Relation between maternal and infant blood folate activities

Distribution and correlates of plasma folate, vitamin B12, and homocysteine in a sample of low-income minority children aged 6 months to 9 years in the U.S

Background

Precision nutrition emphasizes tailoring dietary requirements across populations and life stages. Optimal folate and vitamin B12 levels are important for normal growth and development, but data are lacking for low-income minority U.S. children during early life periods. This study aimed to describe folate, vitamin B12, homocysteine (Hcy) levels, and influencing factors to address the gaps.

Methods

Blood samples from children aged 6 months to 9 years and mothers 48-72 hours postpartum in the Boston Birth Cohort (BBC) were tested for folate, vitamin B12, and Hcy. Maternal and child characteristics, sociodemographic factors, and feeding status were obtained from a standard maternal questionnaire interview at the enrollment and follow-up, and medical records. The distribution of children's folate, vitamin B12, and Hcy were described and factors influencing these biomarkers were analyzed.

Results

A wide distribution of folate, vitamin B12, and Hcy levels was observed in this sample, with longitudinal trends consistent with National Health and Nutrition Examination Survey (NHANES) data. Multivariate analysis showed that very preterm birth correlated with higher folate levels (adjusted β 4.236; 95% CI: 1.218, 7.253; p=0.006). Children aged 1-2 years and 3-8 years had lower folate levels compared to those <1 year (adjusted β -10.191 and -7.499 respectively; p<0.001). Vitamin B12 levels were higher in Black children (adjusted fold change 1.139; 95% CI: 1.052, 1.233; p=0.001) and those children whose mothers' B12 levels were at the highest quartile (Q4) (adjusted fold change 1.229; 95% CI: 1.094, 1.380; p=0.001). Delayed solid food introduction (> 6 months) correlated with lower children's B12 levels (adjusted fold change 0.888; 95% CI: 0.809, 0.975; p=0.013). Hcy levels were lower in Black children (adjusted fold change 0.962; 95% CI: 0.932, 0.993; p=0.018), higher in children with maternal Hcy levels in Q4 (adjusted fold change 1.081; 95% CI: 1.03, 1.135; p=0.002) and in children aged 3-8 years (adjusted fold change 1.084; 95% CI: 1.040, 1.131; p< 0.001).

Conclusions

This study revealed wide variations in plasma folate, vitamin B12, and Hcy levels among low-income minority U.S. children and identified race, maternal levels, child's age, prematurity, and timing of solid food introduction as significant correlates.

Infant blood concentrations of folate markers and catabolites are modified by 5,10-methylenetetrahydrofolate reductase C677T genotype and dietary folate source

BACKGROUND

Folate intake and polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene may affect folate metabolism in infants.

OBJECTIVES

We investigated the association between infant's MTHFR C677T genotype, the dietary folate source, and concentrations of folate markers in the blood.

METHODS

We studied 110 breastfed infants (reference) and 182 infants who were randomly assigned to receive infant formulas enriched with either 78 μg folic acid or 81 μg (6S)-5-methyltetrahydrofolate (5-MTHF) per 100 g milk powder for 12 wk. The blood samples were available at the ages of <1 mo (baseline) and 16 wk. MTHFR genotype and concentrations of folate markers and catabolites [i.e., para-aminobenzoylglutamate (pABG)] were analyzed.

RESULTS

At baseline, carriers of the TT genotype (vs. CC) had lower mean (SD) concentrations (all in nmol/L) of red blood cell (RBC) folate [1194 (507) vs. 1440 (521), P = 0.033) and plasma pABG [5.7 (4.9) vs. 12.5 (8.1), P < 0.001] but higher plasma 5-MTHF [33.9 (16.8) vs. 24.0 (12.6), P < 0.001]. Irrespective of the genotype, infant formula with 5-MTHF (vs. folic acid) caused a significant increase in RBC folate concentration [1278 (466) vs. 947 (552), P < 0.001]. In breastfed infants, plasma concentrations of 5-MTHF and pABG increased significantly by 7.7 (20.5) and 6.4 (10.5), respectively, from baseline to 16 wk. Infant formula that complies with the present EU legislation for folate intake increased RBC folate and plasma pABG concentrations at 16 wk (P < 0.001) than formula-fed infants. At 16 wk, plasma pABG concentrations remained ∼50% lower in carriers of the TT (vs. the CC) genotype among all feeding groups.

