Methylenetetrahydrofolate Reductase Genotype Research Articles

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.

Relationship Between Genetic Polymorphisms of Methylenetetra hydrofolate Reductase (C677T, A1298C, and G1793A) as Risk Factors for Idiopathic Male Infertility

The human methylenetetrahydrofolate reductase (MTHFR) gene plays a crucial role in folate metabolism. Data regarding the influence of MTHFR gene polymorphisms on male fertility status are scarce and conflicting. We determined associations between 3 MTHFR gene polymorphisms (C677T, A1298C, and G1793A), serum folate, and total homocysteine (tHcy) levels, with male fertility status and semen parameters. MTHFR genotypes were determined using polymerase chain reaction restriction fragment length polymorphism (PCR-RLFP) technique and serum tHcy, folate, and vitamin B12 concentrations were measured in 164 men with idiopathic infertility and 328 healthy participants. There was a significant difference in genotype frequency distribution of MTHFR C677T polymorphism between infertile patients and controls (P = .004). The 677T allele carriers (TC or TT) had a significantly increased risk of infertility compared with the CC homozygotes (odds ratio [OR] 1.60, 95% confidence interval [CI] 1.21-2.75, and OR = 2.68, 95% CI = 1.84-3.44, respectively), in a logistic regression model after adjustment for confounding factors. Men with the 677T, 1298C, and 1793G alleles showed significantly higher serum tHcy and lower folate levels (all Ps < .01). We found a positive correlation between serum folate concentrations and sperm density (r = .74, P = .001), percentage of sperm with progressive motility (r = .68, P = .001), as well as percentage of sperm with normal morphology (r = .72, P = .001). MTHFR C677T polymorphism is associated with an increased risk of idiopathic male infertility. Further study on the biologic role that this polymorphism plays in the development of infertility may lead to better understanding of the etiology of impaired spermatogenesis.

Folate supplementation in schizophrenia: A possible role for MTHFR genotype

BackgroundFolate deficiency and the methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism have been linked to negative symptoms in schizophrenia both independently and synergistically. This study examined the effect of folate supplementation on negative symptoms overall and in relation to MTHFR 677C>T genotype. MethodForty-six stable adult schizophrenia outpatients were enrolled and 32 were randomised, double-blind, in a parallel-group, twelve week add-on trial of folate 2mg/d or matching placebo. The primary outcome measure was change from baseline to week 12 on the modified SANS total score using a mixed-model analysis. In addition, we measured the effect of MTHFR genotype on treatment effects and on changes in serum folate by grouping participants with T/T genotype together with C/T genotype and comparing their interactions to patients with C/C genotype. ResultsTwenty-eight participants completed the trial. Folate supplementation did not significantly affect negative symptoms compared to placebo across the entire cohort. However, there was a significant genotype×treatment effect on negative symptoms (F=7.13, df=1,39, p=0.01). In addition, MTHFR status significantly moderated the relationship between change in serum folate and change in negative symptoms: among participants with at least one copy of the T allele negative symptoms were more likely to improve with increased serum folate (p=0.03). ConclusionWe did not detect a therapeutic benefit of folate supplementation in a sample of patients with residual negative symptoms. However, a possible association between genotypes associated with reduced MTHFR activity and benefit from folate supplementation should be investigated further.

Association between Genetic Polymorphisms and Sites of Cervicocerebral Artery Atherosclerosis

