Life Wellbeing Exercise pill on the way? For fruit flies and mice, yes. Humans, keep on jogging
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Exercise pill on the way? For fruit flies and mice, yes. Humans, keep on jogging

Flies pumped up on magic protein didn't have to exercise to enjoy metabolic benefits. Protein-free flies were duds on the track. Photo: Getty
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Gym junkies sometimes bang on about protein supplements as if it’s an heroic act to drink a milkshake. But what if a protein supplement wasn’t just taking the place of food that you eat with a knife and fork, but could replace going to the gym in the first place.

In the last week, US and UK media outlets have been excited by new research that appears to have found the key to developing a pill that protects against muscle wasting and otherwise delivers many of the benefits of an aerobic workout – all without raising a sweat or gasping for breath.

The research, from the University of Michigan, has profound implications for the mental and physical wellbeing of people who can’t engage in aerobic exercise – or simply get around – because of unhealthy ageing, illness and injury.

So where does this magic protein come from?

The protein is a naturally occurring chemical called Sestrin that was known to suppress mechanical and oxidative stress in muscles during exercise.

“Researchers have previously observed that Sestrin accumulates in muscle following exercise,” said Dr Myungjin Kim, a research assistant professor in the university’s Department of Molecular & Integrative Physiology, and one of the co-authors of a paper published this week in Nature.

Dr Kim and company wanted to know more about the protein’s apparent link to exercise. Their first step, according to a statement from the University of Michigan, “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, the scientists “developed a type of fly treadmill.”

They employed two teams of fruit flies: one of them normal, the other genetically bred to lack the ability to make Sestrin.

The flies for were trained for three weeks, the competing teams observed and compared in running and flying ability, and endurance.

“Flies can usually run around four to six hours at this point and the normal flies’ abilities improved over that period,” says Professor Jun Hee Lee, one of the paper’s corresponding authors.

“The flies without Sestrin did not improve with exercise.”

That is, they lacked the improved aerobic capacity, improved respiration and fat burning typically associated with exercise.

What happens if you’re heavily dosed on this stuff?

When normal flies over-expressed Sestrin in their muscles – “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 over-expressed Sestrin “didn’t develop more endurance when exercised.”

In other words – and this will be music to the ears of couch potatoes –  the protein did all the work for them.

Professor Lee suggests that Sestrin works to coordinate aerobic capacity, improve respiration and fat-burning “by turning on or off different metabolic pathways.”

“This kind of combined effect is important for producing exercise’s effects,” he said.

In a separate study, Sestrin was found to help prevent atrophy in a muscle that’s immobilised, “such as the type that occurs when a limb is in a cast for a long period of time.”

In experiments with mice, Sestrin deficiency was again linked to poor performance in physical tests.

Does any of this relate to humans?

Maybe. As the authors write: “Using mice and Drosophila, phylogenetically distant species, we showed that Sestrin’s role in mediating exercise, increasing physical endurance, and improving metabolism is highly conserved across the animal kingdom.

“Therefore, Sestrin may serve as a promising therapeutic molecule for obtaining exercise-like benefits such as improving mobility and metabolism.”

But Sestrins are not small molecules and the development of a protein supplement is proving to be complex and challenging. Still, the researchers are on to it.

Also, the scientists 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,” said Professor Lee.

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