Role of phospholipase D in glucose induced insulin signaling pathway in pancreatic β cells

Abstract

Glucose has been known to induce insulin secretion in pancreatic β cells. In this study, we investigated role of phospholipase D (PLD)-related signaling pathway in insulin secretion caused by high glucose in MIN6N8 cells, a mouse pancreatic β-cell line. PLD was activated maximally at 10min treatment by high glucose (33.3mM). We found that expression of PLD1 was also increased by treatment of high glucose to the cells.1-butanol treatment resulted in decreased insulin secretion, while high glucose-induced insulin secretion was blocked by transfection of PLD1siRNA. These results suggest that high glucose increased insulin secretion through PLD1-related pathway. Next, D609(PC-PLC inhibitor) blocked beta2 (insulin related gene) expression and decreased insulin secretion. Treatment of high glucose induces translocation of PKC and Arf6 which binds to PLD1.Pretreament with PKC inhibitor (RO320432) and Arf inhibitor (BFA) decreased PLD activity as well as insulin secretion, respectively. These results suggest that high glucose-induced insulin secretion might be regulated by Arf6, PKC dependent manner with involvement of PLD1 in MIN6N8 cells. Moreover, expression of Akt and mTOR were increased by high glucose. Wortmamin (PI3K inhibitor), LY294002 (Akt inhibitor), rapamycin(mTOR inhibitor) were all decreased beta2 expression and insulin secretion. Taken together, PLD1 signaling might be a novel pathway for glucose-induced insulin secretion in MIN6N8 cells.