Expression and function of monoacylglycerol lipase in mouse β-cells and human islets of Langerhans

Abstract

Elements of the endocannabinoid system (ECS) are expressed by islet endocrine cells and activation of CB1 and CB2 cannabinoid receptors regulates insulin secretion from mouse and human β-cells. The current study aimed to investigate the expression and function, in mouse and human β-cells, of monoacylglycerol lipase (MGL), an enzyme that facilitates degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG). We found that MGL mRNA is expressed by MIN6 β-cells, mouse islets, human islets and enriched human islet β-cells, and immunohistochemistry indicated that MGL localisation in human islets is consistent with its expression by some β- and -α-cells. Blockade of MGL activity with the pharmacological inhibitor URB602 led to increased [Ca(2+)](i )and enhanced insulin secretion from MIN6 β-cells, and MGL inhibition also elevated insulin and glucagon secretion from isolated human islets in vitro. These data imply a stimulatory role for endogenous 2-AG in islets that is amplified when its degradation is blocked.