StarTalk Radio - Hibernating for Deep Spaceflight with Ryan Sprenger

Episode Date: September 20, 2024

How close are we to enabling  astronauts to go into deep sleep for long space journeys? Neil deGrasse Tyson, Chuck Nice, & Gary O’Reilly team up with Ryan Sprenger, Senior Research Scientist at Fauna Bio, to explore whether humans can hibernate like animals do.NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here:https://startalkmedia.com/show/hibernating-for-deep-spaceflight-with-ryan-sprenger/Thanks to our Patrons Parker Mann, Kwesi collisson, John, Ray, Dr. Cy, Felix the Feline, Jimmy Dunn, Mandi McKay, Kevin Militello, Aaron Streimish, Joshua Beadle, Sam Pennington, Geoffrey Docute, Syler, David Smith, and Matt Talley for supporting us this week. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

Guys, am I right that we just did a whole show that answers the question, does a bear shit in space? Yes, we did. And I'm just upset that I didn't come up with that right there. We got animals on Earth that hibernate. And if we're going to send people through space, every sci-fi story has got a hibernating crew. And we finally found someone who's trying to solve that very problem yes yeah knowing that other mammals can do it and we're a mammal last i checked so we went there on star talk special edition coming up welcome to star, your place in the universe where science and pop culture collide.

StarTalk begins right now. This is StarTalk Special Edition. And since it's Special Edition, you know my two co-hosts, Chuck Nice. Chuck, how you doing, man? Hey, Neil. I'm doing great, thanks. And not only Chuck, we've got Gary O'Reilly. All right, Gary, welcome back. Thank you. Always a pleasure.

Today's topic is like, whoa, how come we didn't do this 10 years ago? We're going to talk about hibernation in space. Oh, don't sleep on this subject. Oh, came in early. I want me some hibernation stories here. So, Gary, set the scene here. What did you put together? We've all seen the sci-fi movies where the crew are in some kind of deep sleep,

hurtling through deep space. But how is that going to be achieved? Turns out, we actually may have to look to Mother Nature for our answer. Animals can hibernate for months at a time, from thin squirrels to big old bears. So if humans want to engage in interplanetary travel, they are most likely going to need to hibernate or enter a state of torpor. Can you get a non-hibernating animal, which is us humans, to hibernate? And for that, we are going to need an expert um cue our guest ryan sprenger phd

senior research physiologist at fauna bio a phd in zoology with expertise in cardiopulmonary physiology also expertise in hibernation and extreme physiology, which I think is a vital component of his background and its effects on the cardiovascular system. Phonobio have been awarded a NASA grant through their NIAC program, which stands for NASA Innovative Advanced Concepts for a study in torpor in animals for space health, or STASH. Plus, the most important thing is, Ryan is a StarTalk fan, which makes him smart as well as cool.

We love it. Ryan, welcome to StarTalk. Thank you so much for having me. I'm excited to be here. So what is torpor? That's a good question. What is torpor? So we define torpor in the field as a state of metabolic depression and body temperature depression and so it's sort of this quiescent state where the body's been turned down oh wait so depression in a biophysiological sense not in a neurological sense a little bit about a biophysiological sunset in its root but you also have a neurophysiological depression but not a depressive state as in an emotional that's all that's all i mean yes yes yeah yeah got it so so it's a dialing down of the metabolism and the body temperature essentially the body pulling torpor so what's

the difference between torpor and hibernation uh this is a this is a fun topic to to discuss at the hibernation conferences that we hold every four years. But what the general field will say is hibernation is the season in which the animals will use torpor. And so torpor is the actual state in which the metabolism is low. Why do you have conferences only every four years? Are you hibernating in between? Yeah, yeah, precisely, precisely. Well, that's when good science gets done as well.

Well, historically, it's taken longer to collect hibernation data because it's a seasonal event. Yeah, you only have a very limited window where you can study. Yeah. You can't go up to a bear in the summertime just like, hey, man, you tired? Can you be tired? You've got two hemispheres where winter is one time and in one and a different in other so you might i mean it depends if you feel like picking up your bags and traveling yeah well actually and that's why it was just this year we decided to shorten that as a community we

decided to shorten that conference because we're learning that hibernation is not just a cold season event we're learning recently that warm animals will hibernate uh animals in warm climates will hibernate they'll hibernate at warm temperatures um so we're learning that that it's more widespread than we thought why do they do it i mean what is what is the purpose of hibernation for like if i'm a bear right we all think of hibernation. We automatically think of bears. So I use them as an example. Well, why not just be awake all year long and go get some food or pack up on calories

like some other animals do and then get through the lean time? What's the idea of dialing yourself down metabolically and taking a long nap. You mentioned it almost in your question. It costs a lot to do things is a really simple way of putting it. Energetically. Energetically. It costs a lot energetically to do things. I'm not thinking the bear's got needs $20 in his wallet to get to the store.

