C677T methylenetetrahydrofolate reductase polymorphism interferes with the effects of folic acid and zinc sulfate on sperm concentration

OBJECTIVE: To determine the frequency of C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism in fertile and subfertile males, and the MTHFR-dependent response of sperm concentration after folic acid and/or zinc sulfate intervention. DESIGN: Double-blind, placebo-controlled intervention study.Two outpatient fertility clinics and nine midwifery practices in The Netherlands. PATIENT(S): One hundred thirteen fertile and 77 subfertile males.Daily capsules of folic acid (5 mg) and/or zinc sulfate (66 mg), or placebo for 26 weeks. MAIN OUTCOME MEASURE(S): Prevalence of C677T MTHFR polymorphism and the response of sperm concentration related to MTHFR carriership after intervention treatment. RESULT(S): The C677T methylenetetrahydrofolate reductase genotypes were comparable in fertile and subfertile males. Independent of fertility state, sperm concentration significantly increased in wild-types after folic acid and zinc sulfate treatment only. Heterozygotes and homozygotes did not significantly benefit from either treatment. CONCLUSION(S):C677T methylenetetrahydrofolate reductase polymorphism is not a risk factor for male factor subfertility. In contrast to heterozygotes and homozygotes for C677T MTHFR polymorphism, sperm concentration in wild-types significantly improved after folic acid and zinc sulfate intervention. A stronger role of other folate genes on spermatogenesis is suggested.     

Severe methylenetetrahydrofolate reductase deficiency revealed by a pulmonary embolism in a young adult

Deficiency in methylenetetrahydrofolate reductase (MTHFR), the enzyme involved in the remethylation of homocysteine to methionine using methyltetrahydrofolate as cofactor, induces hyperhomocysteinaemia, homocysteinuria, hypomethioninaemia and low methylfolate levels. Diagnosis usually occurs during infancy because of various neurological abnormalities. We report MTHFR deficiency diagnosed in an adult woman after a pulmonary embolism. Her adult sister, intellectually retarded, suffered from the same disease. Molecular analysis of the MTHFR gene exhibited four different mutations (two missense mutations, one exon skipping and C677T). The impact of these mutations was analysed through the biological abnormalities in the parents and children.     

The Common 677C>T Gene Polymorphism of Methylenetetrahydrofolate Reductase Gene is not Associated with Breast Cancer Risk

Methylenetetrahydrofolate reductase (MTHFR) is involved in folate metabolism and plays a role in DNA biosynthesis, methylation, and repair in actively dividing cells. A common 677C>T polymorphism in the gene for MTHFR, leading to a thermolabile enzyme with decreased activity, has been associated with reduced plasma folate levels and elevated homocysteine levels and could be a risk factor for breast cancer. In the present case-control study, MTHFR genotype was determined in 500 women with clinically verified breast cancer and 500 female age-matched healthy control subjects. The homozygous TT genotype was found in 13.0% patients and 13.1% controls (P = n.s.). The odds ratio of TT homozygotes for breast cancer was 0.99 (95% confidence interval 0.68–1.43). The MTHFR genotype was furthermore not associated with tumor size, histological grading, estrogen or progesterone receptor status and age at diagnosis. In a subgroup of 116 premenopausal patients, no increased frequency of the homozygous 677T genotype was found (13.8%). Therefore, we conclude that the MTHFR 677C>T polymorphism is not associated with individual susceptibility to breast cancer.     

MTHFR基因多态性与冠心病关系的Meta分析

目的评价中国人群中亚甲基四氢叶酸还原酶(MTHFR)基因C677T多态性与冠心病的相关性。方法通过文献检索收集MTHFR基因C677T多态性与冠心病关系的全文文献,剔除不符合要求的文献,在全面文献回顾的基础上对各研究OR值进行Meta分析。结果共有16篇符合条件的文献纳入分析,Meta分析结果表明,以野生型CC基因别为参照,携带T等位基因的个体发生冠心病的危险性的0R值为1.45,95%可信区间为(1.12,1.89),P<0.01。结论中国人群中T等位基因携带者易于发生冠心病。     

亚甲基四氢叶酸还原酶基因C677T多态性与男性不育的相关性

目的:探讨亚甲基四氢叶酸还原酶(MTHFR)基因C677T多态性与中国东北人群男性不育的关系。方法:应用聚合酶链式反应-限制性片断长度多态性(PCR-RFLP)方法检测53例健康可育男性和182例不育男性的MTHFR基因C677T位点多态性。结果:弱精子症不育组(AS组)和不明原因不育组(UR组,精液常规正常)的3种基因型和T等位基因频率分别与对照组相比,差异均具有统计学意义(P<0.05)。结论:MTHFR基因C677T多态性可能与中国东北人群男性不育有相关性,且与弱精子症和不明原因不育的发生密切相关。     

Screening for methylenetetrahydrofolate reductase C677T and A1298C polymorphisms in Indian patients with idiopathic mental retardation

Abstract

Although genetic, nutritional, and environmental factors have been found to aggravate mental retardation in ～1% of individuals, no cause is known till date. In this study, two genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR), C677T (rs#1801133) and A1298C (rs#1801131), have been investigated in idiopathic mental retardation (IMR) subjects. Significantly higher frequency of the C677 allele was observed in IMR (n = 155; χ² = 5.5; P = 0.019) and moderate IMR (n = 67; χ² = 6.16; P = 0.013) groups as compared to controls (n = 126); for A1298C, no significant difference was noticed. TDT analysis revealed preferential transmission of C677 allele to a small group of mild IMR probands (χ² = 5.545; P = 0.018). Higher frequency of CA haplotype was also noticed in IMR cases as compared to controls (χ² = 6.28; P = 0.012). We infer from the present investigation that these polymorphisms are not contributing to the aetiology of IMR in this population since both case-control and family-based analysis revealed no significant transmission of the mutated allele.     