Ischemic stroke is a multifactorial disease with strong genetic elements. The purpose of this case-control study was to find relationships between apolipoprotein E (APOE), angiotensin-converting enzyme (ACE), and methylenetetrahydrofolate reductase (MTHFR) genotypes and atherosclerosis of the extracranial internal carotid and intracranial arteries in the Thai population. Patients aged >45 years with significant intracranial stenosis (IC group) or extracranial carotid artery stenosis (EC group) diagnosed by duplex ultrasound and/or computed tomography angiography (CTA) or magnetic resonance angiography (MRA) were studied. The control group comprised volunteers with no history of stroke and no evidence of significant cervicocerebral artery stenosis by ultrasound. Genomic DNA was extracted and genotyped for APOE isoforms, ACE insertion/deletion (I/D) polymorphism, and MTHFR C677T polymorphisms. There were 141 cases (83 in the IC group and 58 in the EC group) and 167 controls. The APOE ε3/ε4 genotype and APOE ε4 allele were significantly associated with extracranial carotid artery stenosis (odds ratio, 2.55; 95% confidence interval, 1.07-6.05 and odds ratio, 2.85; 95% confidence interval, 1.35-5.99, respectively). These associations were not observed in patients with intracranial atherosclerosis. There was no significant association between ACE and MTHFR polymorphisms and stenosis at any site. In a multivariate model, sex, diabetes mellitus, hypertension, ischemic heart disease, and APOE ε4 allele remained predictive of extracranial atherosclerosis. In our Thai population, the ε4 allele in the APOE gene contributes to the genetic susceptibility of extracranial internal carotid atherosclerosis. The low prevalence of extracranial carotid stenosis in this population might result from low frequencies of the APOE ε4 allele.

Risk of colorectal cancer associated with the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in the Kashmiri population

Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in folate metabolism and is involved in DNA synthesis, DNA repair and DNA methylation. The two common functional polymorphisms of MTHFR, 677 C→T and 1298 A→C, have been shown to impact various diseases, including cancer. The 677 C→T polymorphism has been widely investigated in different cancers and has been implicated as a risk factor for the development of various cancers. We investigated MTHFR C677T genotype frequency in colorectal cancer cases in the Kashmiri population and correlated this information with the known clinicopathological characters of colorectal cancer, in a case-control study. Eighty-six colorectal cancer cases were studied for MTHFR C677T polymorphism, compared to 160 controls taken from the general population, employing the PCR-RFLP technique. We found the frequency of the three different genotypes of MTHFR in our ethnic Kashmir population, i.e., CC, CT and TT, to be 68.6, 20.9 and 10.4% among colorectal cancer cases and 75.6, 16.9 and 7.5% among the general control population, respectively. There was a significant association between the MTHFR TT genotype and colorectal cancer in the higher age group. We conclude that the MTHFR C677T polymorphism slightly increases the risk for colorectal cancer development in our ethnic Kashmir population.

Methylenetetrahydrofolate reductase genotypes and haplotypes associated with susceptibility to colorectal cancer in an eastern Chinese Han population

Methylenetetrahydrofolate reductase (MTHFR) plays an important role in folate metabolism and is involved in DNA synthesis, DNA repair and DNA methylation. The two common functional polymorphisms of MTHFR, C677T and A1298C have been associated with several diseases, including cancer. We made a case-control study to analyze a possible association of MTHFR gene polymorphisms C677T and A1298C with risk for colorectal cancer in an eastern Chinese Han population of 137 patients with a confirmed histopathological diagnosis of CRC and 145 age- and gender-matched controls with no history of cancer. DNA was isolated from peripheral blood samples and the genotypes were determined by PCR-RFLP. The concentrations of folate in plasma were measured by chemiluminescence immunoassay. The MTHFR 677TT genotype had a protective effect against colorectal cancer, with an odds ratio (OR) = 0.467 (95% confidence interval (CI) = 0.225-0.966). The 1298CC genotype was significantly correlated with a reduced risk of colorectal cancer (OR = 0.192; 95%CI = 0.040-0.916). Compared with the MTHFR 677CC and MTHFR 1298 AA genotypes, for individuals who carried both MTHFR 677CC and 1298CC genotypes, the OR of colorectal cancer was 0.103 (95%CI = 0.012-0.900); among individuals who carried both MTHFR 677TT and 1298AC genotypes, the OR for risk of colorectal cancer was 0.169 (95%CI = 0.044-0.654). MTHFR 677TT+CT genotypes had a significantly lower plasma folate concentration than those with the MTHFR 677CC genotype. MTHFR 1298AC+CC genotypes had a lower plasma folate concentration than those with the MTHFR 1298AA genotype (P < 0.05). In conclusion, subjects with the MTHFR 677TT and MTHFR 1298CC genotypes appeared to have a significantly lower risk for colorectal cancer. MTHFR haplotypes 677CC/1298CC and 677TT/1298AC were less common in cases than in controls. These haplotypes, when compared to the most common haplotype 677CC/1298AA, were associated with a decreased risk for colorectal cancer. We conclude that plasma folate level is influenced by MTHFR genotypes.

