Effects of chitosan and its oligosaccharide on gut microbiota and metabolites disturbed by excessive protein consumption in vivo and in vitro

Chitosan (CTS) and its oligosaccharide (COS) can protect against excessive protein consumption (EPC)-induced constipation by regulating gut microbiota and metabolites. The imbalanced gut microbiota was observed in whey protein isolate (WPI) group by 16S rRNA gene sequencing. However, CTS and COS treatments reversed the abundance changes of several gut microbiota, which led to the balance in the production of metabolites. Interestingly, some metabolites associated with constipation were also regulated by CTS and COS in in vitro colonic fermentation model and EPC-induced constipated rats, including nicotinamide, glutamine, proline, cysteine, choline, tryptophan, and pipecolic acid, which were mainly associated with aminoacyl-tRNA biosynthesis, arginine biosynthesis, and D-glutamine and D -glutamate metabolism pathways. In conclusion, the present study shed light on the effects of CTS and COS on EPC by regulating gut microbiota and metabolites and explored the correlation between gut microbiota and metabolites, reinforcing its potential application as a prebiotic in maintaining intestinal health.