Methionine synthase reductase 66A->G polymorphism is associated with increased plasma homocysteine concentration when combined with the homozygous methylenetetrahydrofolate reductase 677C->T variant

Methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) are important for homocysteine remethylation. This study was designed to determine the influence of genetic variants (MTHFR 677C-->T, MTHFR 1298A-->C, and MTRR 66A-->G), folate, and vitamin B-12 status on plasma homocysteine in women (20-30 y; n = 362). Plasma homocysteine was inversely (P < 0.0001) associated with serum folate and plasma vitamin B-12 regardless of genotype. Plasma homocysteine was higher (P < 0.05) for women with the MTHFR 677 TT/1298 AA genotype combination compared with the CC/AA, CC/AC, and CT/AA genotypes. Women with the MTHFR 677 TT/MTRR 66 AG genotype had higher (P < 0.05) plasma homocysteine than all other genotype combinations except the TT/AA and TT/GG genotypes. There were 5.4-, 4.3-, and 3.8-fold increases (P < 0.001) in risk for plasma homocysteine in the top 5, 10, and 20%, respectively, of the homocysteine distribution for subjects with the MTHFR 677 TT compared with the CC and CT genotypes. Predicted plasma homocysteine was inversely associated with serum folate (P = 0.003) and plasma vitamin B-12 (P = 0.002), with the degree of correlation dependent on MTHFR 677C-->T genotype. These data suggest that coexistence of the MTHFR 677 TT genotype with the MTRR 66A-->G polymorphism may exacerbate the effect of the MTHFR variant alone. The potential negative effect of combined polymorphisms of the MTHFR and MTRR genes on plasma homocysteine in at-risk population groups with low folate and/or vitamin B-12 status, such as women of reproductive potential, deserves further investigation.     

Prevalence and effects of gene-gene and gene-nutrient interactions on serum folate and serum total homocysteine concentrations in the United States: findings from the third National Health and Nutrition Examination Survey DNA Bank

BACKGROUND: Abnormalities of folate and homocysteine metabolism are associated with a number of pediatric and adult disorders. Folate intake and genetic polymorphisms encoding folate-metabolizing enzymes influence blood folate and homocysteine concentrations, but the effects and interactions of these factors have not been studied on a population-wide basis. OBJECTIVE: The objective was to assess the prevalence of these genetic polymorphisms and their relation to serum folate and homocysteine concentrations. DESIGN: DNA samples from 6793 participants in the third National Health and Nutrition Examination Survey (NHANES III) during 1991-1994 were genotyped for polymorphisms of genes coding for folate pathway enzymes 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T and 1298A-->C, methionine synthase reductase (MTRR) 66A-->G, and cystathionine-beta-synthase 844ins68. The influence of these genetic variants on serum folate and homocysteine concentrations was analyzed by age, sex, and folate intake in 3 race-ethnicity groups. RESULTS: For all race-ethnicity groups, serum folate and homocysteine concentrations were significantly related to the MTHFR 677C-->T genotype but not to the other polymorphisms. Persons with the MTHFR 677 TT genotype had a 22.1% (95% CI: 14.6%, 28.9%) lower serum folate and a 25.7% (95% CI: 18.6%, 33.2%) higher homocysteine concentration than did persons with the CC genotype. Moderate daily folic acid intake (mean: 150 microg/d; 95% CI: 138, 162) significantly reduced the difference in mean homocysteine concentrations between those with the MTHFR 677 CC and TT genotypes. We found a significant interaction between MTHFR 677C-->T and MTRR 66A-->G on serum homocysteine concentrations among non-Hispanic whites. CONCLUSIONS: The MTHFR 677C-->T polymorphism was associated with significant differences in serum folate and homocysteine concentrations in the US population before folic acid fortification. The effect of MTHFR 677C-->T on homocysteine concentrations was reduced by moderate daily folic acid intake.     

