The role of the endocannabinoid system in islet biology

Purpose Of Review: The endogenous cannabinoids (endocannabinoids) are long-chain polyunsaturated fatty acids synthesized on demand in situ by catabolism of phospholipid precursors in the cell membrane. Here we discuss the emerging role of the endocannabinoids in the function of the pancreatic islet of Langerhans in particular on the secretion of insulin from the islet beta cell. Recent Findings: It is now established that there is a functional endocannabinoid system in the pancreatic islet of Langerhans and that endocannabinoids are released concurrently with glucose-induced insulin secretion. The majority of the published papers show evidence of negative effects of the endocannabinoids on insulin secretion with antagonism of the cannabinoid 1 receptor improving beta cell function. This indicates that there is a tonic inhibition of insulin secretion by endocannabinoids. Here we examine these reports and recent papers showing that endocannabinoids increase insulin secretion and discuss the discrepancies in these observations. Summary: Conclusions on the exact nature of the effects of endocannabinoids on insulin secretion require rigorous study examining both acute and long-term effects at physiologically relevant doses employing both whole animal and clinically relevant models such as human islets in vitro and explanted in vivo, in rodent models of diabetes.