MT-α-Glucan from the Fruit Body of the Maitake Medicinal Mushroom Grifola frondosa (Higher Basidiomyetes) Shows Protective Effects for Hypoglycemic Pancreatic β-Cells

The hypoglycemic effect of an α-glucan (designated here as MT-α-glucan) from the fruit body of the Maitake medicinal mushroom, Grifola frondosa, on a murine type 2 diabetes mellitus (T2DM) model was evaluated. Body weight and levels of fasting plasma glucose, glycosylated hemoglobin, triglycerides, cholesterol, free fatty acid, nitric oxide (NO), NO synthase, inducible NO synthase, and hepatic malondialdehyde content decreased significantly when MT-α-glucan was administered to T2DM mice. The content of serum insulin, hepatic glycogen, and reduced glutathione and the activity of superoxide dismutase and glutathione peroxidase increased significantly when MT-α-glucan was administered to T2DM mice. Histopathological changes of the pancreas were ameliorated in the treatment group. These data suggest that MT-α-glucan has a hypoglycemic effect on T2DM mice, which might be related to its protective effect of pancreatic β-cells exerted by decreasing levels of factors that destroy β-cells, such as oxidative stress and NO synthesis.