No. It's a very costly way to be a bear, man. Only you can prevent forest fires. Come on, help a brother out. Spirit change. Yeah, energetically, it costs a lot. And so even if you wanted to pack on all that extra weight and try to make it through a period of what we like to term resource deprivation. So this is a period where there's not as much water available.

It's frozen or it's a drought. And there's not a lot of food available because of that reason. And so in these periods of resource deprivation, some mammals have decided over time to, instead of increasing supply, they decrease demand. And that demand being your metabolism that they're turning down. Oh my, that scares me in a way just because I think about the climate and how it's changing. And when you talk about matters of deprivation or lack of resources, we might find a time where maybe those bears won't hibernate because the water won't be frozen. And then we've encroached upon their land and they're like, hey, you guys are supplying us with food? their land and they're like, hey, you guys are supplying us with food? Because you ever see the videos of them tearing open a car to get to that picnic basket?

It's a little scary when you describe hibernation that way for those reasons. Yeah. Well, bears are very strong animals. That goes without saying. But yeah, climate change, actually, that's a big push in the field right now is to try to understand what climate change is going to do to hibernators, particularly the cold climate hibernators. Because again, we're seeing more and more warm climate hibernators. So we have an idea of what it might look like, but it is very different. So it's going to be a big change for a lot of these species there has to be some positive benefit to hibernation otherwise animals will have evolved not to do it most mammals don't do it what are the benefits then to me apart from getting a good nap yeah it would be the dream if you could um yeah the the benefit as far as we can tell is these these animals that use it are more resilient to periods in which there suddenly is an availability of resources. Gotcha.

And so a really great example of this actually is not in the northern hemisphere is where it's cold. It's the southern hemispheres in Australia where you have wildfires, big wildfires. And there's animals down there that after these periods of wildfire where there's now suddenly no food for a while, they'll go into torpor. And so these animals are more resilient now because they don't need that food and they can survive a little bit longer. They can just kind of stretch what resources they currently have in their body.

And so- Well, because cold-blooded animals barely eat anyway, right? I mean, we always show alligators as being voracious eaters, but- Yeah. I mean, we eat a lot because we have to maintain our body temperature apart from the air temperature surrounding us. If they are the air temperature,

then their energy is for what? To run their brain. And if they want to just walk around a little bit. Exactly. So, yeah. And so you're exactly right. The cold-blooded animals, they don't eat a lot. They can go white long periods. Alligatorsigators i think can go months to almost a year without eating yeah oh my god and i've got a funny anecdote about that from my old advisor but there's nothing funny about a hungry alligator i was about to say that no not at all um not when you're around it at least yeah that's right but yeah they don't eat for for long periods of time because they don't have to defend body temperature. So defending body temperature at a stable amount is very, it costs a lot of energy. So we're expending energy all the time just to keep our body temperature at 98.6 is what you're saying.

Exactly. That's where all, so if you don't have that, I'll call it a problem, but if that's not necessary, then you're saving a lot of energy. You barely have to eat at all. You're running to stand still. You barely have to do it all. In fact, it's worse than that or better than that. You burn energy thermally just by maintaining your body temperature, but you also burn energy kinetically, right?

By moving against gravity or just moving at all. Okay. moving against gravity or just moving at all. Okay. Consider how long it would take your body to burn the calories of a cupcake just by existing. You will easily burn the calories of a cupcake just by watching television. You can do that. Okay.

Right. But then say, what do I have to do on a treadmill to burn the calories of a cupcake? It's like, I'm not doing that. Right. But then say, what do I have to do on a treadmill to burn the calories of a cupcake? It's like, I'm not doing that. Right. Yeah. That's damn near an hour running. Exactly.

