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1 Department of Clinical Biochemistry AKH, Aarhus University Hospital, Nørrebrogade 44, DK-8000 Aarhus C, Denmark.
2 Department of Pharmacology,
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Institute of Medicine, and
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Locus for Homocysteine and related Vitamins, University of Bergen, N-5021 Bergen, Norway.
aAuthor for correspondence. Fax 45-89493060; e-mail vakbor{at}hotmail.com.
Background: Vitamin B6 has attracted renewed interest because of its role in homocysteine metabolism and its possible relation to cardiovascular risk. We examined the plasma B6 vitamers, pyridoxal 5'-phosphate (PLP), pyridoxal (PL), pyridoxine (PN), and 4-pyridoxic acid (4-PA) before and after vitamin B6 supplementation.
Methods: Patients (n = 90; age range, 38–80 years) undergoing coronary angiography (part of the homocysteine-lowering Western Norway B-Vitamin Intervention Trial) were allocated to the following daily oral treatment groups: (A), vitamin B12 (0.4 mg), folic acid (0.8 mg), and vitamin B6 (40 mg); (B), vitamin B12 and folic acid; (C), vitamin B6; or (D), placebo. EDTA blood was obtained before treatment and 3, 14, 28, and 84 days thereafter.
Results: Before treatment, PLP (range, 5–111 nmol/L) and 4-PA (6–93 nmol/L) were the predominant B6 vitamers identified in plasma. During the 84-day study period, the intraindividual variation (CV) in patients not treated with vitamin B6 (groups B and D) was 45% for PLP and 67% for 4-PA. Three days after the start of treatment, the increases in concentration were 
10-, 50-, and 100-fold for PLP, 4-PA, and PL, respectively. No significant additional increase was observed at the later time points. The PLP concentration correlated to the concentrations of 4-PA and PL before treatment, but not after treatment. The PL concentration correlated with 4-PA before and after treatment.
Conclusions: Vitamin B6 treatment has an immediate effect on the concentrations and the forms of B6 vitamers present in plasma, and the changes remain the same during prolonged treatment. Our results suggest that the B6 vitamers in plasma reflect vitamin B6 intake.
The following articles in journals at HighWire Press have cited this article:
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  J. H. Page, J. Ma, S. E. Chiuve, M. J. Stampfer, J. Selhub, J. E. Manson, and E. B. Rimm Plasma Vitamin B6 and Risk of Myocardial Infarction in Women Circulation, August 25, 2009; 120(8): 649 - 655. [Abstract] [Full Text] [PDF]
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 M. S. Morris, M. F. Picciano, P. F Jacques, and J. Selhub Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004 Am. J. Clinical Nutrition, May 1, 2008; 87(5): 1446 - 1454. [Abstract] [Full Text] [PDF]
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O. Midttun, S. Hustad, J. Schneede, S. E Vollset, and P. M Ueland Plasma vitamin B-6 forms and their relation to transsulfuration metabolites in a large, population-based study Am. J. Clinical Nutrition, July 1, 2007; 86(1): 131 - 138. [Abstract] [Full Text] [PDF]
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 S. Kaul, A. A. Zadeh, and P. K. Shah Homocysteine Hypothesis for Atherothrombotic Cardiovascular Disease: Not Validated J. Am. Coll. Cardiol., September 5, 2006; 48(5): 914 - 923. [Abstract] [Full Text] [PDF]
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 O. Midttun, S. Hustad, E. Solheim, J. Schneede, and P. M. Ueland Multianalyte Quantification of Vitamin B6 and B2 Species in the Nanomolar Range in Human Plasma by Liquid Chromatography-Tandem Mass Spectrometry Clin. Chem., July 1, 2005; 51(7): 1206 - 1216. [Abstract] [Full Text] [PDF]
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M. E. Rybak, R. B. Jain, and C. M. Pfeiffer Clinical Vitamin B6 Analysis: An Interlaboratory Comparison of Pyridoxal 5'-Phosphate Measurements in Serum Clin. Chem., July 1, 2005; 51(7): 1223 - 1231. [Abstract] [Full Text] [PDF]
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P. G Masse, J D. Mahuren, C. Tranchant, and J. Dosy B-6 vitamers and 4-pyridoxic acid in the plasma, erythrocytes, and urine of postmenopausal women Am. J. Clinical Nutrition, October 1, 2004; 80(4): 946 - 951. [Abstract] [Full Text] [PDF]
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O. Bleie, H. Refsum, P. M. Ueland, S. E. Vollset, A. B. Guttormsen, E. Nexo, J. Schneede, J. E. Nordrehaug, and O. Nygard Changes in basal and postmethionine load concentrations of total homocysteine and cystathionine after B vitamin intervention Am. J. Clinical Nutrition, September 1, 2004; 80(3): 641 - 648. [Abstract] [Full Text] [PDF]
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 P. I. Holm, O. Bleie, P. M. Ueland, E. A. Lien, H. Refsum, J. E. Nordrehaug, and O. Nygard Betaine as a Determinant of Postmethionine Load Total Plasma Homocysteine Before and After B-Vitamin Supplementation Arterioscler Thromb Vasc Biol, February 1, 2004; 24(2): 301 - 307. [Abstract] [Full Text]
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