CONCLUSIONS

Folate intake from infant formula according to the present EU legislation increased RBC folate and plasma pABG concentrations in infants to a greater extent than breastfeeding, particularly in carriers of the TT genotype. However, this intake did not completely abolish the between-genotype differences in pABG. Whether these differences have any clinical relevance, however, remains unclear. This trial was registered at clinicaltrials.gov as NCT02437721.

Evidence from a Randomized Trial That Exposure to Supplemental Folic Acid at Recommended Levels during Pregnancy Does Not Lead to Increased Unmetabolized Folic Acid Concentrations in Maternal or Cord Blood

BACKGROUND

Exposure to higher intakes of folic acid (FA) from fortified foods and supplements, although largely considered beneficial, is associated with unmetabolized FA in the circulation, which has raised some health concerns.

OBJECTIVE

The effect of supplemental FA at a dose of 400 μg/d during pregnancy on unmetabolized FA concentrations in maternal plasma and newborn cord blood plasma was investigated.

METHODS

A new analysis was performed of blood samples from participants in a randomized trial in pregnancy. Women aged 18-35 y, who had taken 400 μg FA/d as recommended in the first trimester, were recruited at the start of trimester 2 and randomly allocated to receive either 400 μg FA/d (n = 59) or a placebo (n = 67) throughout the second and third trimesters until delivery. Unmetabolized FA concentrations in maternal and cord blood samples were measured by LC-tandem MS analysis.

RESULTS

In response to the intervention from gestational week 14 through delivery, a higher proportion of women in the FA compared with the placebo group had detectable FA (≥0.27 nmol/L) in plasma, but the difference in concentrations was not statistically significant (mean ± SD: 0.44 ± 0.80 compared with 0.13 ± 0.49 nmol/L, P = 0.38). FA treatment throughout pregnancy resulted in higher cord blood plasma total folate (50.6 ± 20.1 compared with 34.5 ± 14.4 nmol/L; P = 0.004) and 5-methyltetrahydrofolate (50.4 ± 20.3 compared with 34.5 ± 14.4 nmol/L; P = 0.005) concentrations, but FA was detected only in 8 of 53 available cord blood samples, and the proportion of samples with detectable FA concentrations was similar in FA-treated and placebo groups.

CONCLUSIONS

Plasma concentrations of unmetabolized FA arising from supplemental FA at a dose of 400 μg/d, in addition to FA from fortified foods, were low or undetectable in mothers and newborns. The benefits for mothers and offspring of continuing FA supplementation beyond the first trimester of pregnancy can be achieved without posing any risk of increasing unmetabolized circulating FA, even in those already exposed to FA from fortified foods.

Transfer of folic acid inside the first-trimester gestational sac and the effect of maternal smoking

OBJECTIVE

The objective of the study was to investigate the transfer pathways of folic acid inside the first-trimester gestational sac and to evaluate the impact of maternal smoking.

STUDY DESIGN

Folate and cotinine levels were evaluated in maternal serum (n = 125) and coelomic fluid (n = 42), and immunostaining was used to identify folate receptors in placental villi, decidual tissue, and secondary yolk sacs from normal pregnancies at 6-12 weeks' gestation.

RESULTS

Folate receptors-alpha were found on the apical surface of syncytiotrophoblast, uterine glandular epithelial cells, and mesothelial layer of the yolk sac. Significantly higher (P < .05) median folate levels were found in maternal serum than in coelomic fluid. The median folate maternal serum and coelomic levels were significantly (P < .0001 and P < .005) lower in smokers, compared with nonsmokers.