Exactly. Thermal energy is a huge consumer of energy relative to kinetic energy. But Ryan, get back to your answer there. If they're wildfires and they take out resources, you have to wait until the trees grow back and the bushes grow back. It seems to me that would require a much longer time than a typical hibernating bear for the resources to return

if they have to recover from a wildfire. Yeah, well, I would describe it more of a strategy to stretch how long you can maintain in that area. And so if you stay active, you've in that area and so if you stay if you stay active anything else you've got days right if you stay torpid you've got months and they can stay in torpor i mean there's animals that again and these are in the northern hemispheres but there's animals that can stay torpid for nine months of the year oh and so it's it's quite a while and your your primary growth or your secondary growth i should say your primary

growth sorry your first shrubbery where you can start to get things to eat, like insects and berries if they're coming up in those months. You could stretch yourself to get to those, I would say. Hi, I'm Ernie Carducci from Columbus, Ohio. I'm here with my son Ernie because we listen to StarTalk every night and support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson. Okay, so what does NASA want out of you here? And Fauna Bio, is that a company you started?

What is Fauna Bio? Yeah, Fauna Bio is not a company I started. It was started by three really intelligent ladies, Katie, Linda, and Ashley. I've never heard anyone say, my company was started by three stupid people. Okay, so. That's a good point. That's a good point. I just like to give them credit when it's due. They're really incredible, incredible human beings. The company is based on the premise that a lot of drug development could be benefited by looking at animals that have extreme physiology, or rather looking at animals that are good at defending against diseases that humans are afflicted with naturally. And so one of the models that we use quite regularly is a hibernating species called a 13-line ground squirrel.

And that species is fantastic against things like diabetes, ischemia reperfusion, for example. So this is after traumatic injury, loss of blood flow, loss of oxygen, you return that, you get tissue damage. Wait, you're saying the squirrel is resistant to diabetes? So at the beginning of the hibernation period or before they start their hibernation season, they increase their body mass by over 100% just adipose tissue.

So let's say they weigh 100 grams, they'll go to 250 grams. They've added 150 grams of just fat and they become completely insulin resistant during that period. And by the time the end of the hibernation season comes around, they reverse that insulin resistance and they're back to normal. Wow. It's a naturally reversible model of diabetes, essentially. That's insane. Yes.

That's so, I mean, why isn't everybody studying? I mean, diabetes is a huge, huge problem in this country. Huge. So if we know we mammals are a branch of the tree of life, and so we have more in common with each other than either of us have with any other branch in the tree of life, why can't we just genetically steal these DNA secrets in these animals and then apply it to us for whatever however we need and is that what nasa is trying to get you to do for our future

astronauts yes yes that that is that is what fawn is trying to do using these extreme organism and and and hibernators aren't the only species that are extraordinary there's a spiny mouse for example that has regenerative capabilities. So this is a mammal that can regenerate. Spiny mouse? Yes. Spiny? Spiny mouse that has regenerative capabilities.

What are the regenerative capabilities? Could we grow a tail or a leg, right? I don't know about a whole limb, but certainly tissue replacement. So neural tissue replacement, skin, like normal tissue replacement skin. Is there not a chance for any mammal that hibernates for any length of time losing muscle density? This is another remarkable aspect of the hibernating species that have been studied to date. They don't. So, this is incredible. This is where NASA is interested.

This is where we get into NASA. So, if you break your arm So if you break your arm, if you break your arm, you're like, you go into a cast for however many months that you have it on. You take it off.

Your arms are different sizes. You've lost muscle mass. That's disuse atrophy is what it's called. I'm old enough to remember the old days where you were encouraged to not use the limb at all.

There were no walking casts. There was no exercises you would do. And I had friends who broke limbs and they took off the cast. It was like the limbs of two different people on the same body. Yeah, and hibernators

don't do that. It's incredible. Wow. But you always see in the nature shows where the animal comes out of hibernation and then, sir, what's his name? I forget. And he's just like, and now the feverish search for food begins. Like they immediately.

How dare you forget Sir David Attenborough's name? That's his name, Sir David Attenborough. Yes, exactly. We're allowed to forget. Well, no, he's beloved everywhere. He's not even like the whole world owns that guy. That's why I couldn't remember his name because everybody knows. So you're saying that the weight loss is not muscle density.

It's correct. So they put on fat and then all they do is their body eats the fat. Yep. Oh, because our body eats muscle. Muscle first. Yeah, their body eats the fat. Yep. Ooh, because our body eats muscle. Muscle first. Yeah, our body eats the muscle first. Ryan, why don't you fix us? Actually, we just,

Svana just signed a really awesome partnership with Eli Lilly trying to fix that. Yes, we're doing that. We're actively looking at that, actually. We're looking for new obesity targets to try to see how it is that we can say, have our metabolism say, yeah, we want to just consume adipose. We don't want to consume protein.

