Effects of Capsaicin on the Hypoglycemic Regulation of Metformin and Gut Microbiota Profiles in Type 2 Diabetic Rats.

Dietary capsaicin (CAP), the main irritant component in pepper, can reduce the incidence of diabetes, while metformin (MET) is a first-line oral hypoglycemic drug. The purpose of this study was to investigate whether CAP on the hypoglycemic effect of MET is pertinent to gut microbiota. The glucose and insulin tolerance of diabetic rats were monitored. The glycolipid metabolism was analyzed by detecting blood biochemical parameters. Liver pathological changes were observed by Hematoxylin eosin (HE) staining. The inflammatory cytokines and intestinal tight junction proteins were detected by RT-qPCR and Western blot. 16S rRNA sequencing was employed to analyze gut microbiota profiles. The results showed that CAP and MET co-treatment could significantly reduce fasting blood glucose, improve glucose tolerance, lessen liver injury and inflammatory infiltration, down-regulate inflammatory cytokines and up-regulate intestinal tight junction proteins in diabetic rats by comparing it with MET monotherapy. Moreover, CAP and MET co-treatment altered gut microbiota profiles by regulating microbials' abundances such as Akkermansia. In conclusion, CAP showed the significant hypoglycemic effect of MET and remodulated gut microbiota profiles in diabetic rats.