孕期叶酸摄入与MTHFR基因多态性对产后抑郁的影响

目的 探讨叶酸摄入量与亚甲基四氢叶酸还原酶(MTHFR)基因多态性与产后抑郁的关系.方法 将2014年1月至2016年6月之间来延安大学附属医院产科进行产检的800例孕妇纳入本项研究,采用开放式问卷调查的方式收集妊娠12周和28周妇女服用叶酸的信息,通过PCR-RFLP检测MTHFR基因C677T和A1298C多态性.于产后8周通过爱丁堡产后抑郁量表(EPDS)进行产后抑郁诊断.统计分析叶酸摄入与MTHFR C677T和A1298C基因多态性与产后抑郁的关系.结果 800例受试者中产后抑郁症患者218例,正常582例.产后抑郁妇女与正常妇女妊娠期间每天的叶酸摄入量和不同时间补充叶酸无明显差异,但是产后抑郁妇女血清叶酸水平显著低于正常妊娠妇女(x2=15.76,P＜0.001).两组受试者MTHFR C677T和A1298C多态性位点的基因型频率间差异存在统计学意义,其中杂合子CT(x2=13.67,P＜0.01)、AC(x2=3.39,P=0.02)和纯合子Tr(x2=8.65,P＜0.01)、CC(x2=15.18,P＜0.01)是产后抑郁发生的高风险因子.此外,不同MTHFR C677T和A1298C基因型(CC、CT、rr和AA、AC、CC)产后抑郁的妇女在孕期摄入的叶酸量、不同时间补充叶酸和血清叶酸水平无明显差异(x2值为0.07 ～ 2.79,均P ＞0.05).结论 低叶酸摄入量和不同时间补充叶酸不是产后抑郁发病的风险因素,但叶酸水平与MTHFR C677T和A1298C基因型是产后抑郁发病的独立风险因素.     

The effect of 677C-->T and 1298A-->C mutations on plasma homocysteine and 5,10-methylenetetrahydrofolate reductase activity in healthy subjects

We have studied the effect of common mutations (677C-->T and 1298A-->C) of the methylenetetrahydrofolate reductase (MTHFR) gene in sixty-six healthy French subjects, aged 27-47 years. Serum folate, vitamin B12, and plasma total homocysteine were measured as well as the specific activity of MTHFR in lymphocytes. The frequency of subjects homozygous for the 677TT genotype was 18%, and that of those homozygous for the 1298CC genotype was 12.5%. The frequency of individuals heterozygous for both mutations was 23.5%. The 1298A-->C mutation was associated with decreased MTHFR specific activity in subjects with both 677CC and 677CT genotypes. This activity was 60% for the 677CC/1298AC genotype and 52% for the 677CC/1298CC genotype when compared with the MTHFR specific activity of the 677CC/1298AA genotype. Heterozygotes for both mutations (677CT/1298AC genotype) had 36% of the reference specific activity. Although homocysteine levels in 677TT and 1298CC genotype subjects were higher than for other genotypes, no significant differences were observed among different genotypes. This may be due to high serum folate level in our samples, and suggests that folate therapy may be useful to prevent hyperhomocysteinaemia in homozygous mutant subjects.     

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.     

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.     

中国成年女性一碳单位代谢通路关联基因多态性位点地域分布特征

目的对中国16个省和2个直辖市的成年女性MTHFR和MTRR基因多态性分布特征进行分析,描绘一碳单位代谢通路关联的MTHFR C677T、 MTHFR A1298C和MTRR A66G基因多态性位点在中国的整体分布形态。方法在中国知网、万方数据库、维普中文科技期刊数据库、百度学术上,搜索关键词为"MTHFR"、"MTRR"、"女性"、"基因单核苷酸多态性"的中文文献。纳入的文献可以提供各种基因型对应成年女性的人数,或通过所提供的基因型频率可以计算出对应成年女性的人数。两人分工协作完成数据提取工作,并将提取到的数据以省或直辖市为单位进行合并,计算出各个省及直辖市各种基因型及等位基因分布频率。结果中国成年女性MTHFR 677TT基因型和677T等位基因频率自南向北逐渐稳固升高。MTHFR 1298CC在中国成年女性中占比极小。A1298C和C677T基因两者呈现连锁不平衡,TT/AA基因频率分布特征呈现出自北向南逐渐降低的趋势,在全国范围内TT/AC、 TT/CC和CT/CC的基因型频率均为0。MTRR 66AA在中国成年女性群体中占34%~58%,北部略高于南部;MTRR 66GG占5%~17%。结论基因多态性的风险评估可纳入针对神经管缺陷的一级预防措施。     

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.     

