Puerarin Protects Pancreatic β-Cells in Obese Diabetic Mice via Activation of GLP-1R Signaling

Diabetes is characterized by a loss and dysfunction of the beta-cell. Glucagon-like peptide 1 receptor (GLP-1R) signaling plays an important role in beta-cell survival and function. It is meaningful to identify promising agents from natural products which might activate GLP-1R signaling. In this study, puerarin, a diet isoflavone, was evaluated its beneficial effects on beta-cell survival and GLP-1R pathway. We showed that puerarin reduced the body weight gain, normalized blood glucose, and improved glucose tolerance in high-fat diet-induced and db/db diabetic mice. Most importantly, increased beta-cell mass and beta-cell proliferation but decreased beta-cell apoptosis were observed in puerarin-treated diabetic mice as examined by immunostaining of mice pancreatic sections. The protective effect of puerarin on beta-cell survival was confirmed in isolated mouse islets treated with high glucose. Further mechanism studies showed that the circulating level of GLP-1 in mice was unaffected by puerarin. However, puerarin enhanced GLP-1R signaling by up-regulating expressions of GLP-1R and pancreatic and duodenal homeobox 1, which subsequently led to protein kinase B (Akt) activation but forkhead box O1 inactivation, and promoted beta-cell survival. The protective effect of puerarin was remarkably suppressed by Exendin(9-39), an antagonist of GLP-1R. Our study demonstrated puerarin improved glucose homeostasis in obese diabetic mice and identified a novel role of puerarin in protecting beta-cell survival by mechanisms involving activation of GLP-1R signaling and downstream targets.