The role of methylenetetrahydrofolate reductase C677T polymorphism on the peripheral blood natural killer cell proportion in women with unexplained recurrent miscarriages

ObjectiveTo examine the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and hyperhomocysteinemia in women with unexplained recurrent miscarriages (RM) and to investigate the association between MTHFR genotype variants and alloimmune activation, proportion of peripheral blood natural killer (pbNK) cells.MethodsA total of 39 patients with a history of two or more unexplained miscarriages were recruited to this study. The controls were women who had a live birth without a history of RM (n=50). The proportion of pbNK cells was measured by flow cytometry. Plasma homocysteine levels and the incidence of the MTHFR variant of the RM and control groups were compared. The proportion of pbNK cells was compared to the MTHFR variants in the RM group.ResultsNo differences were found between the two groups' mean plasma homocysteine levels (7.6±1.5 µmol/L vs. 7.1±2.1 µmol/L) or incidence of the MTHFR genotype variant (CC, 35% vs. 33%; CT, 40% vs. 53%; and TT, 25% vs. 14%). In the RM group, individuals with the TT variant (7.7±1.1 µmol/L) had higher homocysteine levels than those with the CC and CT variants (7.4±1.9 µmol/L and 7.4±1.2 µmol/L) and those with the CT variant (19.2±8.1%) had a higher proportion of CD3-/CD56+ pbNK cells than those with the CC and TT variants (17.7±6.6% and 17.9±7. 0%), but the results of both comparisons were statistically insignificant.ConclusionThese preliminary results show no difference in plasma homocysteine levels between the RM and control groups or among MTHFR genotype variants in the RM group, which may suggest that the plasma homocysteine level is difficult to use as a predictive marker of RM in the Korean population. A study of a larger number of patients is needed.

Nutrigenetic impact of daily folate intake on plasma homocysteine and folate levels in patients with different methylenetetrahydrofolate reductase genotypes

Elevated plasma homocysteine level is associated with coronary artery disease (CAD). Homozygosity for the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is typically but inconsistently associated with hyperhomocysteinemia. We examined the impact of daily intake of folate, a co-factor in homocysteine metabolism, on plasma homocysteine and folate levels in CAD patients in relation with MTHFR genotypes. Daily folate intake was assessed from 3-day food records in 99 patients with CAD: 35 with the T/T (homozygous mutant) genotype and 64 with the C/C or C/T (non-T/T) genotypes. Patients with the T/T genotype had higher fasting plasma homocysteine levels (18.4±1.9 vs. 12.6±0.6 μmol/l, P=0.01) and lower plasma folate levels (17.8±1.7 vs. 20.8±1.0 nmol/l, P=0.02). There were no differences between the genotype groups in energy-adjusted folate intake. In patients with the non-T/T genotypes, higher folate intake was associated with higher plasma folate levels and lower plasma homocysteine levels. In T/T homozygotes this association was weaker. Linear regression analysis showed that folate intake, the MTHFR genotype, plasma vitamin B12 levels, and the interaction between plasma folate level and MTHFR genotype, predicted homocysteine elevation. (folate intake, P=0.04, MTHFR genotype, P=0.03, plasma folate, P=0.02, and plasma B12 level, P=0.004). The model explained only 29% of the variance in log-transformed plasma homocysteine levels. T/T homozygotes are more sensitive to the combination of low folate intake, low plasma folate and vitamin B12 level, than patients with non-T/T genotypes. The variability in plasma homocysteine in T/T homozygotes is only partly explained by these variables.