贵阳市育龄女性MTHFR和MTRR基因多态性与自然流产的相关性分析

目的 分析贵阳市育龄女性亚甲基四氢叶酸还原酶(MTHFR)、甲硫氨酸合成酶还原酶(MTRR)基因多态性与自然流产的相关性,降低贵阳市育龄女性自然流产发生率.方法 选取2016-2019年在贵阳市妇幼保健院进行孕前优生咨询的525例育龄女性为研究对象,按照有无自然流产史分为两组,病例组175例女性,对照组350例女性.比...     

胃癌亚甲基四氢叶酸还原酶基因多态性及其与微卫星不稳的关系

目的探讨胃癌亚甲基四氢叶酸还原酶（MTHFR）基因多态性与微卫星不稳的关系。方法采用聚合酶链反应一限制性片段长度多态性技术检测122例胃癌和101名正常对照的MTHFR基因C677T和A1298C多态性；采用PCR为基础的方法检测微卫星不稳定性（MSI）。结果MTHFR C677T多态性可分为677CC、677CT和677TT三种类型。胃癌组3种基因型频率分别为47．5％、39．3％和13．1％；对照组分别为48．5％、42．6％和8．9％，两组相比差异无统计学意义（P〉0．05）。以677CC基因型做为参考，胃贲门癌677CT基因型OR值为0．38，95％CI：0．15～0．98；TT基因型OR值为0．26，95％CI：0．03～2．18；677CT＋TT基因型OR值为0．36，95％CI：0．07～0．98。胃体癌677TT基因型OR值为3．03，95％CI：1．07～8．65。MTHFR A1298C多态性可分为1298AA、1298AC和1298CC3种类型。胃癌组3种基因型频率分别为59．8％、36．1％和4．1％；对照组分别为57．4％，37．6％和5．0％，两组相比差异无统计学意义（P〉0．05）。以1298AA基因型的OR值为1．00，胃窦癌AC基因型的OR值为0．87，95％CI：0．42～1．82，CC基因型的OR值为0．41，95％CI：0．05～3．72。MTHFR 677TT基因型胃癌与微卫星不稳显著相关（P〈0．05），而MTHFR A1298C多态性与微卫星不稳无关（P〉0．05）。结论重庆地区人群中MTHFR C677T多态性是胃贲门癌的保护因素，是胃体癌的危险因素；MTHFR A1298C多态性可能是胃窦癌的保护因素；677TT基因型胃癌的发生可能涉及到MSI途径。     

中国人群中亚甲基四氢叶酸还原酶C677T和A1298C基因多态性与乳腺癌相关性的Meta分析

目的 研究中国人群亚甲基四氢叶酸还原酶（5,10-methylenetetrahydrofolate reductase,MTHFR）基因C677T、A1298C多态性与乳腺癌发病风险的关系.方法 检索PubMed、Embase、Cochrane图书馆、中国生物医学文献数据库（CBM）、中国期刊全文数据库（CNKI）、万方数据库,并结合文献追溯的方法,收集以中国人群为研究对象的关于MTHFR基因C677T、A1298C多态性与乳腺癌发生相关性的病例-对照研究,剔除不符合要求的文献,应用Stata 11.0软件进行Meta分析,对各项研究进行异质性检验以及计算出合并后的OR值及其95％CI.结果 共纳入15个研究,包括乳腺癌病例组3 189例,对照组4 342例,对照组人群基因型分布经检验符合H-W遗传平衡.MTHFR C677T位点TT/CC、CT/CC和TT＋CT/CC基因型与乳腺癌易感性的OR值（95％CI）分别为1.89（1.35～2.64）、1.04（0.94～1.15）和1.18（1.02～1.37）.MTHFR A1298C位点CC/AA、AC/AA和CC＋AC/AA基因型与乳腺癌易感性的OR值（95％CI）分别为1.02（0.73～1.42）、0.90（0.79～1.02）和0.91（0.81～1.03）.结论 MTHFR基因677位点C→T变异与乳腺癌的易感性相关,但仅在TT纯合子时有统计学意义.1298位点A→C变异与乳腺癌的易感性无关联.     

