四川南充市健康体检者同型半胱氨酸代谢酶基因多态性分布及其水平关联

目的 研究南充市汉族人群同型半胱氨酸(Hcy)代谢关键酶基因多态性的分布及与Hcy水平的关联.方法以在南充市中心医院的汉族人群470人为研究对象,抽取受检者血样,收集研究对象一般临床资料,采用循环酶法测定血浆Hcy水平,提取基因组DNA后进行SNP基因多态性检测,分析Hcy代谢关键酶MTHFR C677T、MTHFR ...     

No association between common polymorphisms in genes of folate and homocysteine metabolism and the risk of Down's syndrome among French mothers

The cause of the non-disjunction leading to trisomy 21 remains unclear. Recent evidence has suggested that 5,10-methylenetetrahydrofolate reductase (MTHFR) and/or methionine synthase reductase (MTRR) might contribute to the maternal risk of trisomy 21. The purpose of the present study was to analyse these findings among the French population and to investigate whether common polymorphisms in genes of the folate and homocysteine pathway, including the MTHFR 677C > T, MTHFR 1298A > C, the methionine synthase (MTR) 2756A > G, the cystathionine beta-synthase (CBS) 844Ins68 and the reduced folate carrier (RFC-1) 80G > A polymorphisms, contribute to the risk of trisomy 21. The risk was studied by analysing independent and combined genotypes in 119 case mothers and 119 control mothers. The MTHFR 677T, MTHFR 1298C, MTR2756G, MTRR66G, CBSIns68+ and the RFC-1 80G allele frequencies were not significantly different among French case mothers, compared with control mothers. The risk of having a child with trisomy 21 did not appear to be linked to polymorphisms in genes associated with folate and homocysteine metabolism.     

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.     

Polymorphisms in genes involved in folate metabolism and colorectal neoplasia: a HuGE review

Epidemiologic and mechanistic evidence suggests that folate is involved in colorectal neoplasia. Some polymorphic genes involved in folate metabolism--methylenetetrahydrofolate reductase (MTHFR C677T and A1298C), methionine synthase (MTR A2756G), methionine synthase reductase (MTRR A66G), cystathionine beta-synthase (CBS exon 8, 68-base-pair insertion), and thymidylate synthase (TS enhancer region and 3' untranslated region)--have been investigated in colorectal neoplasia. For MTHFR C677T and A1298C, the variant allele is associated with reduced enzyme activity in vitro. For the other polymorphisms, functional data are limited and/or inconsistent. Genotype frequencies for all of the polymorphisms show marked ethnic and geographic variation. In most studies, MTHFR 677TT (10 studies, >4,000 cases) and 1298CC (four studies, >1,500 cases) are associated with moderately reduced colorectal cancer risk. In four of five genotype-diet interaction studies, 677TT subjects who had higher folate levels (or a "high-methyl diet") had the lowest cancer risk. In two studies, 677TT homozygote subjects with the highest alcohol intake had the highest cancer risk. Findings from six studies of MTHFR C677T and adenomatous polyps are inconsistent. There have been only one or two studies of the other polymorphisms; replication is needed. Overall, the roles of folate-pathway genes, folate, and related dietary factors in colorectal neoplasia are complex. Research priorities are suggested.     

Interactions among polymorphisms in folate-metabolizing genes and serum total homocysteine concentrations in a healthy elderly population

BACKGROUND: Homocysteine concentrations are influenced by vitamin status and genetics, especially several polymorphisms in folate-metabolizing genes. OBJECTIVE: We examined the interactions and associations with serum total homocysteine (tHcy) and folate concentrations of polymorphisms in the following folate-metabolizing genes: methylenetetrahydrofolate reductase (MTHFR), reduced folate carrier 1 (RFC1), and glutamate carboxypeptidase II (GCPII). DESIGN: Healthy volunteers (436 men and 606 women; mean age: 77.9 y) were randomly selected from among residents of Oxford, United Kingdom. We determined the individual effects and interactions of the MTHFR 677C-->T, MTHFR 1298A-->C, RFC1 80G-->A, and GCPII 1561C-->T polymorphisms on serum tHcy and folate concentrations. RESULTS: Subjects with the MTHFR 677TT genotype had higher serum tHcy concentrations than did those with the MTHFR 677CC genotype (P < 0.001), and this effect was greater in subjects with low serum folate status (P for interaction = 0.026). The MTHFR 1298A-->C, RFC1 80G-->A, and GCPII 1561C-->T polymorphisms had no individual effects on serum tHcy or folate concentrations. There was no interactive effect of the MTHFR 677C-->T and MTHFR 1298A-->C polymorphisms on tHcy concentrations. An interaction (P = 0.05) was observed between the MTHFR 677TT and RFC1 80GG genotypes, whereby persons with this genotype combination had a mean (+/-SEM) serum tHcy concentration (18.5 +/- 1.2 micromol/L) that was 5.1 micromol/L greater than the mean value of 13.4 +/- 0.2 micromol/L for the whole population. CONCLUSIONS: Folate and tHcy concentrations were not affected individually by the MTHFR 1298A-->C, RFC1 80G-->A, or GCPII 1561C-->T polymorphisms or by combinations of the MTHFR 677C-->T and MTHFR 1298A-->C genotypes. An interaction between the MTHFR 677TT and RFC1 80GG genotypes was observed whereby persons with this combination had higher serum tHcy.     