The Role of the Methylenetetrahydrofolate Reductase 677 and 1298 Polymorphisms in Cretan Children with Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common form of malignancy in children. Recently, many studies have examined factors influencing both the susceptibility to ALL and the metabolism of widely used chemotherapeutic agents. These factors include, among others, single-nucleotide polymorphisms in various genes, such as the gene encoding for methylenetetrahydrofolate reductase (MTHFR), which has been proven polymorphic at the nucleotide positions 677 and 1298. Thirty-five children with ALL and 48 healthy adults of Cretan origin were genotyped for the presence of the MTHFR 677 and 1298 single-nucleotide polymorphisms. The possible correlation of the polymorphisms with the risk for ALL and the presence of methotrexate-induced toxicities were examined. No significant association between the MTHFR genotypes and the susceptibility to ALL was observed. A borderline statistically significant relationship was detected after methotrexate administration, between the C677T genotype (polymorphisms) and leukopenia (p = 0.050) and between the A1298C polymorphism and normal aspartate transaminase and alanine transaminase values (p = 0.065 and p = 0.053, respectively), which was strengthened for aspartate transaminase, after grouping the A1298A and A1298C genotypes together (p = 0.039). In our population the MTHFR C677T and A1298C polymorphisms are related with hematologic toxicity and hepatotoxicity, respectively, and could be suggested as prognostic factors for these adverse events.

Lack of association between methylenetetrahydrofolate reductase genetic polymorphisms and postmenopausal breast cancer risk

Published data on the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and breast cancer risk are inconclusive. We investigated the independent and the combined effects of two commonly occurring polymorphisms, MTHFR 677C>T (rs1801133) and MTHFR 1298A>C (rs1801131), as well as their interaction with the use of hormone replacement therapy (HRT), to determine their potential contribution to breast cancer risk. We studied 530 breast cancer cases and 270 controls of the same age and ethnicity participating in a case-control study of postmenopausal women. The duration of HRT use was ascertained through a postal questionnaire. Genotyping was conducted by TaqMan® allelic discrimination. Adjusted odds ratios and 95% confidence intervals were calculated using logistic regression. No significant association was observed between either the individual or the combined MTHFR genotypes and the risk of postmenopausal breast cancer. Additionally, no effects resulting from the interaction between MTHFR genotypes and HRT use were detected. Therefore, our data do not support the hypothesis that genetic variation in the MTHFR gene is implicated in the aetiology of postmenopausal breast cancer.

Effects of season of birth and a common MTHFR gene variant on the risk of schizophrenia

Season of birth – in particular winter birth – has been persistently related to increased schizophrenia risk. Variation in folate intake is among the explanations for this seasonal effect. Methylenetetrahydrofolate reductase (MTHFR) is an essential enzyme in the folate mediated methylation transfer reactions. Interestingly, the MTHFR gene has been related to schizophrenia risk in various studies. We investigated a possible interaction between MTHFR 677 C>T polymorphism and winter birth in the development of schizophrenia in a group of 742 schizophrenia patients and 884 control subjects. All subjects were of Dutch ancestry. Winter birth (December up to and including February) was associated with a 20% increase in schizophrenia risk (odds ratio (OR) of 1.20 and 95% confidence interval (CI), 0.96–1.5; P = 0.113). The MTHFR 677TT genotype was associated with an overall schizophrenia risk of 1.13 (95% CI, 0.82–1.57; P = 0.454) compared with the MTHFR 677CC genotype. In the winter period the MTHFR 677TT genotype associated schizophrenia risk was 0.90 (95% CI, 0.47–1.70; P = 0.744). In conclusion, neither winter birth nor MTHFR genotype were significantly associated with increased schizophrenia risk. There was no evidence for interaction between MTHFR 677TT genotype and winter birth in the development of schizophrenia.

