Microbiome may be involved in muscle strength mechanisms in older adults

The gut microbiome has a role in mechanisms related to muscle strength in older adults, according to a new study published in the journal Experimental Gerontology.

The gut-muscle axis, or the relationship between gut microbiota and muscle mass and physical function, has gained momentum as a research topic in the last few years as studies have established that gut microbiota influences many aspects of health. While researchers have begun exploring the connection between the gut microbiome, muscle, and physical function in mice and younger adults, few studies have been conducted with older adults.

To gain insight into this population, the researchers compared bacteria from the gut microbiomes of 18 older adults with high-physical function and a favorable body composition or higher percentage of lean mass, lower percentage of fat mass with 11 older adults with low-physical function and a less favorable body composition. The small study identified differences in the bacterial profiles between the two groups.

Similar bacterial differences were present when mice were colonized with fecal samples from the two human groups, and grip strength was increased in mice colonized with samples from the high-functioning older adults, suggesting a role for the gut microbiome in mechanisms related to muscle strength in older adults.

Specifically, when compared to the low-functioning older adult group, the researchers found higher levels of Prevotellaceae, Prevotella, Barnesiella, and Barnesiella intestinihominis, all potentially good bacteria, in the high-functioning older adults and in the mice that were colonized with fecal samples from the high-functioning older adults.

No significant differences in body composition or endurance capacity were observed in the colonized mice. However, the researchers said the length of the intervention period was short and these data may warrant further study.

For the study, the researchers measured lower extremity function, mobility, and strength in the sedentary older adult group, ages 70 to 85, at the first and one-month study visits. In the mice, they measured body composition with quantitative magnetic resonance imaging, and grip strength and treadmill endurance capacity to test physical function. Fecal samples from the older adults were transplanted into young, gender-matched germ-free mice.

Four weeks after fecal transfer, the researchers measured body composition, physical function, and gut microbiome in the 18 mice colonized with fecal samples from the high-functioning human group and the 18 mice colonized with fecal samples from the low-functioning human group. The authors note the small sample size and brief time period as potential study limitations.