Activated PPARß/δ Protects Pancreatic ß Cells in Type 2 Diabetic Goto-Kakizaki Rats from Lipoapoptosis via GPR40.

GW501516-activated peroxisome proliferator-activated receptor (PPAR) ß/δ and G-protein-coupled receptor (GPR) 40 were shown to protect pancreatic ß cells against lipoapoptosis. Therefore, this study aimed to investigate whether activated PPARß/δ could protect type 2 diabetic rats from lipoapoptosis through regulation of GPR40 and to compare the protective effects of activated PPARß/δ and PPARγ. We made an animal model of type 2 diabetic lipoapoptosis by feeding spontaneously type 2 diabetic Goto-Kakizaki (GK) rats with a high-fat diet (HFD) to evaluate the effects of PPARß/δ on islet ß cell apoptosis. And, treated INS-1 cells with 0.5 mM palmitate (PAM) in the absence/presence of GW501516 (a specific agonist of PPAR ß/δ) and with/without transfection of GPR40 siRNA to explore the underlying molecular mechanism. HFD aggravated GK rats' poorer INSR30, lower mass, greater apoptosis of ß cells, lower mass, and lower expression of GPR40, which were similarly improved by GW501516 at 3 or 6 mg/kg day and pioglitazone. Compared with pioglitazone, GW501516 caused more weight loss and had no effect on insulin resistance. GW501516 protected INS-1 cells from PAM-induced apoptosis by upregulating GPR40 and activating Akt/Bcl-2/caspase-3. Activated extracellular regulated protein kinases (ERK) was relevant to the lipoapoptosis in INS-1 cells, but was not involved in the antilipoapoptotic effect of GW501516. These results showed that the PPARß/δ agonist GW501516 protected ß cells from lipoapoptosis and improved ß cell mass by upregulating GPR40 and activating the Akt/Bcl-2/caspase-3 pathway, but not the ERK-signaling pathway.