Metabolic effects and the methylenetetrahydrofolate reductase (MTHFR) polymorphism associated with neural tube defects in southern Brazil

BACKGROUND: The importance of metabolic factors in neural tube defects (NTDs) has been the focus of many investigations. Several authors have suggested that abnormalities in homocysteine metabolism, such as hyperhomocysteinemia, folate deficiency, and low vitamin B12, may be responsible for these malformations and that both nutritional factors and genetic abnormalities are associated with them. METHODS: We conducted a case-control study to investigate the influence of biochemical and genetic factors in NTDs in infants in southern Brazil. Levels of folate, vitamin B12, total homocysteine (t-Hcy) and the 677C>T and 1298A>C polymorphisms of the MTHFR gene were analyzed in 41 NTD child-mother pairs and 44 normal child-mother control pairs. RESULTS: Subjects in the case group had a higher mean blood folate level than those in the control group. The level of vitamin B12 was lower in mothers in the NTD group than in control mothers (p = 0.004). The level of t-Hcy was not different in the two groups, but t-Hcy and vitamin B12 were correlated (p = 0.002). There was no difference in the genotype distribution for 677C>T and 1298A>C polymorphisms of MTHFR in the case and control pairs. The level of t-Hcy was correlated with 677TT. CONCLUSIONS: Despite the small sample in this study, we suggest that low vitamin B12 and, consequently, hyperhomocysteinemia are important risk factors for NTDs in our population.     

The MTHFR C677T polymorphism and global DNA methylation in oral epithelial cells

DNA methylation is mediated by DNA methyltransferases (DNMTs) that add a methyl group to the 5′-carbon of cytosine. The enzyme methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate in the rate-limiting step of the cycle involving the methyl donor S-adenosyl-L-methionine (SAM). The MTHFR C677T polymorphism results in a thermolabile enzyme with reduced activity that is predicted to influence the DNA methylation status. In this study, we investigated the impact of the MTHFR C677T polymorphism on the global DNA methylation of oral epithelial cells obtained from 54 healthy subjects. There were no significant differences in global DNA methylation among the MTHFR CC, CT and TT genotypes (p = 0.75; Kruskal-Wallis test).     

A1298C polymorphism of the MTHFR gene and neural tube defects in the state of Yucatan, Mexico

BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) of the folate metabolism pathway is a candidate gene for neural tube defects (NTDs). Frequency of the second common polymorphism, A1298C, in the MTHFR gene is not well known in Mexico. Conflicting results exist regarding the association of A1298C-MTHFR with NTDs. One explanation for this controversy might be that alleles are differently distributed among various populations. The aim of the study was to determine the frequency of the A1298C-MTHFR polymorphism and its association with NTDs in a population of Yucatan, Mexico. METHODS: Genotyping was performed by use of polymerase chain reaction with restriction fragment length polymorphisms using MbOII endonuclease (PCR-RFLPs MbOII). Allele and genotype frequencies were compared between cases with NTDs, their mothers and fathers with matched controls based on an association analysis using EpiInfo software. RESULTS: A1298C genotypes were distributed according to Hardy-Weinberg expectations for all studied groups. Frequencies of allele C and heterozygous AC genotype were significantly higher in males (p = .006 and p = .011, respectively) in control group. Significant differences were not observed between cases and controls, except in mothers of NTD cases compared with mothers of healthy offspring for both allele C and heterozygous AC genotype (p = .009 and p = .01, respectively). CONCLUSIONS: The polymorphism A1298C-MTHFR is not associated with NTDs, except for mothers, suggesting only a maternal association with having NTD-affected offspring in the Yucatan population. The frequency of allele C in the control population was 10%, which is significantly lower than in other reported control populations worldwide (p < .01).     

