Glucose-stimulated insulin secretion (GSIS)
The islets were seeded and pretreated in high glucose/STZ with/without OGT2115 for 24 h. The islets were then rinsed and incubated for 1 h at 37°C in Krebs-Ringer bicarbonate (115 mM NaCl, 24 mM NaHCO3, 5 mM KCl, 2.5 mM CaCl2, 1 mM MgCl2, 10 mM HEPES, and 0.2% bovine serum albumin, pH =7.2) containing 5 mM or 25 mM glucose. After incubation, the supernatant was collected and the concentration of insulin was measured with a radioimmunoassay (RIA) kit (Beijing North Institute of Biological Technology, Beijing, China).