Exploring the effects of methylenetetrahydrofolate reductase gene variants C677T and A1298C on the risk of orofacial clefts in 261 Norwegian case-parent triads

Folic acid and the methylenetetrahydrofolate reductase (MTHFR) gene have both been implicated in the etiology of orofacial clefts. The authors selected 261 case-parent triads (173 cases with cleft lip with or without cleft palate (CL/P) and 88 cases with cleft palate only (CPO)) from a Norwegian population-based study of orofacial clefts (May 1996-1998). A case-parent triad design was used to examine whether MTHFR variants C677T and A1298C, and their haplotypes, are risk factors for orofacial clefts. Among CL/P cases, the child's genotype at C677T or A1298C did not influence the risk. However, children of mothers carrying the C677T variant allele had a lower risk of CL/P. For CPO, children carrying the C677T variant allele had about a twofold increased risk, whereas the mother's genotypes did not contribute to the risk. The haplotype-based transmission/disequilibrium test showed that except for 677T/1298A (p = 0.06), none of the other haplotypes showed evidence of excess transmission to the offspring. The authors also explored interaction of C677T with maternal use of folic acid among children with CPO. Surprisingly, the risk associated with the child's carrying either CT or TT was higher (fourfold) when the mother used folic acid. These findings suggest a possible role of MTHFR and folic acid in the causation of orofacial clefts, but the strength and direction of these effects remain to be clarified.     

A common mutation A1298C in human methylenetetrahydrofolate reductase gene: association with plasma total homocysteine and folate concentrations.

Methylenetetrahydrofolate reductase (MTHFR) is one of the main regulatory enzymes of homocysteine metabolism. Previous studies revealed that a common mutation in MTHFR gene C677T is related to hyperhomocysteinemia and occlusive vascular pathology. In the current study, we determined the prevalence of a newly described mutation in the human MTHFR gene A1298C, and the already known C677T mutation, and related them to plasma total homocysteine and folate concentrations. We studied 377 Jewish subjects, including 190 men and 186 women aged 56.8 +/- 13 y (range 32-95 y). The frequency of the homozygotes for the A1298C and the C677T MTHFR mutations was common in the Jewish Israeli population (0.34 and 0.37, respectively). Subjects homozygous (TT) for the C677T mutation had significantly greater plasma total homocysteine concentrations (P < 0.01) than subjects without the mutation (CC). Homozygotes (CC) for the A1298C mutation did not have elevated plasma total homocysteine concentrations. Our study indicated that subjects with the 677CC/1298CC genotype had significantly lower concentrations (P < 0. 05) than those with a 677CC/1298AA genotype. Neither mutation (the A1298C and the C677T) was associated with established cardiovascular risk factors such as hypertension, elevated total cholesterol or body mass index.     

西藏阿里西部区域高血压与同型半胱氨酸和脑卒中风险基因的关系

目的 对西藏阿里西部区域高血压与同型半胱氨酸(Hcy)和脑卒中风险基因的关系进行分析,为更加合理地制定卫生政策、规划卫生资源提供科学的依据,有效提高西部藏族群众的健康状况。方法 分层整群随机抽样。采用“青藏高原慢性病防治”调查问卷对调查对象进行面对面调查,并进行Hcy检查和脑卒中风险基因(MTHFR基因)位点筛查。结果 高血压患病率为18.5%。Hcy中度升高者患高血压的风险是Hcy正常者的2.39倍(95%CI=1.44～3.94,P =0.001)。MTHFR A1298C 中AC基因型的患病率是AA的1.39倍(95%CI=1.05～1.85,P =0.023); MTHFR C677T和 MTHFR A1298C联合分析,CC+AC/CC和CT/TT+AC/CC两种联合方式增加了患高血压的风险(P =0.042,OR=1.47,95%CI=1.02～2.12; P =0.015,OR=1.78,95%CI=1.12～2.85)。Hcy升高合并基因突变组的高血压患病率高于Hcy正常组,差异有统计学意义(P <0.005)。结论 西藏阿里西部区域居民血浆Hcy浓度是高血压患病的影响因素; 不同基因型的联合影响高血压患病; Hcy升高与基因突变型联合显著增加了居民患高血压的风险。     

