Whether it be a brisk walk around the park or high intensity training at
the gym, exercise does a body good. But what if you could harness the benefits
of a good workout without ever moving a muscle?
Michigan
Medicine researchers studying a class of naturally occurring protein called
Sestrin have found that it can mimic many of exercise’s effects in flies and
mice. The findings could eventually help scientists combat muscle wasting due
to aging and other causes.
“Researchers
have previously observed that Sestrin accumulates in muscle following
exercise,” said Myungjin Kim, Ph.D., a research assistant professor in the
Department of Molecular & Integrative Physiology. Kim, working with
professor Jun Hee Lee, Ph.D. and a team of researchers wanted to know more
about the protein’s apparent link to exercise. Their first step was to
encourage a bunch of flies to work out.
Taking advantage of Drosophila flies’ normal
instinct to climb up and out of a test tube, their collaborators Robert
Wessells, Ph.D. and Alyson Sujkowski of Wayne State University in Detroit
developed a type of fly treadmill. Using it, the team trained the flies for
three weeks and compared the running and flying ability of normal flies with
that of flies bred to lack the ability to make Sestrin.
“Flies can
usually run around four to six hours at this point and the normal flies’
abilities improved over that period,” says Lee. “The flies without Sestrin did
not improve with exercise.”
What’s more,
when they overexpressed Sestrin in the muscles of normal flies, essentially
maxing out their Sestrin levels, they found those flies had abilities above and
beyond the trained flies, even without exercise. In fact, flies with
overexpressed Sestrin didn’t develop more endurance when exercised.
The beneficial
effects of Sestrin include more than just improved endurance. Mice without
Sestrin lacked the improved aerobic capacity, improved respiration and fat
burning typically associated with exercise.
“We propose that
Sestrin can coordinate these biological activities by turning on or off
different metabolic pathways,” says Lee. “This kind of combined effect is
important for producing exercise’s effects.”
Lee also helped
another collaborator, Pura Muñoz-Cánoves, Ph.D., of Pompeu Fabra University in
Spain, to demonstrate that muscle-specific Sestrin can also help prevent
atrophy in a muscle that’s immobilized, such as the type that occurs when a
limb is in a cast for a long period of time. “This independent study again
highlights that Sestrin alone is sufficient to produce many benefits of
physical movement and exercise,” says Lee.
Could Sestrin
supplements be on the horizon? Not quite, says Lee. “Sestrins are not small
molecules, but we are working to find small molecule modulators of Sestrin.”
Additionally,
adds Kim, scientists still don’t know how exercise produces Sestrin in the
body. “This is very critical for future study and could lead to a treatment for
people who cannot exercise.”
Journal article: https://www.nature.com/articles/s41467-019-13442-5
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