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

Abstract

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 Ȁ SD age: 41.9 Ȁ 4.8 y) and 30 women (aged 54.0 Ȁ 3.8 y) who were 4.0 Ȁ 1.4 y past menopause. Results: Vitamin B-6 intake in the postmenopausal group (1.97 Ȁ 0.40 mg/d) was significantly greater than that in the premenopausal group (1.63 Ȁ 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 ҃ Ҁ0.37, 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.Am J Clin Nutr 2004;80:946 -51.

Plasma B Vitamers: Population Epidemiology and Parent-Child Concordance in Children and Adults

“…Parent-child correlations in B vitamer concentrations were generally weak. Notably, the lowest variability explained by a shared gene-environment (family) effect was evident for B vitamers that reflect dietary intake in different body fluids (e.g., 9% for 4-pyridoxic acid, 11% for riboflavin, and 16% for FMN) [20,[27][28][29]. Conversely, the B vitamer with the highest percentage of variability explained by family effects was nicotinamide (31%), which is not as representative of niacin intake [5,7,27,30].…”

“…However, proposing developmental differences in metabolic utilization as an explanation for these inter-generational variations may be misleading because: (1) B vitamers are involved in critical physiological metabolic networks across the lifecycle (e.g., the Krebs cycle, the electron transport chain, one-carbon metabolism), and (2) we have only characterised B vitamer profiles at one semi-fasted time point in these dyads, making impacts due to recent dietary intake a possibility [3,13]. Therefore, it remains likely that higher levels of B vitamers simply reflect differences in recent intake or excretion rates [20,28].…”

Direct and Functional Biomarkers of Vitamin B6 Status

“…The inhibition may explain the positive correlation between plasma PLP and inorganic phosphate (139) and the increased plasma PLP in postmenopausal women with elevated serum inorganic phosphate inherent to bone loss (139). Low plasma PLP has been noted in conditions with elevated ALP like liver and bone disease, cancer, pregnancy (6, 11, 143) and diabetes (low PLP/PL ratio) (138, 161); plasma PLP is essentially unaffected by renal function (12).…”

“…However, the increase in plasma PLP in postmenopausal women may partly reflect increased levels of inorganic phosphate inhibiting ALP (139). …”

Dietary Reference Values for vitamin B6

“…The concentrations of total vitamin B6 in plasma (a combined measurement of all vitamin B6 derivatives), of individual vitamin B6 derivatives (PL and PMP) in plasma or erythrocytes, and of PLP in erythrocytes, as well as ratios of concentrations in plasma (PLP, PL and PA) have been assessed in adults (Miller et al, 1985;Pannemans et al, 1994;Hansen et al, 1997Hansen et al, , 2001Huang et al, 1998;Masse et al, 2004;Vasilaki et al, 2008;Ulvik et al, 2014). However, criteria for adequacy of these biomarkers have not been developed and their usefulness for assessment of vitamin B6 status is limited.…”