不良妊娠结局与夫妻MTHFR基因多态性的相关性及叶酸代谢风险评估策略的研究

目的 探讨夫妻亚甲基四氢叶酸还原酶（methylenetetrahydrofolate reductase, MTHFR)基因C677T和A1298C多态性与不良妊娠结局的相关性及现有叶酸代谢风险等级评估策略的可行性。方法 选取145对曾有不良妊娠结局的夫妻和110对正常对照,应用Sanger测序检测MTHFR 677、1298位点多态性,分别比较病例组与对照组间女性、男性各基因型分布是否存在显著差异;据现有叶酸代谢风险等级评估策略对研究对象进行分级,比较两组中不同风险等级病例的分布是否存在显著差异。结果 病例组男性和女性MTHFR 677 位点C/C基因型频率均低于对照组,C/T、T/T基因型频率均高于对照组,两组中男性和女性的MTHFR 677位点3种基因型分布差异均有统计学意义（P＜0.05）;病例组男性和女性MTHFR 1298位点A/C基因型频率均高于对照组,A/A、C/C基因型频率均低于对照组,两组男性和女性MTHFR 1298位点3种基因型分布差异均无统计学意义（P＞0.05）;两组间男性和女性的叶酸代谢风险级别分布差异均有统计学意义（P＜0.05）。结论 女性MTHFR C677T多态性变异与不良妊娠结果有明显相关性,不能排除男性MTHFR C677T多态性改变与不良妊娠结局无关,建议孕前夫妻双方同时进行MTHFR基因多态性检测。可根据叶酸代谢风险分级策略,为夫妻双方制定合理的个体化叶酸增补方案。     

双亲5,10-亚甲基四氢叶酸还原酶基因多态性与子代神经管畸形易感性的关系

目的 定量评价双亲5,10-亚甲基四氢叶酸还原酶(MTHFR)基因C677T多态性与子代神经管畸形(NTDs)发生的关联性及关联强度,为利用双亲MTHFR 677位点基因型预测和评价子代NTDs的发病风险提供依据.方法 制定原始文献的纳入和排除标准及检索策略.检索中外数据库,收集有关亲代MTHFR基因C677T多态性与NTDs相关性的研究报告,按照MTHFR基因677位点基因型分类,分别整理子代患NTDs的双亲基因型频数数据,应用RevMan5.0软件对各文献进行异质性检验和Meta分析,得出合并后的OR值及其95%CI.结果 共33篇文献符合纳入标准.数据合并结果显示,母亲MTHFR基因677位点TT/CC、CT/CC基因型频率与子代NTDs易感性之间有统计学意义,OR值(95%CI)分别为1.68(1.32～2.14)、1.20(1.07～1.35);父亲MTHFR基因677位点TT/CC、CT/CC基因型频率与子代NTDs易感性有统计学意义,OR值(95%CI)分别为1.38(1.08～1.76)、1.32(1.13～1.55).结论 双亲MTHFR基因C677T多态性均是子代NTDs发病的重要危险因素.

Abstract：

Objective To explore the relationship between 5, 10-methylenetrahydrofolate reeducates gene polymorphism of the parents and the susceptibility to their offspring having neural tube defects. To forecast and evaluate the onset risk of neural tube defects (NTDs) on the basis of 5, 10-methylenetrahydrofolate reeducates (MTHFR) C677T polymorphism on parents of the patients.Methods Electronic search strategy was carried out among the five databases from home and abroad to collect qualified research papers, according to the inclusion and exclusion criteria. Case-control studies on association between MTHFR polymorphism and susceptibility to NTDs were collected and divided into two groups as mothers and fathers. The combined OR values and their 95% CI were calculated with Review Manager 5.0. Results 33 eligible studies were included. Statistics of the combined data showed a significant difference between the mothers with NTDs offspring carrying TT/CC, CT/CC of MTHFR gene C677T and controls. The pooled OR (95%CI) were 1.68 (1.32-2.14)and 1.20 (1.07-1.35) respectively. These was a significant difference between the fathers of the offspring with NTDs that carrying of TT/CC, CT/CC of MTHFR gene C677T and controls. The pooled ORs (95%CI) were 1.38 (1.08-1.76) and 1.32 (1.13-1.55) respectively. Conclusion The results suggested that the paternal and maternal MTHFR gene C677T polymorphism were risk factors to NTDs.     