CONCLUSION

Uterine glands and the secondary yolk sac play key roles in supplying folic acid to the developing fetus before the placental circulations are established, and maternal smoking does not seem to impair directly its transfer mechanism in early pregnancy.

Folate and human reproduction

The influence of folate nutritional status on various pregnancy outcomes has long been recognized. Studies conducted in the 1950s and 1960s led to the recognition of prenatal folic acid supplementation as a means to prevent pregnancy-induced megaloblastic anemia. In the 1990s, the utility of periconceptional folic acid supplementation and folic acid food fortification emerged when they were proven to prevent the occurrence of neural tube defects. These distinctively different uses of folic acid may well be ranked among the most significant public health measures for the prevention of pregnancy-related disorders. Folate is now viewed not only as a nutrient needed to prevent megaloblastic anemia in pregnancy but also as a vitamin essential for reproductive health. This review focuses on the relation between various outcomes of human reproduction (ie, pregnancy, lactation, and male reproduction) and folate nutrition and metabolism, homocysteine metabolism, and polymorphisms of genes that encode folate-related enzymes or proteins, and we identify issues for future research.

Do breastfed infants need supplemental vitamins?

Table 2 shows that human milk will not meet the DRI for all vitamins in breastfeeding infants. The most glaring discrepancy between intake and the RDA is for vitamin D, although, as discussed, infants may synthesize this from sunlight exposure. Vitamin K must be given in the newborn period. Deficiencies of other vitamins are rare, especially if mothers are nourished adequately. If breastfeeding infants are to be supplemented with vitamin D or any other vitamins, the standard liquid preparations available all contain large amounts of the water-soluble and fat-soluble vitamins (except for vitamin K), which more than meets the RDA. The milk content of thiamin, pyridoxine, and niacin is correlated highly with maternal intake, and these vitamins are all present in relatively large amounts in standard multivitamin tablets given to lactating mothers. In conclusion, in healthy, breastfed infants of well-nourished mothers, there is little risk for vitamin deficiencies and the need for vitamin supplementation is rare. The exceptions to this are a need for vitamin K in the immediate newborn period and vitamin D in breastfed infants with dark skin or inadequate sunlight exposure.

Characterization of folate uptake in guinea pig placenta

Trophoblast uptake of folate and methotrexate (MTX) was investigated in an in situ or dually perfused (maternal and fetal side) guinea pig placenta by using a single-circulation, paired-tracer technique. For [3H]folate, uptake into trophoblast was rapid (s), high (60-80%) and Na+ independent, and exhibited negligible efflux on both poles of placenta. [3H]folate uptake could be inhibited by folate or 5-methyltetrahydrofolate (CH3THF) but not by equimolar (0.1 microM) MTX, folinic acid, aminopterin, trimoprim, or adenine when these compounds were present in perfusate. Inhibitory effect of folate was time dependent, and its complete reversal by folate-free perfusion required up to 20 min. This suggests the presence of a high-affinity folate carrier that exhibits a slow rate of self exchange. A sudden (bolus) increase of 10 microM folate of CH3THF caused a 70-80% inhibition of [3H]folate uptake, whereas folinic acid, MTX, and trimoprim were two- to threefold less effective. [3H]folate uptake was insensitive to DIDS, SITS, nicotine, ethanol, or phenytoin. For [3H]MTX, uptake was high (60-80%) on both sides of trophoblast, however, as distinct from [3H]folate, rapid and complete efflux followed the initial uptake. [3H]MTX uptake was not inhibited by 0.1 microM MTX, but equimolar folate or CH3THF were highly effective (90%) inhibitors; higher concentration (1 microM) of MTX reduced [3H]MTX uptake by 58%. Transplacental transfer of [3H]folate or [3H]MTX in excess of the leak pathway marker in either direction was not observed. Inhibition obtained by highly concentrated substrate bolus injections indicates saturation (less than 2 microM) of membrane folate carrier.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of maternal and foetal folacin and cobalamin activities at parturition in relation to Plasmodium falciparum infection

