Influences of Supplementary Dietary Tungsten on Methionine Metabolism in Rabbits Fed a Low-Cholesterol plus Methionine Diet

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Hyperhomocysteinemia results from an impaired methionine metabolism. Sulfite oxidase, which is an important enzyme in methionine metabolism, contains molybdenum. In contrast, tungsten has a molybdenum-antagonistic effect. Thus, we hypothesized that dietary tungsten may decrease plasma homocysteine levels and influence methionine metabolism. Male New Zealand White rabbits (n =15) were fed a low-cholesterol basal diet and then placed on three different diets : 0.1% cholesterol (Chol), Chol plus 1% methionine (Met), and Chol plus Met plus 0.1% tungsten (W). The animals received these diets for 20 weeks. Biochemical tests of blood and urine were performed. Plasma homocysteine levels were significantly lower in the Chol + Met+ W group than in the Chol + Met group. Plasma levels of total cholesterol, triglyceride, lipid peroxide, and urinary 24-h taurine concentrations were higher in the Chol + Met + W group than in the Chol + Met group. In comparison, concentrations of 2, 3-diphosphoglycerate (2, 3-DPG), reduced glutathione (GSH) in erythrocytes, and urinary 24-h SO₄^2-were lower in the Chol + Met+ W group than in the Chol + Met group. From these results, tungsten could be expected to exhibit an antiatherogenic effect. Conversely, it may have effects on atherogenic factors. Thus, tungsten may play a number of roles in the methionine metabolism