Shannon Masih

High concentrations of folate and unmetabolized folic acid in a cohort of pregnant Canadian women and umbilical cord blood

BACKGROUND Mandatory fortification, prevalent supplement use, and public health guidelines recommending periconceptional supplementation have increased folic acid intakes in North American pregnant women. However, the effects of increased folic acid intakes during pregnancy on maternal and cord blood folate concentrations have not been well established. OBJECTIVES In this prospective study, we determined maternal and cord blood concentrations of folate and unmetabolized folic acid (UMFA) in a cohort of pregnant Canadian women and their newborns and examined the effect of maternal intakes of folate and folic acid and fetal genetic variants in folate metabolism on folate status. DESIGN Folate and folic acid intakes of 368 Canadian pregnant women were assessed in early (0-16 wk) and late (23-37 wk) pregnancy. Blood concentrations of folate and UMFA were measured with the use of immunoassays and liquid chromatography-mass spectrometry, respectively, in maternal samples in early pregnancy (12-16 wk), at delivery (28-42 wk), and in cord blood. Four fetal genetic variants of the 5,10-methylenetetrahydrofolate reductase (MTHFR) and dihydrofolate reductase (DHFR) genes were assessed for their association with cord blood concentrations of folate and UMFA. RESULTS Geometric mean (95% CI) maternal red blood cell (RBC) folate concentrations were 2417 nmol/L (2362, 2472 nmol/L ) and 2793 nmol/L (2721, 2867 nmol/L ) in early pregnancy and at delivery, respectively. The mean (95% CI) cord RBC folate concentration was 2689 nmol/L (2614, 2765 nmol/L). UMFA was detectable in >90% of maternal and cord plasma samples. Although 3 fetal MTHFR and DHFR genetic variants had no effect, the fetal MTHFR 677TT genotype was associated with significantly lower cord serum (P = 0.03) and higher cord RBC (P = 0.02) folate concentrations than those of the wild type. CONCLUSIONS Notwithstanding differences in assays, maternal and cord RBC folate and plasma UMFA concentrations were higher than previously reported values. Functional ramifications of high folate and UMFA concentrations in maternal and fetal circulation warrant additional investigation because an excess folate status may affect long-term health outcomes of the offspring. This study was registered at www.clinicaltrials.gov as NCT02244684.

Pregnant Canadian Women Achieve Recommended Intakes of One-Carbon Nutrients through Prenatal Supplementation but the Supplement Composition, Including Choline, Requires Reconsideration

BACKGROUND Folate, vitamin B-6, vitamin B-12, and choline are involved in one-carbon metabolism and play critical roles in pregnancy including prevention of birth defects and promotion of neurodevelopment. However, excessive intakes may adversely affect disease susceptibility in offspring. Intakes of these nutrients during pregnancy are not well characterized. OBJECTIVE Our aim was to determine dietary and supplemental intakes and major dietary sources of one-carbon nutrients during pregnancy. METHODS In pregnant women (n = 368) at ≤16 wk postconception, supplement use >30 d before pregnancy was assessed by maternal recall and supplement and dietary intakes in early (0-16 wk) and late pregnancy (23-37 wk) were assessed by food-frequency questionnaire. RESULTS Preconception, 60.1% (95% CI: 55.8, 64.3) of women used B vitamin-containing supplements. This increased to 92.8% (95% CI: 89.6, 95.2) in early and 89.0% (95% CI: 85.0, 92.3) in late pregnancy. Median supplemental folic acid, vitamin B-12, and vitamin B-6 were 1000 μg/d, 2.6 μg/d, and 1.9 mg/d, respectively. Forty-one percent and 50% of women had dietary intakes of folate and vitamin B-6 less than the estimated average requirement (520 mg/d dietary folate equivalents and 1.6 mg/d, respectively). Eight-seven percent of women had choline intakes less than the Adequate Intake (450 mg/d). Dietary intakes did not change appreciably during pregnancy. Fruits and vegetables and fortified foods contributed ∼57% to total dietary folate intake. Fruits and vegetables contributed ∼32% to total dietary vitamin B-6 intake and dairy and egg products contributed ∼37% to total dietary vitamin B-12 intake. CONCLUSIONS Vitamin supplements were an important source of one-carbon nutrients during pregnancy in our sample. Without supplements, many women would not have consumed quantities of folate and vitamin B-6 consistent with recommendations. Given the importance of choline in pregnancy, further research to consider inclusion in prenatal supplements is warranted. This trial was registered at clinicaltrials.gov as NCT02244684.