Folate status response to controlled folate intake is affected by the methylenetetrahydrofolate reductase 677C-->T polymorphism in young women

This study was designed to evaluate the effect of the methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism on folate and homocysteine response in non-Hispanic women consuming a low folate diet followed by a diet providing the Recommended Dietary Allowance (RDA) for folate. Women (aged 20-30 y old) with either the TT (n = 19) or CC (n = 22) MTHFR 677C-->T genotype participated in a folate depletion-repletion study (7 wk, 115 microg dietary folate equivalents (DFE)/d; 7 wk, 400 microg DFE/d). Overall serum folate decreased (P < 0.0001) during depletion and increased (P < 0.0001) during repletion with lower (P = 0.03) postdepletion serum folate in women with the TT versus CC genotype. Folate status was low (serum folate < 13.6 nmol/L) in more women with the TT (59%) compared with the CC genotype (15%) postdepletion. Red blood cell folate for all subjects decreased during depletion (P < 0.0001) and repletion (P = 0.02) with lower (P = 0.04) red blood cell folate in women with the TT compared with the CC genotype postrepletion. Homocysteine increased (P < 0.0001) for both genotype groups postdepletion and decreased (P = 0.02) postrepletion for the CC genotype group only. Homocysteine concentrations tended to be higher (P = 0.09) in the TT versus CC genotype group postdepletion and postrepletion. These data suggest that the MTHFR 677C-->T polymorphism negatively affects the folate and homocysteine response in women consuming low folate diets followed by repletion with the RDA. These results may be important when evaluating the impact of the MTHFR 677C-->T polymorphism in countries in which low folate diets are chronically consumed.     

Dietary and genetic determinants of homocysteine levels among Mexican women of reproductive age

OBJECTIVE: To evaluate the independent and joint effects of dietary folate, vitamin B(12) consumption and methylenetetrahydrofolate reductase (MTHFR) polymorphisms (677C>T and 1298A>C) on the circulating folate and homocysteine (Hcy) levels among Mexican women of reproductive age. DESIGN: A cross-sectional, population-based study. SUBJECTS: The first 130 healthy non-pregnant women (aged 16-34 years) who agreed to participate in a reproductive cohort in Morelos, Mexico. MAIN OUTCOME MEASUREMENTS: Dietary intakes of vitamin B(12) and folate were estimated using a semiquantitative food frequency questionnaire. MTHFR 677C>T and 1298A>C polymorphisms were ascertained using the PCR-based method. Serum levels of Hcy and folate were determined using high-performance liquid chromatography and radioimmunoassay, respectively. RESULTS: Genotype frequencies for the MTHFR 677C>T polymorphism were 21.5% (CC), 52.3% (CT) and 26.2% (TT) among Mexican women. Of the population, 22% had the MTHFR 1298AC genotype, while no individual carried the 1298CC genotype. We observed an increased level of Hcy among carriers of the 677TT genotype, compared to carriers of the 677CC genotype. The highest level of Hcy was observed among MTHFR 677TT carriers with low B(12) intake (<2.0 microg/day), which resulted with a significant interaction (P=0.01). CONCLUSION: Vitamin B(12) is an important determinant of Hcy levels in Mexico. Supplementation of folic acid with vitamin B(12) may be preferable when the MTHFR 677T variant allele is prevalent.     

Methylenetetrahydrofolate reductase polymorphisms and the risk of gestational hypertension

BACKGROUND: Evidence on the association of 5,10 methylentetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms in women with gestational hypertension is inconsistent. It is also unknown whether the fetal genotype is relevant, or whether folic acid supplementation modifies this association. METHODS: The study population was composed of U.S. and Canadian white women with nonmalformed infants participating in the Slone Epidemiology Center Birth Defects Study between 1993 and 2000. Women were interviewed within 6 months after delivery regarding multivitamin use in pregnancy and the occurrence of gestational hypertension, among other factors. DNA was extracted from cheek swabs and gene alleles determined by restriction fragment length polymorphism analysis. We compared the prevalence of the 677TT/CT and 1298CC/AC genotypes between cases with gestational hypertension (54 mothers and their 51 offspring) and controls (100 mothers and their 99 offspring). We also estimated odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression to control for geographic region and calendar year. RESULTS: The T allele was present in 69% of women with gestational hypertension versus 57% of control women (compared with 677CC, OR = 1.9; 95% CI = 0.9-4.0). The offspring of case and control women had a 677TT/CT genotype prevalence of 68% and 47%, respectively (2.4; 1.1-5.0). Among women supplemented with folic acid during the first 5 months of pregnancy, the ORs for maternal and fetal 677TT/CT genotypes were 0.9 (0.3-2.5) and 2.1 (0.7-6.0), respectively. Neither maternal nor fetal 1298CC/AC genotypes were associated with an increased risk of gestational hypertension. CONCLUSION: Maternal and fetal MTHFR C677T polymorphism may be associated with a moderately increased risk of gestational hypertension, and there is a suggestion that this association may be diminished among women receiving folate supplementation during pregnancy.     

