Allicin ameliorates glucose and lipid metabolism via modulation of gut microbiota and bile acid profile in diabetic rats

Diabetes mellitus is a widely prevalent chronic disease, and effective treatments for it remain limited. Allicin has anti-diabetic effect, however, the detailed mechanism has not been well investigated. The diabetic rats were treated with allicin for 6 weeks, and then the fecal samples, serum and tissues were collected for measurement of gut microbiota (GM), bile acids (BAs) and other indexes. Allicin decreased the blood glucose levels, serum lipid levels, and alleviated hepatic lipid deposition of the diabetic rats. Simultaneously, allicin changed the composition of GM and increased secondary BAs in serum. Interestingly, allicin significantly increased the glucagon-like peptide-1 (GLP-1) content in colon homogenate, and reduced the protein expression of fibroblast growth factor 15 (FGF15) in ileum. Moreover, allicin increased 7α-hydroxylase 1 (CYP7A1) expression in liver. The study demonstrated that allicin ameliorates metabolisms in the diabetic rats though modulating gut microbiota, bile acids, and inhibiting enterohepatic FGF15-CYP7A1 signaling.