Vitamin B-6: A status report

Department of Nutrition and Food Management, Oregon State University, Corvallis 97331-5103.
Journal of Nutrition (Impact Factor: 3.88). 12/1990; 120 Suppl 11(11):1503-7.
Source: PubMed


Over the past 50 yr there has been an increased awareness of the importance of vitamin B-6 in human nutrition. The knowledge base for evaluation of vitamin B-6 status has also increased. Indices for vitamin B-6 status can be separated into direct and indirect measures. Among the direct measures, plasma pyridoxal 5'-phosphate (PLP) is considered the most relevant. However, measurement of plasma pyridoxal or total vitamin B-6 and urinary 4-pyridoxic acid are also recommended. Indirect measures of vitamin B-6 include the assessment of urinary excretion of xanthurenic acid following a tryptophan load. This is a valid functional index for otherwise healthy persons. Evaluation of erythrocyte transaminase activity and stimulation with PLP provide an estimate of vitamin B-6 intake over an extended period of time. In addition to biochemical measures, determination of vitamin B-6 and protein intake are necessary. Present evidence suggests plasma PLP, urinary 4-pyridoxic acid, at least one indirect measure, and the intake of vitamin B-6 and protein are needed to properly assess vitamin B-6 status. The levels of plasma pyridoxal and erythrocyte PLP are newer measures of status and, with further refinement of methodology, may provide additional insight into vitamin B-6 status.

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Available from: Jim Leklem
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    • "Measurement of urinary or plasma XA has been used clinically to study vitamin B6 deficiency [8, 13, 14], including febrile disorder [15], theophylline-induced asthma [16], drug-induced diabetes [16], the effect of tryptophan and six of its metabolites on the nicotinic acid pathway [17], and the etiological role in a variety of chronic degenerative disease including a variety of cancers [18–22]. Among the methods developed for quantifying urinary XA [23–28], one tedious and lengthy assay involved the extraction of XA from urine with isobutanol, isolation by thin-layer chromatography, and eventually spectrophotometric determination [25]. "
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    ABSTRACT: A novel spectrophotometric method for the quantification of urinary xanthurenic acid (XA) is described. The direct acid ferric reduction (DAFR) procedure was used to quantify XA after it was purified by a solid-phase extraction column. The linearity of proposed method extends from 2.5 to 100.0 mg/L. The method is precise, yielding day-to-day CVs for two pooled controls of 3.5% and 4.6%, respectively. Correlation studies with an established HPLC method and a fluorometric procedure showed correlation coefficients of 0.98 and 0.98, respectively. Interference from various urinary metabolites was insignificant. In a small-scale screening of elderly conducted at Penghu county in Taiwan (n = 80), we were able to identify a group of twenty individuals having hyperhomocysteinemia (>15 μ mole/L). Three of them were found to be positive for XA as analyzed by the proposed method, which correlated excellently with the results of the activation coefficient method for RBC's AST/B6 functional test. These data confirm the usefulness of the proposed method for identifying urinary XA as an indicator of vitamin B6 deficiency-associated hyperhomocysteinemic condition.
    Full-text · Article · Sep 2013
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    • "For their experiment, using a vitamin B 6 -deficient animal model, Massé et al. (1989) determined both PLP and PL (total vitamin B 6 aldehydes) by HPLC. Leklem (1990) suggested that urinary 4′-pyridoxic acid (4′PA) analysis be added for better assessment of an individual's vitamin B 6 nutritional status. "
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    ABSTRACT: Vitamin B(6) (pyridoxine) metabolism in diabetes has never been investigated except for a few reports on plasma pyridoxal 5'-phosphate (PLP). These studies indicated that this most active (coenzyme) vitamer can be reduced. The present clinical investigation aimed to measure all vitamers in blood and urine by high performance liquid chromatography as well as important related factors, in women during active reproductive years. Thirty-two insulin-treated type 1 diabetic (T1D) patients, without renal complication, and 27 well-matched healthy controls, aged 30 to 40 years old, were recruited using rigorous criteria. Both groups had normal hemoglobin and serum albumin levels. Plasma PLP and pyridoxal (PL) did not differ significantly in the T1D group but alkaline phosphatase (ALP) activity was greater (p < 0.01). This produced a shift in plasma PLP-PL profile, as evidenced by a lower plasma PLP/PL ratio (p < 0.05). Enhanced ALP activity meant more PLP being dephosphorylated to PL (the membrane transfer form), with more ending up in erythrocytes to be rephosphorylated in its active form, as suggested by the significant positive correlation (p < 0.001) between plasma PL and erythrocyte PLP. More PL into blood circulation also means more oxidation of this vitamer to 4'-pyridoxic acid in kidneys, as confirmed by the positive correlation between plasma PL and urinary 4'-pyridoxic acid (p < 0.001). The positive correlation (p < 0.001) between ALP activity and glycosylated hemoglobin indicated a direct effect of the disease. The T1D-induced alteration in vitamin B(6) metabolism, consecutive to enhanced ALP activity, may put patients at greater risk of vitamin B(6) deficiency and diabetic complications.
    Full-text · Article · Feb 2012 · Applied Physiology Nutrition and Metabolism
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    • "Nutritional state of B vitamins Mean ± S.E. Normal range 2) Thiamin Percent activation of enzymes 36.5 ± 4.8 ≤15 Riboflavin Percent activation of enzymes 43.1 ± 3.9 ≤20 Vitamin B6 Percent activation of enzymes 98.8 ± 7.3 ≤80 Erythrocyte folate (nmol/L) 406.6 ± 31.9 ≥362 Plasma folate (nmol/L) 21.3 ± 2.5 ≥15.9 1) Values are the mean ± S.E. 2) See references (Herbert, 1987; Leklem, 1990; Sauberlich et al., 1972; Tanphaichitr et al., 1970 "
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    ABSTRACT: We investigated the nutritional state of B vitamins and the neuropsychological functions in 25 subjects, aged 63.1 +/- 6.3 years, residing in rural areas of Korea. Nutritional states of thiamin, riboflavin, and pyridoxine were assessed enzymatically in the erythrocytes, and folate concentrations were measured microbiologically in the plasma and erythrocytes. A battery of composite neuropsychological test was administered to the subjects. Plasma folate was correlated with the total intelligence score (p=0.049). Folate levels in the erythrocytes were correlated with the performance intelligence scores such as block design (p=0.017) and picture arrangement (p=0.016). The red cell folate was correlated with memory scores such as general memory (p=0.009) and delayed recall (p=0.000). Although it did not reach statistical significance, verbal memory (p=0.053) was highly correlated with the red cell folate. The red cell folate was also correlated positively with the percent of conceptual level response number score (p=0.029), and negatively with the grooved pegboard test score for the non-dominant hand (p=0.010). Fine motor coordination was also influenced by folate nutrition, as finger tapping scores in both hands were significantly correlated with red cell folate (dominant hand; p=0.026, non-dominant hand; p=0.004). Other B vitamins such as thiamin, riboflavin, and vitamin B(6) were not as strongly correlated with neuropsychological function test scores as folate was. These results suggest that folate nutrition influences neuropsychological function test scores significantly in humans. Further studies are needed to explore the relationship between folate or other vitamin B nutrition and neuropsychological functions and the implications thereof.
    Full-text · Article · Mar 2009 · Nutrition research and practice
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