Research suggests a healthy gut microbiome can help you retain muscle mass

 

During hibernation, mammals will go without food or water and rest in a catatonic state for months on end. However, at the end of it all, these animals will continue about their business as if nothing had happened. Part of understanding this mystery is to find out how mammals prevent the degradation of their muscles during long periods of inactivity. New research on thirteen-line squirrels suggests that microbes in the gut are responsible.

A thirteen-lined squirrel presenting its signature stripes. They hold the key to understanding the mechanisms that make hibernation possible for mammals. 

Research was conducted to investigate how thirteen-lined squirrels can maintain their muscle mass over long periods of hibernation in the wintertime. They hypothesized that squirrel's maintain the energy by  breaking down muscle proteins throughout their body. This process produces ammonium, a nitrogen containing substance, which their body converts to urea. Urea is transported to the stomach where gut microbes convert the urea into carbon dioxide and ammonium using enzymes known as ureases. These microbes convert the nitrogen in the ammonium to create amino acids, the building blocks of protein. The process proposed is called the urea nitrogen salvage, and it is the principle that explains how thirteen-lined squirrels effectively “recycle” their muscle mass, and it is all made possible by microbes in their stomach.

In their experiment they compared three different groups of squirrels, an active group of squirrels in the summer, and two hibernating groups in the winter, one after a month of fasting and another after three months of fasting. In each group, they split the population in two: one group with healthy gut microbes and another group which was given antibiotics to kill all their healthy gut bacteria. They identified a bacteria from the genus Alistipes that was able to breaks down urea to be responsible for higher nitrogen retention in their squirrel population. 

While these results seem to be only relevant for squirrels, humans also contain the biological mechanisms required for urea nitrogen salvage. Through changing human microbiomes, we may be able to maintain muscle mass. For those who are inactive for prolonged period, like people suffering from a condition that forces them to be bed-ridden, adjusting the microbiome may be the key to recovery. These results may also help those with muscle loss such as older people and those who are malnourished. To make this application possible, further research is being conducted into a pre/pro-biotic that may be used to conserve muscle protein in humans.