Author
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Novotny, Janet |
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Turnlund, Judith |
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Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/20/2005 Publication Date: 4/1/2006 Citation: Novotny Dura, J., Turnlund, J.R. 2006. Molybdenum disposition in humans during molybdenum depletion and repletion. Journal of Nutrition 136:953-957. Interpretive Summary: Molybdenum is an essential mineral for humans. New dietary recommendations were established for molybdenum in 2002 based on balance studies of molybdenum feeding followed by stool collections to determine how much molybdenum was absorbed. And while balance studies are useful for estimating retention of nutrients that are not altered in the intestine, this approach does not provide information about the nutrient metabolism. We have studied molydbenum metabolism with an alternative approach called compartmental modeling to elucidate how molybdenum is handled by the body during depletion and repletion, and several new insights have been revealed. During high molybdenum intake, the body adapts to eliminate the excess by increasing urinary output and reducing tissue storage. It was also discovered that food-bound molybdenum is about 16% less well absorbed than purified molybdenum. Finally, it was shown that an intake of 43 micrograms per day, which is close to the current dietary recommendation, is sufficient to maintain adequate plasma molybdenum levels. These findings offer a clearer understanding of molybdenum disposition during depletion and repletion, and will be useful to scientists and health professionals. Technical Abstract: A novel compartmental model of molybdenum (Mo) kinetics was developed to determine rates of molybdenum disposition during Mo depletion and repletion. The model was developed based on a clinical study in which 4 men consumed a low Mo diet of 22 micrograms/d for 102 d, followed by a high Mo diet of 428 micrograms/d for 18 d. Stable isotopes Mo-100 and Mo-97 were administered orally and intravenously, respectively, at several time points during the study, and serial samples of plasma, urine, and feces were analyzed for Mo-100, Mo-97, and total Mo. Based on plasma, urine, and fecal Mo levels, kinetic parameters of disposition were determined. Several new insights into Mo metabolism were revealed. First, rates of Mo disposition are dependent on Mo intake. During high Mo intake, urinary Mo excretion was greater than that during low Mo intake. In addition, tissue storage of Mo was lower during high Mo intake than during low Mo intake. This suggests low Mo intake results in an adaptation to conserve body Mo, and/or high Mo intake results in an adaptation to eliminate Mo. The model also suggested that food-bound Mo is about 16% less bioavailable than purified Mo. Finally, the model revealed that an intake of 43 micrograms/d is sufficient to maintain plasma Mo levels at steady state. These findings offer a clearer understanding of Mo disposition during depletion and repletion. |
