Plasma Amino Acid Response to Glucose Administration in Various Nutritive States

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Abstract
An oral glucose load test was administered during the period of postabsorption to subjects in various nutritive states and the amino acids in plasma were measured prior to the test and at several intervals thereafter. For all subjects, the total essential amino acid values declined following glucose administration. The total nonessential amino acid values remained unchanged except for obese subjects and those ingesting a ketogenic diet who showed some decreases. When a lipid load test isocaloric with the glucose test was given, there was no effect on the amino acid concentrations in plasma. Subjects who were receiving a low protein diet and were in a negative nitrogen balance had plasma amino acid responses to glucose administration that were similar to subjects ingesting diets adequate in protein. Obese subjects and those receiving a ketogenic diet showed a greater variability in the plasma amino acid response, particularly in some of the branched chain amino acids. During the 4-hr interval following glucose ingestion, there was a high degree of correlation for the changes occurring among the essential amino acid levels in plasma with the exception of cystine. Since glucose administration stimulates protein synthesis, the proportionate amounts by which the essential amino acids were removed from the plasma subsequent to glucose administration were calculated as the pattern of amino acids in a hypothetical protein mixture. This hypothetical protein was found to be similar in amino acid composition to food proteins of high nutritive value.