Insulin secretion in response to protein ingestion.

Abstract

W\e have reported previously that the oral or intravenous administration of the amino acid l-leucine to healthy subjects results in increases in plasma insulin and decreases in blood glucose and plasma free fatty acids (2, 3). After the administration of leucine to healthy subjects pretreated with either chlorpropamide or tolbutamide (2, 3), and also to some patients with functioning islet cell tumors of the pancreas (4), increments in plasma leucine caused increases in plasma insulin and decreases in blood glucose that were significantly greater than those observed in healthy subjects not pretreated with sulfonylurea drugs. We have also shown that increased release of insulin from the pancreatic beta cells is the mechanism by which leucine increases peripheral levels of insulin (5). We suggested that a rising plasma level of leucine is a physiologic stimulus for the release of insulin, and that the more pronounced sensitivity to leucine hypoglycemia produced experimentally by. administration of sulfonylureas and observed in some patients with idiopathic hypoglycemia or insulin-secreting tumors of the pancreas represents a great exaggeration of a normal physiologic phenomenon (6, 7).In an effort to determine the effect of leucine on insulin release under physiologic circumstances, protein meals rich in leucine were fed to healthy subjects, and the levels of plasma insulin, leucine, amino nitrogen, free fatty acids, and blood glucose

Stimulation of insulin secretion by amino acids.

“…In previous studies we have demonstrated that in healthy subjects the ingestion of protein meals results in large increases in plasma levels of insulin and have concluded that this is an important physiologic phenomenon (1,3). In those experiments the magnitude of the increases in plasma insulin exceeded that expected from the small increases in plasma leucine measured (3).…”

“…In those experiments the magnitude of the increases in plasma insulin exceeded that expected from the small increases in plasma leucine measured (3). In addition, chlorpropamide pretreatment failed to accentuate the protein-induced changes in blood glucose and plasma free fatty acids (3), although it greatly augments such leucine-induced changes (4,5). These findings suggested that amino acids other than leucine or amino acids in combination with leucine stimulate the release of insulin (1,3,6).…”

Can milk proteins be a useful tool in the management of cardiometabolic health? An updated review of human intervention trials

“…It is well established that food proteins and more specifically AA acutely stimulate insulin secretion (70) with several AA possessing direct insulinotropic effects (71,72) .…”

The Different Effects on the Serum Lipids and Fecal Steroids of High Carbohydrate Diets Given Orally or Intravenously

“…Plasma free amino acid levels are known to influence secretion of hormones by the endocrine glands, and may act as regulators for the secretion of insulin, glucagon, growth hormone, and the corticosteroids (31,32). Studies using isolated pancreatic preparations in vitro (33,34) and those using the intravenous administration of various amino acids indicate that elevated levels of certain amino acids in the plasma (particularly arginine, leucine, lysine, and possibly histidine) cause increased insulin secretion (32,(35)(36)(37)(38)(39). However, with the exception of an effect upon plasma cystine levels (40), few differences were noted in plasma amino acid levels in our subjects with the differing routes of alimentation.…”