Anti-diabetic effect of 13d in the STZ-induced diabetic mouse model. (A) Fasting blood glucose levels were measured in STZ-injected mice treated with vehicle control (n = 6) or 13d (n = 7). C57BL/6J mice were injected intraperitoneally once daily for 5 days with STZ (50 mg/kg body weight) and with either vehicle (n = 6 mice) or 13d (5 mg/kg body weight; n = 7 mice). Injections of vehicle or 13d alone were then continued for 2 more weeks. (B) Glucose tolerance test. Blood glucose levels measured at indicated time points after intraperitoneal injection of glucose (2g/kg body weight). (C) Pancreases were sectioned and slides were stained with anti-insulin antibody (green, b-cell marker), anti-glucagon antibody (red, a-cell marker), and DAPI (blue). Slides were imaged with an Olympus FV1000 confocal microscope. Representative images are shown in (C). (D) Quantification of total islet area per section and b-cell number per islet. Total area of all islets per section calculated for a total of six sections using insulin-positive cells to demarcate islets. Data are the means ± SEM of six sections from three mice. *p < 0.05 **p < 0.01, and ***p < 0.001 by Student’s t-test.