What We Can Learn About Diabetes From Hibernating Bears

IRA FLATOW: About one in ten Americans have diabetes. Most of them are type two, the kind that develops when cells become resistant to insulin. Wouldn’t it be cool if we could just flip a switch so those cells become sensitive to insulin again? Well, that’s pretty much what bears do, and it helps them get through a long hibernation.

So of course, researchers are looking at how bears do this, and if we might apply it to treating diabetes in humans. Here to tell us more about this and other grizzly superpowers is Dr. Blair Perry. He’s a post-doc studying genomics at Washington State University in Pullman, Washington. Welcome to Science Friday.

BLAIR PERRY: Thank you so much for having me.

IRA FLATOW: So nice to have you. OK, so before we get into your research, I want to know why is bear hibernation so cool? Why do you want to study it?

BLAIR PERRY: Yeah. So bear hibernation is actually a lot more complicated and interesting than a lot of people realize. So a lot of children’s books and pop culture make you think that bears are simply just going to sleep for the entire winter. But in reality, there’s a lot of really interesting and extreme changes to their physiology and their metabolism that allow them to do that. Pretty much every cell, every tissue in the bear’s body is changing how it processes nutrients to enable them to survive these long periods without access to food.

IRA FLATOW: And one of those adaptations has to do with insulin, right, and bears can turn it on and off.

BLAIR PERRY: Yeah. So when we look at adipose, or fat tissue, in hibernating bears, we see that it becomes resistant to insulin. Like you said earlier, this is typically, in humans, kind of an early sign of progression towards type two diabetes. But in bears, they become resistant to insulin every winter, and then in the spring when they’re returning to, kind of, their active, normal bear activity level, they regain sensitivity to insulin.

So we think that a lot of it has to do with the fact that they’re relying on burning fat during the hibernation months. So in the summer and especially in the fall, they essentially devote all their time and energy to gaining as much weight as possible, putting on as much pounds as they can, so that they can burn that fat for energy and survive the winter. And typically, insulin actually inhibits the ability for adipose tissue to burn that fat, so by turning off sensitivity to it, we think that it kind of boosts their ability to utilize all that fat they’ve gained to essentially power the body during hibernation.

IRA FLATOW: That really is very interesting. And you studied insulin resistance in the bears trying to figure out how they do it. And did you find an answer?

BLAIR PERRY: We think we’re getting close. So this study that we did recently was aiming to identify potential proteins or molecules in the blood of bears that may control their ability to become insulin resistant and to regain that sensitivity in the spring. So by stimulating cultures of bear adipose tissue cells, or fat cells, in the lab with serum from different seasons, during the summer, during the winter when they’re hibernating. And by comparing the differences in the proteins present in the blood serum between these different seasons, we were able to identify eight proteins that we think are actually really important for driving this because they are abundant at different levels in different times during the year.

IRA FLATOW: So these eight proteins that are driving this, are any of them found in humans?

BLAIR PERRY: Yeah. In fact, all eight of these proteins are proteins that are known to be present in humans. And a subset of these, I think three specifically, are actually known in humans to be involved in the reception and processing and response to insulin. We think that perhaps bears are using these proteins in a slightly different way.

Maybe they are having slightly different changes to the bear’s cellular activity than what we see in humans. And so by identifying where that difference is in bears, essentially unlocking this unique adaptation in bears, we might be able to, for example, stimulate similar changes in cellular activity or synthesize similar proteins for humans that might be able to, for example, help to them to regain sensitivity to insulin if they’re in this pre-diabetic insulin resistance state.

IRA FLATOW: And so how similar are humans to bears, if we’re trying to compare stuff like proteins and genes?

BLAIR PERRY: Well, so bears and humans, obviously, look and act and are very different at one level. But when we actually look at the genes that are present, the proteins that are present, and typically how these genes and proteins kind of act to do basic functions like metabolism and things like that, there’s actually a really high degree of similarity. So pretty much every gene that you see in a bear has some related version in a human and vise versa. But oftentimes, these genes will have experience changes during the evolution of these different species that allow them to essentially do things slightly differently than they might in a different species.

