Mouse blood glucose, oral glucose tolerance test and insulin tolerance test

Blood glucose was measured using the glucose dehydrogenase method with the Glucose Oxidase kit (Applygen Technologies Inc., Beijing, China). Briefly, the sample was mixed with the working solution and incubated at 37 °C for 20 min. FBG was calculated using an absorbance reading at 550 nm.

The oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) experiments were performed in each group of mice at week 6. For OGTT, mice were fasted overnight and then orally administrated 2 g·kg⁻¹ glucose. FBG was measured at time 0 (before glucose administration), 30, 60 and 120 min. The area under the curve (AUC) of the OGTT was calculated. For ITT analysis, mice were fasted without access to water for 4 h, and then subcutaneously injected with 1 U·kg⁻¹ insulin (Jiangsu Wanbang Biochemistry Medicine Company, Xuzhou, China). FBG was measured at time 0 (before injection), 30, 60, 90 and 120 min. The AUC of the ITT was then calculated.