1518-PUB: Role of PPARd in Regulating Autophagy Pathway in Improving Islet ß-Cell Function with GLP-1 Receptor Agonist

Aim: To investigate the effect and mechanism of glucagon-like peptide-1 receptor agonist (GLP-1 RA) on the function of islet β cells. Methods: Type 2 diabetes C57BL/6J mice were successfully induced by high fat diet (HFD) feeding for 12 weeks then were randomly divided into HFD+NaCl group (n=5) , HFD+Exenatide group (n=5, 24 nmol•kg-1­•d‑1) and NC group (n=5) . Tolerance tests and insulin measurement were performed after 8 weeks of drug therapy. Weight was measured weekly and fasting blood glucose was measured every 4 weeks. The pancreas were stained with LC3B Immunofluorescence at the end of the experiment. The PA induced primary islet β cells were treated with exendin-4 and PA induced Min6 cells were treated with exendin-4, GW501516 for 24h, which BSA as the control group, then detected the protein levels of PPARδ, LC3B-II and P62. At the same time, PA induced MIN6 cells were treated with GSIS. What's more, we silenced PPARδ transfected with siRNA to verify the role of PPARδ in GLP-1 receptor agonist activation of β-cell autophagy. Results: Compared with the normal control group, the body weight and fasting blood glucose increase and significant peripheral insulin resistance in the high fat group, while the above indexes are significantly improved in the high-fat fed mice after GLP-1 RA treatment. Immunofluorescence biopsies of pancreatic tissue show that LC3B expression decrease after high fat diet, while GLP-1 RA intervention significantly increase. In addition, GLP-1 RA not only can promote the expression of PPARδ and LC3B-II protein and inhibit the expression of P62 protein in primary islet β cells and MIN6 cells, but also significantly increase glucose stimulation insulin secretion in MIN6 cells. More importantly, GW501516 is found to be consistent with GLP-1 RA in MIN6 cells, while GLP-1 RA promote autophagy disappeare after PPARδ expression is silenced. Conclusion: GLP-1 RA can improve the function of islet β cells by activating the autophagy pathway through PPARδ.