Metabolic derangement in response to ingestion of imbalanced amino acid mixtures

In an effort to test the validity of Harper's hypothesis that altered patterns of the free amino acids and the depressed levels of the limiting amino acid in blood and tissue fluids are due to the metabolic derangements of the limiting as well as the nonlimiting indispensable amino acids in response to ingestion of· imbalanced amino acid mixtures. Basal, histidine-imbalanced and corrected diets were prepare. Histidine-U¹⁴C and Threonine-U¹⁴C were used in tracer quantities to study the metabolic behavior of the respective amino acid in rats receiving these diets.

In very short term studies, the isotope content in protein and non-protein fractions of various tissues were determined in rats receiving these diets and sacrificed after 2, 4, and 6 hours. In the imbalanced groups, increased retention of the limiting, as well as the non-limiting indispensable amino acids was observed and indicated enhanced protein synthesis. However, differences in the efficiency of utilization of the respective amino acids were higher for the limiting amino acids and lower for the nonlimiting amino acids.

This supports the hypothesis that these disorders are the initial effects and its metabolic consequences trigger an appetite controlling mechanism which results in depressed food intake and retarded growth.