This gut microbe may help keep you strong as you age

A specific type of gut bacterium, Roseburia inulinivorans, may contribute to enhanced muscle strength and performance in older individuals, according to research published in the journal Gut. The study, conducted by scientists from the Netherlands and Spain, found that this bacterium could be developed into a probiotic to combat age-related muscle wasting.

Muscle mass and strength often decline with age, leading to frailty, reduced mobility, and poorer overall health. Previous research has linked gut bacteria to various health issues, including metabolic, neurodegenerative, and cardiovascular diseases, as well as muscle mass and function control. Researchers analyzed stool samples from 90 young adults aged 18-25 and 33 older adults aged 65+.

Physical fitness was assessed using hand grip strength, leg press, bench press performance, and VO2 max, a measure of cardiorespiratory fitness. Among the detected bacteria, only Roseburia showed a positive association with muscle mass and strength. R faecis and R intestinalis, other Roseburia species, did not exhibit significant associations with muscle strength or cardiorespiratory fitness.

In older participants, those with detectable levels of R inulinivorans had 29% greater handgrip strength compared to those who lacked the bacterium. This difference persisted without a corresponding increase in peak oxygen uptake, suggesting improved fitness. Younger adults with higher levels of R inulinivorans also exhibited stronger handgrip strength and higher VO2 max.

The researchers propose that different Roseburia species might influence specific aspects of muscular performance. Among the older participants, R inulinivorans' relative abundance was lower compared to younger adults, and its abundance generally decreases with age, which aligns with the increased prevalence of sarcopenia, or muscle loss, in older age.

The study also involved mice subjected to antibiotic treatment to eliminate their gut microbiome, followed by weekly administration of Roseburia species for 8 weeks. Mice receiving R inulinivorans experienced a 30% increase in forelimb grip strength, observable after 4, 6, and 8 weeks of treatment. They developed larger muscle fibers and a higher proportion of fast-twitch (type II) fibers in the soleus muscle of their calf.

However, this difference was not significant when comparing R inulinivorans-treated mice specifically with those treated with R intestinalis. The altered muscle fibers were accompanied by changes in metabolic proteins and enzymes responsible for energy production in muscles. The study acknowledges several limitations, including the temporary colonization of human Roseburia species in mice, the absence of direct examination of certain pathways like inflammation or neuromuscular signaling, and the need for long-term research to determine if changes in R inulinivorans levels cause muscle function changes or if the bacterium's abundance changes due to variations in muscle function.

Nevertheless, the findings suggest a gut-muscle axis where R inulinivorans positively modulates muscle metabolism and strength, and its abundance may decline with advancing age, implying a potential role for R inulinivorans as a probiotic candidate for combating age-related muscle wasting.