Therapeutic effect of catalpol on type 2 diabetic mice induced by STZ and high-fat diet and its possible mechanism

To explore the therapeutic effect and possible mechanism of catalpol on type 2 diabetic mice. Twenty-four C57/BL6 male mice were randomly divided into four groups—normal control group (CON, n = 6), diabetic model group (DM, n = 6), the lower dose catalpol treatment (80 mg/kg body weight) group (DM+L, n = 6), and the higher dose catalpol treatment (160 mg/kg body weight) group (DM+H, n = 6). Intraperitoneal glucose tolerance test was performed after 30 days of treatment. Fasting blood glucose (FBG), triglyceride (TG), and total cholesterol (TC) in serum were detected by full automatic biochemical instrument. Enzyme-linked immunosorbent assay was used to detect insulin levels in serum. Insulin resistance level was calculated by trapezoid rule. The morphological changes of pancreatic tissue were observed through HE staining. The protein levels of insulin receptor substrate 1 (IRS1) and glucose transporter type 4 (GLUT4) in the liver and muscle were measured by Western blot (WB). Compared with the DM group mice, the glucose tolerance and insulin resistance in the DM+H group and the DM+L group were improved, the levels of TG, TC, and FBG decreased (p < 0.01). The blood insulin levels were elevated in the DM+H group and the DM+L group (p < 0.01) and the insulin resistance level decreased (p < 0.01, p < 0.05). IRS1 and GLUT4 protein levels in the liver and muscle increased in the DM+H group and the DM+L group (p < 0.01, p < 0.05). Catalpol could be potential medicine to treat type 2 diabetes. Its therapeutic mechanism might be improving insulin-stimulated glucose uptake in the liver and muscle.