Pulsatile insulin secretion.

Insulin is secreted in a pulsatile manner. Recently it has been shown that almost all (approximately 70-100%) of insulin is secreted in discrete insulin secretory bursts occurring approximately every 6 min. Furthermore, it has been revealed that regulation of the rate of insulin secretion is achieved primarily through modulation of the mass of these discrete insulin bursts. Thus meal ingestion increases insulin secretion by enhancing insulin burst mass by approximately 50% but also increases pulse frequency by approximately 50%. Interestingly, the hepatic clearance of insulin is also apparently closely related to the pattern of insulin delivery to the liver. It has been known for many years that the pattern of insulin delivery is abnormal in patients with type 2 diabetes. Recently, with new more sensitive insulin assays (ELISA) and validated methods for pulse detection, it has been possible to examine more precisely the abnormalities of pulsatile insulin in patients with type 2 diabetes. These recent studies suggest that the principal defect of insulin secretion is a deficient pulse mass of insulin with no changes in pulse frequency, and that this defect can be overcome by a period of beta cell rest.