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Nutrient Requirements and Optimal Nutrition

Molybdenum Kinetics in Men Differ during Molybdenum Depletion and Repletion¹

Janet A. Novotny^*,2 and Judith R. Turnlund

^* U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Beltsville, MD 20705 and U.S. Department of Agriculture, Agricultural Research Service, Western Human Nutrition Research Center, University of California, Davis, CA 95616

² To whom correspondence should be addressed. E-mail: novotnyj{at}ba.ars.usda.gov.

In this study we developed an expanded compartmental model of molybdenum (Mo) kinetics to determine rates of molybdenum distribution during molybdenum depletion and repletion. The model was based on a clinical study in which 4 men consumed a low-molybdenum diet of 22 µg/d (0.23 µmol/d) for 102 d, followed by a high molybdenum diet of 467 µg/d (4.9 µmol/d) for 18 d. Stable isotopes ¹⁰⁰Mo and ⁹⁷Mo were administered orally and intravenously, respectively, at several time points during the study, and serial samples of plasma, urine, and feces were analyzed for ¹⁰⁰Mo, ⁹⁷Mo, and total Mo. Based on plasma, urine, and fecal molybdenum levels, kinetic parameters of distribution and elimination were determined. The rates of molybdenum distribution and elimination were different during depletion and repletion. During high intake, urinary molybdenum excretion was greater than during low intake. In addition, fractional tissue storage of molybdenum was lower during high intake than during low intake. This suggests that low intake results in an adaptation to conserve body Mo, and that high intake results in an adaptation to eliminate Mo. The model also suggested that food-bound molybdenum was 16% less bioavailable than purified Mo. Finally, under the conditions of this study, the model suggested that an intake of 43 µg/d (0.45 µmol/d) would be sufficient to maintain plasma molybdenum levels at steady state. This is a minimum estimate because subjects in this study were in a molybdenum-sparing state. These findings provide an understanding of the adaptations in molybdenum metabolism that take place during depletion and repletion.

KEY WORDS: • bioavailability • kinetics • modeling • mineral

This article has been cited by other articles:

				J. A. Novotny and J. R. Turnlund Molybdenum Intake Influences Molybdenum Kinetics in Men J. Nutr., January 1, 2007; 137(1): 37 - 42. [Abstract] [Full Text] [PDF]