Does the interaction between maternal folate intake and the methylenetetrahydrofolate reductase polymorphisms affect the risk of cleft lip with or without cleft palate?

Periconceptional folic acid supplementation may reduce the risk of cleft lip with or without cleft palate (CL(P)). Polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene reduce availability of 5-methyltetrahydrofolate, the predominant circulating form of folate. To determine the effect of MTHFR C677T and MTHFR A1298C genotypes and haplotypes on CL(P) risk and the interaction with maternal periconceptional dietary folate and folic acid supplement intake, the authors conducted a case-control triad study in the Netherlands (1998-2000) among 179 CL(P) and 204 control families. Infant and parental MTHFR C677T and MTHFR A1298C genotypes and haplotypes were not associated with CL(P) risk in the case-control and transmission disequilibrium test analyses. Mothers carrying the MTHFR 677TT genotype and who either did not use folic acid supplements periconceptionally or had a low dietary folate intake, or both, had an increased risk of delivering a CL(P) child (odds ratio (OR) = 5.9, 95% confidence interval (CI): 1.1, 30.9; OR = 2.8, 95% CI: 0.7, 10.5; OR = 10.0, 95% CI: 1.3, 79.1, respectively). No supplement use, low dietary folate intake, and maternal MTHFR 1298CC genotype increased the risk of CL(P) offspring almost sevenfold (OR = 6.5, 95% CI: 1.4, 30.2). Thus, the detrimental effect of low periconceptional folate intake on the risk of giving birth to a CL(P) child was more pronounced in mothers with the MTHFR 677TT or MTHFR 1298CC genotype.     

Association between selected folate pathway polymorphisms and nonsyndromic limb reduction defects: a case-parental analysis

Inadequate folate status resulting from either genetic variation or nutritional deficiencies has been associated with an increased risk of congenital malformations including orofacial clefting, limb, cardiac and neural tube defects. Few epidemiological studies have examined the association between limb reduction defects (LRDs) and folate-related genetic polymorphisms other than MTHFR 677C→T. We conducted a case-parental analysis of 148 families who participated in the National Birth Defects Prevention Study to examine the association between nonsyndromic transverse and longitudinal LRDs with five single nucleotide polymorphisms (SNPs) in genes encoding enzymes in folate and methionine pathways. Log-linear Poisson regression, adapted for analysis of case-parental data assuming an additive genetic model, was used to estimate genetic relative risks and 95% confidence intervals for the association between LRDs and each SNP. Among women who did not take multivitamin supplements, the MTHFR 677T variant acts via the offspring's genome to increase the risk of LRDs. No association between LRDs and any fetal SNP was found among women who used multivitamin supplements. These results suggest the possibility that initiating folic acid supplementation prior to pregnancy may reduce the risk of having a LRD-affected pregnancy, especially in women whose offspring inherit one or two copies of the MTHFR 677T variant.     

Homocysteine Metabolism Gene Polymorphisms (MTHFR C677T,MTHFR A1298C,MTR A2756G and MTRR A66G) Jointly Elevate the Risk of Folate Deficiency

Folate deficiency is strongly associated with cardiovascular disease. We aimed to explore the joint effect of the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase (MTR) A2756G, and methionine synthase reductase (MTRR) A66G polymorphisms on folate deficiency in a Chinese hypertensive population. A total of 480 subjects aged 28–75 were enrolled in this study from September 2005–December 2005 from six hospitals in different Chinese regions. Known genotypes were detected by PCR-RFLP methods and serum folate was measured by chemiluminescence immunoassay. Our results showed that MTHFR 677TT and MTR 2756AG + GG were independently associated with a higher risk of folate deficiency (TT vs. CC + CT, p < 0.001 and AG + GG vs. AA p = 0.030, respectively). However, the MTHFR A1298C mutation may confer protection by elevating the serum folate level (p = 0.025). Furthermore, patients carrying two or more risk genotypes showed higher odds of folate deficiency than null risk genotype carriers, especially those carrying four risk genotypes. These findings were verified by generalized multifactor dimensionality reduction (p = 0.0107) and a cumulative effects model (p = 0.001). The results of this study have shown that interactions among homocysteine metabolism gene polymorphisms lead to dramatic elevations in the folate deficiency risk.     

