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.
Bibliographical noteFunding Information:
Drs Nuttall and Gannon were equally responsible for designing the experiment, evaluating the statistics, interpreting the data analysis, writing the manuscript, and organizing the figures and tables. Dr. Schweim was the clinical study coordinator. This work was supported in part by Merit Review Funds from the Department of Veterans Affairs, a grant from the Minnesota Beef Council, and a grant from the American Diabetes Association. The authors thank the subjects for volunteering for the study, the staff of the Special Diagnostic and Treatment Unit, the staff of the Clinical Chemistry Laboratory, Terry Masai and the Ajinomoto Company for supplying the isoleucine and Rachel Anderson for excellent secretarial support.
- Amino acids
- Glucose removal rate
- Insulin secretion