When Dwarf Lemurs Hibernate, Their Chromosomes Do Something Odd

FLORA LICHTMAN: This is Science Friday. I’m Flora Lichtman. Up next, new research into lemurs, those fluffy, big-eyed primates from Madagascar. Specifically, we’re talking about the fat-tailed dwarf lemur, one of the few primates to hibernate. Lemurologists were curious about what’s going on inside their cells during hibernation, and they found something really surprising. It turns out that these lemurs’ telomeres– those are the ends of their chromosomes– grow longer when they hibernate. Typically, telomeres shorten as we age as our cells continue to divide.

So why do their telomeres lengthen? What does it mean for how they age? Have these lemurs tapped into some longevity hack? Here to take us into the lemur burrow are coauthors on this study who also happen to be married to each other, Dr. Marina Blanco and Dr. Lydia Greene, research scientists at Duke University in Durham, North Carolina. Welcome to Science Friday.

LYDIA GREENE: Thanks very much for having us.

MARINA BLANCO: Thank you.

FLORA LICHTMAN: Lydia, give me the 411 on this lemur species. What do they look like? Where do they live? What’s their deal?

LYDIA GREENE: So imagine a fluffy, fat-tailed squirrel with forward-facing eyes and human-like hands that could grasp onto tree branches and lots of fruit, and then imagine them in the western forests of Madagascar that are dry, deciduous forests, maybe hanging out in a baobab, and facing food scarcity during the dry season. And so they decide to curl up inside a tree hole and live off the junk in their trunk, the fat in their tail that’s been stored up in the preceding season, and basically curl up and just pass the winter by not eating, not foraging, not moving, and saving a lot of energy by living off the fat in their tail.

FLORA LICHTMAN: The junk in their trunk, that’s where they store all their fat, in their tail?

LYDIA GREENE: Yes, as do I.

FLORA LICHTMAN: Is that unusual, though? Like, is that why it’s in their name? I just want to go one level deeper on the tail, I think.

LYDIA GREENE: Yeah, I think I would say that there is a good reason to store your fat in your tail because it’s a pretty safe place to put it. If you were to put your fat around your organs or in other places in your body cavity, that might be more dangerous. We know that those fats are not great for humans either. And so putting it in your tail just is a safe place to keep it out of harm’s way, and you can use it when you need it.

And so they can hibernate for four to seven months a year without eating and also without drinking and without even leaving their tree hole. So they’ll spend up to seven months just living off that fat.

FLORA LICHTMAN: Marina, tell me about what you found in this recent study. What was the kind of the biggest takeaway?

MARINA BLANCO: So we knew that telomere elongation was possible in some animals, particularly in hibernators, because a few studies had been published about 10 years ago where small temperate hibernators could elongate their telomeres after the hibernation season when they had access to rich fruits. And so we knew that hibernators may have a mechanism to elongate telomeres, and we also knew at the time that hibernators tend to live longer lives than similarly sized animals. So we wanted to test if telomere elongation was also possible in dwarf lemurs, which are tropical hibernators.

After we were able to sort of facilitate hibernation in dwarf lemurs at the center, we separated in two groups. And so we had the dwarf lemurs that were housed in rooms with cold temperature during hibernation and no food at all, so they could live off their fats. And then we had a group of dwarf lemurs that were also housed in cold rooms, but they were given a daily ration of food. And so the expectation was that the dwarf lemurs in the cold rooms that had access to food probably could be able to elongate their telomeres because they had, in addition to the fats stored, they have extra food. And so if they needed to protect themselves and their bodies during hibernation that they could be able to elongate their telomeres.

But what we found is that it was actually the dwarf lemurs in the cold rooms with no food the ones that elongated their telomeres at the end of the hibernation season. And so we were a little surprised by that and sort of concluded that it was the lemurs that were at higher risk or maybe more vulnerable at the end of the hibernation season that needed to elongate telomeres to protect themselves.

FLORA LICHTMAN: What does hibernation look like for them?

MARINA BLANCO: So during the hibernation season, these animals do depress their metabolism. They go into these long torpor bouts, but these torpor bouts are interrupted by arousals. And arousals are these short periods where lemurs basically heat up and go from 0 to 100 metabolically, and they stay in this arousal time for about 24 hours. During this time, heart rates go up. Breathing rates go up. They actually sleep. And then after the arousal, they return. They go back down into a torpor bout.

FLORA LICHTMAN: What does a torpor bout look like? What does that mean?

LYDIA GREENE: So, basically, your systems are shut down to a minimum, to a sort of a suspended animation state. So during a torpor bout, your brain basically is flatlining in an EEG. Your heart rates go down to maybe six or eight beats per minute instead of 300 when you’re active. You don’t breathe for several minutes, 8 to 10 minutes.

FLORA LICHTMAN: Wow. You don’t breathe for several minutes?

MARINA BLANCO: No. They have apnea. So they don’t breathe. Everything is really shut down. They’re cold to the touch, so it’s minimum survival mode. But you can stay like this for maybe 7 to 10 days, and after that torpor bout, arousals come. So there is something inherently important about arousing from a torpor bout to sort of reset your systems.