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.     

Dietary Intake of Folate,Vitamin B2, Vitamin B6, Vitamin B12, Genetic Polymorphism of Related Enzymes,and Risk of Breast Cancer: A Case-Control Study in Japan

We investigated associations among intake of folate, vitamin B2, vitamin B6, vitamin B12, and polymorphisms of 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) genes and breast cancer risk in a Japanese population. A hospital based, case-control study was conducted in Nagano Prefecture, Japan, in 388 pairs of patients with histologically confirmed invasive breast cancer and age- and area-matched controls selected from medical checkup examinees. Energy-adjusted intakes of folate and other B vitamins were derived from a validated food frequency questionnaire. Genotyping was completed for MTHFR (C677T and A1298T) and MTR (A2756G). Odds ratios and 95% confidence intervals were calculated by the conditional logistical regression model. Median dietary folate intake (μg/day) in the control group was 438.2 (interquartile range: 354.9–542.9). Neither dietary intake of folate, vitamin B2, vitamin B6, or vitamin B12 nor polymorphisms of MTHFR or MTR genes were significantly associated with breast cancer risk. Further, no significant interaction was found among nutrients, polymorphisms, and breast cancer risk. Associations of nutrients with breast cancer risk did not differ by hormone receptors status. We conclude that dietary intake of folate and related B vitamins and genotypes of MTHFR or MTR have no overall association with breast cancer risk in Japanese women.     

MTHFR、MTRR基因多态性与多囊卵巢综合征的相关性研究

目的探讨亚甲四氢叶酸还原酶(MTHFR)、甲硫氨酸合成酶还原酶(MTRR)基因多态性与多囊卵巢综合征(PCOS)的相关性。方法应用病例对照研究,收集2018年4月-2018年8月在广东省妇幼保健院就诊的育龄期PCOS患者55例为PCOS组,选取46例月经规则、有排卵,并完成一次生育的非PCOS患者作为对照组。在PCOS组中,按HOMA稳态模型(HOMA-IR)分为两组,PCOS胰岛素抵抗(PCOS-IR)组和PCOS非胰岛素抵抗(PCOS-NIR)组,按多毛评分标准(m FG score)和血清游离雄激素指数(FAI)分为两组,高雄激素症组和非高雄激素症组,分别提取血浆,利用荧光定量PCR方法检测MTHFR基因C677T、A1298C及MTRR基因A66G的单核苷酸多态性(SNPs),同时采用化学发光法检测两组血浆维生素B12、叶酸及同型半胱氨酸(HCY)的含量。结果MTHFR基因C677T等位基因C在PCOS组分布频率高于对照组,差异有统计学意义(P<0.05),等位基因C使PCOS的风险增加2.077倍(95%CI:1.132~3.812)。677CC基因型在PCOS组的分布频率明显高于对照组,差异有统计学意义(P<0.05),野生基因型(CC)与纯合突变基因型(TT)相比,患PCOS的风险提高了4.392倍(95%CI:1.005~19.196)。两组MTHFR基因A1298C、MTRR基因A66G各基因型和等位基因频率的分布差异无统计学意义(P>0.05)。在PCOS组中,PCOS-IR组和PCOS-NIR组以及高雄激素症组和非高雄激素症组在MTHFR基因C677T、A1298C及MTRR基因A66G各基因型分布差异无统计学意义(P>0.05),MTHFR C677T、A1298C及MTRR A66G位点分布之间不存在交互作用(P>0.05)。PCOS组中HCY水平较对照组明显升高,差异有统计学意义(P<0.05),两组血清维生素B12、叶酸水平差异均无统计学意义(均P>0.05)。结论MTHFR基因C677T多态性与PCOS的发病有一定的相关性,CC基因型可增加PCOS的发生风险,但与胰岛素抵抗(IR)和高雄激素症的发生风险无关。MTHFR基因A1298C、MTRRA66G各基因型与PCOS的发生、IR及高雄激素症的发生无关,PCOS组HCY偏高。     

