Microbe Found in Human Gut May Enhance Muscle Strength

Recent research indicates a particular microbe in the human gut could play a role in increasing muscle strength.

The intestinal tract hosts a myriad of microorganisms that greatly influence overall health. Known as the gut microbiome, these tiny entities are involved in many bodily functions, including digestion, metabolism, and aspects like immune response, sleep, brain function, and even neurodevelopment.

A new study sheds light on another potential benefit provided by at least one type of gut microbe: enhancing muscle strength.

Not only does the study illustrate this interesting link between gut bacteria and muscle functionality, but it also identifies a specific bacterium from the Roseburia genus as the microbe linked to this effect.

Despite previous knowledge of gut microbes’ importance, not much had been known about their influence on muscle strength, the authors noted, and no specific bacteria were recognized as direct modulators of that function.

By establishing this connection, researchers strengthen the argument for a “gut-muscle axis,” similar to the better-known gut-brain axis, according to Jonatan Ruiz, an exercise physiologist from the University of Grenada in Spain.

“Overall, our findings provide strong evidence revealing a gut-muscle axis where this identified bacterium positively impacts muscle metabolism and strength,” Ruiz explains.

To explore the relationship between specific gut microbes and muscle strength, the researchers analyzed stool samples from two distinct groups: 90 young adults aged 18 to 25 and 33 seniors aged 65 and older.

Most participants led pretty sedentary lifestyles, engaging in less than 20 minutes of exercise on fewer than three days per week. They also maintained a stable weight over the last three months and were non-smokers.

Participants underwent comprehensive assessments of muscle power, including tests for hand grip, leg strength, and upper body power. Additionally, their maximum oxygen consumption was evaluated to gauge cardiorespiratory fitness.

The stool samples displayed extensive microbial diversity, but bacteria from the Roseburia genus emerged as noteworthy due to positive associations with “muscle-related metrics.”

While some Roseburia species didn’t show any connection to the study’s parameters, others demonstrated varying links with certain muscle assessments. For instance, Roseburia intestinalis was evidently connected to leg and upper body strength among young adults.

However, Roseburia inulinivorans particularly drew the researchers’ focus. Its relative abundance was positively linked to multiple strength measurements in humans, such as grip strength and leg press.

The study found that older adults carrying this microbe in their stool exhibited nearly a 30 percent stronger grip compared to those without it.

Also, it seemed to benefit younger individuals; a higher presence of R. inulinivorans was associated with improved grip strength and enhanced cardiorespiratory fitness.

Additional experiments with mice aimed to explore causality and mechanisms observed in humans. The researchers used antibiotics to disrupt the gut flora in mice and then reintroduced bacteria from human intestines over eight weeks.

They reported that R. inulinivorans led to a significant increase in the mice’s forelimb grip strength, about 30 percent higher than the control group.

Beyond muscle performance, the study revealed that mice receiving this bacterium also developed more fast-twitch muscle and larger muscle fibers in the soleus, an essential muscle located in the back of the lower leg.

The findings indicate that R. inulinivorans alters amino acid metabolism, activating pathways that promote muscle fiber growth and a focus on fast-twitch fibers.

Although further research is necessary, this study could lead to developing probiotics aimed at helping individuals maintain muscle strength and fitness as they age, the researchers noted.

“This opens the door to possibilities of using this bacterium as a probiotic to assist with preserving muscle strength during aging,” says Borja Martínez Téllez, an endocrinologist from the University of Almería in Spain.

The study was published in Gut.