Hibernation slows biological aging in bats

The most common bat in the United States, the greater brown bat has an unusually long lifespan of up to 19 years. A new study led by University of Maryland researchers identifies one of the secrets of this bat’s extraordinary longevity: hibernation.

“Hibernation has allowed bats, and probably other animals, to remain in northern or very southern regions where there is no food during the winter,” said the study’s lead author, UMD biology professor Gerald Wilkinson. “Hibernators tend to live much longer than migratory birds. We knew that, but we didn’t know if we would see changes in epigenetic ages due to hibernation.”

The researchers found that hibernation lengthened a big brown bat’s epigenetic clock – a biological marker of aging – by nine months. The study published in the journal Proceedings of the Royal Society Bon August 10, 2022, also included scholars from McMaster University and the University of Waterloo, both in Ontario, Canada.

They analyzed small tissue samples from the wings of 20 large brown bats (Eptesicus fuscus) during two periods: in winter, when they hibernated, and in summer, when they were active. The bats, housed in a research colony at McMaster University, ranged in age from less than 1 year to just over 10 years.

Once the samples were collected, the researchers measured changes in DNA methylation – a biological process linked to gene regulation – between samples taken from the same animal during active and hibernating periods. They discovered that changes in DNA methylation occurred at specific sites in the bat’s genome, and these sites appeared to affect metabolism during hibernation.

“It’s pretty clear that the sites that decrease methylation in winter are the ones that seem to have an active effect,” Wilkinson said. “A lot of the genes closest to them are known to be involved in regulating metabolism, so they’re probably keeping metabolism low.”

Some of these genes are the same ones that Wilkinson and other researchers identified as “longevity genes” in a previous study. Wilkinson said there is significant overlap between the hibernation genes and the longevity genes, further highlighting the link between hibernation and longer lifespans.

The earlier study also established the first epigenetic clock for bats, capable of accurately predicting the age of any bat in the wild. This clock was applied to this latest study, allowing the researchers to show that hibernation reduces a bat’s epigenetic age compared to a non-hibernating animal of the same age.

Studies like these help explain why bats have longer lifespans than expected for a small mammal the size of a mouse. However, they also raise new questions.

“We still don’t have a very good understanding of why some bats can live really long and others can’t,” Wilkinson said. “We have shown that those who live really long all share the ability to hibernate or to freeze frequently. This seems like a logical conclusion, but it is not enough because hibernating rodents do not live to be 20 years old.”

Wilkinson said he plans a follow-up study to compare epigenetic aging in big brown bats in Canada, where they hibernate, to the same species in Florida, where they don’t hibernate. By doing so, Wilkinson hopes to get an even clearer picture of the role hibernation plays in lifespan extension.

The paper, entitled Big Brown Bats Experience Slower Epigenetic Aging during Hibernation, was published in Proceedings of the Royal Society B on August 10, 2022.