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.

中文翻译：

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维生素 B6 状态的直接和功能生物标志物。


B6 状态的测量分为直接生物标志物和功能生物标志物。直接生物标志物可测量血浆/血清、尿液和红细胞中的 B6 维生素，其中最常用的是血浆吡哆醛 5'-磷酸 (PLP)。功能性生物标志物包括红细胞转氨酶活性，以及​​最近参与 PLP 依赖性反应的代谢物的血浆水平，例如犬尿氨酸途径、一碳代谢、转硫作用（胱硫醚）和甘氨酸脱羧（丝氨酸和甘氨酸）。由于炎症、碱性磷酸酶活性、低血清白蛋白、肾功能和无机磷酸盐等潜在混杂因素的影响，最好使用生物标志物组合来评估维生素 B6 状态。最近研究了底物-产物对之间的比率作为减弱这种影响的策略。这些努力提供了有前景的新标志物，例如 PAr 指数、3-羟基犬尿氨酸：黄尿酸比率以及氧化戊二酸：谷氨酸比率。基于质谱的靶向代谢分析或非靶向代谢组学可以使用数据缩减统计同时定量大量代谢物，这些代谢物目前被评估为功能性生物标志物。