Stress has been shown to disturb the balance of human intestinal microbiota and subsequently cause mental health problems, such as anxiety and depression. The gut microbial communities are able to synthesize and/or consume various neuroactive metabolites, and preliminary human studies have also demonstrated the ability of probiotics to modulate the levels of neurotransmitter. However, the study and interpretation of the biological significance of microbial neuroactive compounds have been hindered by the lack of dedicated reference databases and corresponding human intestinal microbiota reference genomes. Our previous study showed that ingesting the probiotic strain, Lactobacillus (L.) plantarum P-8, for 12 weeks could alleviate stress and anxiety of stressed adults. The current study was a follow-up work aiming to further elucidate mechanisms behind the observed beneficial effects by performing deep analysis of the fecal metagenomes of the probiotic (n = 43) and placebo (n = 36) groups. Comparing with the probiotic group, the gut microbiomes of the placebo group showed significantly higher Bray-Curtis dissimilarity between weeks 0 and 12 (p < 0.05). Comparing with week 0, the Shannon diversity index of the placebo group decreased significantly at week 12 (t-test; p < 0.05), but such decrease was non-significant for the probiotic group. Additionally, the fecal metagenomes of the probiotic group showed significant increases in the species-level genome bins (SGBs) of Bifidobacterium adolescent, Bifidobacterium longum, and Fecalibacterium prausnitzii increased, while decreases in the SGBs of Roseburia faeci and Fusicatenibacter saccharivorans. Furthermore, the 12-week probiotic supplementation enhanced the diversity of neurotransmitter-synthesizing and/or -consuming SGBs, and the levels of some predicted microbial neuroactive metabolites (short chain fatty acids, gamma-aminobutyric acid, arachidonic acid, and sphingomyelin et.al). In conclusion, this study revealed the potential mechanism of probiotics in alleviating stress and anxiety via the gut-brain axis. The modulation of the intestinal microbiota by probiotics is an attractive strategy for managing stress and anxiety.
bioRxiv Subject Collection: Neuroscience