Rhaponticin from Rhubarb Rhizomes Alleviates Liver Steatosis and Improves Blood Glucose and Lipid Profiles in KK/Ay Diabetic Mice

We isolated several stilbene compounds including rhaponticin (3',5-dihydroxy-4'-methoxystilbene 3-O-beta-D-glucopyranoside) from extracts of rhubarb rhizomes. These compounds showed significant hypoglycemic effects in streptozotocin (STZ)-induced type I diabetic rats and mice. In this study, we investigated the effect of rhaponticin on glucose utilization, lipid metabolism, and liver and heart function in a KK/Ay type 2 diabetic mouse model. The results showed that oral administration of rhaponticin (125 mg/kg) significantly reduced blood glucose levels and improved oral glucose tolerance of KK/Ay diabetic mice. Elevated plasma triglyceride (TG), low density lipoprotein (LDL), cholesterol (CHO), non-esterified free fatty acids (NEFA), and insulin levels were also markedly attenuated. Serum enzymatic activities of lactate dehydrogenase (LDH), creatine kinase (CK), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) in the rhaponticin-treated group significantly decreased in comparison to the untreated model group. Livers of rhaponticin-treated mice had relatively normal cellular size and decreased fibrosis and steatosis. In addition, rhaponticin administration caused a remarkable increase in the hepatic glycogen content and a significant reduction in the hepatic triglyceride content. These results indicate that rhaponticin has a noticeable antidiabetic effect and could be potentially used as a new agent to treat type 2 diabetes mellitus and its complications.