’t get anything done. The other part is to think like a scientist, and that’s where the creativity comes in. And that’s a much more difficult thing to teach. You can teach people how to do things technically, but to become creative, it’s much more difficult. But I think that you could learn from example, you could learn from reading the literature, learn how people think. And then also look at other great scientists. You go to talks, and you get inspired by what other people do and how people think about problems. I’ll give you an example. Many years ago, I went to a fabulous talk by a really world renowned scientist [who studied] nuclear hormone receptors. And he said that he had a graduate student that knocked out a gene for some type of pathway. And the graduate student at that time, this many years ago, spent a long time making that knockout mouse. And at the end of the day, it had no phenotype. And the graduate student was absolutely devastated because he had spent so much time making this knockout mouse. But the scientist was just elated. He said, You just don’t understand what this actually means. Everything we know about this gene product suggests that there should have been a phenotype. The fact there is no phenotype is a really fabulous discovery. And it turns out that he had the foresight to think about what alternative mechanisms might be available through this model system. And they ended up publishing it in a very high profile magazine. And that’s just another example where maybe an average individual would also be very disappointed. But a very seasoned scientist who’s very creative can see beyond it, and say, well, this is absolutely fabulous. And we can […] think of a way that you can go about trying to answer this question. So being creative, getting inspiration from other people looking at how people approach different types of experiments. I think that to a certain degree, you can learn those types of skills over time and [for] a lot of people, it’s probably within them, but they’ve never been challenged to develop that part of their armamentarium. And so given the opportunity, people can sort of grow into that. I think over time, we’ve given the right types of exposures in the environment.

Peter  12:58 

Yeah, that’s really neat. I hadn’t thought of that before. Being creative in sciences [is] interpreting your results that are very different than your initial hypothesis. And being able to posit alternative mechanisms or different approaches when something doesn’t quite go the right way you think it should be going.

Dr. Wu  13:13 

Exactly. I mean, I think that we all try to do hypothesis driven research. And at the end of the day, if you do an experiment, and it didn’t answer your hypothesis one way or the other, then you probably didn’t design it correctly as long as technically there was no flaw. But at the end of the day, you’re going to get an answer if you did the experiment correctly, and maybe it doesn’t agree with your initial hypothesis. You can’t change the results, but you can change your hypothesis, right? And so then you come up with an alternative hypothesis and you begin to chase it down. But that’s exactly it; that’s the scientific method.

Peter  14:06 

That’s really great advice. Thank you. I wanted to talk a little bit about some of your early research. And I know I’ve mentioned this earlier, the microbiome field has really grown kind of at a breathtaking pace. Eight years ago, you published some landmark work on long term dietary patterns with the microbiota in the gut. And [you] were the first to show that consumption of specific diets of a known composition could not only rapidly change the microbiota composition and as quickly as 24 hours, but result in stable changes for up to 10 days. It’s been a decade almost since then, and I was wondering how you feel about our ability to utilize diet as an intervention to treat diseases of dysbiosis or imbalances in our gut microbes?

Dr. Wu  14:47 

Yeah, I think one of the things that we’ve learned over time that we actually saw in our initial publication a number of years ago is that the human microbiota is actually very resilient to dietary influences and so you can see consistent and maybe somewhat larger effects by using very extreme diets, like the ketogenic diet lacking any carbohydrates or an herbivorous diet. But still one of the largest sources of variance in the composition of the microbiota is inter-subject variability, how different we are from each other. So the usual influence of a diet on the composition of the microbiota actually is smaller that how different we are from each other, demonstrating that again that the human microbiota is actually quite resilient to change induced by diet. In a way, that’s good, because you know, every time you eat, you don’t want your microbiota changing in some type of wild way. Alternatively, if you want to engineer the microbiota into a different types of configuration, it may be more difficult than initially conceived. But there’s another way to think about it. It’s not just the composition of the microbiota, but it’s the metabolites that they actually make. So you may not change the configuration dramatically, but if you feed your microbiota something different, you provide a different type of substrate, you still may have an effect, not by the change in a composition that types of microbes but the products that they actually make. So an example of this would be equine production by the microbiota. So microbes can make a non-steroidal estrogen that is a hormone that has biological activity. And the substrate for that is soy. So in individuals that eat very little soy, there is very little production of equine that you detect in the plasma. But people that eat high levels of soy, in the United States, about 40% of those individuals will have equine. It’s actually interesting that if you’re in Asia, you’re in Japan, about 80% of people will produce equine. So part of it is the amount of soy that you’re actually eating, but part of it is also culturally based different ethnicities will have different compositions of the microbiota, different types of functionality, even independent of diet. So there are constraints. But I think that there are still meaningful outcomes that diet can have and influence the microbiota, particularly through metabolite production.