The glycine N-methyltransferase (GNMT) 1289 C->T variant influences plasma total homocysteine concentrations in young women after restricting folate intake

Glycine N-methyltransferase (GNMT) is a key regulatory protein in folate metabolism, methionine availability, and transmethylation reactions. Perturbations in GNMT may lead to aberrations in homocysteine metabolism, a marker of numerous pathologies. The primary objective of this study was to examine the influence of the GNMT 1289 C-->T alone, and in combination with the methylenetetrahydrofolate reductase (MTHFR) 677 C-->T variant, on plasma total homocysteine concentrations in healthy young women (n = 114). Plasma total homocysteine was measured at baseline (wk 0) and after 2 wk of controlled folate restriction (135 microg/d as dietary folate equivalents). Plasma homocysteine concentrations did not differ among the GNMT C1289T genotypes at baseline. However, after folate restriction, women with the GNMT 1289 TT genotype (n = 16) had higher (P = 0.019) homocysteine concentrations than women with the CT (n = 51) or CC (n = 47) genotype. The influence of the GNMT 1289 C-->T variant on homocysteine was dependent on the MTHFR C677T genotype. In subjects with the MTHFR 677 CC genotype, homocysteine was greater (P < or = 0.05) for GNMT 1289 TT subjects relative to 1289 CT or CC subjects. However, in subjects with the MTHFR 677 TT genotype, plasma homocysteine concentrations did not differ among the GNMT C1289T genotypes. Overall, these data suggest that the GNMT 1289 C-->T polymorphism influences plasma homocysteine and is responsive to folate intake.     

5,10-Methylenetetrahydrofolate reductase genotype determines the plasma homocysteine-lowering effect of supplementation with 5-methyltetrahydrofolate or folic acid in healthy young women

BACKGROUND: Elevated plasma total homocysteine (tHcy) is a risk factor for vascular disease and neural tube defects. The polymorphism in the gene encoding 5,10-methylenetetrahydrofolate reductase (FADH(2)) (MTHFR) influences the tHcy concentration and the response to tHcy-lowering therapy. Supplementation with folic acid (FA) decreases plasma tHcy, but limited data are available on the effect of 5-methyltetrahydrofolate (MTHF). OBJECTIVE: We evaluated the tHcy-lowering potential of low-dose FA and of MTHF with respect to the MTHFR genotype. DESIGN: In this randomized, placebo-controlled, double-blind study, 160 women received 400 microg FA, the equimolar amount of MTHF (480 microg, racemic mixture), or a placebo daily during an 8-wk treatment period. Blood samples were collected at baseline and at 4 and 8 wk. RESULTS: Changes in plasma tHcy concentration depended on the supplemented folate derivative and the MTHFR genotype. Supplementation with FA significantly decreased tHcy concentrations by > or = 13% in women of all 3 genotypes after both 4 and 8 wk. The greatest decrease was 20% (P < 0.05) in the women with the TT genotype after 4 wk. MTHF supplementation also decreased tHcy, but only the women with the CT genotype had a significant decrease after 4 wk (7%; P < 0.05). The largest nonsignificant reduction (15%) occurred in the women with the TT genotype after 4 wk of MTHF supplementation. CONCLUSIONS: The response to tHcy-lowering therapy is influenced by MTHFR genotype. Women with the TT genotype seem to benefit the most from supplementation with either FA or MTHF. In women with the CT or CC genotype, FA is more effective than MTHF in lowering plasma tHcy.     

