The glucose tolerance test (GTT) was performed after overnight fasting (approximately 14 h). Glucose (2 mg of 10% glucose per body mass (kg)) was administered intraperitoneally, then blood glucose levels were measured from the tail-tip using a Care Touch glucometer (Future Diagnostics, Brooklyn, NY, USA) before and at 15, 30, 60, and 120 min after glucose administration. The insulin tolerance test (ITT) was performed after 8 h of fasting. Insulin (0.75 IU insulin (Novolin R Insulin, 100 UN/mL, Novo Nordisk Inc., Plainsboro Township, NJ, USA) per body mass (kg)) was administered intraperitoneally. Blood glucose levels were measured from the tail-tip using a Care Touch glucometer before and at 15, 30, 60, and 120 min after insulin administration. The time course of absolute blood glucose recorded during the ITT and the areas under the blood glucose curves (AUC) were used to evaluate insulin sensitivity. After completion of the test, the mice were returned to their home cage and given free access to food and water.
Fasting plasma insulin was measured from blood obtained during euthanasia using a mouse insulin kit (ALPCO Diagnostics, Salem, NH, USA). Absorbance at 450 nm was assessed via a microplate reader. The detailed procedure was followed according to the manufacturer’s instructions.
Fasting plasma insulin was measured from blood obtained during euthanasia using a mouse insulin kit (ALPCO Diagnostics, Salem, NH, USA). Absorbance at 450 nm was assessed via a microplate reader. The detailed procedure was followed according to the manufacturer’s instructions.