Differences in the gut microbiome and reduced fecal butyrate in elders with low skeletal muscle mass

Despite animal studies revealing a causal link between the gut microbiota and skeletal muscle mass, the role of the gut microbiome and its metabolites in humans having low muscle mass remains unclear.Eighty-eight subjects older than 65 years were measured for sarcopenia-related parameters, including body composition, grip strength, gait speed and flexibility. Participants were divided into normal muscle mass group (NM, n = 52) and low muscle mass group (LM, n = 36) and fresh fecal samples were collected for metagenome and short chain fatty acids (SCFAs) analysis.The richness and evenness of gut microbiota diversity were significantly decreased in the subjects with low muscle mass, including observed ASVs, Shannon and Chao 1 index. A significant difference of gut microbiota profile was noted between NM group and LM group. The Firmicutes/Bacteroidetes ratio was significantly reduced in the LM group. A significant decrease in the abundance of a SCFA-producer, Marvinbryantia spp., whereas a remarkable enrichment of a flavonoid degrader, Flavonifractor spp., was observed in the LM elders. Comparing with the NM group, the fecal butyrate significantly diminished in the LM group and correlated with skeletal muscle mass index.This is the first study that demonstrates the reduced fecal butyrate in elders with low muscle mass and highlights the associated gut microbiome changes. The identified gut microbial features and fecal butyrate level may serve as potential biomarkers for early detection of sarcopenic patients.