Effect of orally administered isoleucine with and without glucose on insulin, glucagon and glucose concentrations in non-diabetic subjects

Abstract

Summary Objective The objective of the present study was to determine the degree to which ingested isoleucine modified the glucose, insulin and glucagon responses to ingested glucose. Design Nine healthy subjects were studied on 4 separate occasions. Plasma isoleucine, glucose, insulin, glucagon, and total alpha amino nitrogen were measured at various times during a 2.5 h period after ingestion of isoleucine (1 mmol/kg lean body mass), 25 g glucose, isoleucine + glucose, or water alone, given in random order. Results Following isoleucine ingestion, the isoleucine concentration increased ∼24-fold. The glucose decreased, the insulin remained unchanged. When isoleucine was ingested with glucose the increase in isoleucine was less, insulin increased, and the maximum concentration was 43% higher than that following ingestion of glucose alone. The glucose concentration increase was less and it decreased more rapidly following isoleucine + glucose, compared to glucose alone. Consequently, the glucose area response was markedly attenuated (61%). Isoleucine had little effect on the glucagon concentration. Conclusion Isoleucine per se does not stimulate a rise in insulin and has little effect on glucagon but does decrease the glucose concentration. It synergizes with ingested glucose in stimulating insulin secretion and in decreasing the glucose response.