Peter  17:24 

I wanted to touch upon your comment on creativity earlier, what if, in your previous work when you were looking at the effects of diet on microbiota composition, you hadn’t found an effect on the different diet compositions on rapid changes in the gut microbiota and sustained changes? How would you have been able to […] posit a response to that? Could it have just been the metabolites that had been different or what would be an alternative hypothesis if you did not find changes in microbiota composition following diet?

Dr. Wu  17:53 

Well, you know, one obvious issues we didn’t study the right diet, right? And so maybe it was was the composition of the diet. Maybe it was the duration of the diet, or maybe it was the type of subjects that we actually had in the study, right? Maybe a vegan would respond differently than an omnivore. Or maybe it was age dependent. There are many different variables that could explain differences. And that’s one of the challenges when doing human subject research. So we do mouse research, because genetically, they’re inbred. And they’re living in very similar types of environments. And there’s a very high signal-to-noise ratio. [But in] doing human subject research, they’re free living individuals, genetically diverse eating many different types of things. So we do these controlled feeding experiments and in the hospital setting to try to control as many variables as possible. But when we don’t see some type of effect that we anticipate and see, well, maybe that’s just normal physiology and normal human biology. But it also brings the point that in fact, humans are intrinsically very noisy, and there may have been an effect, but maybe we didn’t see it because we didn’t do a robust enough type of intervention. So two lessons that we have learned during human subject research is that we try to think about interventions that are going to be reasonably robust that will exceed the noise level that we see in individuals. And we try to do longitudinal prospective studies, where we’re not just looking at cross sectional or looking at one time, we’re looking at an individual over time. And so each individual may be different. But within that individual, there might be changes that are consistent. And so there are two important lessons that we’ve learned over time by doing these types of human subjects studies.

Peter  19:41 

How do you define your timeframe for a longitudinal study? How long do you typically look for?

Dr. Wu  19:47 

You know, it depends on what your outcome is, right? And so we know that in terms of change in the microbiota, it’s relatively rapid, and our notion is a lot of the metabolites that are produced by the microbiota are also relatively rapid. So a couple of days might be enough and our first study was 10 days. On the other hand, if you’re looking at other inputs, development of obesity, metabolic syndrome, cardiovascular disease, that that takes a long time. That takes decades to do. But I think the opportunity in the microbiome field or metabolites from microbes may be their surrogate biomarkers, intermediate biomarkers, where they actually track with the development, eventually a disease. For example, high blood pressure, you know, high blood pressure is a biomarker and a causative factor in development of heart disease many decades later, but do you know that it’s a good biomarker? So maybe the gut microbiota could be a signature that you would see relatively early on, that may predispose or be associated with disease at a much later time point. So again, it depends on what the question is.

Peter  20:57 

In one of your talks, you were mentioning how inflammatory bowel disease has been primarily treated with kind of anti-inflammatory medications. But we’re starting to realize the effects of industrialization on the increase of inflammatory bowel disease and the effect of environment on IBD, or inflammatory bowel disease. Do we have an idea of what gut microbes are triggering kind of this auto-inflammatory response? Or do we believe that the inflamed environment of the gut leads to different bacterial populations? I think piggybacking off […] my question earlier on, how long should you be looking at the microbiome for development of IBD? Or do we even have an idea of kind of this correlation?

