Direct and Functional Biomarkers of Vitamin B6 Status.

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Ueland PM, Ulvik A, Rios-Avila L, Midttun O, Gregory JF

Direct and Functional Biomarkers of Vitamin B6 Status.

Annu Rev Nutr. 2015;35:33-70. doi: 10.1146/annurev-nutr-071714-034330. Epub 2015 May 13.

PubMed ID

25974692 [ View in PubMed

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Abstract

Measures of B6 status are categorized as direct biomarkers and as functional biomarkers. Direct biomarkers measure B6 vitamers in plasma/serum, urine and erythrocytes, and among these plasma pyridoxal 5'-phosphate (PLP) is most commonly used. Functional biomarkers include erythrocyte transaminase activities and, more recently, plasma levels of metabolites involved in PLP-dependent reactions, such as the kynurenine pathway, one-carbon metabolism, transsulfuration (cystathionine), and glycine decarboxylation (serine and glycine). Vitamin B6 status is best assessed by using a combination of biomarkers because of the influence of potential confounders, such as inflammation, alkaline phosphatase activity, low serum albumin, renal function, and inorganic phosphate. Ratios between substrate-products pairs have recently been investigated as a strategy to attenuate such influence. These efforts have provided promising new markers such as the PAr index, the 3-hydroxykynurenine:xanthurenic acid ratio, and the oxoglutarate:glutamate ratio. Targeted metabolic profiling or untargeted metabolomics based on mass spectrometry allow the simultaneous quantification of a large number of metabolites, which are currently evaluated as functional biomarkers, using data reduction statistics.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Pyridoxine	Alkaline phosphatase, tissue-nonspecific isozyme	Protein	Humans	Unknown	Substrate	Details