Opossums, Hydras And Hummingbirds: What We’re Learning About Aging From Animals – OPB News

The hydra, a tiny sea creature, appears to never age. Scientists are studying it to learn what secrets it may hold to longevity.

Leonardo Santamaria for NPR

A stint as lion tamer in Hollywood got Steven Austad interested in animal biology. And soon he turned from training animals to studying them. Hes now chair of the biology department at the University of Alabama at Birmingham, where his research focuses onaging.

Hes learned that aging happens at different rates in different animals, without following any clear rules. Austad says its not heart rate that predicts lifespan. An animals size has something to do with it, but some animals defy that pattern. And even more perplexing are animals that dont seem to age at all like a tiny sea creature called ahydra.

Austad spoke with Invisibilias Lulu Miller to discuss what science has uncovered about animal aging processes, and how researchers might be able to use what theyve learned to extend human lifespans. Theres no immortality on the horizon or anything close to it but its likely science can eventually lengthen our lives by at least a little, Austadsays.

This interview has been edited for clarity andlength.

How did you go from lion taming for the movies to studyingaging?

I was a reporter for the Oregonian newspaper in Portland. And a friend of mine had a couple of African lions for pets, because he was crazy. He got an offer to use them in a movie, and he needed somebody to help him transport them from Portland to Hollywood. And he talked me into helping out. When I got down there, the movie producer offered me a job and I said, You understand I dont know anything at all about this, right? And he said, thats okay. It awakened my interest in animals and what makes animals tick. After I got fairly seriously injured one time, I thought maybe this is not really what I want to do the rest of my life. So I decided to study animals in graduateschool.

What did you like about traininglions?

What I liked the most about lions is because they live in social groups, they like contact. Theyre almost like dogs, more like dogs than cats, except they sometimes will try to kill you. But I just love the intimate contact with them. For the first year, I never took a day off. I worked seven days aweek.

How did opossums short life span get you interested inlongevity?

We were working on some animals in South America opossums. I discovered that they age really quickly, almost like mice. And that was so puzzling to me that I completely abandoned what I was working on. It was the size and the longevity combination. I think we all have this kind of intuitive feel from being around animals that smaller animals are going to [have] shorter lives. So you know, a dog has a longer life than a mouse, and a horse has a longer life than a dog, and an elephant has a longer life than a horse. And this just seemed to grossly violate that. I had to recapture them every month, and I would come upon one that was in prime physical health, and two months later it would have cataracts, and it would have lost muscles, and had parasites all over it, and arthritis. It all happened soabruptly.

So, are size and lifespan linked in animals ornot?

Yeah, its a very general pattern. Its true of mammals. Its true of birds. Its true of reptiles. Its true of almost every group of animals. We know that smaller ones are shorter-lived and bigger ones are longer-lived. But there are exceptions, and actually I think the exceptions are the ones that are most interesting from a scientificperspective.

What is the billion beats hypothesis and why do you questionit?

Ive spent a good deal of my career trying to kill it, but obviously, I havent been able to. The [idea] is that life is inherently destructive and that burning energy is inherently destructive. Lets say all mammals have a kind of a fixed amount of energy that they can burn over the course of a lifetime. And if they burn it fast, theyll be short-lived, like mice. And if they burn it slow like an elephant, they can live much longer than that. The reason that I dont really buy it, is that if you actually look at a whole bunch of animals, it turns out that smaller ones actually have more heartbeats and use more energy over the course of a lifetime than large ones. And then there are these massive exceptions to it. Hummingbirds have a heart rate of over 1,200 beats per minute, which is kind of like a machine gun, but yet they can live in the wild into theirteens.

How do you think we should look at the link between size andlifespan?

I have developed something called the longevity quotient, which really is a way to say: Is an animal long-lived or short-lived for its size? Dogs, for instance, have a longevity quotient of one, which means theyre exactly an average mammal in terms of how long they live. And we have a longevity quotient of about four and a half, so we live about four and a half times as long as a mammal of our size should live. Mice live about 70% as long as an average mammal of thatsize.

And theres a very small animal thats actually one of the longest lived creatures,right?