Association between MTHFR C677T polymorphism and primary open-angle glaucoma: A meta-analysis

Epidemiological studies have evaluated the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and primary open-angle glaucoma (POAG) risk. However, the results remain conflicting. The aim of this study was to investigate the association between MTHFRC677T polymorphism and POAG risk. All genetic association studies on MTHFR C677T polymorphism and POAG were systematically searched by the electronic databases PubMed, Embase and Web of Science. Study selection, data abstraction and study quality evaluation were conducted in duplicate independently. The strength of association between MTHFR C677T polymorphism and POAG was measured by odds ratios (ORs) and 95% confidence intervals (CIs). Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 10 studies including 1224 cases and 1105 controls were included in our final meta-analysis. There was no evidence of significant association of the overall population (for allelic model: OR = 1.17, 95% CI = 0.94–1.46; for additive model: OR = 1.15, 95% CI = 0.85–1.57; for dominant model: OR = 1.19, 95% CI = 0.92–1.55 and for recessive model: OR = 1.11, 95% CI = 0.83–1.49). Significant associations were found between MTHFR C677T polymorphisms and POAG in allelic model (OR = 1.39, 95% CI = 1.05–1.83) and additive model (OR = 1.88, 95% CI = 1.04–3.43) for population-based (PB) subgroup. This meta-analysis suggested that there were significant associations between MTHFR C677T polymorphism and POAG in allelic model and additive model for PB subgroup which indicated that the T allele or TT genotype might increase the risk of POAG, whereas no evidence of significant association was shown of the overall studied population. However, this conclusion should be interpreted cautiously. More large sample-size and multi-ethnicity studies with well-defined POAG patients and well-study design are needed in the future study.     

Prevalence of methylenetetrahydrofolate reductase C677T polymorphism in eastern Uttar Pradesh

AIM:

This study was aimed to evaluate the 5, 10-methylenetetrahydrofolate reductase (MTHFR) C677T mutation in eastern Uttar Pradesh population.

MATERIALS AND METHODS:

Polymerase chain reaction (PCR) using specific primers followed by amplicon digestion by Hinf I restriction enzyme was used for MTHFR C677T polymorphism analysis. Total 250 subjects were analyzed.

RESULTS:

The CC genotype was found in 192 subjects, followed by CT in 56 subjects and TT in 2 subject. Genotype frequencies of CC, CT and TT were 0.768, 0.224 and 0.008, respectively. The frequency of C allele was found to be 0.88 and that of T allele was 0.12.

CONCLUSION:

It is evident from the results of the present study that the percentage of homozygous genotype (CC) is highest in the target population.     

Association of homocysteine and methylene tetrahydrofolate reductase (MTHFR C677T) gene polymorphism with coronary artery disease (CAD) in the population of North India

The implications of the methylene tetrahydrofolate reductase (MTHFR) gene and the level of homocysteine in the pathogenesis of coronary artery disease (CAD) have been extensively studied in various ethnic groups. Our aim was to discover the association of MTHFR (C677T) polymorphism and homocysteine level with CAD in north Indian subjects. The study group consisted of 329 angiographically proven CAD patients, and 331 age and sex matched healthy individuals as controls. MTHFR (C677T) gene polymorphism was detected based on the polymerase chain reaction and restriction digestion with HinfI. Total homocysteine plasma concentration was measured using immunoassay. T allele frequency was found to be significantly higher in patients than in the control group. We found significantly elevated levels of mean homocysteine in the patient group when compared to the control group (p = 0.00). Traditional risk factors such as diabetes, hypertension, smoking habits, a positive family history and lipid profiles (triglyceride, total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol), were found significantly associated through univariate analysis. Furthermore, multivariable logistics regression analysis revealed that CAD is significantly and variably associated with diabetes, hypertension, smoking, triglycerides and HDL-cholesterol. Our findings showed that MTHFR C677T polymorphism and homocysteine levels were associated with coronary artery disease in the selected population.     

