Lactobacillus plantarumDR7 Modulated Bowel Movement and Gut Microbiota Associated with Dopamine and Serotonin Pathways in Stressed Adults

We have previously reported that the administration ofLactobacillus plantarumDR7 for 12 weeks reduced stress and anxiety in stressed adults as compared to the placebo group, in association with changes along the brain neurotransmitters pathways of serotonin and dopamine-norepinephrine. We now aim to evaluate the effects of DR7 on gut functions, gut microbiota compositional changes, and determine the correlations between microbiota changes and the pathways of brain neurotransmitters. The administration of DR7 prevented an increase of defecation frequency over 12 weeks as compared to the placebo (p= 0.044), modulating the increase of stress-induced bowel movement. Over 12 weeks, alpha diversity of gut microbiota was higher in DR7 than the placebo group across class (p= 0.005) and order (p= 0.018) levels, while beta diversity differed between groups at class and order levels (p< 0.001). Differences in specific bacterial groups were identified, showing consistency at different taxonomic levels that survived multiplicity correction, along the phyla of Bacteroides and Firmicutes and along the classes of Deltaproteobacteria and Actinobacteria. Bacteroidetes, Bacteroidia, and Bacteroidales which were reduced in abundance in the placebo group showed opposing correlation with gene expression of dopamine beta hydrolase (DBH, dopamine pathway;p< 0.001), while Bacteroidia and Bacteroidales showed correlation with tryptophan hydroxylase-II (TPH2, serotonin pathway;p= 0.001). A correlation was observed between DBH and Firmicutes (p= 0.002), Clostridia (p< 0.001), Clostridiales (p= 0.001),Blautia(p< 0.001), andRomboutsia(p< 0.001), which were increased in abundance in the placebo group.Blautiawas also associated with TDO (p= 0.001), whereasRomboutsiahad an opposing correlation with TPH2 (p< 0.001). Deltaproteobacteria and Desulfovibrionales which were decreased in abundance in the placebo group showed opposing correlation with DBH (p= 0.001), whereasBilophilawas associated with TPH2 (p= 0.001). Our present data showed that physiological changes induced byL. plantarumDR7 could be associated with changes in specific taxa of the gut microbiota along the serotonin and dopamine pathways.