Direct and Functional Biomarkers of Vitamin B6 Status

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.

[Sufficiency with water-soluble vitamins and state of bone in pregnant women]

Vitamin status and bone strength have been estimated in 91 pregnant women (29.3 ± 4.6 years old) from Moscow by non-invasive methods. Sufficiency with vitamins C, B2, B6 has been evaluated by morning urinary excretion of ascorbic acid, riboflavin and 4-piridoxic acid determined by visual titration and fluorimetric methods. The rate of bone resorption has been measured by the ratio of urinary calcium and creatinine, determined by complexometric titration and spectrophotometrically. The study of the bone strength has been conducted using an ultrasonic densitometer (the speed of the ultrasonic waves along the cortical layer). The lack of vitamin C was found in 20.4% .of the women surveyed, vitamin B2--in 27.4%. Vitamin B6 deficiency was detected most frequently (90%). Excretion of vitamins B2 and B6 in women in the third trimester of pregnancy was lower as compared with the women in the first and second trimester. In 53.3% of the women surveyed an increase in urinary excretion of calcium per creatinine has been observed. Excretion of group B vitamins (especially vitamin B6, 1.75 fold, p < 0.05) in women taking vitamin supplements was higher compared to non-taking vitamins that indicates the better sufficiency of the organism with these vitamins. Among women who took vitamin complexes, inadequate supply with water-soluble vitamins C, B2 and B6 was detected less frequently (the difference was significant for vitamin B2) than among women who did not intake vitamin complexes (in 11.9, 27.7 and 42.4% vs 16.1, 54.8 and 48.8 %). The rate of bone resorption (Ca/creatinine) in women taking vitamins was smaller (0.19 ± 0.09 vs 0.24 ± 0.14, p > 0.05). Ca/creatinine ratio was within normal range in 40% of women who intake vitamins, while in women not taking vitamins--only in 22.2%; this value exceeded the upper limit of norm in the rest. The strength of bone was broken in women in the second and third trimester of pregnancy, having worse supply of vitamins. The percentage of agreement of the results of osteopenia diagnosis assessment (ultrasound densitometry and urinary Ca/creatinine) was 42.2%. Thus, the conclusion has been confirmed that the evaluation of the status of bone is possible only basing on the results of determination of several parameters.

Patients with gastrointestinal tract disorders receiving parenteral nutrition need a higher dose of vitamin C

BACKGROUND/AIMS

Appropriateness of the vitamin doses in Japanese commercial multi-vitamin preparations for parenteral nutrition therapy was investigated in patients with gastrointestinal tract disorder by evaluating the vitamin status (blood concentrations and urinary excretions of vitamins B1, B2, B6, and C) of them.

METHODOLOGY

Commercial multivitamin preparations were administered continuously with a commercial PN solution over 5 days to 10 patients with gastrointestinal tract disorder. Blood concentrations of vitamins B1, B2, B6, and C were measured on the mornings of day 1, day 4, and day 6. Urinary excretions were measured in 24-h urine collections collected after day 3 and after day 5.

RESULTS

Blood concentrations of vitamins B1, B2, and B6 increased but remained within or slightly above the normal throughout the study, and urinary excretion values were normal in all patients. However, blood vitamin C concentration surpassed the lower limit of normal (5.5 microg/mL) only on day 6. Urinary vitamin C excretion was below normal (20.0 mg/day) in all and 7 patients on days 3 and 5, respectively.

CONCLUSIONS

In patients with gastrointestinal tract disorder, the doses of vitamins B1, B2, and B6 of Japanese commercial multi-vitamin preparations are adequate but that of vitamin C (100 mg/day) is inadequate and should be increased.

Effects of excess pantothenic acid administration on the other water-soluble vitamin metabolisms in rats

To acquire the data concerning the tolerable upper intake level which prevents health problems from an excessive intake of pantothenic acid, an animal experiment was done. Rats of the Wistar strain (male, 3 wk old) were fed on a diet which contains 0%, 0.0016% (control group), 1%, or 3% calcium pantothenate for 29 d. The amount of weight increase, the food intake, and the organ weights were measured, as well as the pantothenic acid contents in urine, the liver and blood. Moreover, to learn the influence of excessive pantothenic acid on other water-soluble vitamin metabolism, thiamin, riboflavin, a vitamin B6 catabolite, the niacin catabolites, and ascorbic acid in urine were measured. As for the 3% addition group, enlargement of the testis, diarrhea, and hair damage were observed, and the amount of weight increase and the food intake were less than those of the control group. However, abnormality was not seen in the 1% addition group. The amount of pantothenic acid in urine, the liver, and blood showed a high correlation with intake level of pantothenic acid. It was only for 4-pyridoxic acid, a vitamin B6 catabolite, in urine that a remarkable difference was observed against the control group. Moreover, the (2-Py+4-Py)/MNA excretion ratio for these metabolites of the nicotinamide also indicated a low value in the 3% pantothenic acid group. As for the calcium pantothenate, it was found that the 3% level in the diet was the lowest-observed-adverse-effect-level (LOAEL) and the 1% level was the no-observed-adverse-effect-level (NOAEL).

B-6 vitamers and 4-pyridoxic acid in the plasma, erythrocytes, and urine of postmenopausal women

BACKGROUND

Although many studies have reported reduced vitamin B-6 status with aging, little information is available about the specific effects of menopause.

OBJECTIVE

We aimed to examine vitamin B-6 metabolism in premenopausal and early postmenopausal women.

DESIGN

We examined dietary intake and vitamin B-6 metabolites in the plasma, erythrocytes, and urine of 30 premenopausal women (x +/- SD age: 41.9 +/- 4.8 y) and 30 women (aged 54.0 +/- 3.8 y) who were 4.0 +/- 1.4 y past menopause.

