JOE PALCA, HOST:
This is SCIENCE FRIDAY. I'm Joe Palca.
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Next up: Do you know that pythons can go without eating for months at a time? Well, here's a diet for you. But it's what their bodies and, in particular, their hearts do after they finally had a meal after this long gap that's even more remarkable.
What is that? Well, my next guest can tell us. Dr. Leslie Leinwand is a professor of the Biofrontiers Institute at the University of Colorado, Boulder. Her study on the python heart appeared in the journal Science, and she joins us from Killarney, Ireland, where she was nice enough to interrupt her vacation to come on to the program. Welcome.
DR. LESLIE LEINWAND: Thank you for having me, Joe.
PALCA: You're welcome. And if you'd like to join us, this is going to be - I mean, this heart study is just amazing. You got to hear about it, but it's 1-800-989-8255, 1-800-989-TALK, or you can tweet us @scifri.
So, Dr. Leinwand, I guess that's the question. Why - you - you're a molecular biologist, biochemist and you study hearts in humans. What got you interested in the python?
LEINWAND: Well, when I read an article written by my colleague, Stephen Secor, a collaborator, and his colleague, Jared Diamond, about the amazing biology of these animals, I was immediately drawn to it. I have had such a curiosity about how they could go for such long periods of time without eating and nothing terrible happened to them.
And when they do eat, they eat this massive meal, and what happens is quite extraordinary that the mass of most of their organs, including the heart, almost doubles in size in less than 24 hours, then goes right back down again after they've digested the meal. And we were quite interested in that because we're cardiac biologists, after all, and we were interested in enlargement and how a heart gets smaller after it's enlarged.
PALCA: So wait a minute. When human hearts get larger, sometimes that's associated with increased illness, but that's not happening here. What's going on there that's not going on here?
LEINWAND: Yes. So, in many cases, people's hearts get larger because they've got high blood pressure for - that's untreated for, you know, many years, and that's a bad thing. But people like Lance Armstrong or Michael Phelps or a highly conditioned athlete also have bigger hearts, and that's associated with increased cardiovascular health.
LEINWAND: So our hypothesis was that the pythons would not have evolved something happening with their heart that would be akin to a diseased state, but instead might be more like a highly conditioned athlete's heart.
PALCA: So why would these organs in the heart grow after a meal?
LEINWAND: Because they need to to be able to digest this massive meal. The meal can be equal to the body mass of the python, which is quite an extraordinary metabolic demand to be put on that animal.
PALCA: So, in other words, just to finish eating their meal, to finish digesting it, they need a lot more energy and a lot more blood pumping through the - their bodies and like that.
LEINWAND: Exactly, exactly.
PALCA: I see. And why - the python is a reptile. I mean, it still is not clear to me that anything it's doing would have any relevance to a mammal.
LEINWAND: Well, we weren't sure that it would, but we bet on it. It was an instinct that I and my postdoc both had, that we would be able to translate these findings into mammals. But to tell you the truth, it was one of the first experiments that the postdoc did after establishing that we could grow these reptiles and feed them the meals and their organs would increase.
She asked a pretty simple question, which was if there was something circulating in the python blood that might be able to make heart cells from a mammal, a rat, in culture get bigger, which would mimic the python's heart getting bigger. And, lo and behold, that experiment worked.
I thought it was a big leap to go from - directly from python blood on to mammalian heart cells, but it worked. And that gave us the resolve that if we did keep after this and study this organism, that we might, in fact, be able to translate the - further findings to humans.
PALCA: We're talking about a remarkable study involving python hearts that appeared in Science not too long ago with Dr. Leslie Leinwand. Give us a call. If you want to join the conversation, our number is 800-989-8255. That's 800-989-TALK. And it's something in the blood. Were you able to find out what in the blood was causing this growth spurt?
LEINWAND: Yes, we were. We were able to identify three fatty acids, and those were basically the fuel of the heart that enables it to generate the energy that is required to digest this meal and pump this blood. And in terms of - if you looked at the blood from these snakes after they've eaten one of these meals, they're almost milky. They're almost white with so much fat in it that it seemed like a likely candidate that it might be the fats in the blood themselves.
PALCA: And they were a certain set of fats or...
PALCA: ...ratio of fats or how did that work?
