BACKGROUND: The effects of vitamin B-6 status on steady-state kinetics of homocysteine metabolism in humans are unclear. OBJECTIVE: The objective was to determine the effects of dietary vitamin B-6 restriction on the rates of homocysteine remethylation and synthesis in healthy humans. DESIGN: Primed, constant infusions of [(13)C(5)]methionine, [3-(13)C]serine, and [(2)H(3)]leucine were conducted in healthy female (n=5) and male (n=4) volunteers (20-30 y) before and after 4 wk of dietary vitamin B-6 restriction (<0.5 mg vitamin B-6/d) to establish whether vitamin B-6 status affects steady-state kinetics of homocysteine metabolism in the absence of concurrent methionine intake. Effects of dietary vitamin B-6 restriction on vitamin B-6 status, plasma amino acid concentrations, and the rates of reactions of homocysteine metabolism were assessed. RESULTS: Dietary vitamin B-6 restriction significantly reduced plasma pyridoxal 5-phosphate (PLP) concentrations (55.1 +/- 8.3 compared with 22.6 +/- 1.3 nmol/L; P=0.004), significantly increased plasma glycine concentrations (230 +/- 14 compared with 296 +/- 15; P=0.008), and significantly reduced basal (43%; P < 0.001) and PLP-stimulated (35%; P=0.004) lymphocyte serine hydroxymethyltransferase activities in vitro. However, the in vivo fluxes of leucine, methionine, and serine; the rates of homocysteine synthesis and remethylation (total and vitamin B-6-dependent); and the concentrations of homocysteine, methionine, and serine in plasma were not significantly affected by dietary vitamin B-6 restriction. CONCLUSIONS: Moderate vitamin B-6 deficiency does not significantly alter the rates of homocysteine remethylation or synthesis in healthy young adults in the absence of dietary methionine intake.
BACKGROUND: The effects of vitamin B-6 status on steady-state kinetics of homocysteine metabolism in humans are unclear. OBJECTIVE: The objective was to determine the effects of dietary vitamin B-6 restriction on the rates of homocysteine remethylation and synthesis in healthy humans. DESIGN: Primed, constant infusions of [(13)C(5)]methionine, [3-(13)C]serine, and [(2)H(3)]leucine were conducted in healthy female (n=5) and male (n=4) volunteers (20-30 y) before and after 4 wk of dietary vitamin B-6 restriction (<0.5 mg vitamin B-6/d) to establish whether vitamin B-6 status affects steady-state kinetics of homocysteine metabolism in the absence of concurrent methionine intake. Effects of dietary vitamin B-6 restriction on vitamin B-6 status, plasma amino acid concentrations, and the rates of reactions of homocysteine metabolism were assessed. RESULTS: Dietary vitamin B-6 restriction significantly reduced plasma pyridoxal 5-phosphate (PLP) concentrations (55.1 +/- 8.3 compared with 22.6 +/- 1.3 nmol/L; P=0.004), significantly increased plasma glycine concentrations (230 +/- 14 compared with 296 +/- 15; P=0.008), and significantly reduced basal (43%; P < 0.001) and PLP-stimulated (35%; P=0.004) lymphocyte serine hydroxymethyltransferase activities in vitro. However, the in vivo fluxes of leucine, methionine, and serine; the rates of homocysteine synthesis and remethylation (total and vitamin B-6-dependent); and the concentrations of homocysteine, methionine, and serine in plasma were not significantly affected by dietary vitamin B-6 restriction. CONCLUSIONS: Moderate vitamin B-6 deficiency does not significantly alter the rates of homocysteine remethylation or synthesis in healthy young adults in the absence of dietary methionine intake.
Authors: Vanessa R da Silva; Maria A Ralat; Eoin P Quinlivan; Barbara N DeRatt; Timothy J Garrett; Yueh-Yun Chi; H Frederik Nijhout; Michael C Reed; Jesse F Gregory Journal: Am J Physiol Endocrinol Metab Date: 2014-05-13 Impact factor: 4.310
Authors: Barbara N DeRatt; Maria A Ralat; Vegard Lysne; Fariba Tayyari; Indu Dhar; Arthur S Edison; Timothy J Garrett; Øivind Midttun; Per Magne Ueland; Ottar Kjell Nygård; Jesse F Gregory Journal: J Nutr Date: 2017-08-09 Impact factor: 4.798
Authors: Yvonne Lamers; Bruce O'Rourke; Lesa R Gilbert; Christine Keeling; Dwight E Matthews; Peter W Stacpoole; Jesse F Gregory Journal: Am J Clin Nutr Date: 2009-06-10 Impact factor: 7.045
Authors: Vanessa R da Silva; Luisa Rios-Avila; Yvonne Lamers; Maria A Ralat; Øivind Midttun; Eoin P Quinlivan; Timothy J Garrett; Bonnie Coats; Meena N Shankar; Susan S Percival; Yueh-Yun Chi; Keith E Muller; Per Magne Ueland; Peter W Stacpoole; Jesse F Gregory Journal: J Nutr Date: 2013-08-21 Impact factor: 4.798
Authors: Lynn B Bailey; Patrick J Stover; Helene McNulty; Michael F Fenech; Jesse F Gregory; James L Mills; Christine M Pfeiffer; Zia Fazili; Mindy Zhang; Per M Ueland; Anne M Molloy; Marie A Caudill; Barry Shane; Robert J Berry; Regan L Bailey; Dorothy B Hausman; Ramkripa Raghavan; Daniel J Raiten Journal: J Nutr Date: 2015-06-03 Impact factor: 4.798