Autophagy regulates pancreatic beta cell death in response to Pdx1 deficiency and nutrient deprivation

There are three types of cell death; apoptosis, necrosis, and autophagy. The possibility that activation of the macroautophagy (autophagy) pathwaymayincrease beta cell death is addressed in this study. Increased autophagy was present in pancreatic islets from Pdx1^+/- mice with reduced insulin secretion and beta cell mass. Pdx1 expression was reduced in mouse insulinoma 6 (MIN6) cells by delivering small hairpinRNAsusing a lentiviral vector. The MIN6cells died after 7 days of Pdx1 deficiency, and autophagy was evident prior to the onset of cell death. Inhibition of autophagy prolonged cell survival and delayed cell death. Nutrient deprivation increased autophagy in MIN6 cells and mouse and human islets after starvation. Autophagy inhibition partly prevented amino acid starvation-inducedMIN6cell death. The in vivo effects of reduced autophagy were studied by crossing Pdx1^+/- mice to Becn1^{+/ -}mice. After1weekona high fat diet, 4-week-oldPdx1^+/- Becn1^+/- mice showed normal glucose tolerance, preserved beta cell function, and increased beta cell mass compared with Pdx1^+/- mice. This protective effect of reduced autophagy had worn off after 7 weeks on a high fat diet. Increased autophagy contributes to pancreatic beta cell death in Pdx1 deficiency and following nutrient deprivation. The role of autophagy should be considered in studies of pancreatic beta cell death and diabetes and as a target for novel therapeutic intervention.