The Differential Translation Capabilities of the Human DHFR2 Gene Indicates a Developmental and Tissue-Specific Endogenous Protein of Low Abundance.

A functional role has been ascribed to the human dihydrofolate reductase 2 (DHFR2) gene based on the enzymatic activity of recombinant versions of the predicted translated protein. However, the in vivo function is still unclear. The high amino acid sequence identity (92%) between DHFR2 and its parental homolog, DHFR, makes analysis of the endogenous protein challenging. This paper describes a targeted mass spectrometry proteomics approach in several human cell lines and tissue types to identify DHFR2-specific peptides as evidence of its translation. We show definitive evidence that the DHFR2 activity in the mitochondria is in fact mediated by DHFR, and not DHFR2. Analysis of Ribo-seq data and an experimental assessment of ribosome association using a sucrose cushion showed that the two main Ensembl annotated mRNA isoforms of DHFR2, 201 and 202, are differentially associated with the ribosome. This indicates a functional role at both the RNA and protein level. However, we were unable to detect DHFR2 protein at a detectable level in most cell types examined despite various RNA isoforms of DHFR2 being relatively abundant. We did detect a DHFR2-specific peptide in embryonic heart, indicating that the protein may have a specific role during embryogenesis. We propose that the main functionality of the DHFR2 gene in adult cells is likely to arise at the RNA level.

Pregnancy homocysteine and cobalamin status predict childhood metabolic health in the offspring.

BACKGROUND: Inadequate pregnancy cobalamin status has been associated with adverse offspring metabolic health in Indian and Nepalese studies. Studies of pregnancy cobalamin status and mid-childhood health outside of Asia are scarce. METHODS: Associations between pregnancy fasting plasma total homocysteine (tHcy), cobalamin status (plasma cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA)) and mid-childhood metabolic score (MetSco) ((including fat mass index (zFMI), homeostatic model assessment of insulin resistance (zHOMA-IR) and dyslipidemia (zTG - zHDLc)/2) z-scores)) were investigated in a prospective study of 293 mother-child dyads. RESULTS: Highest versus low-mid pregnancy tHcy tertile was associated with higher mid-childhood MetSco, specifically with higher child zFMI. Stratifying by sex, the maternal tHcy-child MetSco association was limited to boys and confirmed for zFMI and zHOMA-IR. The maternal tHcy-child zFMI association was not mediated by birth weight z-score. First trimester plasma cobalamin was not associated with child outcomes, but other indicators of cobalamin status were. Lowest versus mid-high plasma holoTC tertile was associated with MetSco (specifically zFMI and zHOMA-IR) and highest versus low-mid plasma MMA tertile with higher MetSco and dyslipidemia in boys. CONCLUSIONS: Moderately elevated pregnancy tHcy and low cobalamin status were associated with mid-childhood metabolic score in boys. The pregnancy tHcy-child zFMI association was not mediated by birth weight. IMPACT: Fasting plasma total homocysteine (tHcy) during pregnancy and low cobalamin status during early pregnancy are associated with mid-childhood metabolic score and its components in the offspring. These findings were only significant in male offspring. The study provides new evidence that impaired one carbon metabolism during pregnancy is associated with negative health outcomes in the offspring, in a population with low prevalence of cobalamin deficiency. The maternal-offspring associations were observed in the functional markers of cobalamin status (holotranscobalamin and methylmalonic acid) and tHcy, not with plasma cobalamin concentration. Screening for low pregnancy cobalamin status should be considered.

Moderately elevated first trimester fasting plasma total homocysteine is associated with increased probability of miscarriage. The Reus-Tarragona Birth Cohort Study.

The association between elevated early pregnancy fasting plasma total homocysteine (tHcy) and miscarriage risk was investigated prospectively in participants (n = 544) from the Reus-Tarragona Birth Cohort study. Pregnancy was confirmed before 12 gestational weeks (GW) by ultrasound scan and a fasting blood sample collected. Pregnancies with complications other than miscarriages were excluded. Miscarriages were diagnosed by ultrasound scan and gestational age at the time of miscarriage estimated by embryo size, where possible. Cases in which blood samples were collected more than a week after the miscarriage, or the miscarriage was of known cause, were excluded. Fasting plasma folate, vitamin B12, tHcy, cotinine (biomarker of smoking), red blood cell (RBC) folate, MTHFR 677C > T (rs1801133) and SLC19A1 80G>A (rs1051266) genotypes were determined. The exposed group consisted of participants with first trimester tHcy ≥ P90 (7.1 µmol/L) (n = 57) and unexposed of those with tHcy < P90 (n = 487). Adherence to folic acid supplement recommendations, plasma folate, plasma vitamin B12, RBC folate and prevalence of optimal RBC folate status (≥ 906 µmol/L) were lower in the exposed compared to unexposed group. The prevalences of the MTHFR 677 TT genotype and miscarriage were higher in the exposed group. The relative risks (95% CI) of pregnancy ending in miscarriage were 2.5 (1.1, 5.7) and 2.1 (1.0, 4.5) for participants in the high tHcy and suboptimal RBC folate groups (compared to the reference groups) respectively. Adherence to folic acid supplement recommendations was positively associated, while the MTHFR 677 TT versus CC genotype and smoking versus non-smoking were negatively associated, with RBC folate status.