And it is during those arousals where their bodies really are at a vulnerable stage because imagine these metabolic surges that have to happen in very few hours. And I think that’s when we start looking at potential mechanisms of protection that these animals have to protect themselves from these arousals that could be dangerous.

FLORA LICHTMAN: And that’s why you think the telomeres are lengthening is that when they arouse, there could be a lot of damage to cells, and so you would want some protection, extra protection. Is that the idea?

LYDIA GREENE: Yeah, and I was going to add more context. At some point, you need to rewarm up again to go through these arousals to sort of maintain physiological health. And so during these arousals, they’re essentially burning their fats to warm up, and there’s a lot of potential damage that can happen to the cells as a result of that intense fat burn. And so there might be a reason why an animal sort of at the end of the hibernation season when they’re burning through the ends of their fat may put a last surge to lengthen their telomeres as a way to protect the integrity of the cell at the very end of the season.

FLORA LICHTMAN: I mean, Lydia, we know that telomere shortening is associated with aging. Did these lemurs live longer?

LYDIA GREENE: Yeah, so there’s a fascinating correlation between hibernation and longevity and that mammals that hibernate tend to live longer lives than do similarly sized counterparts that don’t hibernate. So the counterpart to the dwarf lemurs would be the bush babies that are about the same-sized primates, but they have much shorter lifespans– what, Marina, like 12 to 13 years? Whereas dwarf lemurs can live to almost 30.

And so we’ve known for a long time that there’s this interaction between longevity and hibernation, but the mechanisms are not well understood, particularly in these dwarf lemurs. And so what we found in these animals is you might expect that the stress of hibernation would shorten telomeres much faster than it would in a nonhibernator, but what we seem to find is that these animals have some ability to lengthen their telomeres to protect themselves, and maybe that is what helps them live longer lives, despite the fact that they’re going through these stressful periods.

FLORA LICHTMAN: Well, that’s what I was going to ask. I mean, does this mechanism or understanding this mechanism tell us anything about longevity? Of course, people are very interested in this.

LYDIA GREENE: Yeah, I don’t think we’ve hacked the fountain of youth yet, but I do think that this provides some sort of tantalizing clues about how longevity can be maximized. But I think the question for us is still always going back to this mechanism of, how are telomeres lengthening? And we talk a lot about this lengthening in this project, but also two weeks after they come out of hibernation, their telomeres had shortened again. So maybe that stress of those first two weeks of being aroused and of trying to find a mate– because that’s the reproductive season.

So it’s not that their telomeres lengthened and stayed long. They actually ultimately shortened again, and they started off the hibernation season of year two with the same length that they started off the hibernation season of year one. So it’s not like they’re sort of indefinitely lengthening their telomeres. But I do think that if we continue this work and if colleagues and peers and collaborators continue this work, there’s a lot we can learn about the mechanisms underlying telomere dynamics that could, downstream, be applied to people.

FLORA LICHTMAN: Yeah, I’m interested in this. I mean, I know bats can be a kind of poster child of longevity. And I know that in some species, researchers have found their telomeres lengthening during hibernation. Do we need to get all the people who study animal superagers together to work on this mystery?

LYDIA GREENE: Yeah, and I think we can throw in there people that do deep diving in the bottom of the ocean and people that are traveling to outer space because there’s also been some interesting findings that maybe they are able to lengthen their telomeres under sort of the extreme physiological stress of humans at the maximum of their physiological potential.

FLORA LICHTMAN: It’s really fascinating. What have we missed about this study?

LYDIA GREENE: These are critically endangered primates from Madagascar, and so we’re not going to be doing the invasive work to really challenge their cells in ways that would allow us to understand the mechanisms. But we can potentially grow cell lines from these animals and expose the cells in a Petri dish to the sort of challenge that the animal would experience, and so we can answer some of these questions without doing any invasive work on the animals themselves.

But I also think that there’s real value in us looking to Madagascar and looking to wild populations of dwarf lemurs to try to understand the variety of conditions and environmental heterogeneity and environmental challenge that they’re experiencing in the wild and to start modeling some of these telomere dynamics just from the same cheek swabs we applied to these captive animals to understand, what are the dynamics going on in the wild for animals hibernating under cold conditions, for animals hibernating under warm conditions, for animals hibernating at the beginning of their lives or hibernating at the end of their lives? And I think there’s all sorts of questions we can also ask in the wild.

So I think this dual approach of sort of the natural ecology, natural history perspective in Madagascar, coupled with really high-quality, rigorous lab work that doesn’t have the animal involved in it is really, I think, the duality of the approach that we see.

FLORA LICHTMAN: OK, well, when you head to Madagascar for your fieldwork, please phone us in, and thank you both for joining me today.

LYDIA GREENE: Thank you so much for having us.

FLORA LICHTMAN: Dr. Marina Blanco and Dr. Lydia Greene, research scientists at Duke University in Durham, North Carolina.

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