Metabolic shifts and structural changes in the gut microbiota upon branched-chain amino acid supplementation in middle-aged mice

The importance of gut microbiota to health has gained extensive attention and is strongly correlated with diet. Dietary supplementation with a branched-chain amino acid-enriched mixture (BCAAem) exerts a variety of beneficial effects in mice and humans. In mice, BCAAem supplementation can promote longevity, but its influence on the gut ecosystem and the underlying mechanism remain unclear. To address this issue, BALB/C mice were fed a BCAAem-supplemented diet and their gut microbiomes were analysed by 16S rDNA sequencing. Quantitative polymerase chain reaction was performed to identify Bifidobacterium spp. in the gut, and gas chromatography-mass spectrometry was conducted for faecal-metabolite detection. The results showed that the structure of the gut microbiota changed, and BCAAem-supplementation in mice slowed the change speed of gut microbiota which is due to age. In addition, the abundance of the Akkermansia and Bifidobacterium increased in BCAAem-supplemented mice, while the ratio of Enterobacteriaceae decreased in BCAAem-supplemented mice. Moreover, 12 different metabolites, representing sugar and lipid metabolism, were altered between the supplemented and control groups. Thus, BCAAem influences the gut microbiota and gut metabolism. In addition, the BCAAem-supplemented group presented lower serum concentrations of lipopolysaccharide-binding protein. The changes are indicative of lower antigen loads in the host gut. These results suggest that dietary supplementation with BCAAem may be considered for improving health and promoting healthy aging.