The effect of prenatal smoke exposure on child neuropsychological function: a prospective mother-child cohort study.

Objective: To study prospectively the effect of prenatal smoke exposure (PSE) on child neuropsychological function and intelligence quotient (IQ).Background: PSE has been associated with adverse effects on child neurodevelopment. However, some studies reported that these associations disappear after adjustment for potential confounders.Methods: A cohortof 248 mothers-child dyad was followed from the first trimester of pregnancy until children were 7.5 years old. PSE was recorded during pregnancy by questionnaire and plasma cotinine. The Wechsler Intelligence Scale for Children, the Neuropsychological Assessment of Executive Functions for Children (ENFEN) and the School Neuropsychological Maturity Questionnaire were administered at 7.5 years of age. The effect of PSE on child IQ and neuropsychological function was assessed with ANCOVA, adjusting for obstetric, neonatal and sociodemographic factors.Results: Children whose mothers smoked throughout pregnancy scored lower in interference (ENFEN) compared to unexposed children (F = 4.1; p = .008). The results showed no differences in other executive functions, verbal and visual memory and IQ between the PSE groups.Conclusion: PSE had little effect on child neuropsychological outcome and was limited to mental flexibility. Nevertheless, these findings support further efforts aimed at encouraging mothers to quit smoking in pregnancy.

Early pregnancy folate-cobalamin interactions and their effects on cobalamin status and hematologic variables throughout pregnancy.

Background: Periconception folic acid supplementation is widespread, but how it interacts with cobalamin status is rarely considered. Objective: The aim of this study was to investigate whether first-trimester folate-cobalamin interactions affect pregnancy cobalamin status, hematologic variables, and pregnancy outcomes. Design: In the longitudinal Reus-Tarragona Birth Cohort study from <12 gestational weeks throughout pregnancy, fasting plasma and red blood cell (RBC) folate, plasma cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA), total homocysteine (tHcy), hemoglobin, mean cell volume (MCV), postglucose-load serum glucose, gestational hypertension, gestational age at birth, and birth weight were recorded in 563 participants. Results: The highest plasma folate concentrations occurred in the first trimester when folic acid supplement use was extensive. Supplementation beyond the first trimester interacted with time of pregnancy on plasma folate, RBC folate, and tHcy throughout pregnancy (P-interaction <0.001). Plasma folate and RBC folate were higher and tHcy was lower in continued supplement users than in nonusers. Elevated plasma folate (≥30 nmol/L) occurred in 78.9% of women who exceeded the recommended 400 µg folic acid/d. First-trimester folate-cobalamin status interactions were associated with MMA (P-interaction <0.001) throughout pregnancy. When plasma cobalamin was suboptimal (≤221 pmol/L; n = 36), participants with elevated plasma folate (n = 11) had higher MMA concentrations than did those with nonelevated plasma folate (n = 23). First-trimester folate-MMA status interactions were associated with MCV throughout pregnancy (P-interaction <0.01) and with cord plasma holoTC (P-interaction <0.05). The mean difference (95% CI) in MCV (fL) between women with elevated and nonelevated plasma folate status was -2.12 (-3.71, -0.52) for top-quartile plasma MMA (≥0.139 µmol/L) and 0.60 (-0.39, 1.60) for plasma MMA <0.139 µmol/L. Cord plasma holoTC was higher in women with elevated compared with nonelevated plasma folate status only for MMA <0.139 µmol/L. Folate-cobalamin interactions were not associated with the other investigated outcomes. Conclusion: First-trimester folate-cobalamin status interactions were associated with plasma MMA and MCV throughout pregnancy. This trial was registered at www.clinicaltrials.gov as NCT01778205.

Maternal Folate Status and the BHMT c.716G>A Polymorphism Affect the Betaine Dimethylglycine Pathway during Pregnancy.