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。     

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。比较两组育龄女性MTHFR C677T、A1298C及MTRR A66G基因型和等位基因分布。结果病例组MTHFR C677T野生基因型CC型69例(39.4%),杂合突变CT型76例(43.4%),纯合突变TT型30例(17.1%),对照组MTHFR C677T野生基因型CC型154例(44.0%),杂合突变CT型164例(46.9%),纯合突变TT型32例(9.1%),两组比较差异具有统计学意义(χ²=7.20,P<0.05);病例组的T等位基因频率为38.9%,较对照组T等位基因频率(32.6%)明显升高,差异有统计学意义(χ²=4.07,P<0.05)。两组MTHFR A1298C基因型分布比较差异无统计学意义(P...     

河北省9地区汉族育龄期女性MTHFR C677T、A1298C和MTRR A66G基因多态性分布研究

目的　分析河北省9个地区汉族育龄期女性亚甲基四氢还原酶（MTHFR）C677T、A1298C和甲硫氨酸合成酶还原酶（MTRR）A66G基因多态性的分布特征,以指导河北省地区汉族育龄女性叶酸的增补以及出生缺陷的预防。方法　共计1267位汉族育龄期女性位研究对象,采集静脉血,提取基因组DNA,采用KASP基因分型技术进行MTHFR和MTRR基因多态性检测,统计分析9个地区的基因多态性频率分布特征。结果　9地区MTHFR A1298C 位点基因型频率和等位基因频率比较差异有统计学意义（P＜0.05）,9地区MTHFR C677T 位点等位基因频率比较差异有统计学意义（P＜0.05）,9地区MTHFR C677T 位点基因型频率、MTRR A66G位点基因型频率和等位基因频率比较差异无统计学意义（P＞0.05）。结论　河北地区汉族女性MTHFR和MTRR基因多态性存在差异,具有一定的地域特异性。     

海南省汉族和黎族妇女亚甲基四氢叶酸还原酶和甲硫氨酸合成酶还原酶基因多态性分布研究

目的:比较海南省汉族和黎族妇女亚甲基四氢叶酸还原酶(MTHFR)C677T、A1298C及甲硫氨酸合成酶还原酶(MTRR)A66G多态性分布情况,获取其多态性位点的群体遗传学特征。方法:采用横断面调查研究方法,以海南省内11437例汉族与黎族孕妇为对象,采集口腔黏膜上皮细胞,提取DNA,采用Taqman-MGB技术,进行编码基因MTHFR和MTRR的相关多态性位点检测。结果:汉族妇女MTHFR C677T位点基因型纯合突变TT型高于黎族妇女,黎族妇女MTHFRA1298C基因型纯合突变CC型、MTRR A66G基因型纯合突变GG型的频率高于汉族妇女(P<0.01)。结论:海南省汉族与黎族妇女MTHFR和MTRR基因多态性分布存在差异。     

MTHFR和MTRR的SNP多态性与汉族孕妇复发性流产的相关性分析

目的 探究MTHFR和MTRR的SNP多态性与汉族孕妇复发性流产的相关性.方法 选取2012年1月至2015年2月无明确原因复发性流产而至昆山市第四人民医院妇产科就诊的非妊娠妇女190例归为观察组,另外选取同时间段进行体检的健康非妊娠妇女180例为对照组,比较两组妇女MTHFR基因C677T、A1298C和MTRR基因A66G基因位点的单核苷酸多态性(SNP).结果 观察组妇女MTHFR基因C677TT等位基因分布频率为32.11%,对照组为21.94%,观察组显著高于对照组(χ2=9.647,P=0.002).观察组妇女MTHFR基因A1298C等位基因分布频率为34.47%,对照组为30.83%,两组比较无显著性差异(χ2=1.113,P=0.291).观察组妇女MTRR基因A66GG等位基因分布频率为32.37%,对照组为15.28%,观察组显著高于对照组(χ2=29.558,P=0.000).结论 MTHFR基因C677T位点、MTRR基因A66G位点的多态性与复发性流产密切相关.     

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.     