Maternal Choline Status, but Not Fetal Genotype, Influences Cord Plasma Choline Metabolite Concentrations

BACKGROUND Choline deficiency during pregnancy can lead to adverse birth outcomes, including impaired neurodevelopment and birth defects. Genetic variants of choline and one-carbon metabolism may also influence birth outcomes by altering plasma choline concentrations. The effects of maternal ad libitum choline intake during pregnancy and fetal genetic variants on maternal and cord concentrations of choline and its metabolites are unknown. OBJECTIVES This prospective study sought to assess the effect of 1) maternal dietary choline intake on maternal and cord plasma concentrations of choline and its metabolites, and 2) fetal genetic polymorphisms on cord plasma concentrations. METHODS The dietary choline intake of 368 pregnant Canadian women was assessed in early (0-16 wk) and late (23-37 wk) pregnancy with the use of a food frequency questionnaire. Plasma concentrations of free choline and its metabolites were measured in maternal samples at recruitment and delivery, and in the cord blood. Ten fetal genetic variants in choline and one-carbon metabolism were assessed for their association with cord plasma concentrations of free choline and its metabolites. RESULTS Mean maternal plasma free choline, dimethylglycine, and trimethylamine N-oxide (TMAO) concentrations increased during pregnancy by 49%, 17%, and 13%, respectively (P < 0.005), whereas betaine concentrations decreased by 21% (P < 0.005). Cord plasma concentrations of free choline, betaine, dimethylglycine, and TMAO were 3.2, 2.0, 1.3, and 0.88 times corresponding maternal concentrations at delivery, respectively (all P < 0.005). Maternal plasma concentrations of betaine, dimethylglycine, and TMAO (r(2) = 0.19-0.51; P < 0.0001) at delivery were moderately strong, whereas maternal concentrations of free choline were not significant (r(2) = 0.12; P = 0.06), predictors of cord plasma concentrations of these metabolites. Neither maternal dietary intake nor fetal genetic variants predicted maternal or cord plasma concentrations of choline and its metabolites. CONCLUSION These data collectively indicate that maternal choline status, but not fetal genotype, influences cord plasma concentrations of choline metabolites. This trial was registered at clinicaltrials.gov as NCT02244684.

Low Serum Vitamin B-12 Concentrations Are Prevalent in a Cohort of Pregnant Canadian Women