Neural tube defects and folate pathway genes: family-based association tests of gene-gene and gene-environment interactions

BACKGROUND: Folate metabolism pathway genes have been examined for association with neural tube defects (NTDs) because folic acid supplementation reduces the risk of this debilitating birth defect. Most studies addressed these genes individually, often with different populations providing conflicting results. OBJECTIVES: Our study evaluates several folate pathway genes for association with human NTDs, incorporating an environmental cofactor: maternal folate supplementation. METHODS: In 304 Caucasian American NTD families with myelomeningocele or anencephaly, we examined 28 polymorphisms in 11 genes: folate receptor 1, folate receptor 2, solute carrier family 19 member 1, transcobalamin II, methylenetetrahydrofolate dehydrogenase 1, serine hydroxymethyl-transferase 1, 5,10-methylenetetrahydrofolate reductase (MTHFR), 5-methyltetrahydrofolate-homo-cysteine methyltransferase, 5-methyltetrahydrofolate-homocysteine methyltransferase reductase, betaine-homocysteine methyltransferase (BHMT), and cystathionine-beta-synthase. RESULTS: Only single nucleotide polymorphisms (SNPs) in BHMT were significantly associated in the overall data set; this significance was strongest when mothers took folate-containing nutritional supplements before conception. The BHMT SNP rs3733890 was more significant when the data were stratified by preferential transmission of the MTHFR rs1801133 thermolabile T allele from parent to offspring. Other SNPs in folate pathway genes were marginally significant in some analyses when stratified by maternal supplementation, MTHFR, or BHMT allele transmission. CONCLUSIONS: BHMT rs3733890 is significantly associated in our data set, whereas MTHFR rs1801133 is not a major risk factor. Further investigation of folate and methionine cycle genes will require extensive SNP genotyping and/or resequencing to identify novel variants, inclusion of environmental factors, and investigation of gene-gene interactions in large data sets.     

Plasma folate as marker of folate status in epidemiological studies: the European Investigation into Cancer and Nutrition (EPIC)-Potsdam study

Folate deficiency is often discussed as a potential risk factor for CVD and some cancers. Reliable assessment of folate status in large-scale epidemiological studies is therefore of major importance. The present study assessed the value of plasma folate (PF) compared with erythrocyte folate (EF) as a marker of folate status in 363 participants in the European Investigation into Cancer and Nutrition (EPIC)-Potsdam cohort. EF and PF, total homocysteine (tHcy), pyridoxine, cobalamin, creatinine, total protein and packed cell volume were determined; glutamate carboxypeptidase (GCP) C1561T, reduced folate carrier (RFC) G80A and methylenetetrahydrofolate (MTHFR) C677T polymorphisms were analysed. Anthropometric measurements were taken and dietary intake was assessed with the EPIC-Potsdam food-frequency questionnaire. Comparison of EF and PF with factors that may modulate their concentrations was performed. Cross-classification of blood folates in quintile categories resulted in correct classification into the same or adjacent category of 75.5 % of all subjects. Age, BMI, pyridoxine and cobalamin, fruit and vegetable intake, and vitamin supplementation 24 h before blood draw were positively associated with EF and with PF. For tHcy an inverse association was found. Participants with the MTHFR 677TT genotype showed significantly elevated EF concentrations compared with those with 677CT genotype; EF and PF were more strongly correlated (r 0.78, P<0.0001) for participants with MTHFR 677TT genotype than for those with the 677CC or 677CT genotype. In summary, our present results indicate that plasma folate seems to be a suitable marker for assessment of folate status for use in large-scale epidemiological studies.     

Thermolabile methylenetetrahydrofolate reductase,homocysteine, and cardiovascular disease risk: the European Concerted Action Project

BACKGROUND: Homozygotes for the thermolabile mutation (TT genotype) of the methylenetetrahydrofolate reductase (MTHFR; EC 1.5.1.20) enzyme have elevated plasma concentrations of the cardiovascular disease risk factor homocysteine, particularly if folate depleted. OBJECTIVE: We examined the relations between thermolabile MTHFR, plasma homocysteine, plasma folate, and vascular disease risk. DESIGN: This was a case-control comparison in 711 vascular disease cases and 747 controls from 9 European countries. RESULTS: The TT genotype was associated with higher homocysteine and lower plasma folate than the CC and CT genotypes in both cases and controls and a nonsignificant increase in vascular disease risk (1.26; 95% CI: 0.88, 1.81; P = 0.20). The frequency of the TT genotype in cases was not significantly different from that in controls (12.8% compared with 10.8%). After adjustment for traditional risk factors, the TT genotype was associated with an odds ratio of 1.48 (1.0, 2.20) for risk of vascular disease. This risk was attenuated after further adjustment for homocysteine. In subgroups with homocysteine concentrations >or= 9 micro mol/L, risk tended to be higher in CC than in TT subjects. However, CC subjects were characterized by a higher prevalence of the conventional risk factors associated with both elevated plasma homocysteine and serum creatinine. After adjustment, the risk of vascular disease associated with each genotype was not significantly different. CONCLUSIONS: There was a strong graded association between homocysteine and vascular risk in all genotypes. MTHFR genotype is a key determinant of plasma total homocysteine concentrations. The initially nonsignificant risk estimate associated with the TT genotype was strengthened after adjustment for conventional cardiovascular disease risk factors but was attenuated after adjustment for plasma folate and total homocysteine. The modest risk increase conferred by the TT genotype is mediated mainly by increased total homocysteine and low plasma folate concentrations.     

