Episode 16: Tracking Our Behavior

Peter Weng 0:15
Hi, and welcome back to the gastronauts podcast. My name is Peter,

reem hasnah 0:19
and my name is Reem hasnah.

Peter Weng 0:22
And we’ll be your hosts. Here at gastronauts we’re committed to exploring communication throughout the body with a focus on the crosstalk between gut and brain. We invite speakers in this field to share both their research and their life journeys. So come join me as we explore the steps that go into shaping a scientist on the gastronauts podcast.

Today, we have two great scientists, Dr. Yulong Li and Dr. Michael Krashes. Dr. Li is a professor at the School of Life Sciences in Peking University. He received his PhD at Duke University, where he utilized single molecule techniques to understand the role of specific proteins in neurotransmitter release. He then pursued a postdoc at Stanford University in the lab of Richard Chen, where he developed a genetically encoded pH probe to monitor activity dependent release of neurotransmitters. And now his lab has expanded on his previous work and developed advanced imaging probes to untangle the exact chemical signals that neurons are using to communicate in specific circuits. And using these probes, Dr. Li’s lab has worked to identify new receptors and neurotransmitters and characterize their roles in specific neural circuits.

reem hasnah 1:49
I’ll be introducing Dr. Michael Krashes. He’s a section chief at the an ID DK at the National Institute of Health. He received his PhD from the University of Massachusetts Medical School, his work focused on memory circuits and older memory processing and Drosophila. His lab currently focuses on how the brain brings together information sense from the external environment and its own internal states, including the memory. Welcome, Dr. Michael to this episode, I would love to know why both of you have really been motivated to be in the science field. So I know that’s Michael, I heard an interview that he went into science because of your mother. So why did she influence this?

Dr. Michael Krashes 2:36
Yeah, so I mean, I think my mom was a chemist, and was, you know, very heavily involved in the sciences, and just was always very curious. And I fell in love with biology, kind of in high school. And then in college, I kind of just messed around and didn’t really get a lot of science background in college, and then kind of after graduating college, I kind of just kind of kicked around for three years before going back to graduate school. And it was really my mom, my mom that pushed me to do so. But again, you know, Scott, who’s on this call, was my graduate advisor, so he can he back this up, I really had no idea what I was getting into. As far as going to graduate school, I thought I would just go get my PhD, become a professor and be rich, that turns out not to be what happens. I didn’t know what a postdoc was before I started graduate school. In fact, probably not until about two years into graduate school, but it was really, you know, being pushed by my mom to at least get into science, but then having incredible mentors, throughout my my career and support from others in the field. I mean, Scott was just wonderful to me, and really directed my research. He knew what my interests were, I was actually going to leave and go into industry after after graduating from his lab, but he kind of knew that that’s not where my heart was, and pushed me to my postdoc advisor, who was Brad Lowe, who was very big in like the energy balance field. And again, just tremendous mentoring by him, and just the support that I’ve received from the two of them. But again, you know, people that I mean, I can see people in this phone call, I mean, from trainees to, you know, people that have interacted that were graduate students that were postdocs. I see p eyes here, you know, all people whose research I’m so motivated, inspired by, I think that’s what really kind of pushed me to where I am now.

reem hasnah 4:27
And yulong What was your motivation behind being a scientist and a person who develop techniques?

Dr. Yulong Li 4:34
I think I’d love to find since out, you know, the curiosity that was sort of with me since childhood, but I was from a small town in China and my parents been practical and I think my father actually wants me not to go to high school, Senior High School. By going to the professional school, because there was graduate, you can find a very secure job, just in our small town. And around then I, I just I refuse I was like, now this small town is so small, you know, 15 minutes biking, you know from one end to the other end. And so I was sort of just, you know, thinking I need to go to senior high school and then go into the college. And I think, fortunately, even though my parents are practical, and but they all value my own opinion. So they respect my opinions, I, if I decided to go to sort of senior high school and then go into this college entrance exam to apply for colleges, they say, well, we give our best advice. But if you choose to go to your way, good luck, and they still support me so. So that’s part of the way. But I also found that being a scientist or study, including now supervising students, I think has the same sense of financial stability. Okay, probably not expect to be enraged, but at least have some sort of enough support will also assure people that they can sort of focus during research. And you don’t want a career that people are worrying about whether they can go by every day and still concentrate, and doing research. So So I think, have steady and secure support for, from grad student to postdoc, and also to two faculties, which junior faculty will brief good, so people can focus on the important part of science, rather than worrying about their own division.

