Hypoglycemic, hypolipidemic and antioxidant effects of Sarcandra glabra polysaccharide in type 2 diabetic mice

Sarcandra glabra (Thunb.) Nakai is a traditional Chinese herbal medicine and dietary supplement used for treating several diseases. The anti-diabetic activity of S. glabra polysaccharides is reported for the first time. The in vitro alpha-glucosidase inhibition assay indicated that the acidic S. glabra polysaccharide (SGP-2) has an IC50 of 87.06 +/- 11.76 mu g mL(-1), which was much lower than acarbose at 338.90 +/- 46.86 mu g mL(-1). Moreover, high fat diet (HFD) with streptozotocin (STZ) induced diabetic mice were administered SGP-2 (150, 300, or 600 mg kg(-1) per day, respectively) for 3 weeks. Postprandial blood glucose levels (PBGL), total cholesterol, triglyceride and free fatty acid levels in diabetic mice treated with SGP-2 were significantly decreased (p < 0.05) compared to those of the model group. The results of the oral glucose tolerance test (OGTT) and the homeostasis model assessment-insulin resistance (HOMA-IR) index indicated that SGP-2 could significantly improve (p < 0.05) the insulin resistance and glucose tolerance in diabetic mice. Furthermore, the activities of antioxidant enzymes, hexokinase and pyruvate kinase were significantly increased (p < 0.05) in SGP-2 treated groups. Thus we proposed that SGP-2 exerted hypoglycemic activity by relieving insulin resistance, reducing postprandial blood glucose levels and ameliorating lipid metabolism, as well as alleviating oxidative stress. These data suggested that SGP-2 with anti-hyperglycemic activity could be used in medicinal preparations for diabetes mellitus and its complications.