The methylenetetrahydrofolate reductase C677T mutation induces cell‐specific changes in genomic DNA methylation and uracil misincorporation: A possible molecular basis for the site‐specific cancer risk modification

The C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with a decreased risk of colon cancer although it may increase the risk of breast cancer. This polymorphism is associated with changes in intracellular folate cofactors, which may affect DNA methylation and synthesis via altered one‐carbon transfer reactions. We investigated the effect of this mutation on DNA methylation and uracil misincorporation and its interaction with exogenous folate in further modulating these biomarkers of one‐carbon transfer reactions in an in vitro model of the MTHFR 677T mutation in HCT116 colon and MDA‐MB‐435 breast adenocarcinoma cells. In HCT116 cells, the MTHFR 677T mutation was associated with significantly increased genomic DNA methylation when folate supply was adequate or high; however, in the setting of folate insufficiency, this mutation was associated with significantly decreased genomic DNA methylation. In contrast, in MDA‐MB‐435 cells, the MTHFR 677T mutation was associated with significantly decreased genomic DNA methylation when folate supply was adequate or high and with no effect when folate supply was low. The MTHFR 677T mutation was associated with a nonsignificant trend toward decreased and increased uracil misincorporation in HCT116 and MDA‐MB‐435 cells, respectively. Our data demonstrate for the first time a functional consequence of changes in intracellular folate cofactors resulting from the MTHFR 677T mutation in cells derived from the target organs of interest, thus providing a plausible cellular mechanism that may partly explain the site‐specific modification of colon and breast cancer risks associated with the MTHFR C677T mutation. © 2008 Wiley‐Liss, Inc.     

育龄女性MTHFR基因多态性与叶酸浓度的关系研究

目的通过对孕期育龄女性叶酸代谢关键酶5,10-亚甲基四氢叶酸还原酶(MTHFR)C677T的基因多态性检测,分析MTHFR C677T基因多态性与外周血红细胞中叶酸浓度之间的关系。方法收集孕期育龄女性100例,采用基因芯片法检测外周血红细胞中MTHFR C677T的基因多态性,并对所有研究对象中的育龄女性给予口服800μg/d叶酸1个月,抽取口服叶酸前后EDTA抗凝血各5mL,化学发光法检测口服叶酸前后不同基因型女性外周血细胞中叶酸浓度的变化。结果 100例育龄妇女MTHFR C677T基因CC型、CT型、TT型的检出频率分别为26%、54%、20%;CC型受试者口服叶酸前后平均红细胞叶酸浓度之间差异无统计学意义(P0.05),CT型和TT型受试者口服叶酸后红细胞叶酸浓度较口服前升高,差异有统计学意义(P0.05)。结论外周血中MTHFR C677T基因分型可以影响细胞内叶酸的浓度,口服叶酸可以提高育龄女性红细胞内叶酸浓度。     

MTHFR C667T多态性与先兆子痫易感性的荟萃分析

目的探讨MTHFRC667T基因多态性对先兆子痫(PE)易感性的影响。方法检索CBMdisc、Pubmed等数据库,按纳入标准纳入有关MTHFRC667T基因多态性与PE的病例对照研究进行荟萃分析。结果共纳入24篇文献(26个病例对照研究),共计PE患者3017例,对照者4910例。研究分析显示MTHFRC667T基因多态性与PE存在明显关联[基因频率对比的OR(95%CI)=1.17(1.05～1.30),POR=0.006;隐性遗传对比模型的OR(95%CI)=1.18(1.01～1.38),POR=0.047;显性遗传对比模型的OR(95%CI)=1.20(1.08～1.34),POR=0.001;纯合子对比模型的OR(95%CI)=1.27(1.07～1.52),POR=0.008]。亚组分析显示,MTHFRC667T基因多态性与PE在亚洲人种中存在明显关联,但在欧洲人群及非洲分群中不存在明显关联。结论 MTHFRC667T多态性与PE易感性存在明显关联,但这种关联关系存在明显人种差异。     

The effects of homocysteine and MTHFR genotype on hip bone loss and fracture risk in elderly women

Summary  Few studies have evaluated the effects of homocysteine and methylenetetrahydrofolate reductase (MTHFR) genotype on age-related bone loss. In our 5-year cohort study with 1,213 women aged 70–85 years, high homocysteine is associated with greater hip bone loss but not fracture risk. The effect of MTHFR genotype on bone density and fracture is weak. Introduction  Previous studies on the effects of homocysteine and MTHFR genotype on bone mineral density (BMD) and osteoporotic fracture risk have shown inconsistent results. Few studies have evaluated their effects on age-related bone loss. We evaluated the effects of homocysteine and MTHFR genotype variation on hip BMD and fracture risk over 5 years in a cohort of 1,213 community-dwelling women aged 70–85 years. Methods  Nutritional intake and prevalent fracture status were assessed at baseline, plasma homocysteine was measured at year 1, and hip dual-energy X-ray absorptiometry (DXA) BMD was measured at years 1 and 5. Clinical incident osteoporotic fractures confirmed by radiographic report were collected throughout the study and the MTHFR gene C677T and A1298C polymorphisms genotyped. Data were analyzed using analysis of covariance and Cox proportional hazard regression. Results  The highest tertile of homocysteine was associated with a greater hip BMD loss over 4 years (−2.8%) compared to the middle (−1.6%) and lowest tertiles (−1.2%) (P < 0.001). This effect remained after adjustment for covariates. There was no effect of homocysteine on fracture prevalence or incidence. MTHFR gene variation was only weakly related to one of the bone outcome measures. Conclusion  In this study population, high homocysteine is associated with greater hip bone loss but not fracture risk.