Antidiabetic effect of a newly identified component of Opuntia dillenii polysaccharides

The aim of this study was to determine the most effective hypoglycemic component of polysaccharides from Opuntia dillenii Haw. by preliminary screening and to specifically study the antidiabetic effects of O. dillenii polysaccharide (ODP)-Ia in mice with streptozotocin (STZ)-induced diabetes. Three kinds of ODPs - ODP-Ia, ODP-Ib, and ODP-II' - were isolated by using an ultrasonic extraction method and diethylaminoethyl (DEAE)-Sepharose fast-flow column chromatography. The mice were administered ODPs for 3 weeks. Gavage administration of ODP-Ia significantly decreased (P<0.05) their intake of food and water; the fasting levels of blood glucose (BG), total cholesterol (TC), triglycerides (TGs), plasma urea nitrogen (PUN), and malondialdehyde (MDA); and the activity of glucose-6-phosphatase (G-6-Pase). In contrast, it significantly increased (P<0.05) the body weights, hepatic glycogen (HG) levels, high-density lipoprotein cholesterol (HDL-C) levels, and the hepatic superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in diabetic mice. However, ODP-Ia did not significantly increase insulin levels in the mice with STZ-induced diabetes. We propose that ODP-Ia exerts its antihyperglycemic effect by protecting the liver from peroxidation damage and by maintaining tissue function, thereby improving the sensitivity and response of target cells in diabetic mice to insulin.