Tryptophan and zinc: effect of co-administration on plasma free amino acid homeostasis

Abstract

One of the main hydrophobic amino acids – tryptophan and essential trace element zinc perform numerous and largely overlapping functions in the mammalian body. A huge number of zinc-containing compounds – proteins, en­zymes, transcription factors, and hormones interact with tryptophan metabolites. We have attempted to identify the main effects of amino acids and trace elements on amino acid metabolism in order to determine the general mechanisms and the feasibility of their possible therapeutic use.We have found that the course administration of tryptophan at a dose of 40 mg/kg in blood plasma reduces the total amount of ARUC and increases the concentration of free tryptophan. In animals treated with zinc diaspartate or zinc diaspar­tate together with tryptophan, the total amount of amino acids and their nitrogen-containing metabolites in blood plasma de­ creases. The analysis of individual concentrations of amino acids and their nitrogen-containing metabolites showed that the coadministration of tryptophan and zinc diaspartate is accompanied by statistically significant changes in the concentrations of most of the studied parameters of the amino acid pool (19 out of 35 parameters). It should be noted that the changes in the content of free amino acids and their nitrogen-containing metabolites are unidirectional in the groups of animals treated with zinc diaspartate or zinc diaspartate together with tryptophan (coincidence of effects is 90 %). Thus, our studies showed that the course administration of zinc diaspartate at a dose of 25 mg/kg (2 times higher than an average therapeutic dose) has a pronounced metabolic effect, characterized by changes in the concentrations of free amino acids and their nitrogen-containing metabolites in blood plasma. The course administration of tryptophan at a dose of 40 mg/ kg of body weight (1/2 of a therapeutic dose) has no significant effect on the parameters of the blood plasma aminogram. With the coadministration of zinc diaspartate and tryptophan in the above doses, the revealed changes can be more attributed to the effects of zinc diaspartate.