Table of Contents
Journal of Amino Acids
Volume 2014 (2014), Article ID 521941, 6 pages
Clinical Study

Interaction of Ingested Leucine with Glycine on Insulin and Glucose Concentrations

1Endocrinology, Metabolism, and Nutrition Section, Minneapolis VA Health Care System, One Veterans Drive, Minneapolis, MN 55417, USA
2Department of Medicine, University of Minnesota, Minneapolis, MN 55455, USA
3Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA

Received 18 April 2014; Accepted 14 June 2014; Published 10 July 2014

Academic Editor: Dorothy Gietzen

Copyright © 2014 Jennifer F. Iverson et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The majority of individual amino acids increase insulin and attenuate the plasma glucose response when ingested with glucose. Objective. To determine whether ingestion of two amino acids simultaneously, with glucose, would result in an additive effect. Leucine (Leu) and glycine (Gly) were chosen because they were two of the most potent glucose-lowering amino acids when given individually. Materials and Methods. Nine subjects received test items on four separate days. The first was a water control, then 25 g glucose, or Leu + Gly (1 mmol/kg fat-free mass each) ±25 g glucose, in random order. Glucose, insulin, and glucagon were measured frequently for 2.5 hours. Net areas were calculated. Results. The glucose area response decreased by 66%. The insulin area response increased by 24% after ingestion of Leu + Gly + glucose compared to ingestion of glucose alone. The decrease in glucose response was not additive; the increase in insulin response was far less than additive when compared to previously published individual amino acid results. The glucagon concentration remained unchanged. Conclusion. There is an interaction between Leu and Gly that results in a markedly attenuated glucose response. This occurred with a very modest increase in insulin response. Changes in glucagon response could not explain the results. The mechanism is unknown.