Study of specific genetic and epigenetic variables in multiple myeloma

Few studies have examined the association between methylenetetrahydrofolate reductase (MTHFR) SNPs, epigenetic changes, and multiple myeloma (MM). We wished to determine genotype distributions for MTHFR 1298AC SNP in cases of MM and healthy controls and to examine whether there is any correlation between the methylation status of the CpG island of CDKN2A and Snk/Plk2 and MTHFR genotypes and with overall survival (OS) and other relevant clinical parameters. Bone marrow and peripheral blood were obtained from 45 patients with MM and 77 controls, respectively. The frequencies of the MTHFR 1298AA, 1298AC, and 1298CC genotypes were 53.3%, 40%, and 6.7% for the patient population and 50.6%, 41.6%, and 7.8% for the controls. No statistically significant difference was found in genotype distribution between cases and controls. No correlation was noted between MTHFR genotypes and OS, disease stage, bone disease, anemia, and extramedullary disease. Regarding CDKN2A and Snk/Plk2 CpG island methylation analysis, we found 12 of 45 patients and 27 of 45, respectively, to be methylated. CDKN2A and Snk/Plk2 methylation did not correlate with MTHFR genotypes. Herein, we report the identification of Snk/Plk2 as a novel methylated gene in MM and show that methylation is not influenced in this CpG island or in that of a previously described methylated gene, CDKN2A, in MM. Further evaluation in a larger sample of patients is needed in order to better define the prognostic and clinical value, if any, of MTHFR 1298 polymorphisms and CDKN2A and Snk/Plk2 methylation in the pathogenesis of MM.

Genetic susceptibility of methylenetetrahydrofolate reductase (MTHFR) gene C677T, A1298C, and G1793A polymorphisms with risk for bladder transitional cell carcinoma in men

We performed a case-control study of 158 bladder transitional cell carcinoma (TCC) cases and 316 controls to investigate the association between methylenetetrahydrofolate reductase (MTHFR) C677T, A1298G, and G1793A polymorphisms and bladder cancer susceptibility by polymerase chain reaction restriction fragment length polymorphism (PCR-RLFP) technique. The controls were frequency-matched to the cases by age (± 5 years), ethnicity, and smoking status. We also measured serum levels of total homocysteine (tHcy), folate, and vitamin B12. It was found that the 1298AC (odds ratio, OR = 3.74; 95% confidence interval, CI = 2.34-5.47; P = 0.001) and 1298CC (OR = 3.46, 95% CI = 2.37-5.52; P = 0.001) genotypes of MTHFR A1298C were significantly associated with increased risk of bladder TCC. The MTHFR C677T and G1793A polymorphisms were not associated with bladder TCC. After stratification for grade and stage, we observed that the 677TT (OR = 4.47, 95% CI = 2.74-6.72; P = 0.001) and MTHFR 1298CC (OR = 4.78, 95% CI = 2.82-6.89; P = 0.001) genotypes of MTHFR were associated with increased risk of muscle-invasive bladder TCC. We also found that the MTHFR 677CT+1298AA genotypes were associated with an approximately 70% reduction in risk of bladder cancer (OR = 0.31; 95% CI = 0.15-0.68) compared to the combined referent genotype. There were 8 haplotypes and 16 haplotype genotypes based on these three variants. When we used the haplotypes and assumed that the 677T, 1298C, and 1793G alleles were risk alleles, the adjusted odds ratios increased as the number of risk alleles increased: 1.00 for 0-1 variant, 1.88 (1.4-2.7) for any two risk alleles and 2.07 (1.6-2.8) for any three risk alleles. Serum tHcy levels were significantly higher in carriers of the 677T, 1298C, and 1793G alleles compared to noncarriers (all P < 0.01). There was no significant correlation between serum levels of tHcy and folate and bladder cancer risk. Further studies in larger samples size and different ethnicity are required to confirm our findings.

SHMT1 1420 and MTHFR 677 variants are associated with rectal but not colon cancer