Peter Weng 7:00
Yes, I think one of the key things from you and Michael, about what they said here was the importance of finding a good mentor, find a good good team of people, whether they have something that you see that you want to do in the future, whether they have the financial security, it’s something that you can look and aspire to be. And that’s been really important. And it was a recurring theme. From what Lisa had mentioned in the previous episode, just reach out to these people who you really want to be.

reem hasnah 7:24
I have a question for Dr. Michael actually have an interest of mine is memory and memory that we make for food? Do you think this memory is created in utero so that the pregnant moms eat different kinds of food and the babies would make memory of what they are eating?

Dr. Michael Krashes 7:42
Yeah, yeah. So I mean, a lot of this kind of beauty studies have been actually done, where the moms, for example, are given exposure to a high fat diet. And then that response is then translated down to pops. work from Young’s burnings group, has shown this really, really nicely. A lot of the changes that happen in the dopamine circuit can occur by just feeding the mom the high fat diet. So yeah, I think it actually predisposes the offspring as well.

reem hasnah 8:13
So you think our guts makes memories since day zero?

Dr. Michael Krashes 8:17
Did I mean, I think I think it definitely is involved.

Peter Weng 8:21
super interesting. Michael, I have a brief follow up. One of your previous papers, you mentioned the challenges of using optogenetics to study agrp neurons in the presence of food. And I was wondering, this optic stimulation is just such a blunt and like aggressive tool to really activate the cells. I guess this is both for you. And you long, how can technology be developed, and additional studies be performed to more accurately mimic physiologic hunger,

Dr. Michael Krashes 8:48
some of the approaches that have been done, you know, in the last couple of years, have been able to kind of record neural activity and then feed back that activity directly to those particular neural subsets. Most of this has been done in the prefrontal cortex or you know, where you can kind of get a large swath of neurons and record their activity. And then you can kind of this is like, it’s like holographic imaging, but then you can then playback exactly kind of that signal, and hopefully induce the exact same behavior that you would see that occurs when the animals actually perform that behavior.

Dr. Yulong Li 9:24
So I think that technology in a way, for example, calcuim imiging, really lower the bar for neuroscientists to study the brain, in a way study the brain activity, and previously, probably only physiologist or electrophysiologist, using sophisticated inaturalist that they can sort of detect, spiking and then study the sort of activity of the brain with precisions but calcium imaging and use You can, for example, really sort of allowed one to look at a single cell type, and a variety of animal systems. And Southland that, there’s just no easy ways to do it, I throw into the brain. So I think the technology and increase of the convenience of lectures and sensitivity or to really allow a larger group of scientists, including your scientists to really assess the uncharted territories, and our neuromodulators sensors, as well as some of the colleagues in the field, in the same way is also trying to make the boundary lower to the bar for people to study is the important signaling molecules. And I think calcine, what did you add? Those are good, but they are still incomplete, and a neuromodulator, with different chemical majors. By Design, they are quite critical. And, and therefore it’s important to measure that dynamics.

reem hasnah 11:04
So I have a question along these lines for both of you, actually. So before we make a statement of that the role of cell type x is modulating behavior, why we need to make sure that this tool that we’re using is repeated can be repeated by different people and repeated by different labs. So how you go through choosing the tools that you use in your labs, and for the experiments, especially with food derived experiments, it gets harder and harder.

Dr. Michael Krashes 11:30
Yeah, so I mean, for the first part, like looking at specific cell types, I mean, this is one of the reasons why I can’t kind of separate myself from agrp neurons. And moving on from saying agrp neurons. I mean, I do honestly think there’s still so much more to discover. But it is a population of neurons that I know if anyone use these tools that I’m using, or that labs using to kind of activate or inhibit or record from, you know, every lab is going to see the same thing. So this is very reproducible. And, and again, that to me is the most important thing about science is that any lab can do this and see something similar. And then when you kind of build on top of that knowledge, that’s how you make progress. And then as far as the tools, I mean, it’s true there is I mean, I’m not a tool developer, I’m one of the people that actually throughout my, my scientific career has taken advantage of the really smart people that have actually developed the tools, whether it was my work in Drosophila, where you know, I use trip a one, which is a heat sensitive way to kind of activate neurons and just saw flat or trip, I’m eight, which is as you know, the menthol receptor, but then can be expressed in flies, and we can change neural activity in that manner, whether it was Shiri into software, or using optogenetics, and human genetic methods in mice, I think the idea is, you know, you obviously know a good tool when you can, when it’s seen in publication after publication after publication, there are a number of tools that, you know, you see once published in a methods paper. And, you know, I think those tools may, they may or may not work as advertised. But I think the the tools that you see published the most are probably the ones that most people are using, and there’s a reason that they’re using them because they work really well and do what they’re supposed to do. And again, reliably across, you know, neurons regardless of what type of neurons or even glial whatever cells people are working with. But if they’re supposed to do what they’re supposed to do, I think that’s why people have kind of continued to use that. So that’s why you see the G camp, you see these new sensors that you Yulong developing these grab sensors, you’re seeing the D light, and you’re you know, these are, these are the tools that are highly used over and over again, because of their efficacy for actuallyworking.

