Involvement of P2Y signaling in the restoration of glucose-induced insulin exocytosis in pancreatic β cells exposed to glucotoxicity.

Abstract

Purinergic P2Y receptors, by binding adenosine triphosphate (ATP), are known for enhancing glucose-stimulated insulin secretion (GSIS) in pancreatic β cells. However, the impact of these receptors in the actin dynamics and insulin granule exocytosis in these cells is not established, neither in normal nor in glucotoxic environment. In this study, we investigate the involvement of P2Y receptors on the behavior of insulin granules and the subcortical actin network dynamics in INS-1 832/13 β cells exposed to normal or glucotoxic environment and their role in GSIS. Our results show that the activation of P2Y purinergic receptors by ATP or its agonist increase the insulin granules exocytosis and the reorganization of the subcortical actin network and participate in the potentiation of GSIS. In addition, their activation in INS-1832/13 β-cells, with impaired insulin secretion following exposure to elevated glucose levels, restores GSIS competence through the distal steps of insulin exocytosis. These results are confirmed ex vivo by perifusion experiments on islets from type 2 diabetic (T2D) Goto-Kakizaki (GK) rats. Indeed, the P2Y receptor agonist restores the altered GSIS, which is normally lost in this T2D animal model. Moreover, we observed an improvement of the glucose tolerance, following the acute intraperitoneal injection of the P2Y agonist concomitantly with glucose, in diabetic GK rats. All these data provide new insights into the unprecedented therapeutic role of P2Y purinergic receptors in the pathophysiology of T2D.