Specific PERK inhibitors enhanced glucose-stimulated insulin secretion in a mouse model of type 2 diabetes

We have reported that partial PERK attenuation using PERK inhibitors (PI) enhanced glucose-stimulated insulin secretion (GSIS) from pancreatic islets and mice through induction of ER chaperone BIP. Therefore, we investigated if PI would have the same effects in a diabetic condition as well.

GSK2606414 was treated to mouse islets under 20-mM glucose and 0.5-mM palmitate to examine GSIS. To generate a mouse model of type 2 diabetes mellitus (DM), male C57BL/6J mice were fed with high-fat diet and injected with streptozotocin. Several doses (6-16 mg/kg/day) of GSK2656157 and glimepiride were administrated to the mice for 8 weeks, and metabolic phenotypes were evaluated such as body weight, blood glucose levels, insulin secretion and sensitivity, and then changes in the pancreas were measured.

High-glucose and palmitate treatment significantly increased PERK phosphorylation in the isolated islets. Suppression of GSIS and glucose-stimulated Ca²⁺ transit was also observed. PI at 40 nM which decreased PERK phosphorylation by 40% significantly recovered the GSIS and cytosolic calcium. In the mice where significant weight gain and prominent hyperglycemia were induced, PI at 10 mg/kg/day significantly enhanced GSIS and reduced blood glucose levels compared to the vehicle. The effects were similar to those by 10 mg/kg/day of glimepiride. Administration of PI did not induce changes in beta cell mass or pancreatic insulin contents, however, high dose PI decreased pancreatic weight.

PI at low dose significantly enhanced GSIS in vitro and in vivo under metabolic stress and improved hyperglycemia in the mice mimicking type 2 DM, suggesting a potential as a new therapeutic approach for type 2 DM.