In STZ-induced diabetic rats, ER stress in the hippocampus was significantly increased, as evinced by the increase in glucose-regulated protein 78 (GRP78), cleaved caspase-12, and C/EBP homologous protein (CHOP), all of which were reversed by NaHS, indicating that H2S inhibited diabetes-associated ER stress. This evidence concerns the gene CASP12 and diabetes mellitus.