We don't want to consume carbohydrates. You want to have your metabolism and eat it too. Exactly. Yeah, that's what we want to do. Ryan, in our research, we came across a nugget of information that is worrying and amazing in the same breath. How did we find out that hibernating animals have a level of protection from radiation? Yeah, this started in the early 50s. I think 51 was the first study that looked at irradiating hibernators. And so they basically gave them huge doses of gamma radiation. And what they learned was that these hibernators. And so they basically gave them huge doses of gamma radiation. And what they learned was that these hibernating species survived the radiation far better than a rat, for example.

And their protection against the radiation increased if they were in torpor. And so these species are uniquely protected against radiation the study started in the early 50s we still have not a great idea of why it's not because the fat absorbs the gamma rays is it no we think it has to do with reactive oxygen species please explain that what that is yeah reactive oxygen species are well i guess i'm not a chemist i couldn't tell you exactly what a reactive oxygen species is but it's a product of your metabolism. And so these reactive oxygen species, as the term suggests, they react with oxygen and they cause all sorts of bad stuff to happen in your tissue, damage, tissue damage essentially. And so when radiation comes in and hits a hydrogen, so like a proton comes in and hits a hydrogen or interacts with oxygen, it creates these reactive oxygen species that damage your body.

or interacts with oxygen, it creates these reactive oxygen species that damage your body. And so if you've ever been to the store and everybody, the craze right now is antioxidants. If you've seen that in the store in your food, they're designed to counteract reactive oxygen species.

I'm not anti anything, by the way. That's fair. And so that's where we think a lot of the protection is coming from is because these animals are really good at natural antioxidants. So they have them during the torpid state but also with the with the reduction of metabolism you get a reduction of the mitochondrial function you get less oxygen

in these tissues as well as less water so there's less things for that radiation to interact with and create these reactive oxygen species so less things you mean there's less active biology to disrupt. Is that a way to say that? And do the animals come out of hibernation after being radiated with gamma rays going like, bear, smash! What does that mean? No, no.

The bear doesn't have to become whole. I do not want anyone to have gamma rays at a bloody bear. Do not want that going green and Hulk. Don't, yeah. The chance is small, but it's big enough. One of five gamma rays at a bloody bear. Do you know what that goes? No, please don't. Yeah. The chance is small, but it's big enough. So now when squirrels go and they're not hibernating then,

they just fill their lair with nuts and stay in for the winter and eat? Is that the deal? Or are they actually hibernating too? So the ones that everybody's seen in their life, the tree squirrels, big bushy tails, they don't hibernate you're right they they can't they're food caching animals so instead of instead of turning down demand they store away supply essentially for the winter so i can't sneak up on them during winter and get them no unfortunately not there goes that there goes that theory The squirrel is different from poking the bear. Yeah, that's very true. So there's no understanding biologically why a hibernating mammal would have more radiative resistance.

It's not clear why that would be so evolutionarily. Is that right? That's a really great point. There really seems to be no reason evolutionarily why they would act i shouldn't say actively but why that trait might be selected for so it's probably a passive consequence of some other thing that they've been defending against uh with the physiology of hibernation or torpor i should say so sort of accidentally becoming more protected against radiation is how i describe it all right so so where does this go you're trying to help NASA, at least for Mars missions,

where it's nine months there and nine months back and two years on planet. Are there specific missions they're tasking you to think about? So right now we're in the phase, conceptual phase of NIAC. There's three phases.

Conceptual, phase two is more you make the concept come to life and phase three is sort of flight mission uh we're in the conceptual design nasa has uh turns its attention towards trying to figure out the hazards of space because with the mars missions planned coming up they don't have really a good answer for things like radiation disuse atrophy lengthy stay in space essentially and so they started to drive down different ways to mitigate this. And one of the ways that they've been really interested in is

hibernation. And so our unit, what we're designing with NIAC right now is actually just the ability for the first time in human history to study hibernation in space, because we don't even know if hibernation will work in space. Nobody's even thought to send a hibernating animal up and say, does it happen? Are there any primates that hibernate because i'm thinking theoretically if there are then that might be possible for humans even closer to us in the tree of life right rather than trying to think about how we rework a bear or a squirrel or whatever it might be or most there is one primate uh my son that makes two primates then at least um oh there is okay there is that there are so fat-tailed lemurs from madagascar they will use torpor quite quite well actually

um so there is a more related species to us that will that can use hibernation is this during ski season in madagascar i mean what would they drought drought is the big one in Madagascar? I mean, when would they? Drought. Drought is the big one for Madagascar. Drought. Yeah. Drought. Right. So during the dry periods.