BackgroundAssociation between rectal or colon cancer risk and serine hydroxymethyltransferase 1 (SHMT1) C1420T or methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms was assessed. The serum total homocysteine (HCY), marker of folate metabolism was also investigated.MethodsThe SHMT1 and MTHFR genotypes were determined by real-time PCR and PCR-RFLP, respectively in 476 patients with rectal, 479 patients with colon cancer and in 461 and 478, respective controls matched for age and sex. Homocysteine levels were determined by HPLC kit. The association between polymorphisms and cancer risk was evaluated by logistic regression analysis adjusted for age, sex and body mass index. The population stratification bias was also estimated.ResultsThere was no association of genotypes or diplotypes with colon cancer. The rectal cancer risk was significantly lower for SHMT1 TT (OR = 0.57, 95% confidence interval (CI) 0.36-0.89) and higher for MTHFR CT genotypes (OR = 1.4, 95%CI 1.06-1.84). A gene-dosage effect was observed for SHMT1 with progressively decreasing risk with increasing number of T allele (p = 0.014). The stratified analysis according to age and sex revealed that the association is mainly present in the younger (< 60 years) or male subgroup. As expected from genotype analysis, the SHMT1 T allele/MTHFR CC diplotype was associated with reduced rectal cancer risk (OR 0.56, 95%CI 0.42-0.77 vs all other diplotypes together). The above results are unlikely to suffer from population stratification bias. In controls HCY was influenced by SHMT1 polymorphism, while in patients it was affected only by Dukes' stage. In patients with Dukes' stage C or D HCY can be considered as a tumor marker only in case of SHMT1 1420CC genotypes.ConclusionsA protective effect of SHMT1 1420T allele or SHMT1 1420 T allele/MTHFR 677 CC diplotype against rectal but not colon cancer risk was demonstrated. The presence of SHMT1 1420 T allele significantly increases the HCY levels in controls but not in patients. Homocysteine could be considered as a tumor marker in SHMT1 1420 wild-type (CC) CRC patients in Dukes' stage C and D. Further studies need to clarify why SHMT1 and MTHFR polymorphisms are associated only with rectal and not colon cancer risk.

Polymorphisms of methylenetetrahydrofolate reductase are associated with a high risk of nasopharyngeal carcinoma in a smoking population from southern China

Methylenetetrahydrofolate reductase (MTHFR) plays a central role in converting folate to a compound which serves as a methyl donor for DNA methylation, an epigenetic modification known to be dysregulated in carcinogenesis. This case-control study assessed the contribution of MTHFR polymorphisms to the risk of nasopharyngeal carcinoma (NPC). MTHFR genotypes C677T and A1298C in 529 NPC patients and 577 frequency-matched controls were determined by PCR-based restriction fragment length polymorphism. We found a 1.57-fold increased risk of NPC in subjects with the MTHFR 1298AC genotype compared to subjects with the MTHFR 1298AA genotype. In addition, an elevated NPC risk was also found in subjects with both the MTHFR 677CT and 1298AC genotypes [odds ratio (OR) = 2.15, 95% confidence interval (CI) = 1.37-3.39] compared to subjects with the 677CC/1298AA genotypes. Furthermore, we observed an additive interaction between MTHFR polymorphisms and smoking status on the increased risk of NPC. The OR was 6.72 (95% CI = 1.85-24.48) among heavy smokers (pack-years ≥15) carrying 677TT compared with nonsmokers carrying the 677CC genotype. The OR was 7.23 (95% CI = 4.22-12.38) or 12.75 (95% CI = 2.74-59.3) among subjects carrying the 1298AC or 1298CC genotype in heavy smokers (pack-years ≥15) compared with 1298AA in nonsmokers. Our results provide the first molecular epidemiological evidence that MTHFR polymorphisms associate with the risk of NPC and this association is especially noteworthy in heavy smokers.

Could genetic analysis be useful in reducing cerebrovascular risk in hypertensive subjects with hyperhomocysteinemia and patent foramen ovale? A 2-year follow-up study

