INS and type 1 diabetes mellitus: GSIS tests showed that under high glucose stimulation (20 mM incubation for 30 min), T1DM and nondiabetic (ND) SC-β cells secreted 2.0 ± 0.4 and 1.9 ± 0.3 mIU of human insulin per 103 cells, respectively, and both of these cells functioned similarly to adult primary islets in a previous study.