So what chance is there that we share part of that code that will allow us as humans? We think actually a pretty good chance. So if you look evolutionarily, it seems that hibernation is a pretty basal condition. And what I mean by basal is that it's pretty far down in the tree of life. Deep in the tree of life. That it started to crop. Yep. So you wouldn't have to gene splice it.

You would just have to gene enable it. Unlock it. That's what we're thinking. Yeah, that's what we're thinking. Interesting. So now how do we know physiologically how they, because, you know, without water, we die very quickly. So what is happening physiologically? Are they storing water?

Do their cells just retain it? I mean, what's going on? Do we know? Yeah, we have an idea. Yeah, they recycle. You got a photo machine in the back. No one's ever been deep into a bear cave to to deny that story yeah that's true that well actually i might know somebody who has been um used to know someone who did yeah used to that's

i mean specifically with the with the madagascar fat tail because they're primates and so like i said we we die very quickly without water so what's going on with them yeah that that unfortunately we don't know. Okay. They're incredibly endangered species. So more invasive studies on them are just, they just don't happen. So what we can do is whole animal physiology or survival physiology, but we can't really tell cellularly what's going on with the water and lemurs. Now we can infer from other hibernating species.

And we know that they're really good at recycling the water that they do have. So there's a change in renal function essentially that allows them to recycle a little bit better that means they don't eat they don't pee the whole time they don't eat they don't drink they don't pee they don't poop it's a complete shutdown in metabolism wow and everything that comes from it and so what can what what bodily system what brain system is is controlling all of this because it can't just be and that's it something's got to still be going on to control this yeah there's tissues that are still active so so there are neural tissues that are still active generally speaking the cortex is quite quiescent so it's there's not a lot going on in the cortex the neural tissue that we see going

on is coming from either the brain well both the brainstem and the hypothalamus so brainstems controlling all heart rate respiratory rate things like that keeping your blood moving even though it's moving more slowly and your your lungs functioning obviously with that there's muscles that do stay active like the diaphragm some of the upper respiratory muscles will stay active the hypothalamus i don't know if you've if you've read about this tissue before. It's basically one of the main tissues controlling metabolism and body temperature. And so they are regulating really tightly where their metabolism is at and where their body temperature is at with the hypothalamus. So that tissue is remaining active as well. And that's actually in and of itself

really interesting because you have tissues that are functioning in a mammal at four degrees celsius which is something that a human couldn't do right now we couldn't bring a human down to four degrees celsius and ask those tissues to continue to work you'd get complete neuronal failure and so they've they've developed or evolved these ways to maintain tissue function despite it being really cold man this sounds like sci-fi. It's so cool. That's amazing. Can we get quantitative here? My basal metabolism,

so just keeping my body temperature for 24 hours, I run through between 2,200 and 2,400 calories. Not for a man your size. Well, for me. Nah. Come on, man man what are you saying you're too big to be living on those 2 000 calories get out i didn't say 2 000 i said 2400 22 20 around

there okay all right if you say so i mean if that makes you comfortable let me live in my own life when he's watching tv when he's watching okay so if i'm in one of these hybrid native states what does my calorie needs drop to if you're in the hibernating state so it it depends on what series round numbers just call it 2000 so now what it depends on what depth of hibernation we achieve so if you're a total depth total for the deepest depth, you would be down in the tenths of a calorie. So it's about a nine per day. Per day? Yeah.

What? From 2,000 down to less than one calorie per day? So the deepest hibernators that we've seen, they'll reduce metabolism by about 99%, a little bit more than 99%. Wow. Dang. That's insane. So how- Okay, but that's still-

Wait. I want this so bad. I want this so bad. I want this so badly. And that metabolism that's going, it's only adipose. Just to be clear, 99% drop on 2,000 calories is 20 calories. Oh, okay. Yeah, you're right. I'm bad at math, I suppose.

Okay. It's not a fraction of that. But I did say it's more than 99%. It would be in nearing the single digits of calories is what you would expect. That is crazy. Okay. So to Chuck's point, how can you induce a state of thought? Because you can't just say, right, lie down there and don't think about calories. Things have got to happen.