Homocysteine concentrations in adults with trisomy 21: effect of B vitamins and genetic polymorphisms

BACKGROUND: The effects of supplementation with B vitamins and of common polymorphisms in genes involved in homocysteine metabolism on plasma total homocysteine (tHcy) concentrations in trisomy 21 are unknown. OBJECTIVES: We aimed to determine the effects of orally administered folic acid and of folic acid combined with vitamin B-12, vitamin B-6, or both on tHcy in adults with trisomy 21. The study was also intended to analyze the possible influence of gene polymorphisms. DESIGN: One hundred sixty adults with trisomy 21 and 160 healthy, unrelated subjects aged 26 +/- 4 y were included. Plasma tHcy, red blood cell folate, serum folate, and vitamin B-12 were measured. Genotyping for the common methylenetetrahydrofolate reductase (MTHFR) 677C-->T, MTHFR 1298A-->C, cystathionine beta-synthase 844Ins68, methionine synthase 2756A-->C, methionine synthase reductase 66A-->G, and reduced folate carrier 80G-->A polymorphisms was carried out. RESULTS: The mean tHcy concentration (9.8 +/- 0.7 micromol/L) of cases who did not use vitamins was not significantly different from that of controls (9.4 +/- 0.3 micromol/L). Plasma tHcy concentrations (7.6 +/- 0.3 mmol/L) in cases who used folic acid were significantly lower than in cases who did not. Folic acid combined with vitamin B-12 did not significantly change tHcy concentrations compared with those in cases who used only folic acid. Folic acid combined with vitamins B-6 and B-12 significantly lowered tHcy (6.5 +/- 0.5 micromol/L). The difference in tHcy according to MTHFR genotype was not significant. However, tHcy concentrations were slightly higher in TT homozygotes among the controls but not among the cases. CONCLUSION: This study provides information on the relation between several polymorphisms in genes involved in homocysteine and folate metabolism in adults with trisomy 21.     

Physiologic changes in homocysteine metabolism in pregnancy: a longitudinal study in Spain

Objective

The aim was to investigate whether pregnancy-induced changes in total homocysteine (tHcy) are associated with folate and vitamin B12 nutritional status, genetic C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) enzyme, and gestation outcome at a time when folic acid supplementation started to be recommended in the Spanish health system.

Methods

In total 154 pregnant women were recruited from among gynecologic patients of the Alcorcón Public Hospital Outpatient Clinic (Madrid, Spain). Blood tests were performed at weeks 15, 24, and 32 of pregnancy. Total Hcy, folate, and vitamin B12 serum fasting concentrations were measured using an IMx system. Genotype analyses were done by polymerase chain reaction/restriction fragment/length polymorphism analysis.

Results

Folate and vitamin B12 serum concentrations decreased significantly (P < 0.01) through pregnancy and reached the lowest values in the third trimester. Serum tHcy concentrations were significantly (P < 0.01) lower in the second trimester but increased in the third trimester. Frequencies of MTHFR C667T genotype were CC (35.7%), CT (57.2%), and TT (7.1%). Total Hcy concentration was not statistically influenced by maternal genotype. Plasma folate was the single negative predictor of maternal tHcy in the first trimester of pregnancy; 11.1% of gestations resulted in intrauterine growth restriction, 7.9% in gestational diabetes mellitus, and 4.8% in gestational hypertension. No significant differences in serum folate, vitamin B12, or tHcy concentrations were found in complicated pregnancies and these were unrelated to MTHFR genotype.