IRA FLATOW: That’s fascinating. I mean, I normally think of bears as being outdoor creatures, right. Where did you get all the blood samples to do this stuff?

BLAIR PERRY: Right. So we’re actually very fortunate to work with the Washington State University Bear Center, which is one of a kind facility, the only kind like it in the world, in Pullman, Washington that has a captive population of bears that are often bears that were getting into trouble in national parks, things like that, and had to be moved. And at this facility, we can study these bears year round.

We can take small non-invasive, non-damaging blood samples and tissue samples, and really have this unprecedented and really unique and exciting access to studying all aspects of bear biology that normally would be very dangerous, if you’re doing this in wild bears for the researchers and for the bears, potentially. And oftentimes, you know, frankly impossible. For example, it’s really hard to find and get tissue samples from hibernating bears in the wild.

IRA FLATOW: You’ve got grizzlies cooperating with you? [LAUGHTER]

BLAIR PERRY: We do. Yes. So as you might expect, they’re very, very food motivated. And they’re also very, very smart, which is something that a lot of people don’t realize. So they pick up really quick on things that we want them to do by rewarding them with treats, which in this case is actually honey.

So the children’s books did get that part right. They do love honey. But for example, they’ll come up to the edge of their enclosure, they’ll put their paw through a little opening so that we can take a small blood sample. Just a tiny little pinprick to them. And then they get a nice big dose of honey water, which they absolutely love.

IRA FLATOW: Wow. You talk here about the insulin resistance in bears and what we can learn from that. What else can bears possibly tell us about human health?

BLAIR PERRY: Right. So pretty much any aspect, any tissue that you look at during hibernation is typically doing something that’s pretty remarkable and pretty different than what you would expect to see in a human. So for example, they aren’t sleeping the entire winter. They do lay around a lot. They’re relatively lazy during this time.

But we don’t see any degradation of muscle tissue or loss of muscle tone. And in humans, for example, if someone was injured or had to be in bed for a long period of time, that’s really a very detrimental thing, and that you see their muscle tone start to degrade. Bears don’t experience any of those harmful losses of muscle. So that’s one aspect that we’re interested.

IRA FLATOW: Really.

BLAIR PERRY: Yeah. Exactly. Their heart rate decreases slightly during hibernation. So we’re interested also in understanding how they’re able to maintain normal body functions with this decreased cardiac output. They don’t urinate or defecate for the entirety of hibernation, which in humans would obviously put you in a pretty uncomfortable and pretty dangerous situation. So really if you just look at a hibernating bear, pick a tissue, pick a part of their body, there’s probably something really interesting going on there that in some way or another parallels something in humans typically related to a disease or some negative condition in terms of human health.

IRA FLATOW: Is there anything about the hibernating process itself and the changes that go on in the bear, as you speak, that might be applicable to hibernating people?

BLAIR PERRY: Yeah. So that’s not something that my research is specifically getting out right now, but it is something that has been discussed and thought about in the hibernation research world. For example, there have been discussions about ways that, in the future, we might be able to apply our understanding of hibernation and other mammals to, for example, help humans make very long space journeys and things like that, where you might be able to essentially induce hibernation in humans so that they can go these long periods of time traveling to Mars or beyond, or something like that.

And you know, obviously, I think we’re still a little ways away from that, but there’s some real, I think, interesting and exciting applications to trying to instead of look at specific aspects of hibernation and understand how we can apply that to humans, trying to essentially apply the whole thing to humans. And like you said, enable humans to hibernate in a way similar to the bears.

IRA FLATOW: I see that we have barely scratched the surface [LAUGHTER] of all the things to be learned. Dr. Blair Perry is a post-doc studying genomics at Washington State University based in Pullman, Washington. Thank you for joining us today.

BLAIR PERRY: Thank you so much for having me.

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