Just put it out of your mind. Yeah, just yeah about it meditation tape you're halfway there and how long do you expect a human to be able to go in the state of torpor because you know you still got that squirrel that did nine months is that viable for a human well to answer your first question how we get, so naturally there's a lot of circadian rhythm that's associated with it. So the light cycles will kind of tell these animals where they should be. Obviously there's, there's the facultative side of it, which is basically means as soon as the food is taken away, that tells them I should go into hibernation. So

your pet hamster, if you've ever heard the stories of people walking in on their thought dead hamster, that's a facultative hibernator. So that trigger for them is the food's gone away i must hibernate now so they'll go into torpor and so there's different ways of doing it we're actually getting really good at over the last 10 years we were getting really good at taking animals that shouldn't be in hibernation and putting them into hibernation and so rats for example are a prime example of this we can go in and we can change things in the hypothalamus to make them drop metabolism and drop body temperature to look like it's in their intorper you take food away from a human they get hangry they will be very angry yeah so you've got to so you're going to have to possibly chemically

induce this yeah there's probably some chemical induction that that will that will be involved in that process yeah when you talk about the circadian rhythm of human beings, it's pretty particular. So, you know, you put somebody to sleep for a couple months, there's going to be a huge adjustment period when they come out of that. I mean, you want to talk about being disoriented and like, and now they're up in space on top of that. It's a lot of stuff to throw it seems like a lot man people get really hangry for less that's true what we learned though is that

that circadian clock in the hybridators it actually continues to function in torpor but more slowly because the metabolism is slower and so the same amount of time has elapsed in the circadian clock, despite it being a month versus a day, for example. And so that might help with that disorientation. we bring it back to earth just temporarily if a bear comes out of torpor it has a reboot what if that reboot doesn't quite work a hundred percent yeah yeah you know the organs have to go back to a hundred percent when you're in space and a human's going to come out and the reboot doesn't quite... This is something that the movies don't get right. Oh, it's the only thing the movies don't get right. Yeah.

Okay. Yeah. The only thing. Everything. The other thing is we can't freeze people. That's gone out the window a few years ago. It's incredibly taxing to come out of hibernation. It's actually the most physiologically demanding part of hibernation, I would argue.

Because everything has to come online in the correct order so the heart can't bump too fast before the peripheral tissues are ready uh you can't you can't inflate the lung too much because it's still cold so you can you can break alveoli so there's and so there's an incredibly coordinated event of these animals coming out of hibernation so that process is actually quite slow uh in a rodent it could take as as long as an hour or two to come out in a human in a bear it's a little bit less because their body temperature started a little higher the metabolic rate's a lot they don't go as deep into hibernation but it still takes time and it's dangerous at At the beginning of Austin Powers, where they brought him out of deep freeze and they fought him out. He peed for like three minutes.

No point was that for comedic effect. I'm just saying we all pee like a lot when you wake up in the morning. And this was obviously a, an extension of that. So I'm still wondering how you pee if you're not going to pee when you hibernate you're gonna you're gonna have a big ass pee when you wake up out of that no well maybe and and i know i know from experience there's not a lot of urine uh after the hibernation period not not that i hibernated i've seen it in these

animals but that would be, he slipped up. That's really going to have an effect on the kidneys and the kidney function. Yeah, renal function is quite dramatically changed in hibernation. But yeah, the bladders aren't full at the end of the hibernation period. They don't urinate. And so it has a lot to do with the recycling of that water, but also the reduction in metabolism. So you're just not using as much of that water as well. You know, in sleep, you're still quite metabolically active in sleep.

For an animal that doesn't naturally hibernate, say a human, coming out of hibernation, a torpor, if it's not programmed naturally to get it right, it could go cataclysmically wrong yeah certainly yeah yeah well what a great thought is the closest thing to torpor for a human being going into a coma and would there be any benefit in sustaining us the same way we sustain people who are put into like a medically induced coma or like yeah that's a great thought actually i i would argue the closest state to hibernation that that humans achieve is actually sleep what we're thinking is that hibernation is an extension of sleep but i but i will i will squash the the media uh mistake it hibernation isn't sleep actually they don't sleep in hibernation in fact it seems that they come out of hibernation to sleep but they're not sleeping when they're in torpor. But everything physiologically speaking

in sleep is very similar to hibernation, except it's just far deeper in hibernation. But you're exactly right. I think what human hibernation is going to look like is some sort of assisted state because we're not natural at it right now. And there's a lot of hurdles that we'll have to overcome to get to the point where we can just induce hibernation in a person and then have them come out by themselves. I think in the meantime, it will have to be some sort of assisted state where we're maintaining fluids or nutrient balance at the right level, a whole host of things, really. How close are we to this being real? a whole host of things really how close are we to for this being real that's a great question uh we don't know i i you know it's certainly not a five year sort of thing that we can get humans

into hibernation um but you know maybe are we looking in the closer to 10 15 years i would say realistically are you the first volunteer i would happily actually there's a lab there's a lab with some massive funding as well trying to extend the depth of metabolic depression in humans, or reduction in humans, I should say, from sleep using chemicals. And that's the closest I think we are right now to getting humans into a more metabolically lowered state. So we're already starting to cross that starting line, I would say say to getting humans closer to a metabolically lowered state can we jump start that by gene therapy jump start the entrance into like a torpid state you mean yeah can we give the upgrades to the areas that we that we because i'm on the team now, that you know are really necessary

for these things to be in the right place and go in the right direction? I think we're going to need to do that. I just, what we don't know yet is exactly where to put those jumper cables. All right. Where's the right spot to be making these changes to do it, to go into a torpid state more reliably.

