Horm Metab Res 2006; 38(8): 518-523
DOI: 10.1055/s-2006-949523
Original Clinical

© Georg Thieme Verlag KG Stuttgart · New York

Effect of Orally Administered Phenylalanine with and without Glucose on Insulin, Glucagon and Glucose Concentrations

F. Q. Nuttall 1 , K. J. Schweim 1 , M. C. Gannon 1 , 2 , 3
  • 1Section of Endocrinology, Metabolism & Nutrition, VA Medical Center, Minneapolis, Minnesota, USA
  • 2Department of Medicine, University of Minnesota, Minneapolis, MN, USA
  • 3Department of Food Science, University of Minnesota, Minneapolis, MN, USA
Further Information

Publication History

Received 15 August 2005

Accepted after revision 12 January 2006

Publication Date:
29 August 2006 (online)

Abstract

Objective: As part of our studies of the metabolic effects of ingested proteins, we are currently investigating the effects of ingestion of individual amino acids. The objective of the present study was to determine whether ingested phenylalanine stimulates insulin and/or glucagon secretion, and if phenylalanine ingested with glucose modifies the insulin, glucagon or glucose response to the ingested glucose. Design: Six healthy subjects were tested on 4 separate occasions. Plasma phenylalanine, glucose, insulin, glucagon, and total alpha amino nitrogen (AAN) (i.e., total amino acids) concentrations were measured at various times during a 2.5 h period after ingestion of 1 mmol phenylalanine/kg lean body mass, 25 g glucose, 1 mmol phenylalanine/kg lean body mass+25 g glucose, or water only, given in random order. Results: Following phenylalanine ingestion, the circulating phenylalanine concentration increased ∼ 14 fold and remained elevated for the duration of the experiment. Glucagon and AAN increased, insulin increased modestly, and glucose was unchanged when compared to water ingestion. When glucose was ingested with phenylalanine, the circulating phenylalanine, glucagon, AAN, and insulin area responses were approximately the sum of the responses to phenylalanine alone and glucose alone. However, the plasma glucose area response was decreased 66% when phenylalanine was co-ingested with glucose. Conclusion: In summary, phenylalanine in an amount moderately greater than that in a large protein meal stimulates an increase in insulin and glucagon concentration. It markedly attenuates the glucose-induced rise in plasma glucose when ingested with glucose.

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Correspondence

Frank Q. NuttallM.D., Ph.D. 

Chief·Endocrinology, Metabolism & Nutrition·Professor of Medicine·VA Medical Center

One Veterans Drive Minneapolis·MN 55417·USA

Phone: +1/612/467 44 24

Fax: +1/612/725 22 73

Email: Nutta001@umn.edu