Polymorphisms of key enzymes in homocysteine metabolism affect diet responsiveness of plasma homocysteine in healthy women

High plasma total homocysteine (tHcy), low dietary intake of folate and other B vitamins, and genetic polymorphisms related to metabolism of homocysteine may interactively contribute to the risk of cardiovascular disease. We investigated whether known mutations in genes regulating homocysteine metabolism affect the responsiveness of serum folate and plasma tHcy to high intake of natural folate from food. Healthy females (n = 37) aged 22-57 y volunteered to participate in a crossover dietary intervention with two 5-wk diet periods (low and high folate diets). Concentrations of serum and RBC folate, serum vitamin B-12 and plasma tHcy were measured at baseline and at the end of each diet period. The prevalences of C677T transition of methylenetetrahydrofolate reductase (MTHFR) gene, 844ins68 of cystathionine beta-synthase (CBS) gene and A2756G mutation of methionine synthase (MS) gene were determined. Compared with the low folate diet, the high folate diet increased the serum folate concentration by 85% (P < 0.001), 77% (P < 0.001) and 55% (P < 0.05) in the subjects with the genotypes C/C (n = 19), C/T (n = 13) and T/T (n = 5), respectively, of the MTHFR gene. Also, the plasma tHcy of the subjects with the genotypes C/C, C/T and T/T was decreased by 11% (P < 0.001), 15% (P < 0.01) and 18% (P < 0.05), respectively, during the high folate diet period. The subjects carrying the G2756 allele of the MS gene (n = 15) had a more extensive reduction (P < 0.05) of plasma tHcy during the high folate diet period than the subjects with the genotype A/A (n = 22). The 844ins68 of CBS gene did not affect plasma tHcy concentrations or diet responsiveness. In conclusion, diet responsiveness of plasma homocysteine may be genetically regulated.     

Alcohol intake and methylenetetrahydrofolate reductase polymorphism modify the relation of folate intake to plasma homocysteine

BACKGROUND: Folate intake increases plasma folate and reduces total homocysteine (tHcy) concentrations, which may lower coronary artery disease (CAD) and cancer risks. Folate metabolism may be altered by alcohol intake and 2 common polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, 677C-->T and 1298A-->C. OBJECTIVE: We examined whether the associations between folate intake and plasma folate and tHcy concentrations were modified by alcohol intake or variations in the MTHFR gene. DESIGN: We conducted a cross-sectional analysis among 988 women by using multivariate linear regression models to estimate mean plasma tHcy and folate concentrations. Folate intake was the sum of food and supplemental sources. RESULTS: We observed an inverse association between folate intake and tHcy, which was modified by alcohol intake (P for interaction = 0.04) and MTHFR677 genotype (P for interaction = 0.05) but not by MTHFR1298 genotype (P for interaction = 0.97). In the lowest quintile of folate intake, moderate drinkers (>/=15 g alcohol/d) had significantly higher tHcy concentrations (15.2 +/- 2.9 nmol/mL) than did light drinkers (11.3 +/- 0.7 nmol/mL) and nondrinkers (11.0 +/- 0.8 nmol/mL). However, the reduction in tHcy between the highest and lowest quintiles of folate intake was significantly greater in moderate drinkers (-6.6 nmol/mL) than in light drinkers (-2.3 nmol/mL) and nondrinkers (-2.1 nmol/mL). The elevated tHcy in women with low folate intake who also consumed moderate amounts of alcohol was even higher (22.4 +/- 4.8 nmol/mL) in the presence of the variant MTHFR677 allele. The positive association between folate intake and plasma folate was somewhat modified by alcohol intake (P for interaction = 0.08) but not by either MTHFR genotype. CONCLUSIONS: Moderate alcohol intake and low MTHFR activity have adverse effects on tHcy, but those effects may be overcome by sufficient folate intake.     

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.     

亚甲基四氢叶酸还原酶和甲硫氨酸合成酶还原酶基因多态性研究

目的:探讨编码叶酸代谢通路中关键酶的基因多态性与新生儿神经管缺陷(NTDs)间的关联性,及在部分中国女性人群中的分布特征,从而指导孕期叶酸补充和风险监测。方法:采用循证医学方法对5,10-亚甲基四氢叶酸还原酶(MTHFR)C677T、A1298C和甲硫氨酸合成酶还原酶(MTRR)A66G与NTDs的关联性进行Meta分析,并在中国的北方(山东、河南)和南方(四川、海南)地区进行了1 017例样本的分子流行病学研究。结果:MTHFR C677T位点TT基因型相对于CC型的比值比为3.35(95%CI:1.39～8.13),TT型在北方和南方女性人群中的频率分别为37.35%和10.44%,差异有统计学意义;MTHFR A1298C和MTRR A66G虽然从生物学机制上与NTDs的发生密切相关,但尚需进行大规模的人群研究。结论:基于MTHFR和MTRR多态性检测的孕期叶酸补充指导和监测将是进一步降低新生儿出生缺陷的重要方法。     

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.     

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.