2.6.1. Induction of Diabetes in Mice

Diabetes was induced in mice fasted overnight by a single intraperitoneal (ip) injection of streptozotocin (STZ; Sigma, St. Louis, MO, USA) in a dose of 45 mg/kg. The STZ was dissolved in citrate buffer as the vehicle (0.1 M, pH 4.5) before use for 15 min, then nicotinamide (110 mg/kg BW in normal physiological saline) was administered [10]. Finally, a solution of 5% glucose was provided to prevent hypoglycemia. Fasting blood glucose levels were measured for 72 h and then the STZ injection was administered with a glucometer in the blood drawn from the tail vein. Diabetes was confirmed in the mice with fasting blood glucose above 250 mg/dl (13.8 mM), which was measured by Accu-Chek Glucometer (Accu-Chek^® Active, Roche Diagnostics GmbH, Hannheim, Germany) and expressed in terms of mg/dl.