Dr. Wu  21:36 

Yeah, yeah. So there […] are a lot of insightful questions and in what you just said […] We think the environment is important, because there’s a rapid, really increasing incidence of many different inflammatory diseases associated with industrialization. So that’s an environmental effect, but it’s a complex process. So inflammatory bowel disease, like a lot of complex disease states, is part genetic part environment. In inflammatory bowel disease, there’s a genetic influence. It’s relatively modest, but it’s very important. Otherwise we’d all have inflammatory bowel disease. So there’s a genetic predisposition that’s actually in most cases necessary to a certain degree, that imparts a risk to fully developed that phenotype. Unfortunately, for inflammatory bowel disease, we do think environmental factors are important. And there’s just so much data in animal models and what we know about immunology and physiology, that gut microbes are just fundamentally important the development of inflammatory bowel disease. The issue is cause and effect […] we actually cause the dysbiosis; we cause those different structure in the microbiota because inflammation of our intestinal tract, based on work of a lot of people, is an environmental stress that changes the composition of the microbiota. But in return that dysbiotic, or different type of configuration, […] helps perpetuate inflammatory bowel disease based on animal model systems, where we take those organisms that are more abundant in inflammatory bowel disease and put them in an animal model, it tends to be disadvantageous lead to inflammation in animal models. And we even have a little evidence in humans, that fecal microbiota transplantation taking fecal material from a healthy individual transplant again, and people with inflammatory bowel disease, particularly all sort of colitis, can lead to a modest yet meaningful response. Now, I caution people that are listening to this podcast. I’m not saying that fecal transplantation is a treatment for inflammatory bowel disease. It’s too early yet to say that definitively. But there are some intriguing results and in several clinical studies to suggest that on the horizon maybe changing the microbiota significantly, and I’m not even excluding fecal transplantation, might have some utility in the future, not now. Because I would say now it’s still highly experimental. The most important aspect of this is that people are quite interested in preventing disease. And so the notion is that if you were genetically predisposed to development of inflammatory bowel disease, based on your pedigree, you have a family history of inflammatory bowel disease is there something that you could do earlier in age, or stay away from something or do something to your microbiota or your environment that would prevent you from getting disease? That’s the Holy Grail. There are studies ongoing where they’re actually tracking individuals before they get inflammatory bowel disease to ask, (well, unfortunately, some of those people will get inflammatory bowel disease but they will have collected biospecimens before they got disease) what did it look like before and could we have predicted that person would get inflammatory bowel disease and maybe you if you had changed something, maybe you can prevent That the development of laboratory policies prevention is so much more impactful. But it’s very difficult to prove, takes a lot of time, takes a large number of individuals, but ultimately, that’s the holy grail prevent the development of disease.

Peter  25:16 

You were mentioning fecal microbiota transplant earlier as not necessarily a treatment for inflammatory bowel disease. But in my medical school courses, we have been taught that FMT or fecal microbiota transplant is a treatment for clostridium difficile colitis. How did someone come about with this idea? Or do you even know the history of how FMT came about and how people thought of this as a possible treatment?

Dr. Wu  25:41 

Yeah, you know, transplantation of fecal material actually, historically, I think originated in like 3000 BC in China. As I understand […] this yellow soup where they would take fecal material and make something edible out of it. In the livestock industry transplantation has been used for a long period of time in livestock, I think it was several decades ago and I think it was by a surgeon that actually published an article about, about transfer of fecal material. So you know, it’s been out there for a while, and more recently, based on some initial observations and a pivotal clinical study that ended up in a New England Journal of Medicine that really provided I think, reasonable evidence that fecal microbiota transplantation is an effective modality of treatment for our clostridiodes difficile infection with a with a cure rate 80 to 90% in certain populations.

Peter  26:48 

Yeah, that’s really incredible. Do we have any idea of what the needle in the haystack of the fecal microbiota transplant is or do we have any idea of a particular microbe that could [provide] the causative effect of this or is it just completely unknown right now?

Dr. Wu  27:05 

Yeah, I think that based on animal model systems, there are a number of different hypotheses. One is is competitive niche exclusion so basically you inoculate somebody that has clostridiodes difficile with a complete community and it basically crowds out that organism closes off the niche so the clostridiodes difficile and will not be as abundant and stop producing toxin. Other ideas are that bile acids are really important. In clostridiodes difficile biology. Primary bile acids, which basically come out of your liver in the small intestine, are germinant for clostridiodes difficile

[and]

will cause them to start to grow. But then your microbiota will convert those primary bile acids into secondary bile acids in your colon. The secondary bile acids are actually toxic to clostridiodes difficile [and] will actually kill those organisms. So one of the notions is that the risk factor for the development of C. difficile is actually use of antibiotics. So Eric Pamer(?) and other people have shown that when you take certain types of antibiotics, you can reduce the representation of certain types of bacteria that make the conversion from primary to secondary bile acids. If you reduce secondary bile acids, then you’re not going to be killing off the C diff and [preventing] overgrowth.

