1 Food, Nutrition and Health, Faculty of Land and Food Systems, the University of British Columbia, Vancouver, BC, Canadá. 2 Nutrition Institute, Federal University Rio de Janeiro, Brazil. 3 USDA, Western Human Nutrition Research Center, Davis, Canadá.
Background. Vitamin B6 in form of pyridoxal 5´-phosphate (PLP) has a key role in fatty acid metabolism. Dietary vitamin B6 restriction was shown to decrease docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (AA) concentrations in healthy adults. Aim. To assess the relationship between plasma PLP and DHA, EPA, AA, linoleic acid (LA) and α-linolenic acid (ALA) concentrations across pregnancy. Methods. A prospective cohort study in 213 healthy Brazilian pregnant women (20-40y) was conducted in Rio de Janeiro, Brazil. Participants were followed across trimesters (5th-13th, 20th-26th and 30th-36th gestational week). Fasting plasma PLP (nmol/L) and serum fatty acid (μg/L) concentrations were measured with HPLC and GCMS, respectively. ANOVA for repeated measures was used to compare PLP and PUFA concentrations between trimesters. A longitudinal linear mixedeffect regression models was used to evaluate the association between ΔPLP (i.e., difference between the 3rd and 1st trimester PLP concentrations) and PUFA concentrations across pregnancy. The model was adjusted by first trimester plasma PLP concentrations, gestational week, smoke habit, dietary vitamin B6, fish and individual fatty acid intake. Results. Plasma PLP concentrations [median (IQR)] decreased from [35.4 (27.7-44.0)] in the 1st to [21.1 (16.5- 27.2)] in the 2nd to [16.7 (12.9-21.5)] in the 3rd trimester (both p<0.0001). DHA, AA, LA, ALA concentrations increased across pregnancy (p<0.05). ALA concentrations increased between the 1st and 2nd (p<0.05), decreasing between the 2nd and 3rd trimester (p<0.05). Δ plasma PLP concentrations were positively associated with DHA (β=0.254, p=0.011) and n-6/n-3 ratio (β=-0.012, p=0.01). Conclusions. First-trimester plasma PLP concentration and its changes across trimesters were positively associated with DHA concentrations and n-6/n-3 ratio in healthy pregnant women.