Learning how exercise works

Exercise protects against a host of illnesses, from heart attacks and dementia to diabetes and infection. How it does so, however, remains surprisingly mysterious. But a paper just published by Beth Levine of the University of Texas Southwestern Medical Centre and her colleagues sheds some light on the matter.

Dr. Levine and her team were testing a theory that exercise works its magic, at least in part, by promoting autophagy. This process, whose name is derived from the Greek for “self-eating”, is a mechanism by which surplus, worn-out or malformed proteins and other cellular components are broken up for scrap and recycled.

Dr. Levine reckons that manipulating autophagy may offer a new approach to treating diabetes. And their research is also suggestive in other ways. 

Autophagy is a hot topic in medicine, as biologists have come to realise that it helps protect the body from all kinds of ailments. 

Autophagy is an ancient mechanism, shared by all eukaryotic organisms (those which, unlike bacteria, keep their DNA in a membrane-bound nucleus within their cells). It probably arose as an adaptation to scarcity of nutrients. Critters that can recycle parts of themselves for fuel are better able to cope with lean times than those that cannot. But over the past couple of decades, autophagy has also been shown to be involved in things as diverse as fighting bacterial infections and slowing the onset of neurological conditions like Alzheimer’s and Huntington’s diseases.

Most intriguingly of all, it seems that it can slow the process of ageing. Biologists have known for decades that feeding animals near-starvation diets can boost their lifespans dramatically.

A few anti-ageing zealots already subsist on near-starvation diets, but Dr Levine’s results suggest a similar effect might be gained in a much more agreeable way, via vigorous exercise. The team’s next step is to test whether boosted autophagy can indeed explain the life-extending effects of exercise. That will take a while. Even in animals as short-lived as mice, she points out, studying ageing is a long-winded process. 

But she is sufficiently confident about the outcome that she has, in the meantime, bought herself a treadmill.