Hibernating Squirrels Can Teach Astronauts Metabolic Treat to Prevent Muscle Loss

During hibernation, bears and ground squirrels stop eating until the spring comes. They rely solely on the fat reserves they have stored up in their bodies so they would not experience muscle loss and reduction in the function of the muscle. But scientists are yet to find out about the mechanism behind this.

But, new research led by researchers from Université de Montréal claimed to have figured it out, and the implications of its findings could be used for the future of space travel. They studied the so-called 13-lined ground squirrel commonly found in North America and confirmed the theory of "urea nitrogen salvage" that was first theorized in the 1980s.

What is Urea Nitrogen Salvage?

A correct balance of Nitrogen is essential for life. According to a 2005 paper in Nutrition Research Reviews, mammals' major sources of nitrogen are the amino acids and peptides derived from ingested proteins.

In mammalian catabolism, its immediate end product is ammonia that is further broken down and results in the formation of urea. But mammals cannot break down urea, which is a by-product that is found in urine. But urea in the bloodstream can pass through the gastrointestinal tract, where the bacteria utilizes the ammonia as a nitrogen resource and produce amino acids and peptides necessary for growth.

These microbial products can be absorbed back into the body in a process known as "urea nitrogen salvaging" (UNS), used for synthetic processes.

How Could Scientists Use Urea Nitrogen Salvage in Space Travel?

The urea nitrogen salvage is supposedly the metabolic trick hibernating squirrels do to maintain muscle mass even after months of hibernation. But how could this be applied to space travel?

According to Phys.org, researchers posit that the same principle could be applied in helping astronauts minimize their muscle loss problems when in space. Astronauts usually lose muscle mass due to microgravity-induced suppression of protein synthesis, which they try to reduce by intense exercise while deployed in space.

If this metabolic trick could work on them, it would augment astronauts' muscle protein synthesis processes to achieve better muscle health during long voyages into the deep space in a spacecraft that is too tight or small for an exercise machine to fit.

Researchers said that since muscle proteins are suppressed during spaceflight, these proteins can be compared to those enhanced by urea nitrogen salvage during hibernation.

To further enhance their hypothesis, researchers are continuing their work through a Canadian Space Agency research grant at UdeM. Biologist Matthew Regan from UdeM said that this process might benefit muscle health during spaceflight if they could prove that there is an overlap of proteins observed during space travel and the ones during hibernation.

Researchers described the full findings of their study, titled "Urea Nitrogen Recycling via Gut Symbionts Increases in Hibernating Ground Squirrels Over the Winter," which was published in Science.

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