This protein may help cut flab without moving a muscle

Called 'Sestrin', the protein might harness the benefits of a good workout without ever moving a muscle, say researchers from University of Michigan.

While studying a class of naturally-occurring protein called Sestrin, they 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 ageing and other causes.

Researchers have previously observed that Sestrin accumulates in muscle following exercise," said Myungjin Kim, research assistant professor in the Department of Molecular & Integrative Physiology.

Kim, working with professor Jun Hee Lee and a team of researchers wanted to know more about the protein's apparent link to exercise.

Taking advantage of Drosophila flies' normal instinct to climb up and out of a test tube, their collaborators from Wayne State University in Detroit developed a kind 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," said 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," Lee said, adding that this kind of combined effect is important for producing exercise's effects.

Lee also helped another collaborator, Pura Munoz-Cánoves 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," Lee said.

Could Sestrin supplements be on the horizon? Not quite, said Lee, adding that Sestrins are not small molecules, but "we are working to find small molecule modulators of Sestrin".