RESULTS

Vitamin B-6 intake in the postmenopausal group (1.97 +/- 0.40 mg/d) was significantly greater than that in the premenopausal group (1.63 +/- 0.50 mg/d). Plasma pyridoxal phosphate (PLP) and pyridoxal concentrations and erythrocyte PLP, pyridoxal, and pyridoxamine phosphate concentrations were in the normal range in both groups and did not differ significantly between the 2 groups. Plasma and erythrocyte 4-pyridoxic acid (4-PA) concentrations were significantly higher in the postmenopausal group than in the premenopausal group, which may have been due at least partly to the slightly higher vitamin B-6 intake of the former group. Erythrocyte 4-PA was correlated (r = -0.37, P < 0.01) with serum estradiol in both groups. Urinary 4-PA did not differ significantly between the 2 groups. The serum phosphate concentration was higher in the postmenopausal group than in the premenopausal group, and it was correlated (r = 0.40, P < 0.01) with plasma PLP. Inhibition of alkaline phosphatase by the increased phosphate may help to increase plasma PLP.

CONCLUSION

Menopause may not necessarily be associated with a decrease in vitamin B-6 status.

Assessment of Vitamin B-6 Estimated Average Requirement and Recommended Dietary Allowance for Adolescents Aged 13–15 Years Using Vitamin B-6 Intake, Nutritional Status and Anthropometry

Because of limited available information, the Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) of vitamin B-6 for adolescents were recently estimated by extrapolation from adult values. To determine vitamin B-6 requirements and to provide recommendations for intakes, vitamin B-6 intake, nutritional status and anthropometry were studied in 134 healthy adolescents (63 boys and 71 girls) aged 13-15 y in Tainan, Taiwan. Direct and indirect vitamin B-6 indicators were measured in plasma, erythrocytes and urine. The anthropometric data of the adolescents in this study were similar to those of the first Nutrition and Health Survey in Taiwan (NAHSIT), conducted from 1993 to 1996, showing the normal growth and development of this adolescent group. All subjects had plasma pyridoxal-5'-phosphate (PLP) concentrations > or = 20 nmol/L, indicating an adequate vitamin B-6 status. The mean dietary vitamin B-6 intakes of boys and girls were 1.04 +/- 0.24 and 0.83 +/- 0.26 mg/d, respectively. Vitamin B-6 status indicators, including plasma PLP, erythrocyte alanine activity coefficient (EALT-AC), aspartate aminotransferase activity coefficient (EAST-AC) and urinary 4-pyridoxic acid (4-PA), were correlated with vitamin B-6 intake (r = 0.84, -0.84, -0.77 and 0.86, respectively, P < 0.01). Adequate values of plasma PLP (> or = 20 nmol/L), EALT-AC (<1.25), EAST-AC (<1.8) and urinary 4-PA (>3.0 micromol/d) were used to determine the EAR according to the Dietary Reference Intake committee methodology. The present study suggests that vitamin B-6 EAR (RDA) for adolescent boys and girls aged 13-15 y are 1.07 (1.28) and 0.90 (1.08) mg/d, respectively.

The status of plasma homocysteine and related B-vitamins in healthy young vegetarians and nonvegetarians

BACKGROUND

Exclusion of animal products and having only plant protein in vegetarian diets may affect the status of certain B-vitamins, and further cause the elevation of plasma homocysteine concentration.

AIM

The purpose of this study was to assess the status of homocysteine and related B-vitamins in vegetarians and nonvegetarians. The effects of biochemical parameters of B-vitamins and dietary protein on plasma homocysteine were also examined.

METHODS

The study was performed at the Chung Shan Medical University, Taichung, in the central part of Taiwan. Thirty-seven vegetarians (28.9 +/- 5.5 y) and 32 nonvegetarians (22.9 +/- 1.6 y) were recruited. Nutrient intake was recorded using 3-day dietary records. Fasting venous blood samples were obtained. Plasma homocysteine, folate and vitamin B-12 were measured. Vitamin B-6 status was assessed by direct measures [plasma pyridoxal 5'-phosphate (PLP) and urinary 4-pyridoxic acid (4-PA)] and indirect measures [erythrocyte alanine (EALT-AC) and aspartate (EAST-AC) aminotransaminase activity coefficient].

RESULTS

There was no significant difference in vitamin B-6 intake between the two groups, although the vegetarian group had a significantly lower vitamin B-12 intake than the nonvegetarian group. Vegetarian subjects had significantly lower mean plasma PLP and vitamin B-12 concentrations than did nonvegetarian subjects (p < 0.05); however, a significantly higher mean plasma folate concentration was found in the vegetarian group. Vegetarian subjects had a significantly higher mean plasma homocysteine concentration than nonvegetarian subjects (13.2 +/- 7.9 vs. 9.8 +/- 2.2 micromol/L). Negative correlations were seen between plasma homocysteine and vitamin B-12 concentrations in the vegetarian (p = 0.004), nonvegetarian (p = 0.026), and pooled (p < 0.001) groups. From best subsets regression analyses, the plasma homocysteine concentration could be significantly predicted by total protein intake (p = 0.027) and plasma vitamin B-12 concentration (p = 0.005) in the pooled group. When the intake of protein is not considered, vitamin B-12 concentration is still a strong predictor of plasma homocysteine concentration (p = 0.012).

CONCLUSIONS

Vitamin B-12 intake and mean plasma vitamin B-12 concentration were lower for vegetarian subjects than for nonvegetarian subjects, leading to an increase in plasma homocysteine concentration. Vitamin B-6 and folate had little effect on plasma homocysteine concentration when individuals had adequate vitamin B-6 and folate status.