Glucose and pyruvate tolerance tests

For pyruvate or glucagon tolerance test, fasted HFD-fed mice were treated with oral administration of astragaloside IV (50, 100 mg/kg) or metformin (200 mg/kg). Then after 2 h, mice were intraperitoneally injected with pyruvate (2 g/kg) for pyruvate tolerance test, or orally administrated with glucose (2.0 g/kg) for glucose tolerance test. Blood samples were collected from the orbital sinus at regular intervals for the assay of glucose using a commercial Kit. Blood glucose area under curve (AUC) was calculated as the follows: 0.5 × [Bg0 + Bg0.5]/2 + 0.5 × [Bg0.5 + Bg1.0]/2 + [Bg1 + Bg2]/2 (Bg0, Bg0.5, Bg1.0, and Bg2.0 referred to the blood glucose content at 0, 0.5, 1.0, and 2.0 h).