Peter  28:34 

Are secondary bile acids produced by the human at all or is it solely produced by bacteria?

Dr. Wu  28:37 

It’s a bacterial process. So bacteria have different types of enzymes that can actually transform bile acids and it’s a normal physiology that actually occurs in mammalian systems and clostridiodes difficile infection takes advantage of that. In terms of bile acid physiology, because in part, the use of antibiotics. There’s even a notion that the host immune response may be important. There are individuals that get recurrent clostridiodes difficile infection. Is it because it’s that particular microbe or because their immune response is not able to deal with that particular infection? There’s some interest in developing vaccines for the prevention of C. difficile infection, meaning that it may not just be the bacteria may not just be the environment like bile acids, but it may be the host immune response. So we know a little bit about the pathogenesis of C. difficile infection, but there’s still a lot more that needs to be understood.

Peter  29:42 

Are there any therapeutics to stop the production of secondary bile acids?

Dr. Wu  29:46 

In bacteria? Yeah, so actually diseases that disrupt the microbiota that lead to dysbiosis actually reduce the conversion from primary to secondary bile acids. So actually in clostridiodes difficile infection is a reduction in conversion from primary to secondary bile acids. And inflammatory bowel disease, there’s a reduction in the conversion of primary to secondary bile acids. And the reason is that the enzymes that are responsible for the conversion from primary to secondary bile acids are not very abundant in the organisms that are associated with dysbiosis. So you get the dysbiosis. And you can’t make that conversion of your bile acids.

Peter  30:36 

That’s pretty neat. We’ve been talking about […] this dysbiosis and this change in our microbiota and how different microbes in our gut are able to produce certain metabolites and others aren’t. And we also mentioned earlier that our gut microbiome is relatively stable, it can sustain perturbations from a lot of the foods that we eat. Is there a particular time in life that you think that the gut microbiome is most plastic or most modifiable?

Dr. Wu  31:01 

Yeah, I think there’s a lot of interest early on in life. I’m involved in a prospective cohort of infants with a number of […] investigators that are following infants from birth out the several years of age. We have a study ongoing at Children’s Hospital of Philadelphia called I-gram infant growth and Microbiome Project. We track infants from birth, all the way out to two years of age. As an infant, you’re born sterile, and then you become colonized. And that colonization actually occurs in a very systematic way, which begins with a very few number of organisms. And over time, you acquire more and more organisms out to the year, age of two or three, then your microbiota is as rich as an adult. So during the first couple of weeks or months after birth, your microbiota is very plastic and bounces around a lot. There’s a lot of things coming in, moving in and moving out. And the notion is that when you don’t have a lot of things in the environment, that it’s, it’s less resilient. So you think about it as a lawn. Like if you have a really plush, grassy lawn, you don’t have a lot of weeds in it. But if you have a lawn like mine at home that has a lot of holes in it, there are weeds in it, right? And so if you have a very rich microbiota or rich lawn, you don’t have a lot of perturbation, so it’s […] it’s much more stable. So an infant’s microbiota, because it doesn’t contain as many different types of organisms, is more prone to perturbation. And what does perturbation mean? Use of antibiotics […] early on in life. Think about ear infections, the use of antibiotics. There’s an association between antibiotic use and the development of a topic disease later on in life and obesity. These are just associations. The type of feeding, breastfeeding versus formula feeding could have a significant effect on a competition on microbiota because it’s not as resilient and human milk oligosaccharides that you find in breast milk are very bifidogenic, because certain types of bacteria called bifidobacteria […] grow out. Just another example that early life microbiota is less resilient and very malleable to environmental changes.

Peter  33:19 

Even the type of delivery: C sections versus vaginal deliveries have been associated with differences.

Dr. Wu  33:22 

Now they’re not, at least in our studies, not enormous. But for the first period early on in life, you can find differences between the two, but then eventually those things go away. Otherwise, I’d be up to look at somebody’s fecal sample as an adult and say, well, you were born by C section or by vaginal birth. We can’t do that. Because that difference actually disappears later on.

Peter  33:46 

So it is very malleable in the early months.

Dr. Wu  33:50 

Yeah. By the age of two or three, Jeff Gordon, and other people have shown that it’s pretty much as rich as an adult.