Dr. Yulong Li 13:53
So, again, I think a lot more people use and as a way, they can validate the performance of distances. So for our group, as Michael Krashes set, for example, our intense group from UC Davis also developed D Ly, although a medium D one receptor, and we are using a D two receptor, so that sort of principle actually are sort of corroborated by a different group. And also we share those to us in advance to different groups to test in different scenarios, and also get a feedback and then going through the iterative improvements. Indeed, there’s a difference in terms of you know, the species the temperature might be different, and the cell type might be different for the virus. So there are a lot of parameters cannot easily just be tested by us in the lab. So we, again, we try our best to, to validate our own hands but also distribute to people in different groups to to validate And also I think making to us, test in vivo is critical. And I love tools and we make them. And I admire Roger Chen, who make those tools. And now also a lot of tools published by Cambridge, geneticist. But I think, for neuroscience, probably the most important thing is to test it in vivo, which is more challenging. And a lot of people demonstrate proof principle in cultured cells. And my own group, we want to publish since at least when I was telling my students, we want to have the in vivo evidence, and we want it to work in vivo, before we publish this, and so I think that has a higher power in a way that if you have the in vivo signal to noise ratio, and usually in other conditions, that it should be more robust, for example, in the slides, or in culture systems.

Peter Weng 15:58
Yeah, I think a really neat point that you own brings up is the importance of collaboration, you’ve shared some of those sensors with our laboratory. And it’s been really great to hear about collaboration, we actually have a question from Daria,regarding collaboration.

Daria 16:12
So I am a doctoral student in the Department of Nutrition at the University of North Carolina, and I do sort of translational work in the gut microbiome and diabetes. And I have really a general question for you. I have been involved in some limited research collaborations with collaborators in China. And I was wondering if you could speak to sort of the environment that would or would not allow for continued efficient collaboration between China and the US, given all the really great work that’s being done in both countries? And sort of, I’m wondering how you see this playing out in the future? You know, given some of the challenges that have arisen recently?

Dr. Yulong Li 16:52
Yeah, I think it’s really a good question. You know, I spent 11 years in the states from my high school and postdoctoral training, and then I have my own lab in Beijing for more than seven years. I think the scientists are open. And at least for me, I have a very pleasant collaboration with scientists around the world, including a lot of labs in the US, I think the geopolitical issues are, indeed host constraints. That is certainly worrisome. And there are different cultures and different systems, I think, one of the ways to have the collaboration could be that laying out the the collaboration in a more open tense that in case and, you know, given to the political competition or issues between the governments, so if the parties can lay out attempts, more transparent to stairways that might ease the issues, for example, you know, the why heard is that, you know, they’re, especially the Chinese Americans, some of the friends they worry about the compliment the US government might, you know, might be treated in such a way that they are an export of the sensitive information. So, at least as best I can think of, and but but generally, among scientists, I actually have quite pleasant sort of feedbacks and experience, and also the US scientists that I encounter and interact and collaborate. They’re also worrying about the political environment at my limit, and have fallen soundly to the faithful and completing reports system to disclose the collaboration in advance, and also timely, and that can sort of reduce the concern, I think.

reem hasnah 19:16
So we have a question from Elaine.

Elaine 19:18
Hello, thank you. Question for Michael Krashes. Thank you very much indeed for your really interesting talk. I was wondering, though, is the overriding desire for high calorific food do with the evolution of survival? So in other words, do we sort of instinctively need to eat more sort of high calorie, high energy food when it’s available if we don’t know where the next meal is coming from? Obviously, that’s much less of a problem now for most of us, but you know, for the mice and rats that you were talking about, and perhaps for humans, way back when meals weren’t Simply available.

Dr. Michael Krashes 20:01
Yeah, I mean, I, I can’t tell you the exact reason for it. But that’s precisely how I think about it is that is that we’re attracted to the energy dense foods because we’ve just evolutionarily conserved to try to go after, you know, the most calories for the the limited time that we have. Because again, we were we used to forage for food, you know, so that we were able, then. So I think that we try to get as many calories as we can, in a short amount of time as we can. And you know, in particular, fat is really involved in the actual evolution of the human brain. And it’s why the brain became bigger and bigger as as evolved was because of the fat that we consume from our food. So I think fat in particular, is extremely, you know, attractive to us humans. And I think that’s conserved and unfortunately, yes, as you mentioned, in you know, an obesogenic environment that we’re kind of many of us live in now, that can have a very detrimental effect. Yeah.Thank you.

