A healthy microbiome may be necessary for muscle growth

US researchers have found that, in order for muscles to grow following exercise in mice, an intact microbiome is necessary.

The gut microbiome refers to the trillions of bacteria (and other microbes) that live inside our digestive systems. Over the last decade, research has found that these bacteria make substances that are needed for our health, with some studies suggesting the gut microbiome may also be important for the health of skeletal muscles. But is a healthy gut microbiome necessary for skeletal muscle to adapt to exercise?

To answer this question, researchers led by the University of Kentucky let mice voluntarily exercise on running wheels every day for nine weeks, with some mice administered antibiotics through their drinking water. The antibiotic treatment killed the bacteria of the gut microbiome. They then compared the muscles of healthy mice to the mice without an intact microbiome to see if the muscles adapted differently to wheel running.

The researchers found that the muscles of mice without an intact microbiome did not grow as much as the muscles of healthy mice, even though both groups of mice ran the same amount over the nine weeks of wheel running. These findings, published in The Journal of Physiology, indicate that a healthy gut microbiome is necessary for skeletal muscles to fully grow after exercising. They contribute to a growing body of evidence showing a connection between the gut microbiome and skeletal muscles, and suggest the gut microbiome makes substances that help skeletal muscles to become larger after exercising.

Although the researchers used a relatively low dose of antibiotics compared to previous studies, a limitation of the study is that they do not know if the antibiotics might have directly affected the ability of skeletal muscle to adapt to exercise. They also only used female mice in this initial study, so they do not know if the findings will be the same in male mice or if the findings will translate into humans.

Nevertheless, if further research can identify the substances that the bacteria of the gut are making to help muscles grow following exercise, we might be able to use some of those substances to promote the growth of muscles in people suffering from the loss of muscle as typically seen with ageing or cancer.

“From an athletic standpoint, world-class runners were found to have more of a particular type of bacteria that provided an additional source of energy which was thought to help them run faster,” said Kentucky’s John McCarthy, senior author on the study. “Thus, the gut microbiome makes substances that appear to be important for skeletal muscles to fully adapt to exercise as well as help improve athletic performance.

“We are currently trying to determine how exercise changes the composition and function of the gut microbiome. This investigation, along with other studies in bacteria, will allow us to identify the substances made by the gut microbiome that help skeletal muscle to grow larger in response to exercise.”

Image credit: ©stock.adobe.com/au/antondotsenko

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