Streptozotocin-Induced Diabetic Mouse Model

Streptozotocin (STZ) was used to prepare the diabetic mouse model. STZ is a nitrosourea analogue that causes insulin-dependent DM [8 (link)]. STZ (FUJIFILM Wako Pure Chemical Co., Ltd., Tokyo, Japan) was intraperitoneally (i.p) injected at 200 mg/kg of body weight dissolved in an ice-cold 0.1 M citrate buffer. Control mice received an equal volume of citrate buffer by i.p. injection. Blood glucose levels were measured with LabAssay^™ Glucose (FUJIFILM Wako Pure Chemical Co., Ltd.). One week after the STZ injection, DM was confirmed by the presence of hyperglycemia, and only mice with blood glucose levels >16.7 mmol/l were included in this study. Mice that did not become DM and mice weighing < 20 g at 10–12 weeks old were not used. We used insulin (Lantus insulin glargine, Sanofi-Aventis, Bridgewater, NJ) to temporarily decrease blood glucose levels and maintain glucose levels between 100 and 200 mg/dl. Insulin at a dose of 1.5 U/kg was subcutaneously injected 3 hours before measuring blood glucose levels. The dose of STZ and insulin was determined based on a previous report [9 (link),10 (link)].