LEINWAND: So it was a specific combination of three fatty acids that in - it requires just those three and in a certain combination. We've tested other ones, and it really is these three. And those three are not found typically in that combination in any, let's say, dietary source that a human might eat.
PALCA: Hmm. All right. Well, let's invite some of our listeners into the conversation. And let's go first to Doug(ph) in Denver, Colorado. Doug, welcome to SCIENCE FRIDAY. You're on the air.
DOUG: Thanks very much to your staff for my allowing my call through.
DOUG: I'm curious as to what happens with the python being as they are reptiles, therefore coldblooded? And in their environment, a temperature change occurs that creates for a significant cooling even as they're trying to or are working to digest one of their very often quite large meals. I've heard that they can eat an animal as large as a deer whole. And I'm wondering how cooler temperatures would impinge upon this biological effect or biological phenomenon of the enlarged heart, the increased blood flow if suddenly temperatures were to turn cooler in their environments.
PALCA: What about that, Dr. Leinwand?
LEINWAND: Yes. So, certainly, we, nor anyone else that I know of, has deliberately put the pythons in the cold after they have eaten such a meal. They do generate quite a bit of heat when they're digesting this meal. And as you probably know, the reptiles will stretch themselves out in the sun to generate heat, or cool themselves down in the water if it's too hot. I would guess that a decrease in temperature that was extreme might have, you know, some physiological impact, but it might not be so relevant to the wheres that pythons live in the wild normally.
PALCA: OK. Doug, thanks for that question. It's very interesting.
LEINWAND: Thank you.
PALCA: Let's take another call now and go to Vic(ph) in New York City. Vic, welcome to SCIENCE FRIDAY. You're on the air.
VIC: Oh, thank you very much. I'm wondering, what is the application, though, for humans? Is it for people who might be born with a defective heart, somehow the mechanism - the muscle is defective? Or is this for people who have abused their - just, you know, been, you know, through their lifestyle have ruined their hearts and somehow this will undo that damage or help to repair?
LEINWAND: Well, our hope is not that we would be suggesting that people take some pill instead of exercise. But it's well known that when people exercise, it's very cardio protective. And when people with heart disease can exercise, it also is very beneficial. Unfortunately, many people who have heart failure, let's say, when the heart is not functioning well at all, can't get the benefits of exercise because they can't undergo that kind of exercise.
So we're at least envisioning testing in animals, whether or not these fatty acids might be beneficial in the setting of heart failure. And heart failure, as you may know, can be brought about by many, many different causes. And certainly lifestyle contributes to it, but it's by far not the only thing that can result in heart failure.
PALCA: OK. Vic, thanks very much for that call.
VIC: Thank you.
PALCA: You're welcome. Let's now go to Eric(ph) in New York City. Eric, welcome to the program. You're on the air.
ERIC: Hey. How are you?
ERIC: Thank you for doing this. I'm really excited about it because I work with snakes all the time. I've worked with reptiles for 15 years. And my question is...
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ERIC: ...fact that the snake's heart enlarges during the time that they're eating, does this affect the growth rate at all? Because I've worked with Burmese pythons. Actually, that's my other question (unintelligible) - what type of snake was it? What type of python was it?
LEINWAND: These are Burmese pythons.
ERIC: What type was it?
LEINWAND: These are Burmese.
PALCA: These are Burmese pythons. Yes.
ERIC: It was a Burmese python. OK, perfect. Yeah. So I have had a Burmese python, and I actually still work with them now. And the one that I have, it grew from one foot to three feet, I'm sorry, one foot to nine feet in two years time. So in a very short period of time it grew really fast.
And at one point in time, I did an experiment where - not an experiment, like, you know, official but, you know, I fed it a whole bunch - I fed it about nine mice at one time, and it ate all of these mice. And I remember, literally, I was like, I'm going to measure it to see if it grew.
It grew about two inches just from that one time eating. So my question is does the growth rate - the heart size increasing, does that affect the growth rate at all, do you think? Hope you know.
PALCA: OK. Eric, good question. Thanks. So is the - does the animal, in toto, grow or just these heart organs?
LEINWAND: Yes. So these are experiments where the animals have been fasted first as they are in the wild, so they are not being continuously fed. Anecdotally, I could tell you that when we have done something somewhat similar to what you have done, we see that the animals just grow continuously and they get larger and larger and larger. And people are thinking that that, in fact, is what is happening with the pythons in the Florida Everglades because their source of food is not so limiting as it is in their native environments.
