A new research has found why brief bodily stresses are good for your health and longevity. It’s all about a cellular process called autophagy, that’s key for extending lifespan and is also critical to the benefits of temporary stress.

Brief heat shock reduces protein aggregation in a C. elegans model of Huntington’s disease.
Credit: Caroline Kumsta, Ph.D.

The old saying has it right. Biologists have known for quite a while that enduring a short period of (mild) stress makes simple organisms and human cells survive additional stress later in life. In other words, what doesn’t kill you (and does not cause permanent damage) does make you stronger. Now, researchers believe they finally know why. The key is autophagy — a natural, destructive mechanism of the cell that disassembles unnecessary or dysfunctional components. It’s a way of recycling cells’ old, broken, or unneeded parts so that they can be ‘reused for parts.’ Autophagy had previously been linked to longevity by Malene Hansen, Ph.D., who is also the lead author of this study.

The teams incubated worms at 36 °C, significantly above the temperature they are usually kept at in the laboratory, for one hour. This certainly wasn’t pleasant for the worms, but it wasn’t life threatening. Because worms are so easy to study, they easily proved that autophagy increased after the “worm sauna.”

“We used C. elegans — tiny roundworms used to study fundamental biology — to test the importance of autophagy in becoming stress resistant,” says Caroline Kumsta, Ph.D., staff scientist in Hansen’s lab and lead author of the study. “They’re a great model system because they’re transparent, so you can easily observe what goes on inside them, most of their genes and molecular signaling pathways have functional counterparts in humans, and they only live a few weeks, which greatly facilitate measuring their lifespans.”

After this, they had a feeling such stresses might also help with another problem: the buildup of aggregated proteins, which is potentially very dangerous for cells. In order to test this, Kumsta used worms that model Huntington disease, a disorder caused by neuronal proteins that start to stick together into big clumps as patients age. She developed a similar type of experiment, exposing worms to a heat stress and then studying protein build-up. Results were similar.

“Our finding that brief heat exposure helps alleviate protein aggregation is exciting because it could lead to new approaches to slow the advance of neurodegenerative diseases such as Huntington’s,” says Hansen. “The results may also be relevant to Alzheimer’s and Parkinson’s, which are similarly caused by clumping-prone proteins.”

So the question is — should we start taking a sauna? This is just a worm study but there’s a good chance human cells will react in the same way, as lab studies have already indicated.

“A lot of people ask us if this means they should start going to the sauna or do hot yoga,” jokes Kumsta. “That may not be an entirely bad idea — epidemiological studies do indicate that frequent sauna use is associated with longer life. But we have a lot more research to do to figure out whether that has anything to do with the beneficial induction of autophagy by heat stress that we see in C. elegans.”

Journal Reference: Caroline Kumsta, Jessica T. Chang, Jessica Schmalz, Malene Hansen. Hormetic heat stress and HSF-1 induce autophagy to improve survival and proteostasis in C. elegans. Nature Communications, 2017; 8: 14337 DOI: 10.1038/ncomms14337

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