轻中度高血压患者中MTHFR C677T与血清叶酸水平变化的相关性研究

目的探讨轻中度高血压患者亚甲基四氢叶酸还原酶（MTHFR）C677T多态性位点与血清叶酸水平变化间的关系。方法从哈尔滨、沈阳、北京、西安、上海、南京6城市收集的480位28～75岁轻中度原发性高血压患者,按1：1：1的原则随机分为3组;对照组、0．4mg叶酸组、0．8mg叶酸组每日分别服用10mg马来酸依那普利、10mg马来酸依那普利＋0．4mg叶酸、10mg马来酸依那普利＋0．8mg叶酸,连续服用8周。收集治疗前后的血清叶酸水平、MTHFR C677T位点的基因型及其他相关指标。本研究对主要资料完整者371人（男156人,女215人）的MTHFR C677T位点与血清叶酸水平变化间的关系进行统计分析。结果①对照组中C677T基因型对叶酸变化水平无明显作用,各基因型间的差异均无统计学意义。②试验组中血清叶酸变化水平在C677T CC、CT和TT基因型间的变化趋势基本一致,TT型增加水平最少,CC型增加最多。以677CC基因型人群的叶酸变化水平为参照,合并叶酸组中TT基因型在调整前（β=3．99,P=0．034）后（β=5．68,P〈0．001）差异均有统计学意义;0．4mg叶酸组和0．8mg叶酸组TT基因型在调整前（β分别为5．33和2．64,P分别为0．061和0．280）差异无统计学意义,调整后（β分别为5．60和4．68,P分别为0．031和0．050）差异有统计学意义。各组中CT基因型调整前后的差异均无统计学意义（P〉0．05）。结论轻中度高血压患者中MTHFR C677T的基因型对叶酸的疗效具有一定的作用。     

叶酸代谢相关基因MTHFR、MS基因多态与胰腺癌风险关联

目的 探讨亚甲基四氢叶酸还原酶（MTHFR）及甲硫氨酸合成酶（MS）基因多态与胰腺癌风险的关系.方法 采用以医院为基础的病例对照研究（胰腺癌新发病例101例,对照337人）方法,进行MTHFR C677T、A1298C及MS A2756G基因多态与胰腺癌风险关联分析,采用PCR-RFLP方法进行两候选基因分型.结果 携带MTHFR-677 CT及TT基因型者发生胰腺癌风险是CC基因型个体的2.17（95%CI：1.26～3.85）及3.53（95%CI：1.85～6.84）倍,呈明显的等位基因-效应关系;未观察到MTHFR 1298多态单独对胰腺癌发生的影响,但发现它与C677T有联合作用.MTHFR677CT与TT基因型与吸烟、饮酒有明显的正向交互,产生交互作用的ORint值分别为1.78（P=0.0010）和2.10（P=0.0051）.未发现MS A2756G多态与胰腺癌的发生之间存在统计学的显著关联.结论 MTHFR C677T多态与胰腺癌发生风险显著关联,且与吸烟、饮酒存在正向交互作用.     

5,10-methylenetetrahydrofolate reductase common mutations, folate status and plasma homocysteine in healthy French adults of the Supplementation en Vitamines et Mineraux Antioxydants (SU.VI.MAX) cohort

