Considering the Comparative Biology of Long-Lived Mammals
This popular science article covers some of the high points of the past few decades of research into the comparative biology of aging. Why are some mammals exceptionally long-lived for their size? What are the mechanisms of interest, and can any of those mechanisms inform the development of therapies to extend healthy human life spans? Answers remain to be determined in a concrete fashion for these and other, related questions. Metabolism and its relationship to aging is a very complex area of study, a great deal of the space remains poorly mapped, and as of yet it is hard to say as to whether any of the work in progress is even in principle capable of yielding useful paths to near term implementations in human medicine.
Perhaps the most remarkable animal Methuselahs are among bats. One individual of the species Myotis brandtii, a small bat about a third of the size of a mouse, was recaptured, still hale and hearty, 41 years after it was initially banded. "It's equivalent to about 240 to 280 human years, with little to no sign of aging. So bats are extraordinary. The question is, why?" There are two ways to think about this question. First: What are the evolutionary reasons that some species have become long-lived while others have not? And second: What are the genetic and metabolic tricks that allow them to do that?
The outline of an answer is beginning to emerge as researchers compare species that differ in longevity. Long-lived species, they've found, accumulate molecular damage more slowly than shorter-lived ones do. Naked mole rats, for example, have an unusually accurate ribosome, the cellular structure responsible for assembling proteins. It makes only a tenth as many errors as normal ribosomes. And it's not just mole rats: In a follow-up study comparing 17 rodent species of varying longevity, researchers found that the longer-lived species, in general, tended to have more accurate ribosomes.
One of the principles beginning to emerge from comparative studies of aging is that different species may follow different paths to longevity. All long-lived mammals need to delay the onset of cancer, for example. Elephants do this by having multiple copies of key tumor-suppressing genes, so that every cell has backups if one gene breaks during the wear and tear of life. Naked mole rats, on the other hand, gain cancer resistance from an unusual molecule involved in sticking cells together, while bowhead whales have amped up their DNA-repair pathways.
Link: https://www.theatlantic.com/science/archive/2021/05/worlds-oldest-animals-whale-bats/618824/