Folacin deficiency in malaria endemic areas is not reported other than in severely malnourished children. This is surprising in view of the high incidence in these areas of malaria in pregnancy, with its complications of prematurity and low birth weight, all of which can predispose to folacin deficiency. This paper reports results of folacin and cobalamin activities of blood samples collected from women at parturition and their newborns in a holoendemic area in West Kenya. Evidence is given that Plasmodium falciparum infection has little influence on cord plasma or red cell folacin activities. Mean values for folacin and cobalamin are not low when compared with reported values from neonates from temperate climates.

Plasma and red cell folate values in newborn infants and their mothers in relation to gestational age

The plasma and red blood cell folate concentrations have been studied in 344 newborn infants at 20 to 43 weeks of gestation and in 286 of their mothers at delivery. Folic acid supplementation was no given to the mothers during pregnancy. The mothers had no signs of folate deficiency as judged from their plasma and red blood cell folate concentrations and the red blood cell picture. The infants had significantly higher plasma folate concentrations than in adult control subjects, and six to eight times higher plasma folate concentrations than found in their mothers throughout the observation period. The red cell folate concentrations in the infants were significantly higher than in adult control subjects, and the concentrations were about two times higher than found in their mothers until 34 to 37 weeks of gestation. Term infants had significantly higher red cell folate concentrations than infants of lower gestational age. During the last weeks of pregnancy an increased transfer of folate to the fetus probably takes place.

Plasma and red blood cell folate in breastfed infants

We have studied growth, red blood cell status and folate concentrations in plasma and red cells in a group of 35 breastfed infants during the first year of life. Folic acid supplementation was not given to the mothers during pregnancy or lactation, and none of them developed megaloblastic anaemia. The growth and red blood cell status of the infants were both normal. At birth, and throughout the period of observation, the folate concentrations in plasma and red cells were significantly higher than in the adult reference material. A positive correlation between plasma and red cell folate was demonstrated. During the latter part of pregnancy and lactation the foetuses and infants seem to be protected against folate deficiency. We regard the folate status of normal breastfed infants as optimal. The optimal supply of the vitamin in artificial nutrition should be the amount of folate necessary to maintain plasma and red cell folate concentrations similar to those found in breastfed infants.

Transfer of folate to the fetus

The accumulation of tritium-labelled folate in the product of conception was examined in eight women undergoing hysterotomy for termination of pregnancy. Folic acid containing a small quantity of tracer material (50n Ci/mug.) was injected intravenously 20 minutes before operation in 4 patients but 24 hours beforehand in the remainder. After operation, maternal blood, placenta, fetal blood, and fetal liver were examined for radioactivity as was the daily urine output during the patient's postoperative hospital stay. The results indicated that only 1/2 per cent of the injected material accumulated in the product of conception--uptake was primarily by fetal liver and no large placental pool of folate was involved. Approximately half of the injected load was excreted in the urine--the majority in the first 24 hours--and the remainder was presumed to have been retained by maternal tissues. Bioassay with L. casei and chromatography on TEAE cellulose suggested that extensive metabolism of the injected material had taken place and that fetal uptake might be more efficient than indicated by counting radioactivity alone.

Renal loss of folate in the newborn infant

Renal excretion of folate during the first 5 days of life has been measured in 10 infants of 31 to 40 weeks' gestation and compared with inulin clearance. Average daily folate loss per unit surface area (23 μg/m²) was nearly 8 times as high as in adult life and more than enough to account for the observed fall in plasma folate activity. No difference was detected between the pattern of folate excretion in preterm and term infants. Poor tubular reabsorption of filtered folate is thought to be responsible for the loss observed.