Hydras were discovered actually in the early 1700s by Van Leeuwenhoek, who invented the first decent microscope. Theyre freshwater animals, maybe a quarter to a half inch in length. They almost look like a sea anemone, theyre just smaller and skinnier. They really started to be studied in earnest a few years later by a Swiss biologist named Trembley who discovered if he cut them in half across the middle, the bottom would grow a new top, and the top would grow a new bottom. It turns out that you can even treat them with chemicals that basically dissolve all the things that make their cells stick together. Youd make a pile of cells and they will eventually reassemble into a hydra. He started chopping them up in all kinds of ways to see exactly what you needed to regenerate. He eventually created a hydra that had multiple heads. Thats how it really came to be [called a] hydra, because a hydra in Greek mythology was this monster that had manyheads.

And what did we learn about aging from the hydra? How is it even possible for them to have this kind oflongevity?

Hydras have stem cells in them. When they divide, one half of it remains a stem cell, but the other half will eventually turn into part of the tentacle or part of the mouth or part of the body wall. It changed the way we thought about animal development at that point in time. We didnt really know how animals develop [in the 1700s], and one idea was that animals were just very, very tiny replicas of themselves when they were in an embryonic stage, and that pre-formed thing just grew. At that point they thought, maybe inside of a human egg theres a little tiny human and it hatches out into a baby and then it just grows and grows and grows. The hydra pretty much killed that idea because we could take just part of it, which clearly did not contain a whole hydra, and grow a whole new hydra out ofit.

Are hydras reallyimmortal?

Rumors really started to accumulate in the 1950s. People had followed individual hydras for a few years, and they didnt seem to die at any higher rates. So there was a rumor that they might be potentially immortal. Daniel Martinez in the late 1990s actually reported that they didnt age. Few people believed him. At least for as long as anybodys had the patience to follow individual hydras that has been about seven years at the most theres no indication that they age at all. It is possible that if we followed them long enough, we would discover that they aged, but no one has had the patience to do it. Certainly it would be a very, very long time. Theyre not the only animal that doesnt age, but theyre one of the few, and the others that dont appear to age are really close relatives the various kinds of jellyfish, forinstance.

What has been unlocked in the science of aging by looking athydras?

So the idea that if you manipulate single genes, it can have a dramatic effect on aging was really discovered in the late 1980s I would say. And then through the 90s it was confirmed and other genes werediscovered.

One of those genes directly interacted with this gene FOXO. Finding this in everything from little worms to people [with long lifespans] suggested that the activity of FOXO might be a key to understanding slow aging. So the hydra work really confirmed what had been seen in a number of otheranimals.

How has research on slowing agingprogressed?

Starting about 30 years ago, people discovered that there were genes that if you either knocked down their activity or souped up their activity could really have a major impact on aging. We started to look at drugs that could affect aging, and we now have at least half a dozen drugs that we know affect aging in a lot of different animals. Some of those things will turn out not to work in humans, but Im quite confident that we will develop ways to improve human health either by injections, by transfusions, by taking certain pills every day. And thats what the biotech industry is going nuts with rightnow.

You often hear people fantasize that were going to live 500 or 1,000 years in the future, and I dont buy that at all. We havent been able to do that with different species. What we can do is we can increase the longevity of mice, worms and flies lets say by 20% many, many ways. And so I think thats a reasonable idea. Whats unclear is how much of that will be healthylife.

Are there drawbacks to potentially extendinglifespan?

Lets imagine that we discover a gene mutation that doubles lifespan. If this is so great, why didnt nature do this a long time ago? If it has an effect on reproduction or the [time] to sexual maturity, it may turn out from an evolutionary standpoint not to be a good gene, but to be a bad gene. For all of the benefits that we get in terms of health, there may be some downsides to some of these treatments. We need to becareful.

Knowing everything you do about aging, do you live anydifferently?

I dont take anything. I dont do any weird diets. I do a lot of sensible stuff. I exercise a lot. I eat right. I dont smoke. Once theres enough evidence, I may try some other stuff. I dont think theres evidence enough in humans to be doing anything else right now.

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Opossums, Hydras And Hummingbirds: What We're Learning About Aging From Animals - OPB News