Conclusion

Although tHcy seems to be physiologically low in this Spanish population and unrelated to folate and B12 nutritional status, C677T MTHFR genotype, and some pregnancy complications, we support the statement that appropriate folate concentration may be important throughout pregnancy to prevent abnormalities associated with altered status (e.g., neural tube defects). According to our study, supplementation with folic acid seems to achieve this purpose because diet alone may be insufficient. In addition, a poor vitamin B12 status, as measured by plasma levels, may indicate that supplementation of both vitamins is needed.     

The C677T polymorphism in the methylenetetrahydrofolate reductase gene (MTHFR), maternal use of folic acid supplements, and risk of isolated clubfoot: A case-parent-triad analysis

Worldwide, 1-4 per 1,000 births are affected by clubfoot. Clubfoot etiology is unclear, but both genetic and environmental factors are thought to be involved. Low folate status in pregnant women has been implicated in several congenital malformations, and folate metabolism may be affected by polymorphisms in the methylenetetrahydrofolate reductase gene (MTHFR). Using a case-parent-triad design, the authors investigated whether the MTHFR C677T polymorphism, and maternal periconceptional folic acid supplement use, influenced risk of isolated clubfoot. Three hundred seventy-five United Kingdom case-parent triads were recruited in 1998-1999. Among the children, there was a significant trend of decreasing clubfoot risk with increasing number of T alleles: relative risk for CT vs. CC = 0.75, 95% confidence interval: 0.57, 0.97; relative risk for TT vs. CC = 0.57, 95% confidence interval: 0.35, 0.91; p trend = 0.006. This association was not modified by maternal folic acid use. Maternal MTHFR genotype did not influence clubfoot risk for the offspring overall, although a possible interaction with folic acid use was found. This is the first known report of a specific genetic polymorphism associated with clubfoot. The direction of the association is intriguing and suggests that DNA synthesis may be relevant in clubfoot development. However, clubfoot mechanisms are poorly understood, and the folate metabolism pathway is complex. Further research is needed to elucidate these relations.     

Homocysteine Lowering by Folate-Rich Diet or Pharmacological Supplementations in Subjects with Moderate Hyperhomocysteinemia

Background/Objectives: To compare the efficacy of a diet rich in natural folate and of two different folic acid supplementation protocols in subjects with “moderate” hyperhomocysteinemia, also taking into account C677T polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene. Subjects/Methods: We performed a 13 week open, randomized, double blind clinical trial on 149 free living persons with mild hyperhomocyteinemia, with daily 200 μg from a natural folate-rich diet, 200 μg [6S]5-methyltetrahydrofolate (5-MTHF), 200 μg folic acid or placebo. Participants were stratified according to their MTHFR genotype. Results: Homocysteine (Hcy) levels were reduced after folate enriched diet, 5-MTHF or folic acid supplementation respectively by 20.1% (p < 0.002), 19.4% (p < 0.001) and 21.9% (p < 0.001), as compared to baseline levels and significantly as compared to placebo (p < 0.001, p < 0.002 and p < 0.001, respectively for enriched diet, 5-MTHF and folic acid). After this enriched diet and the folic acid supplementation, Hcy in both genotype groups decreased approximately to the same level, with higher percentage decreases observed for the TT group because of their higher pre-treatment value. Similar results were not seen by genotype for 5-MTHF. A significant increase in RBC folate concentration was observed after folic acid and natural folate-rich food supplementations, as compared to placebo. Conclusions: Supplementation with natural folate-rich foods, folic acid and 5-MTHF reached a similar reduction in Hcy concentrations.     

Methylenetetrahydrofolate reductase 677C-->T genotype modulates homocysteine responses to a folate-rich diet or a low-dose folic acid supplement: a randomized controlled trial