Objectives Potential causes of cryptogenic cerebrovascular (CV) events are patent foramen ovale (PFO) and hyper homocysteinemia (H-Hcys), this latter a well-established risk factor for thrombosis particularly in the presence of mutation for the methylenetetrahydrofolate reductase (MTHFR) gene. This study investigated if in uncomplicated hypertensive subjects (HTs) with isolated PFO and H-Hcys, a different MTHFR polymorphism pattern for C667 → T gene mutation could influence PFO management and to reduce the CV risk. Methods In thirty-two HTs aged 55.6 ± 14.4 years, PFO was diagnosed by echocardiography. MTHFR genotype was evaluated by a multiplex polymerase chain reaction with reverse line blot hybridization assay. In relation to the T allele distribution, HTs were divided in normal (CC), heterozygote (CT) and homozygote (TT) for the MTHFR genotype. All subjects received a supplementation of oral folate (5 mg daily) and were evaluated yearly for 2 years. Analysis of variance for repeated measures (ANOVA) was used to compare changes of Hcys at baseline and at the end of follow-up and differences between continuous variables were evaluated in the three MTHFR groups with the Tukey's post hoc test after adjustment for confounders. Results At the follow-up, Hcys levels significantly normalized from baseline both in TT (38.1 ± 6.7 vs. 15 ± 3.6, p < 0.01) and CT (26.6 ± 2.3 vs. 9.2 ± 1.6, p < 0.01) but not in CC subjects (18.2 ± 1.8 vs. 16.0 ± 1.6, NS). Independently of age, BMI, vitamin treatment both systolic and diastolic blood pressure (BP) significantly decrease at the follow-up in all the MTHFR genotypes. No CV events were observed during the follow-up. Conclusions In HTs with isolated PFO and H-Hcys, oral folate supplementation reduces Hcys levels both in TT and CT subjects with C667→T mutation of MTHFR. In addition the BP normalization probably contributed to reduce CV risk in these genotypes.

Gender‐specific association of methylenetetrahydrofolate reductase genotype and haplotype with the aggressiveness and prognosis of clear cell renal cell carcinoma in Japanese patients

To determine if the two common polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, C677T and A1298C, affect tumour aggressiveness or prognosis of clear cell renal cell carcinoma (CCRCC) in Japanese patients. MTHFR C677T and A1298C polymorphisms have been reported to cause decreased enzyme activity, which reduces the quantity of methyl groups available for DNA methylation and leads to mis-incorporation of uracil into DNA, resulting in single-strand DNA breaks. These effects might induce the accumulation of several genetic changes, leading to the development and progression of CCRCC. Therefore, we investigated the associations between MTHFR genotypes and haplotypes and the clinicopathological characteristics and survival rates in 240 Japanese patients with histopathologically confirmed CCRCC. MTHFR C677T and A1298C were genotyped and haplotypes were analysed using appropriate software. The variant genotypes of MTHFR A1298C were significantly associated with some advanced characteristics of CCRCC in all patients, and these associations were stronger among men. However, among women, the variant genotypes of MTHFR C677T were associated with some advanced characteristics of CCRCC and the C677T variant genotypes or the 677T-1298A haplotype was significantly associated with decreased overall survival (P = 0.007 and P = 0.009, respectively). To our knowledge, this is the first report on the association between MTHFR polymorphisms and CCRCC aggressiveness or prognosis. These results suggest that the MTHFR genotypes and haplotype might be useful, in a gender-specific manner, as predictive factors for the clinical course of CCRCC. Furthermore, these findings will contribute to the understanding of the mechanisms underlying CCRCC progression.

Global DNA hypomethylation is associated with NTD‐affected pregnancy: A case‐control study

Neural tube defects are severe, common birth defects that result from failure of neural tube closure. They are considered to be a multifactorial disorder, and our knowledge of causal mechanisms remains limited. We hypothesized that abnormal DNA methylation occurs in NTD-affected fetuses. The correlations of global DNA methylation levels with complexity of NTDs and known risk factors of NTDs, MTHFR genotype and fever, were analyzed. A hospital-based case-control study was performed. Epidemiologic data, pathologic diagnosis, and methylenetetrahydrofolate reductase (MTHFR) genotype analysis were completed. Array comparative genomic hybridization was used to exclude cytogenetic abnormalities. Global DNA methylation statuses were determined for both brain and skin tissue. Sixty-five NTD-affected fetuses and 65 normal controls matched for gestational and maternal ages were collected. In brain tissue, global DNA methylation levels were significantly decreased in cases compared with controls (4.12 vs. 4.99%; p < 0.001). DNA hypomethylation (<4.35%) resulted in a significant 5.736-fold increased risk for NTDs (95% confidence interval, 1.731-19.009; p = 0.004). Nonisolated NTDs had lower levels of global DNA methylation than did isolated NTDs (3.77 vs. 4.70%; p = 0.022). After stratifying subjects by MTHFR genotype, we observed a skewed distribution of global DNA methylation levels. For genotype C/C, global DNA methylation status was the same in the two groups (4.51 vs. 4.72%; p = 0.687). For T/T, cases had significantly lower global methylation levels than did controls (5.23 vs. 3.79%; p < 0.001). Global DNA hypomethylation in fetal brain tissue was associated with NTD-affected pregnancy. DNA methylation levels were correlated with NTD complexity. The MTHFR genotype contributed to global DNA hypomethylation. Birth Defects Research (Part A), 2010. (c) 2010 Wiley-Liss, Inc.