BACKGROUND Among Canadian women of reproductive age, 5% and 20% have serum vitamin B-12 concentrations indicative of deficiency (<148 pmol/L) and marginal status (148-220 pmol/L), respectively. Given the association between suboptimal vitamin B-12 and adverse pregnancy outcomes, an understanding of vitamin B-12 status during pregnancy, and factors that influence it, is required. OBJECTIVE This prospective analysis from the PREFORM (PREnatal FOlic acid exposuRe on DNA Methylation in the newborn infant) study investigated 1) vitamin B-12 status in a cohort of Canadian pregnant women and their newborns, 2) the association of maternal dietary vitamin B-12 intake with maternal and cord blood concentrations of vitamin B-12 and its biomarkers, and 3) the association of fetal genetic polymorphisms with cord blood concentrations of vitamin B-12 and its biomarkers. METHODS In pregnant Canadian women (n = 368; mean ± SD age: 32 ± 5 y), vitamin B-12 intakes were assessed in early (0-16 wk) and mid- to late (23-37 wk) pregnancy. Serum vitamin B-12 and plasma total homocysteine (tHcy) and methylmalonic acid (MMA) in maternal blood at 12-16 wk of pregnancy and at delivery (28-42 wk) and in cord blood were measured and compared by using regression analyses. The associations of 28 fetal genetic variants in vitamin B-12 metabolism and cord blood vitamin B-12, tHcy, and MMA concentrations were assessed by using regression analysis, with adjustment for multiple testing. RESULTS A total of 17% and 38% of women had deficient and 35% and 43% had marginal serum vitamin B-12 concentrations at 12-16 wk of pregnancy and at delivery, respectively. Only 1.9-5.3% had elevated MMA (>271 nmol/L), and no women had elevated tHcy (>13 μmol/L). Maternal dietary vitamin B-12 intake during pregnancy was either weakly associated or not associated with maternal and cord blood vitamin B-12 (r(2) = 0.17-0.24, P < 0.0008), tHcy (P = NS) and MMA (r(2) = 0.05-0.11, P < 0.001). Fetal genetic polymorphisms were not associated with cord blood concentrations of vitamin B-12 and its biomarkers. CONCLUSIONS Deficient and marginal serum vitamin B-12 concentrations are prevalent in Canadian pregnant women with the use of traditional cutoffs, despite supplement use. Given the growing interest among women to adhere to a vegetarian diet that may be lower in vitamin B-12, and vitamin B-12s importance in pregnancy, the functional ramifications of these observations need to be elucidated. This trial was registered at clinicaltrials.gov as NCT02244684.

Fetal one-carbon nutrient concentrations may be affected by gestational diabetes

Both insufficiency and excess of one-carbon nutrients (folate, choline, vitamins B6 and B12) during pregnancy have been associated with gestational diabetes mellitus (GDM). However, the precise nature of this association has not been clearly established. We hypothesized that GDM may affect one-carbon nutrients concentrations in the fetus, thus possibly participating in epigenetic programing of the offspring. Maternal blood was collected at recruitment (12-16 weeks). At delivery (28-42 weeks), both maternal and cord blood were collected. Blood concentrations of one-carbon nutrients and their metabolites were compared between the two groups. A total of 368 women were included in the study, of whom 19 (5.6%) were later diagnosed with GDM. No significant differences were found in maternal blood concentrations of one-carbon nutrients and their metabolites between the GDM and control groups at recruitment or at delivery. In cord blood, however, serum folate (87.7 [IQR 70.4-103.9] vs 66.6 [IQR 45.5-80.3] nmol/L, P = .025) and plasma TMAO (2.82 [IQR 1.3-3.2] vs 1.35 [IQR 1.0-2.0] μmol/L, P = .017) concentrations were higher, while plasma betaine concentrations were lower (17.5 [IQR 16.3-19.4] vs 21.1 [IQR 18.0-24.1] μmol/L, P = .019) in infants born to mothers with GDM compared with control. Our data suggest that while maternal blood concentrations of one-carbon nutrients and their metabolites may not affect the risk of GDM, GDM may alter concentrations of serum folate, plasma betaine and TMAO in cord blood. These alterations in one-carbon nutrient concentrations in fetal circulation may impact epigenetic programing, thereby contributing to physiologic changes and disease susceptibility in adulthood associated with GDM offspring.

One-Carbon Metabolism Nutrients and Epigenetics: A Mechanistic Link Between Aberrant One-Carbon Metabolism and Cancer Risk?

In relation to the genome, investigation of the epigenome is emerging as an equal, if not more influential factor in modulating human health and disease. Since epigenetic modifications are gradual in onset and potentially reversible, determining factors that modulate the epigenome is critical for possible preventive and therapeutic interventions. The development and progression of cancer is mechanistically linked to a number of epigenetic changes, including global DNA hypomethylation and gene-specific CpG promoter DNA hypermethylation. Environmental factors, including diet, have been shown to affect cancer risk, via epigenetic and non-epigenetic mechanisms. In this regard, one-carbon nutrients are prototypic dietary factors that may modulate cancer risk via epigenetic mechanisms. This chapter will discuss the role of nutrients involved in one-carbon metabolism and their effect on cancer risk via epigenetic modifications with a particular focus on DNA methylation.