We know the hypothalamus is going to be important to this endeavor. We know that changes there are going to be key, but we don't know exactly where in the hypothalamus yet. Okay. But there's a lot of problems with it that come with just depressing metabolism and lowering body temperature and things like that. There's a lot of problems that we'll have to solve at the same time. And what about, because we talked about the cast and the atrophy, so muscle atrophy, even if we just sit around, so, you know, just the fact that we're not exercising, which is what our bodies are kind of made to do. So, how do you combat the muscle atrophy associated with being asleep for a couple of months.

Yeah, yeah. And that's one of the big problems that we're going to have to face. And that's why studying hibernators, natural hibernators, I think is going to be key to figuring that question out. We don't know, really. What we know is that it's a balance between protein degradation and protein synthesis. That's really where the muscle tissue balance comes from. It's either you increase synthesis to maintain tissue or you decrease degradation. And what we see in

the hibernators is they actually do a little bit of both in torpor. So they'll decrease their degradation pathways and they'll increase their synthesis pathways. So they're actually making a little bit of new muscle too in the hibernation season. And so what we have to figure out from them is what is it that they're doing to maintain both of those sort of at a higher level. And the answer to that is just, we don't know. You wouldn't be able to use one of those like electronic muscle stimulators

that you see advertised in the back of the magazines. Like, you know, put this on, you'll have six pack abs in three weeks. Yeah, forced muscle contraction. It's probably not the way I would go. I think there's, I think there's a more sophisticated way of doing it, but that's more or less what like,

for example, an astronaut has to do is without the electron stimulation, they have to basically weight train or resistance train resistance. Yeah. A lot of the time that they're in, in space is because they have to sort of combat that, that microgravity that saying that's not giving the muscle cues to stay full of tissue.

They'll start to degrade. All right, this is a question for Neil because you just made me think of it. So I'm sorry that I'm directing attention away. But you just said in space they weight train. So the weights don't have any weight. You know what I mean? It's resistance bands. You do springs. Ah, okay. Like the rubber bands. any weight in or you know what i mean like they're all that way just a few springs yeah

okay like the rubber bands okay okay all right let's link up to a positive future ryan um say you are able to induce a state of torpor we're in our spacecraft we're going interplanetary what are the logistics that we will need is Is it a nice cozy bed? Are you going to be slopping around in amniotic fluid? What do we need? We need oxygen. We need to be consideration of the CO2 that we're expelling, hydration, all these other things. What are the logistics that we need to be coming to terms with yeah i well i need a tempur-pedic mattress okay well there you go let me know retrofit the pods with the tempur-pedic mattress yeah yeah i've liked watching movies in the sense of there's a lot of creativity with what

they sort of make these pods look like if you're weightless you won't need a mattress just thought i just got a point yeah yeah advertise, we are used by NASA. Yes, they do. And you only need it for the eight minutes you're going into them. Right.

And the rest of the time you're weightless, it doesn't matter if there's a mattress there at all. That's true, because the depression that is from the takeoff, and

that's it. That's it. Yeah. So what do they sleep in in space? Space. Space. Space.

No, they have these little sleeping bags that they slide in. Oh, yeah. It keeps them warm. Okay. But they interrupt it. Keeps them from floating around. No, that's totally fine. Yeah, especially keeps you from floating around into somebody else's.

Well, to that same token, I think someone in a torpid-like state in space is going to need some sort of sequestering environment. So like a pod, kind of like what you would see in the movies. And I would say, yeah, CO2 is probably my main concern when it comes to hibernation. Once you have that lowered metabolic rate, O2 becomes less of a concern. Obviously, you still need it, but you don't need as much. But CO2 will still eventually build up. So you're going to have to sequester CO2 away or recycle it into O2. I think that humans are going to need some sort of supportive fluids. And the real question is, what is the hibernation going to look like? Because in natural hibernation, they don't just go into torpor and stay in torpor. They actually go into torpor and they periodically spontaneously come out of torpor for about 24 hours and nobody has any idea why.

