Objectives: First, we observed that copper and histidine levels were increased in the sera of undernourished women. The objective of this study was to clarify the reason for the increase in copper and histidine. Furthermore, we tried to determine the compound (s) to which the increased copper was binding, and examined the effect of the increased copper and histidine on lipid peroxidation. Methods: We investigated young women's diets and took blood samples, and the contents of histidine in the sera were determined by HPLC. The contents of copper were determined by flameless atomic absorption spectroscopy. The subjects were classified into three groups according to the concentration of histidine in the sera. The contents of copper and lipid peroxide in the sera were compared among the high histidine group and the other groups. We also examined the ability of the complexes to prevent LDL oxidation induced by copper, using an in vitro assay. Results: The contents of lipid peroxide were lower in the high histidine group than in the other groups. Furthermore, the complexes of histidine and copper inhibited the formation of peroxidized lipids in an in vitro assay. Conclusions: These results indicate that histidine masks copper, reducing oxidation reaction. They also suggest that the complexes are suited for plasma antioxidation, preventing oxidative modification of lipids in the sera of undernourished women. The increased histidine appeared to be an effective trap for active oxygen.
