Kinetic modeling of folate metabolism through use of chronic administration of deuterium-labeled folic acid in men

This study was conducted as an initial investigation of in vivo folate kinetics in healthy men (n = 4) and made use of a chronic-administration protocol with stable-isotope labeling. Subjects were given 0.453 mumol (200 micrograms) total folic acid in aqueous solution daily throughout the 18-wk stud...

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Bibliographic Details
Published in:The American journal of clinical nutrition 1997-01, Vol.65 (1), p.53-60
Main Authors: Stites, TE, Bailey, LB, Scott, KC, Toth, JP, Fisher, WP, Gregory, JF
Format: Article
Language:English
Subjects:
Adult
Biological and medical sciences
Chromatography, High Pressure Liquid
Deuterium
Eating - physiology
Enzymes. Coenzymes. Vitamins. Pigments
Folic Acid - administration & dosage
Folic Acid - metabolism
Fundamental and applied biological sciences. Psychology
Glutamic Acid - metabolism
Humans
Kinetics
Male
Men
Metabolism
Metabolisms and neurohumoral controls
Models, Biological
Nutritional Status
Vertebrates: anatomy and physiology, studies on body, several organs or systems
Vitamin B
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Summary:This study was conducted as an initial investigation of in vivo folate kinetics in healthy men (n = 4) and made use of a chronic-administration protocol with stable-isotope labeling. Subjects were given 0.453 mumol (200 micrograms) total folic acid in aqueous solution daily throughout the 18-wk study while they consumed self-selected folate-adequate diets. After a 2-wk pretrial period with unlabeled folic acid, subjects were given 0.227 mumol (100 micrograms) pteroyl-L-[2H4]glutamic acid/d ([2H4]folic acid) combined with 0.227 mumol nonlabeled folic acid or [2H2]pteroylhexaglutamic acid/d for the next 8 wk; then for the next 8 wk the [2H4]folic acid was withdrawn and the subjects received only nonlabeled folic acid. Little unmetabolized folic acid was excreted in urine. Isotopic enrichment of urinary folate during [2H4]folic acid administration and withdrawal was consistent with a kinetic model having a rapid turnover pool and a slow turnover pool. In contrast with previous two-pool models, provisions were made for folate turnover by urinary folate excretion (as measured here) and by fecal excretion and catabolic processes. The precision of modeling will be improved in future studies by measurement of enrichment of additional pools. However, this study shows clearly the slow turnover of the whole-body folate pool (< or = 1% per day) and the feasibility of further long-term kinetic analysis.
ISSN:0002-9165
1938-3207
DOI:10.1093/ajcn/65.1.53