Article

Vitamin B-6: A status report

Department of Nutrition and Food Management, Oregon State University, Corvallis 97331-5103.
Journal of Nutrition (Impact Factor: 4.23). 12/1990; 120 Suppl 11(11):1503-7.
Source: PubMed

ABSTRACT 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, Aug 13, 2015
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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.
    Applied Physiology Nutrition and Metabolism 02/2012; 37(1):167-75. DOI:10.1139/h11-146 · 2.23 Impact Factor
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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.
    Nutrition research and practice 03/2009; 3(1):43-8. DOI:10.4162/nrp.2009.3.1.43 · 1.13 Impact Factor
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    • "The very low-density lipoprotein value was calculated from the value of triacylglycerol divided by 5. Automated high-sensitivity CRP (hs-CRP) measurement concentration was performed using particle-enhanced immunonephelometry with an image analyzer [24]. Adequate vitamin B6 status has been suggested to be a PLP level Ͼ30 nmol/L [25]. Recently, however, vitamin B6 deficiency has been redefined as a plasma PLP concentration Ͻ20 nmol/L [26] [27]. "
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    ABSTRACT: Whether vitamin B6 exerts an independent or a synergic effect in combination with inflammation for the risk of coronary artery disease (CAD) is unclear. The purpose of this study was to investigate whether plasma pyridoxal 5'-phosphate (PLP) is dependent on or independent of the inflammation marker C-reactive protein (CRP) to associate with the risk of CAD. This was a hospital-based case-control. Patients were identified with cardiac catheterization as having at least 70% stenosis of one major coronary artery were assigned to the case group (n = 184). The control group (n = 516) was comprised of healthy individuals with normal blood biochemical values. All subjects' height, weight, blood pressure, plasma PLP, homocysteine, high-sensitivity CRP (hs-CRP), and lipid profiles were measured. Plasma PLP concentration was only negatively associated with hs-CRP level in the control group (beta = -0.001, P = 0.03) but not in the CAD or pooled groups. The magnitude of the risk of CAD for low plasma PLP (odds ratio [OR] 2.39) and high hs-CRP (OR 3.37) was very similar. Low plasma PLP concentration combined with low hs-CRP level (OR 2.34) and high plasma PLP concentration combined with high hs-CRP level (OR 3.61) were independently associated with risk for CAD. However, the combined presence of low PLP and higher hs-CRP levels enhanced the risk of CAD and the magnitude was substantially greater (OR 4.35). Plasma PLP and hs-CRP are independently associated with an increased risk of CAD, the combined presence of low PLP and high hs-CRP enhanced the risk of CAD, and the magnitude was almost double.
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