Aging superpowers: Animals may hold the key to better human health

Scientists who want to understand why some of us live longer and healthier have traditionally focused on studying centenarians. Yet biologist Emma Teeling thinks the answer can be found among bats in the belfries of the Gothic cathedrals in Brittany, France.

Every spring, she and her team travel there to trap hundreds of baby and mother bats to collect their blood to sequence their DNA. Given that the mothers return to their birthplaces to deliver babies, the cathedrals offer a perfect setting to recatch the same bats and study how they've aged.

Teeling is convinced these tiny Myotis myotis bats, which weigh at most 1.6 ounces, have aging superpowers that offer clues for improving humans' health. "Bats can tolerate viruses, rarely get cancer and don't show signs of aging," said Teeling of the University College Dublin.

Of the 19 species of mammals that outlive humans when adjusted for body mass, 18 are bats. She documented one bat that was trapped as an adult and recaught 41 years later — a remarkable feat of aging considering the bat was about one-third the size of mice, which only live a couple of years.

"I wanted to understand the molecular mechanisms that kept them healthy," she said. Of particular interest are the bats' telomeres, the protective end caps of chromosomes that in most mammals — including humans — shorten as they age. Yet the telomeres of the Myotis myotis bats stayed the same size year after year, Telling's team found. They compared the associated 225 genes in the bats' cellular pathway with those of 52 other mammals and discovered two genes that existed only in the bats, and which might repair the DNA damage that occurs with aging.

They reported sequencing 1.7 trillion base pairs of RNA from 150 bats to find the regulatory genes involved in those aging pathways. The future goal: "To manipulate those pathways in humans by drugs or potentially gene therapy and ultimately limit and slow down diseases associated with aging in humans," Teeling said.

Animals have long been a fundamental part of medical research to test everything from drugs to surgical techniques. Yet a new wave of researchers are looking at animals' biology to learn how we might live and thrive longer.

Scientists have historically depended on worms and rodents for aging studies, yet a 2017 paper by National Institute on Aging researchers makes the case to focus more on nonhuman primates that share 92 percent of genes with humans and have an "aging process that more closely resembles the human experience."

Although in 2015 the National Institutes of Health said it would stop using chimpanzees in biomedical studies, researchers said that rhesus monkeys and marmosets are useful models to learn about the mechanisms that "lead to age-related decline seen universally, across species."

Corinna Ross, a primatologist at the Texas Biomedical Research Institute in San Antonio, said marmosets are ideal research subjects because they have a similar metabolism and get similar age-related diseases as humans.

"They age five times faster than humans. That means we can study aging interventions in a much shorter time frame than in humans," Ross said.

Neuroscientist Yuko Hara was curious why some female rhesus monkeys were mentally sharper than other monkeys as they aged. She and her team found that monkeys that were given hormone therapy following menopause had better cognitive performance than those who didn't.

The lowly two-inch striped zebrafish, which shares 70 percent of its genes with humans, is also gaining popularity.

"I'm not sure the world is aware these fish are amazing genetic models for humans. I tell people we're walking fish," said environmental biologist Keith Tierney. Although they have a life span of only three years, they grow into adults within three months and give scientists the chance to see the effects of interventions quickly.

Zebrafish also experience the same kind of muscle loss in old age that humans do. Tierney is starting a study that feeds zebrafish various diets to see how it impacts their athletic performance and muscle tone. "We put them in special zebrafish treadmills to see how fast they move and how much oxygen they use," Tierney said. "The goal is to learn how to keep our human aging population healthy on less expensive green proteins, which are easier on the environment."

However, some experts caution against drawing too many parallels, especially since many clinical trials of drugs that show promise in animals fail in humans. "If we study the DNA of aging in a mouse, it's not going to give us a predictive value for what happens in humans," said Ray Greek, an anesthesiologist.

Other experts, such as Stanford epidemiologist John Ioannidis, argue that animal studies are necessary to test the safety and effectiveness of interventions before trying them out on humans. "The information we can get from animals before jumping to humans is invaluable," he said.