And then they go back in and they just repeat that cycle throughout the entire hibernation season. It's like us waking up in the middle of the night. Exactly. What's the timeline on that cycle throughout the entire hibernation season. It's like us waking up in the middle of the night. Exactly. What's the timeline on that cycle? Depending on the species. So on the most robust hibernators, like the 13-line ground squirrel, they'll stay in that torpor period for about 20-ish days. And then they'll arouse spontaneously, go into this what we call intervout arousal.

And they'll stay in that between 12 and 24 hours, and then they'll go back into torpor for that about 20 days. And when they come out of hibernation, that's actually when they sleep during the hibernation season. So they still, it seems that they still must sleep like all other mammals. So the sleeping, which we always heard about as a neurological necessity, what you're saying is whatever's going on in hibernation does not serve the body's needs that we get from sleeping. Precisely. Interesting. So you still have to come out and sleep.

Maybe the cycle of torpor for humans might be a little different where we're in torpor for four days and then we come out for three days instead of being in for a month and you know is is that our formula might be different yeah our formula i think our formula will certainly be different and actually the bear is a prime example of why our formula would be different bears don't have the interval arousals and so there is some sleep associated with their torpor like state and that's why we think it's more of this continuum from sleep to deep torpor, is that bears sort of are on the closer to the sleep side, where they don't need these interbot erosals, so they must be sleeping

in some fashion in their torpor hibernation season. And so I suspect humans will fall on that side. They'll look more like a bear. Do you participate in the fat bear photo contest? I don't, and I'm just hearing of this now, so I think I might have to. Yeah, every fall, I think it is, people put, they get, you know, whoever's in the wilderness,

they get the fattest bear photo they possibly can. Yeah. And there's some fat ass bears. Oh, they get really big. Yeah. Oh my God. So all anapose tissue is what they're putting on too. It's all what? All fat tissue. That's what they Yeah. Oh, my God. All anapose tissue is what they're putting on, too. It's all what?

All fat tissue. That's what they put on. It's all fat. So, Ryan, at some point, you're going to want to test on a little, well, say, little furry creature and send them into space. Tell me it's not good. Last I saw your chest hair, you would count as a furry creature. Yeah. Yes.

However, you're not suggesting you send a big old bear up into space no no i i mean in reality that would be the most informative thing to put into space would be the bear because i think that's what human hibernation is going to look like but i i don't think that's ever going to happen in the near future imagine it wakes up grumpy yeah imagine grumpy bears in space you know just to for reality check here the only difference between a bear in a cave and a bear in space is that a bear in space is weightless unless the spacecraft spins up and creates artificial gravity if it creates artificial gravity then the difference between a bear in space and a bear in a cave is zero there is no difference other than

like there's no salmon swimming by right so what are we actually testing for is it just a zero g effect yeah well well so zero g and radiation those are the two things that you're really not getting on earth that you will be getting in space now this is outside of low earth orbit obviously yeah yeah there's a low radiation again just for to be clear when you're in low earth orbit you're still shielded by earth's magnetic field a lot of the high energy rays wow if you're going to go to anywhere other than low earth orbit you have a radiation dose that will matter to you and course, if you're more radiatively resistant in hibernation state, then it all works out. So maybe all of the radiatively resistant hibernating animals came from space. In that line of thinking, that makes sense.

The aliens brought them and the ones that didn didn't survive the radiation, they died. The ones that did came to Earth. There it is. That's the newest big thing. And that's your next Pixar movie. But to space animals here. I'd watch it. I'd watch it.

Just to see. So, Ryan, we got to call it quits there. But this has been a highly illuminating conversation. I'm delighted to learn that we got top people working on this. I've always been jealous of other animals. People say, oh, the human body is some perfection. No, it's not. There's plenty of other animals that have features that I would delight in

that we don't, among them regenerating limbs, hibernation sounds like fun if you just want to chill for a couple of months, all of months. All of this. So I'm glad to know we got good people such as yourself and your three leaders tackling these kinds of biomedical challenges and applying them to NASA. This is all great to learn here. Thank you so much for having me. It's been a really great time talking to all of you.

And hopefully it was a fun conversation for everybody. Yeah. Gary, always good to have you. Thank you, Neil. Always a pleasure, my friend. All right. Chuck it, baby. You know it. Neil deGrasse Tyson here closing out yet another edition of StarTalk Special Edition. This one on hibernating

in space. As always, I bid you to keep looking up.