677TT Genotype Is Associated with Elevated Risk of Methotrexate (MTX) Toxicity in Juvenile Idiopathic Arthritis: Treatment Outcome, Erythrocyte Concentrations of MTX and Folates, and MTHFR Polymorphisms

To investigate whether methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and erythrocyte concentration of methotrexate (EMTX) could serve as predictors of methotrexate (MTX) efficacy and toxicity in patients with juvenile idiopathic arthritis (JIA). Genetic analyses and EMTX and folate assessment were performed in 69 patients with JIA aged 2.5-19.6 years (30 male) treated with MTX using a dose-escalation protocol and classified as full responders (disease inactivity; n = 51) or nonresponders (< 30% improvement in pediatric American College of Rheumatology-30 criteria while receiving ≥ 15 mg/m(2)/week parenteral MTX for at least 3 months; n = 18). Nonresponders were treated with the higher median MTX dose (17.2 vs 12.6 mg/m(2)/week; p < 0.0001) and accumulated more EMTX (217 vs 106 nmol/l; p < 0.02) and erythrocyte folates (763 vs 592 nmol/l; p = 0.052) than responders. Analysis of MTHFR allele and genotype frequencies in relation to response failed to detect association. The frequency of any adverse effect was 29.4% in responders and 33.3% in nonresponders (p = 0.77). The frequency of 677T allele was elevated in patients with adverse effects (52.4% vs 20.9%; OR 3.88, 95% CI 1.8-8.6, p < 0.002). The probability of any adverse effect was significantly higher in patients with 677TT compared to the 677CC genotype (OR 55.5, 95% CI 2.9-1080, p < 0.001). MTHFR genotyping may have a predictive value for the risk of MTX-associated toxicity in patients with JIA. Despite the lack of therapeutic effect, nonresponders accumulated adequate concentrations of EMTX.

Maternal MTHFR genotype and haplotype predict deficits in early cognitive development in a lead-exposed birth cohort in Mexico City

Maternal folate nutritional status and prenatal lead exposure can influence fetal development and subsequent health. The methylenetetrahydrofolate reductase (MTHFR) gene is important for folate metabolism, and 2 common polymorphisms, C677T and A1298C, reduce enzymatic activity; C677T is present at high penetrance in Mexican populations. The objective of this study was to examine potential links between maternal and child MTHFR polymorphisms and child neurodevelopment in a lead-exposed population. Data regarding MTHFR polymorphisms C677T and A1298C, peri- and postnatal lead measures, and Bayley Mental Development Index at 24 mo of age (MDI-24) scores were available for 255 mother-child pairs who participated in the ELEMENT (Early Life Exposures in Mexico to Environmental Toxicants) study during 1994-1995. In covariate-adjusted regression models, maternal MTHFR 677 genotype predicted MDI-24 scores, in which each copy of the maternal MTHFR 677T variant allele was associated with lower MDI-24 scores (beta = -3.52; 95% CI: -6.12, -0.93; P = 0.004). Maternal MTHFR haplotype also predicted MDI-24 scores (mean +/- SE: 93.3 +/- 1.2 for 677C-1298A compared with 89.9 +/- 0.8 for 677T-1298A; P < 0.05). MDI-24 scores were not associated with maternal MTHFR 1298 genotype or child MTHFR genotypes. We did not observe significant MTHFR genotype x lead interactions with respect to any of the subject biomarkers of lead exposure. The maternal MTHFR 677T allele is an independent predictor of poorer child neurodevelopment at 24 mo. These results suggest that maternal genetic variations in folate metabolism during pregnancy may program offspring neurodevelopment trajectories. Further research is warranted to determine the generalizability of these results across other populations.