Glucose, insulin, and pyruvate tolerance tests.

For glucose tolerance test (GTT), mice were fasted overnight and intraperitoneally injected with glucose (1 g/kg body weight). For insulin tolerance test (ITT), mice were fasted for 4 hours and intraperitoneally injected with human insulin (0.75 U/kg body weight). For pyruvate tolerance test (PTT), mice were fasted for 6 hours and intraperitoneally injected with pyruvate (1 g/kg body weight). Blood samples were collected from tail veins 0, 15, 30, 60, and 120 minutes after injection and used to measure blood glucose levels. Plasma insulin levels were measured using mouse insulin ELISA kits (Crystal Chem).