The effect of the betaine: homocysteine methyltransferase BHMT c.716G>A (G: guanosine; A: adenosine) single nucleotide polymorphism (SNP) on the BHMT pathway is unknown during pregnancy. We hypothesised that it impairs betaine to dimethylglycine conversion and that folate status modifies its effect. We studied 612 women from the Reus Tarragona Birth Cohort from ≤12 gestational weeks (GW) throughout pregnancy. The frequency of the variant BHMT c.716A allele was 30.8% (95% confidence interval (CI): 28.3, 33.5). In participants with normal-high plasma folate status (>13.4 nmol/L), least square geometric mean [95% CI] plasma dimethylglycine (pDMG, µmol/L) was lower in the GA (2.35 [2.23, 2.47]) versus GG (2.58 [2.46, 2.70]) genotype at ≤12 GW (p < 0.05) and in the GA (2.08 [1.97, 2.19]) and AA (1.94 [1.75, 2.16]) versus GG (2.29 [2.18, 2.40]) genotypes at 15 GW (p < 0.05). No differences in pDMG between genotypes were observed in participants with possible folate deficiency (≤13.4 nmol/L) (p for interactions at ≤12 GW: 0.023 and 15 GW: 0.038). PDMG was lower in participants with the AA versus GG genotype at 34 GW (2.01 [1.79, 2.25] versus 2.44 [2.16, 2.76] and at labour, 2.51 [2.39, 2.64] versus 3.00 [2.84, 3.18], (p < 0.01)). Possible deficiency compared to normal-high folate status was associated with higher pDMG in multiple linear regression analysis (ß coefficients [SEM] ranging from 0.07 [0.04], p < 0.05 to 0.20 [0.04], p < 0.001 in models from early and mid-late pregnancy) and the AA compared to GG genotype was associated with lower pDMG (ß coefficients [SEM] ranging from -0.11 [0.06], p = 0.055 to -0.23 [0.06], p < 0.001). CONCLUSION: During pregnancy, the BHMT pathway is affected by folate status and by the variant BHMT c.716A allele.

Early pregnancy B vitamin status, one carbon metabolism, pregnancy outcome and child development.

Periconception supplementation with folic acid is recommended until 12 gestational weeks to prevent neural tube defects. Doses of folic acid contained in supplements and timing and length of use during pregnancy vary. The effects of status in periconception and pregnancy folate, cobalamin, betaine and their interactions on one carbon metabolism (1C), as well as the global effect of 1C on foetal growth and pregnancy outcome, are reviewed. Results from prospective studies are reviewed. Cessation of folic acid supplement use after the first trimester is associated with a sharp drop in plasma folate status and enhanced conversion of betaine to dimethylglycine. Dimethylglycine production is also higher in mothers with low folate status than in those with normal-high folate status. The effects of high doses of folic acid on one carbon metabolism in mothers with low early pregnancy cobalamin status and on foetal growth are also reviewed. Several studies report that moderately elevated early pregnancy fasting plasma total homocysteine (tHcy) is inversely associated with birth weight and a predictor of intrauterine growth retardation. There is also evidence for increased risk of preterm birth when maternal folate status is low.

Low folate status enhances pregnancy changes in plasma betaine and dimethylglycine concentrations and the association between betaine and homocysteine.

BACKGROUND: Folate, choline, and betaine participate in homocysteine metabolism. It is not known whether they interact during pregnancy. OBJECTIVE: The objective was to investigate how folate status affects choline, betaine, and dimethylglycine during pregnancy. DESIGN: Fasting plasma folate, cobalamin, free choline, betaine, dimethylglycine, and total homocysteine (tHcy) were measured longitudinally at <12, 15, 24-27, and 34 gestational weeks (GW); at labor (nonfasting); and in the cord in participants (n = 522) from the Reus-Tarragona Birth Cohort (NUTrició i Creixement Intrauterí Retardat phase). Timing, dose, and duration of folic acid supplement use were recorded. Folate status was classified as below (low) or above (high) median plasma folate at baseline (27.6 nmol/L) and at 24-27 GW (11.4 nmol/L). Associations between folate or betaine with tHcy were investigated by using multiple linear regression analysis. RESULTS: Plasma betaine decreased by 34.8% (1.0%) throughout pregnancy, and dimethylglycine increased by 39.7% (2.7%) between 24-27 GW and labor (all P < 0.001). Compared with high folate status, low status was associated with a higher dimethylglycine/betaine ratio from 15 GW and with lower plasma betaine and higher dimethylglycine from 24 to 27 GW, for the rest of pregnancy. Regression analysis showed that by 24-27 GW, both plasma folate and betaine were inversely associated with tHcy when folate status was low and that the association between betaine and tHcy depended on folate status at 24-27 and 34 GW (interaction terms: P < 0.001 and P < 0.01). Betaine was inversely associated with tHcy at labor regardless of folate status. CONCLUSION: Low folate status enhances the reduction in betaine and the increase in dimethylglycine during pregnancy and strengthens the association between betaine and tHcy. This trial was registered at clinicaltrials.gov as NCT01778205.

Association between blocking folate receptor autoantibodies and subfertility.

The association between blocking folate receptor (FR) autoantibodies and subfertility was investigated in a longitudinal study of women attempting to become pregnant. Seventeen women with subfertility (failure to conceive during 12 menstrual cycles) and 25 control women (women who conceived and went on to have normal pregnancy outcomes) were studied. Subfertility risk was 12 times higher in women with blocking FR autoantibodies compared with those without (odds ratio, 12; 95% confidence interval, 1.9-129.6).