Association between maternal COMT gene polymorphisms and fetal neural tube defects risk in a Chinese population

Maternal tea consumption was reported to increase the risk of fetal neural tube defects (NTDs). Catechol‐O‐methyltransferase (COMT) may be involved in the metabolism of polyphenolic methylation of tea, thus influence the risk of fetal NTDs. Methods: A total of 576 fetuses or newborns with NTDs and 594 healthy newborns were included in the case–control study. Information on maternal tea consumption, sociodemographic characteristics, reproductive history, and related behavior was collected through face‐to‐face interviews. Maternal blood samples were collected to examine polymorphisms in COMT, and the possible interaction of COMT and tea consumption was analyzed. RESULTS: After controlling for potential confounders, homozygotes of rs737865 showed an elevated risk for total NTDs (odds ratio [OR] = 2.04, 95% confidence interval [CI], 1.24–3.35) and for the anencephaly subtype (OR = 1.99, 95% CI, 1.17–3.39). The CC genotype of rs4633 was positively associated with the overall risk of NTDs (OR = 3.66, 95% CI, 1.05–12.83). Heterozygotes for rs4680 were associated with a decreased risk of spina bifida (OR = 0.71, 95% CI, 0.51–0.98). The COMT rs4680 A allele was negatively related with the risk of spina bifida, with adjusted OR = 0.64 (95% CI, 0.45–0.89). An interaction between tea consumption (1 to 2 cups/day) and the rs4680AA/AG genotype was found in the spina bifida subtype (P_interaction = .08). Conclusion: Several COMT variants were associated with elevated risk of NTDs in a Chinese population. Maternal tea consumption may be associated with an increased risk for fetal NTDs in genetically susceptible subgroups. Birth Defects Research (Part A) 100:22–29, 2014. © 2013 Wiley Periodicals, Inc.     

Reduced folate carrier A80G polymorphism and susceptibility to neural tube defects: A meta-analysis

The reduced folate carrier (RFC1) plays a crucial role in mediating folate delivery into a variety of cells. RFC1 polymorphism (A80G) has been reported to be associated with increased risk of neural tube defects (NTDs). However, results derived from individually underpowered studies are conflicting. We performed a systematic search of MEDLINE and EMBASE databases and carried out a meta-analysis on the association between RFC1 polymorphism (A80G) and NTDs risk. Overall, a significant correlation between RFC1 A80G polymorphism and NTDs risk was found neither in infants nor in maternal (allele contrast in infants: OR_RE = 1.15, 95% CI: 0.92–1.45; allele contrast in mothers: OR_RE = 1.24, 95% CI: 0.98–1.56). The present meta-analysis failed to support a positive association between RFC1 A80G polymorphism and susceptibility to NTDs. It is important to realize, however, that socio-economic factors, and gene–environment and gene–gene interactions, could have influenced the outcome of our meta-analysis. For this reason, a relationship between the A80G polymorphism and NTD risk cannot be entirely discounted.     

High-density single nucleotide polymorphism screen in a large multiplex neural tube defect family refines linkage to loci at 7p21.1-pter and 2q33.1-q35

BACKGROUND: Neural tube defects (NTDs) are considered complex, with both genetic and environmental factors implicated. To date, no major causative genes have been identified in humans despite several investigations. The first genomewide screen in NTDs demonstrated evidence of linkage to chromosomes 7 and 10. This screen included 44 multiplex families and consisted of 402 microsatellite markers spaced approximately 10 cM apart. Further investigation of the genomic screen data identified a single large multiplex family, pedigree 8776, as primarily driving the linkage results on chromosome 7. METHODS: To investigate this family more thoroughly, a high-density single nucleotide polymorphism (SNP) screen was performed. Two-point and multipoint linkage analyses were performed using both parametric and nonparametric methods. RESULTS: For both the microsatellite and SNP markers, linkage analysis suggested the involvement of a locus or loci proximal to the telomeric regions of chromosomes 2q and 7p, with both regions generating a LOD* score of 3.0 using a nonparametric identity by descent relative sharing method. CONCLUSIONS: The regions with the strongest evidence for linkage map proximal to the telomeres on these two chromosomes. In addition to mutations and/or variants in a major gene, these loci may harbor a microdeletion and/or translocation; potentially, polygenic factors may also be involved. This single family may be promising for narrowing the search for NTD susceptibility genes.     