And so the snakes do appear to have a very, very large capacity to continue to growing if food is plentiful. In their normal environment, food is not so plentiful, which is why they are these opportunistic predators. So these experiments that are in this publication that's being referred to are conducted on snakes that have been fasted. So the snake itself with just one big, big meal does not tend to get longer or its skull enlarged.
PALCA: Hmm. I'm wondering though, these organs that grow, it's - certainly the process by which they shrink is interesting too. I mean, are they losing cells? Are they losing size of cells? I mean, what's happening in the shrinkage part of the story?
LEINWAND: Well, I think that's - I agree with you. I think that that is equally interesting to the growth and is something that we've only just started understanding. One of the things that is true that when - and I should've said this at the beginning - when the hearts and the organs get bigger, they're not just swelling up with fluid. They're really building new tissue as they grow. So they got to get rid of it somehow, and our suspicion is that it's going to be somewhat organ specific.
I think in the case of the heart, we're expecting that the cells are going to shrink. I think in some organs where the cells are likely to be dividing that there probably going to lose cells. But as I said, I think it's going to be quite organ specific, and we're excited about going into that new area of research.
PALCA: We're talking with Dr. Leslie Leinwand about an experiment she did with pythons or an observation she made in pythons about how their heart grows after a large meal. I'm Joe Palca, and this is SCIENCE FRIDAY from NPR. So, Dr. Leinwand, what's next? I mean, what do you look for? Are you going to continue with snakes? What do you have to do next to extend this research?
LEINWAND: Well, we're certainly going to continue with the snakes. We've kind of got our hands full with the experiments that we're doing now. And our next step is to try to ask whether the fatty acids will have some kind of beneficial effect in the setting of heart disease. We believe that this is a crucial experiment to do, and we're gearing up to do that. We're also interested in the potential to learn something about how snakes may be protected from various insults that would be toxic to you or me such as these extremely high triglycerides, and we have some insight into that.
Also, insulin levels appear to go very, very high and nothing harmful happens to the snake, so we believe that there is a lot to be learned from many of the other organ systems in the snake as well as understanding how the organs get smaller again after the meal is digested.
PALCA: OK. We have time for another caller too. Let's go to Shawn(ph) in Butler, New Jersey. Shawn, welcome to SCIENCE FRIDAY. You're on the air.
SHAWN: Thank you. My question is this: You mentioned about the snakes have fatty blood. If you were to move this into humans, wouldn't that create problems for humans because we store fat and reptiles don't store fat?
LEINWAND: So what we have seen so far is that because it is these three specific fatty acids, we are seeing no signs whatsoever of any kind of toxicity. We have put these fatty acids into mice and - into just healthy mice, and we've screened for many, many markers and assays in the blood that would tell us whether we're creating any kind of toxic state as we would see with other types of fatty acids or individual ones. We're not seeing any of that.
PALCA: So - but it's not - I mean, you're certainly - you're a long way from saying take these fatty acids to improve your heart.
LEINWAND: Oh, absolutely. We're very, very early stages, and that's why we're going quite slowly with these animal studies because we want to make sure that we're not inducing any kind of toxicity. But as I said, so far, we have no indications that we're inducing anything toxic.
PALCA: Do you have any sense that the - we were talking that there - this healthy heart that you - that these athletes' heart that the Lance Armstrongs have where their hearts grow and grow stronger. Is there any sense that the mechanism might be the same between pythons or might there be something completely different going on between pythons and humans?
LEINWAND: Well, it's probably too early to say. We're going to be doing some experiments to ask about these fatty acids in the context of highly conditioned mouse athletes that run enormous amounts, and we can begin to probe that, but it's a relatively unexplored area.
PALCA: All right. Well, I'm afraid that's all the time we have for this segment. And so, Dr. Leinwand, you can go back to vacation now.
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LEINWAND: Thanks so much, Joe. Nice to talk to you again.
PALCA: Thank you. Dr. Leslie Leinwand is a professor of the Biofrontiers Institute at the University of Colorado, Boulder. And thanks to all of you for listening today. Transcript provided by NPR, Copyright NPR.