You Old Bat; Let’s Talk the Biology of Longevity
There is a remarkable diversity of lifespans produced by evolution, but as a rule of thumb across species (but not within species) body size correlates with lifespan. The bigger you are, the longer you tend to live for a number of reasons, including a slower metabolism, and genetic safeguards against age-related conditions, amongst others. Bats, however, seem to skirt this rule.
Bats — the only flying mammal — display a few other characteristics that are unique among mammals: a low rate of tumorigenesis and an extraordinary proclivity to host viruses without presenting any signs of disease (allegedly the origin of COVID-19). Notably, they also have the longest lifespans of all mammals relative to body mass and exhibit little signs of ageing. Bats are unique not just for how long they live, but the quality of their longer lives — which does not dampen in the same pattern as other mammalian species (like humans). Some bat species can live for at least 40 years in the wild; 10 times as long as the laboratory mouse, which is roughly the same size. This biological anomaly has been difficult to research given bats nocturnal nature, flight, and general elusiveness — but the creature is aiding our own understanding of the causal mechanisms and variations of ageing.
A new study emphasizes that bats exhibit a unique, age-related gene expression pattern associated with DNA repair, immunity, and autophagy. Autophagy — Greek for self-devouring — is the process where the cell removes unnecessary or dysfunctional components — a sort of housekeeping. There are many variations of autophagy, but the process is usually similar. A membrane develops around the cellular waste, this fuses with a lysosome (remember that from middle school biology), which degrades by enzymes. The cellular waste is dissolved into constituent materials and then mostly reused (the original circular economy). Our body’s ability to autophagy is critical to cellular homeostasis, so its dysfunction has been implicated in the major functional declines that come with aging. In bats it seems that 10 genetic markers allow for autophagy to be maintained well into old age unlike in mice and humans.
It could be that at least part of bats’ longevity is the product of their adaption to flight. Flying is an intensely high metabolic activity; a consequence of which is the production of a vast number of toxic by-products and provokes a severe systemic inflammatory response called the cytokine storm leading to cellular damage and death. In addition to their increased genetic ability to perform autophagy late into their lives, bats have evolved an anti-inflammatory response that prevents the release cytokines — the facilitators of inflammation.
Enhanced autophagy and anti-inflammation have also been suggested as a part of a super anti-viral mechanism in bats, which have a proclivity for being hosts of super-viruses, despite not demonstrating clinical illness themselves. Unlike the human defense to a viral infection in which fighting the virus leads to an over-inflammatory response, bats have a distinctive parallel antiviral and anti-inflammatory response — allowing them to host otherwise harmful viruses. Beyond Covid-19, there have been several major outbreaks of deadly viral diseases, including Hendra, Nipah, Ebola virus diseases, SARS and MERS that are suspected zoonotic transmission of bat-borne viruses.
Autophagy is now being investigated as a therapeutic target against ageing and age-related diseases. There are of course major ethical issues to the extension of lifespans, especially due to human consumption patterns and population growth, but the increase of “healthspans” may make our later years more productive and fulfilling.
Derek Brooks, VP Investments
Poop core in Jamaica records 4,300 years of bat diet and environment.
World Economic Forum outlined the biggest benefit technology will have on ageing and longevity. The list emphasizes connectivity and the chance to age-in-place.
Being Mortal: Medicine and What Matters in the End by Atul Gawande addresses end-of-life care, hospice care, and also suggests that medical care should focus on well-being rather than survival.
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