Association between MTHFR polymorphisms and orofacial clefts risk: A meta‐analysis

BACKGROUND The roles of C677T and A1298C polymorphisms in methylenetetrahydrofolate reductase (MTHFR) gene in orofacial clefts (OFCs) risk have been substantially explored, but the results remain conflicting. To address this gap, we conducted a meta‐analysis involving all eligible studies. METHODS: Electronic literature searches of the PubMed, EmBase, and Medline databases were performed up to October 31, 2011. Fixed‐effects or random‐effects models were used to calculate the pooled odds ratios (ORs) for two genetic comparisons (heterozygous mutation vs. wild type, homozygous mutation vs. wild type). RESULTS A total of 18 studies were ultimately identified. The pooled results revealed no statistical association between infant and maternal C677T and A1298C variants and risk of cleft lip with or without palate (CL/P) or cleft palate only (CPO), except for the maternal 677TT genotype for CL/P, the OR was 1.32 (95% confidence interval [CI], 1.06–1.63) as compared to the normal 677CC genotype. In the subgroup analyses on CL/P data based on ethnicity and source of control subjects, almost all of the results were replicated as nonsignificant associations in both examined polymorphisms, whereas the pooled risk estimate calculated for maternal 677TT genotype in the white population remained statistically significant, with an OR of 1.36 (95% CI, 1.05–1.76). CONCLUSIONS This meta‐analysis suggests that maternal MTHFR 677TT genotype might increase the risk of having a CL/P offspring in the white population. However, these findings remain to be confirmed by additional investigations. Birth Defects Research (Part A) 2012. © 2012 Wiley Periodicals, Inc.     

Association between the methionine synthase A2756G polymorphism and neural tube defect risk: A meta-analysis

Many studies have accessed the association between methionine synthase (MTR) A2756G polymorphism and neural tube defect (NTD). However, the conclusions are inconsistent. Our study aimed to clarify the nature of the genetic risks contributed by this polymorphism for NTD using meta-analysis. We searched electronic literature from the PubMed, EMBASE, and Medline databases, from which 10 articles were selected according to the inclusion criteria. The meta-analysis was conducted in 3 groups, namely, NTD patients, mothers with NTD offspring and fathers with NTD offspring. Pooled odds ratios (ORs) and 95% confidence intervals were used to evaluate the strength of the association and the result was corrected by multiple testing. To sum up, no associations between the MTR A2756G polymorphism and NTD risk were found among the 3 groups in all genetic models. However, as their sample size is not large enough, this result needs further research.     

MTHFR C677T polymorphism,GSTM1 deletion and male infertility: a possible suggestion of a gene–gene interaction?

Abstract

Methylenetetrahydrofolate reductase (MTHFR) is a gene involved in the process of DNA synthesis and methylation. The MTHFR C677T polymorphism has been associated with male infertility. A prospective study was conducted on men seeking care at the infertility clinic in Milano to determine if the MTHFR C677T polymorphism is associated with infertility, and if such an association is modified by a common deletion of one of the glutathione transferases, GSTM1. One year after enrolment, 46 subjects reported having had a child, while 59 were still childless. Subjects carrying the MTHFR C677T homozygous variant polymorphism were at increased risk of being infertile after 1-year follow-up (OR 3.7, 95% CI?=?1.4–10.4); carriers of the homozygous variant MTHFR genotype and of a functional copy of GSTM1 appear to have a significantly higher risk of infertility (n=11; OR?=?22.0 95% CI?=?3.8–127.9) than subjects who carry the wild-type genotype for both genes. Such risk becomes non-significant when the GSTM1 deletion is also present (n=5; OR?=?1.1 95% CI?=?0.2–5.1). A possible explanation of this unexpected result could lie in the known involvement of glutathione transferases in the metabolic pathways of both methylation and transulfuration. The interaction found deserves confirmation and replication in a larger population, since it may be relevant to several chronic diseases such as cardiovascular diseases and cancer.