Peter  33:58 

Really neat. One last question that I wanted to ask was tying this a little bit back to some of the talks that you gave earlier. And I was fortunate to be able to attend both of your seminars, one for Gastronauts and the other one for the Pediatric Obesity Microbiome and Metabolism Mini-symposium. I felt like the two talks had very different flavors, one focusing on […] clinical correlations associated with microbiota and the other one on the impact of physiologic processes, bile salts, urea production and such on the microbiota. I was wondering, how have you been able to teach yourself to effectively communicate to both clinicians and basic scientists?

Dr. Wu  34:35 

You know, that’s that’s a really interesting question. I don’t think anybody’s ever asked me that before. I think that it just comes with practice. I mean, I think about it would be people ask me, “How do you think about talking to individuals that don’t have a scientific background? And so you know, I give talks at fundraisers and things like that, and I think about how would I explain what I do to my mom, for example, that might have a passing interest. What I do, but if I explain it for more than five minutes, she’s not really going to care anymore. So what’s that elevator talk? And how can I convey that information in […] reasonable terms that somebody that doesn’t have a scientific background, really understands. Part of it is also I do believe being a physician helps me with this because a physician, you know, our training is based on a scientific method, right, and the first two years of medical school [are] all about basic science, the type of work, but as a good physician, you have to be able to communicate to your patients, and sometimes very complex ideas in ways that they need to understand. Because informed consent is really fundamentally important. People have to understand what the potential benefits and potential risks are. And some of these concepts are very, very difficult. So I do believe at least for myself, that being a physician and I was a physician before I was a scientist, essentially, […] has helped me Me communicate better scientific principles because I’ve essentially had to do it my entire career as a physician in the patients that I take care of.

Peter  36:10 

That’s a neat perspective. Do you have any tips on how you think we can improve collaboration between people in the basic sciences and clinicians? Not everyone can be a physician scientist, but can we improve […] collaborations between people who are working in the academic medicine field and people who are doing basic science?

Dr. Wu  36:25 

Yeah, I think that a lot of it has to be is sort of respect for each other. I deeply respect clinicians, because I mentioned this earlier today that I think interesting observations by clinicians can sometimes be fundamentally important for us as scientists to think about hypotheses to try to address so for example, […] I’m a basic scientist, but I’m also a clinician when I when I think about trying to start another program, where I’m going to do basic science I have to find a partner. If I’m going to do a translational type of project, I have to find a clinician that really has deep knowledge of that patient population. And it’s very often that I’ll ask them very early on and in the relationship, you tell me, what are some of the most difficult things that you face [with] your patients? Because maybe we can together think about an intervention or an approach in which we might be able to use science to try to address that question, or that need. That’s not an easy thing to do. But it’s a starting point, right, and as a beginning conversation respecting the value of people that take care of patients, because at the end of day, that’s very practical, right? You could do the best science in the world and it’s super exciting, but at the end of the day, when you’re sick and you have a problem, you turn to your physician and physicians get to take care of you,[so] a physician sees the patient side of it, they see human physiology and so I I think that that’s enormously valuable. But at the end of the day also, to move science forward, to be a good physician is also to be a scientist. That’s the way that we’re trained. So they’re actually interdigitated. And I think a lot of it is respect for what each party brings to the table and acknowledging that if you work together, you can move things forward a lot faster than if you were to do it individually.

Peter  38:27 

That’s some really great advice. Well, thank you so much for your time. Dr. Wu, it was great having you.

Dr. Wu  38:31 

Alright. My pleasure. Thanks a lot.

Peter  38:46 

Dr. Wu gave us some really neat insights into the interplay between the microbiome and our gut, as well as a look into where he believes the microbiome field will be. And in order for us to reach the future, he believes budding scientists will need to hone in on their creativity. Only through evaluation and reevaluation of what has been done can we develop new approaches, or methodologies to bring us to the future. Thank you all so much for listening, and we’ll see you on the next episode. If you like what you’ve heard, we’d love it if you could leave us a review. For more of our content, you can follow us on Twitter @Gutbrains or visit our website at thinkgastronauts com. The Gastronauts Podcast would be impossible without the incredible team that we have here. Meredith Schmehl is our producer and theme music composer. And special thanks to the founders of Gastronauts, Dr. Diego Bohórquez, and the Bohórquez laboratory