RESUMO
Berberine (BBR) is the main pharmacological active ingredient of Coptidis, which has hypoglycemic effect, but its clinical application is limited due to its poor oral bioavailability. Polyphenols, derived from cinnamon, are beneficial for type 2 diabetes mellitus (T2DM). The combination of both may have an additive effect. The aim of this study was to investigate the hypoglycemic effect and mechanism of combined medication in diabetic rats. The modeling rats were randomly divided into 5 groups (berberine group, cinnamon group, combined group, metformin group, diabetic control group) and normal control group. The animal experiments were approved by the Animal Ethics Committee (approval number: HMUIRB2022003). The subjects were given orally, and the control group was given equal volume solvent and body weight was measured weekly. Thirty days after administration, oral glucose tolerance test and insulin sensitivity test were performed, and fasting blood glucose (FBG), glycated serum protein (GSP), and serum insulin (INS) levels were detected; high-throughput sequencing technology was used to detect intestinal microbiota structure; real-time quantitative PCR (RT-qPCR) and Western blot were used to detect G protein-coupled receptor 5 (TGR5) and glucagon-like peptide-1 (GLP-1) expression levels. The results showed that, compared with the diabetic control group, the levels of FBG (P < 0.01) and GSP (P < 0.01) in the combined group were lower, and the insulin resistance was improved, which was better than that in the berberine group. Combined treatment increased the relative abundance of Bacteroides, Prevotella and Lactobacillus, reversed the decrease in Lactobacillus in the berberine alone induction group, and the combination of the two could promote the expression of TGR5 and GLP-1. In summary, the combined application of cinnamon and berberine can regulate glucose metabolism better than the application of berberine alone. Berberine combined with cinnamon can improve the function of pancreatic islet β cells in diabetes mellitus type 2 rats by changing the intestinal microbiota, increasing the expression of TGR5 and GLP-1 proteins, and thereby better regulating glucose metabolism.