Along the similar lines. Another question from Michael, about willpower and the ability to resist cravings.

Michael 21:11
Yeah. Hi. So I am Michael from the Air Force Research Labs, actually, it says a question to Dr. crashes, some people seem to have more willpower to to not eat these high density out high energy foods. Is that is that more of a learned response? Or is that? I mean, how do you sort of reconcile those those sorts of things?

Dr. Michael Krashes 21:31
Yeah, I mean, so I don’t think there’s a good answer to that. What I will say is that, that mice, just like humans, really show a tremendous variability when they are exposed to these high fat diets. On average, these animals are gaining quite a bit of weight over the the experimental period where they’re exposed to high fat diet. Again, on average, these animals are completely ignoring the standard diet, because now they’re just eating a high fat diet. But in reality, just like humans, you know, there are annoying people that can eat like crap, and not gain much weight at all. And what we noticed is that it didn’t matter how much body weight these animals gained over that exposure period, we always saw that those animals showed that devaluation for the standard diet, both in their home cage and even when we did the experiments where we fasted those animals and gave them a standard diet back that those animals were still they still did not want to eat the standard diet. So I do think there’s, you know, there’s, there’s a number of factors that I’m sure that are involved in the production disposition of how the body actually reacts to to like a palatable diet. And I think that’s what we’re trying to figure out exactly what those factors are. But again, I think it’s going to be many factors and working together. So to identify, you know, particularly one of those is going to be really difficult. Thank you.

reem hasnah 22:51
So we have one more question for Michael from Hilary.

Hilary 22:55
Hi, my name is Hilary ship. I’m a postdoc at Stony Brook University. My question is about how chemo sensory cues interact with feeding. So I noticed that the animals fed the high fat diet avoided the standard pellet, like right away. And so I’m wondering if they use taste or smell cues rather than the post ingestive cues? And if so, how do those chemosensory cues then, like reach and modulate the agrp cells?

Dr. Michael Krashes 23:22
What is such a great question? And actually, we have something that we is in review right now, because we had that same question, which is basically what role does you know, olfaction play in this kind of rapid preference, and then prolonged preference and devaluation? So the preference for the high fat diet and the devaluation standard diet. So we did these gain of function and loss of function experiments where, you know, we positioned animals to be able to say, smell the high fat diet in their home cage, but never eat it. So they, you know, they, they kind of make the Association, the smell of the high fat diet, but they could never eat it. And they actually never showed devaluation for standard diet. So it would suggest that they would have to actually consume it. It’s smell alone is not sufficient for them to kind of show devaluation. And then on the opposite end of the spectrum, we actually ablated the olfactory bulb, so we did these Baalbek dummies, so you know, render the mice and cosmic, and even in anomic mice, they very rapidly made the decision that they just wanted to eat the the high fat diet as opposed to the standard diet. So at least olfaction itself, you know, of course, we took this reductionist approach, at least the faction itself doesn’t seem to be heavily involved in that process. We were looking to do some experiments on taste. Unfortunately, there’s not kind of a really nice knockout model in mice for tastes, but there are some experiments you can do by entering say the stomach or entering the calories before it’s actually absorbed into the digestive tract, to kind of look at the role of two One thing I do want to point out, and I’m glad that I can do this in this question is, when we published this study, recently, another study came out from Zack Knight’s lab, it was driven by Lisa Butler, who has her own lab now at Northwestern. And what they showed very, very nicely, I mean, we also did some infusion experiments where we directly infuse calories directly into the gut to kind of bypass all their chemosensory information that you’re, you’re talking about. But I think they did a much better job. And they went even further to show that it was actually this specific macronutrient of high fat diet is is the one that’s kind of devalued at the level of agrp neurons. And that happens presumably through through cck, like this signaling peptide cck in response to fat, so I think I think there’s still questions out there to be answered, but at least on the surface, what I can tell you from our recent work is that olfaction does not seem to be involved in this process.

Hilary 25:56
Cool. Thankyou.

reem hasnah 26:09
Thank you all for listening, and we’ll see you on the next episode. For more of our content, you can follow us on Twitter. At the gut brain matters or visit our website think astronauts calm, the gastronauts podcast would be impossible without our incredible team. Meredith is our producer and theme music composer. And special thanks to the founder of gastronauts Dr. Diego Bohorquez forecast and the Bohorquez laboratory