BACKGROUND: Low folate status and elevated plasma homocysteine are associated with increased risk of neural tube defects and cardiovascular disease. Homocysteine responses to folate may be influenced by genetic variants in folate metabolism. OBJECTIVE: We determined the effect of folate-enhancing dietary interventions on plasma folate and plasma total homocysteine (tHcy) with respect to the methylenetetrahydrofolate reductase 677C-->T genotype. DESIGN: A total of 126 healthy subjects (42 TT, 42 CT, and 42 CC genotypes) completed 3 dietary interventions (4 mo each) in random order: 1) exclusion diet (avoidance of folic acid-fortified foods and ingestion of a placebo daily), 2) folate-rich diet (increased intake of fortified and naturally folate-rich foods to achieve 400 microg folate/d), and 3) supplement (exclusion diet plus a folate supplement of 400 microg/d). RESULTS: Plasma folate was higher (P < or = 0.001) and plasma tHcy lower (P < or = 0.001) after the folate-rich and supplement interventions than after the exclusion diet. Plasma folate was significantly greater after supplementation than after the folate-rich diet, but there was no significant difference in tHcy concentration (P = 0.72). TT homozygotes had higher plasma tHcy (14.5 compared with 8.9 micromol/L, P < or = 0.001) and lower plasma folate (14.8 compared with 19.0 nmol/L, P < or = 0.01) than did subjects with the CC genotype after the exclusion diet. CT heterozygotes had intermediate concentrations. The trend toward higher tHcy in TT homozygotes persisted throughout the study but was less marked with increasing folate intake (TT compared with CC after supplementation, P = 0.097). CONCLUSIONS: A folate-rich diet including folic acid-fortified foods or low-dose supplements effectively increases folate status. TT homozygotes require higher folate intakes than do individuals with the CT or CC genotype to achieve similar tHcy concentrations but are responsive to folate intervention.     

孕妇血浆同型半胱氨酸水平及影响因素分析

目的 了解孕妇孕期Hcy水平及变化趋势，探讨孕期Hcy水平的影响因素。方法 选择2019年4月-6月在成都市双流区妇幼保健院参加孕期检查并计划在该院分娩的266名孕妇为研究对象，前瞻性随访至生产。通过问卷调查收集相关信息，实验室检测孕早、中、晚血清叶酸和血浆Hcy浓度，以及孕妇MTHFR基因rs1801133和rs1801131位点基因型，采用混合效应模型分析Hcy水平的影响因素。结果 研究对象平均年龄(27.70±3.68)岁，孕妇早、中、晚期血清叶酸中位数分别为20.85、15.30和13.07nmol/L，血浆Hcy平均值分别为6.73、5.35和5.40μmol/L，Hcy水平在孕中期下降后基本保持不变。混合效应模型结果表明，孕妇孕中、晚期Hcy浓度低于孕早期水平，MTHFR rs1801133位点基因型为CT和TT的孕妇相较CC型孕妇Hcy水平更高,叶酸制剂补充周长越久的孕妇Hcy水平更低。结论 应重点关注MTHFR rs1801133基因突变的孕妇，适当延长叶酸制剂补充时长和增大补充剂量以降低孕期Hcy水平。     

Impact of Voluntary Folic Acid Fortification of Corn Masa Flour on RBC Folate Concentrations in the U.S. (NHANES 2011–2018)

Surveillance data have highlighted continued disparities in neural tube defects (NTDs) by race-ethnicity in the United States. Starting in 2016, the Food and Drug Administration (FDA) authorized voluntary folic acid fortification of corn masa flour to reduce the risk of neural tube defects (NTDs) among infants of Hispanic women of reproductive age. To assess the impact of voluntary corn masa fortification, cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 2011–2018 for Hispanic women of reproductive age with available red blood cell (RBC) folate concentrations were analyzed, with additional analyses conducted among Hispanic women whose sole source of folic acid intake was fortified foods (enriched cereal grain products (ECGP) only), excluding ready-to-eat cereals and supplements. RBC folate concentration (adjusted geometric mean) among Hispanic women of reproductive age did not differ between 2011–2016 and 2017–2018, though RBC folate concentration increased significantly among lesser acculturated Hispanic women consuming ECGP only. Concentrations of RBC folate for those born outside the U.S and residing in the U.S <15 years increased from 894 nmol/L (95% CI: 844–946) in 2011–2016 to 1018 nmol/L (95% CI: 982–1162; p < 0.001) in 2017–2018. Primarily Spanish-speaking Hispanic women of reproductive age who only consumed ECGP saw an increase from 941 nmol/L (95% CI: 895–990) in 2011–2016 to 1034 nmol/L (95% CI: 966–1107; p = 0.03) in 2017–2018. By subpopulation, we observed no significant changes in the proportion at risk of NTDs (<748 nmol/L) and no changes in the model-based estimated NTD rates following voluntary corn masa fortification. This analysis suggests that there is a remaining risk among Hispanics for folate sensitive NTDs, though continued monitoring of folate status in future NHANES data cycles will help inform the long-term efficacy of voluntary fortification of corn masa flour.