Non-obese diabetic (NOD) mice

A total of 100 female NOD mice aged 6 weeks old, weighing 16–20 g, were purchased from the Nanjing Laboratory Animal Center (Nanjing, China). Mice were fed specific pathogen-free grade mouse chow and water ad libitum. Animals were housed at a temperature of 22–23°C and a humidity of 60%, with a 12 h light/dark cycle. The fasting plasma glucose (FPG) of all mice were examined at day 7 after mice were obtained. Notably, NOD mice can spontaneously develop type 1 diabetes and are useful animal diabetic models (24). Mice with an FPG ≥16.6 mmol/l that occurred twice on different days that was confirmed by pathological examination were considered as diabetic mice. Cells that exhibited a significant decrease in islet β cells or isletitis were considered diabetic for the purposes of the present study.