The Local Paracrine Actions of the Pancreatic α-Cell

Secretion of glucagon from the pancreatic alpha -cells is conventionally seen as the first and most important defense against hypoglycemia. Recent findings, however, show that alpha -cell signals stimulate insulin secretion from the neighboring beta -cell. This article focuses on these seemingly counterintuitive local actions of alpha -cells and describes how they impact islet biology and glucose metabolism. It is mostly based on studies published in the last decade on the physiology of alpha -cells in human islets and incorporates results from rodents where appropriate. As this and the accompanying articles show, the emerging picture of alpha -cell function is one of increased complexity that needs to be considered when developing new therapies aimed at promoting islet function in the context of diabetes.