Effect of Lactobacillus rhamnosus MN‐431 Producing Indole Derivatives on Complementary Feeding‐Induced Diarrhea Rat Pups Through the Enhancement of the Intestinal Barrier Function

Scope Many infants suffer from complementary feeding‐induced diarrhea (CFID). Studies have shown that intestinal microbes can enhance the intestinal barrier and prevent diarrhea by producing indole derivatives that promote pregnane X receptor (PXR) expression. Methods and Results In this study, the indole test and determination of the PXR concentration are performed on tryptophan broth cultures of 320‐suspected Lactobacillus and Enterococcus strains. Four strains that produce indole derivatives that promote the expression of PXR are screened as potential functional probiotics. Both Lactobacillus rhamnosus MN‐431 ( L. rhamnosus MN‐431) and Lactobacillus oris FN‐448 ( L. oris FN‐448) can colonize the intestine of rat pups, and L. rhamnosus MN‐431 can significantly decrease the incidence of diarrhea and intestinal permeability in rat pups. Using real‐time qPCR and the analysis of the intestinal morphology using immunohistochemistry, it is observed that the metabolized tryptophan from L. rhamnosus MN‐431 can reduce small intestinal mucosal damage by stimulating PXR/NF‐κB signaling and activating PXR and aryl hydrocarbon receptor. The intestinal barrier is also enhanced by promoting the expression of tight junction proteins such as Occludin and zonula occludens‐1 in baby rats. Conclusion The results demonstrate that L. rhamnosus MN‐431 can metabolize tryptophan to prevent infantile CFID by promoting the expression of PXR.