The 677cytosine mutation identified in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has been frequently associated with an elevated plasma homocysteine concentration. The aim of the present study was to determine the impact of this MTHFR common mutation on plasma and erythrocyte folate (RCF) and plasma total homocysteine (tHcy) concentrations in healthy French adults. A cohort of 291 subjects living in the Paris area and participating in the Supplementation en Vitamines et Mineraux Antioxydants (SU.VI.MAX) study were analysed to assess the impact of MTHFR polymorphism 677C-->T on folate status and plasma tHcy concentration. The frequency of the mutant homozygote for 677C-->T polymorphism (677TT genotype) in the present cohort was 16.8%. There were significant differences in plasma tHcy between 677CC, 677CT and 677TT genotype groups. The RCF concentrations were significantly different between each genotype, the lowest levels being associated with the 677TT genotype. When segregated by gender, no differences in tHcy between homozygous 677TT, heterozygous 677CT and wild-type 677CC genotype groups in women were observed. The fasting tHcy in women was unrelated to the 677C-->T mutation. However, tHcy was significantly increased in men with the homozygous 677TT genotype. We also analysed the possible implication of a second new MTHFR polymorphism (1298A-->C) in subjects with mild hyperhomocysteinaemia (4th quartile of homocysteinaemia; tHcy >11.1 micromol/l). The polymorphism 1298A-->C did not have a notable effect on tHcy or on the RCF levels. Our observations confirm a relatively high frequency of the 677TT genotype in the French population. Women with this genotype did not show the same increase in tHcy observed in men. In the present study dietary folate intake was not measured. Thus, the interaction of dietary folate with the MTHFR genotype in the French population needs further study.     

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.     

Methylenetetrahydrofolate reductase 677C-->T variant modulates folate status response to controlled folate intakes in young women

A common genetic variant in the methylenetetrahydrofolate reductase (MTHFR) gene involving a cytosine to thymidine (C-->T) transition at nucleotide 677 is associated with reduced enzyme activity, altered folate status and potentially higher folate requirements. The objectives of this study were to investigate the effect of the MTHFR 677 T allele on folate status variables in Mexican women (n = 43; 18-45 y) and to assess the adequacy of the 1998 folate U.S. Recommended Dietary Allowance (RDA), 400 micro g/d as dietary folate equivalents (DFE). Subjects (14 CC, 12 CT, 17 TT genotypes) consumed a low folate diet (135 micro g/d DFE) for 7 wk followed by repletion with 400 micro g/d DFE (7 CC, 6 CT, 9 TT) or 800 micro g/d DFE (7 CC, 6 CT, 8 TT) for 7 wk. Throughout repletion with 400 micro g/d DFE, the TT genotype had lower (P 0.05) in their response relative to the CC genotype. Throughout repletion with 800 micro g/d DFE, the CT genotype had lower (P 0.05) in the measured variables between the TT and CC genotypes. Repletion with 400 micro g/d DFE led to normal blood folate and desirable plasma tHcy concentrations, regardless of MTHFR C677T genotype. Collectively, these data demonstrate that the MTHFR C-->T variant modulates folate status response to controlled folate intakes and support the adequacy of the 1998 folate U.S. RDA for all three MTHFR C677T genotypes.     

Contribution of thermolabile methylenetetrahydrofolate reductase variant to total plasma homocysteine levels in healthy men and women. Inter99 (2)

Elevation in plasma total homocysteine (tHcy) is believed to be causally related to cardiovascular disease. Like age and sex, the thermolabile variant of methylenetetrahydrofolate reductase (MTHFR(C677T)) is an important nonmodifiable determinant of tHcy, which may be considered when describing normal ranges of tHcy in the general population. We investigated the simultaneous effect of sex, age, and MTHFR(C677T) genotype on the distribution of tHcy in a cross-sectional study design. THcy concentrations and MTHFR(C677T) genotype were determined in a population-based sample of 2,788 Danish men and women aged 30-60 years participating in the Inter99 Study. The prevalences of MTHFR(C677T) genotypes were 48.8% (CC), 42.4% (CT), and 8.8% (TT). The overall median tHcy was 8.1 micromol/l, and the 2.5-97.5 percentiles were 4.8-17.8 micro mol/l. The estimated proportionally higher level of tHcy in men compared to women was 14.3% (P<0.001). A significant interaction term was found between age and MTHFR(C677T) genotype (P<0.001). The estimated changes in tHcy per 5 years of age were 1.5% in CC individuals (P<0.01), 2.1% in CT individuals (P<0.001), and -4.1% in TT individuals (P<0.01). The T allele was associated with elevated tHcy. However, the proportionally higher level of tHcy in TT individuals compared to CT and CC individuals decreased with increasing age. The MTHFR(C677T) polymorphism explained 6% of the phenotypic variation in tHcy. In conclusion, we found that tHcy is associated with sex, age, and MTHFR genotype. Our results indicate that the effect of age is modified by MTHFR genotype.