Genetic polymorphisms in methylenetetrahydrofolate reductase and thymidylate synthase and risk of pancreatic cancer.

BACKGROUND & AIMS: Human pancreatic cancer might be associated with folate deficiency and impaired metabolism. We tested this hypothesis by examining the contribution of functional polymorphisms in methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TS) to risk of cancer. METHODS: DNA from 163 pancreatic cancer patients and 337 control subjects was genotyped for MTHFR (677C > T and 1298A > C) and TS (5'-untranslated region tandem repeat and G/C). Association with risk of pancreatic cancer was estimated by logistic regression. All statistical tests were two-sided. RESULTS: We observed an increased risk of pancreatic cancer associated with the MTHFR 677CT (odds ratio [OR], 2.60; 95% confidence interval [CI], 1.61-4.29; P = .0005) or 677TT (OR, 5.12; 95% CI, 2.94-9.10; P < .0001) genotype compared with the MTHFR CC genotype. An increased risk of pancreatic cancer was also associated with the TS 3Rc/3Rc genotype (OR, 2.19, 95% CI, 1.13-4.31; P = .022) compared with the TS 3Rg/3Rg genotype. Joint effect between MTHFR C677T polymorphism and smoking or drinking increased risk of pancreatic cancer in a super-multiplicative manner. The ORs for smoking, the polymorphism, and both factors combined were 0.70 (95% CI, 0.30-1.63), 2.17 (95% CI, 1.17-4.21), and 3.10 (95% CI, 1.54-6.51), respectively. This joint effect was much stronger in heavy smokers (OR, 6.69; 95% CI, 3.39-13.63; P < .0001). The ORs for drinking, the polymorphism, and both factors combined were 0.98 (95% CI, 0.40-2.30), 2.81 (95% CI, 1.65-4.98), and 4.39 (95% CI, 2.25-8.78), respectively. CONCLUSION: The MTHFR and TS polymorphisms are genetic determinants for developing pancreatic cancer.     

Genetic susceptibility and environmental factors of esophageal cancer in Xi＇an

AIM: To analyse the role of genetic susceptibility and environmental factors in the process of esophageal cancer (EC) formation in Xi‘an, China. METHODS: A hospital based case-control study, combined with molecular epidemiological method, was carded out. A total of 127 EC cases and 101 controls were interviewed with questionnaires containing demographic items, habit of tobacco smoking, alcohol drinking, and family history of EC. Polymorphism of CYPIA1 and GSTM1 of 127 EC cases and 101 controls were detected by PCR method. The interactions between genetic susceptibility and environmental factors were also discussed. RESULTS: Tobacco smoking, alcohol drinking and a family history of EC were risk factors for EC with an OR of 2.04 (95% CI 1.15-3.60), 3.45(95% CI 1.74-6.91), 3.14 (95% CI 1.28-7.94), respectively. Individuals carrying CYP1A1 Val/Val genotype compared to those with CYP1A1 Ile/Ile genotype had an increased risk for EC (OR 3.35, 95% CI 1.49-7.61). GSTM1 deletion genotype was a risk factor for EC (OR1.81, 95% CI 1.03-3.18). Gene-environment interaction analysis showed that CYPIA1 Val/Val genotype, GSTM1 deletion genotype had synergetic interactions with tobacco smoking, alcohol drinking and family history of EC. CONCLUSION: Tobacco smoking, alcohol drinking and a family history of EC are risk factors for EC. CYP1A1 Val/Val and GSTM1 deletion genotypes are genetic susceptibility biomarkers for EC. There are synergic interactions between genetic susceptibility and environmental factors.     

亚甲基四氢叶酸还原酶基因C677T多态与结直肠癌遗传易感性的相关性

目的:探讨亚甲基四氢叶酸还原酶基因(MTHFR)C677T多态与结直肠癌(CRC)遗传易感性的关系.方法:采用TaqMan方法检测CRC 449例与对照672例的MTHFR C677T的基因型分布及差异.以非条件Logistic回归法计算表示相对危险度的比值比(OR)及其95%可信区间(CI).OR值均经性别、年龄、吸烟、饮酒、体质量指数和一级亲属CRC家族史等因素校正.结果:CRC组677T等位基因频率显著低于对照组,其为CRC发生的保护因素(OR:0.70,95%CI:0.58-0.83,P<0.01).与CC纯合子相比,CT杂合子的CRC风险显著降低至0.73倍(95%CI:0.56-0.95,P<0.05),而TT纯合子的CRC风险进一步降至0.47倍(95%CI:0.33-0.68,P<0.01).在非饮酒人群中,C677T的CRC风险保护效应略有增强;而在饮酒人群中,CT和TT基因型携带者的CRC发病风险虽仍低于CC基因型携带者,但差异无统计学意义.在CRC人群中,荷大肿瘤(最大直径>4cm)者携带TT基因型的比例高于荷小肿瘤者(16.3% vs 8.3%,P<0.05);荷黏液腺癌者携带TT基因型的比例高于荷乳头状腺癌及管状腺癌者(22.2% vs 17.1%,10.3%,P=0.084).结论:MTHFR C677T降低CRC发病风险,饮酒可能削弱该多态的CRC风险保护效应.TT基因型可能与CRC肿瘤进展有关.     

MTHFR gene polymorphism is susceptible to diabetic retinopathy but not to diabetic nephropathy in Japanese type 2 diabetic patients

AIMS: Previously, we have proposed that methylenetetrahydrofolate reductase (MTHFR) gene polymorphism (C677T) could be a risk factor for diabetic retinopathy. To support our suggestion, we examined in detail the association of MTHFR polymorphism with diabetic retinopathy and nephropathy in Japanese type 2 diabetic patients. METHODS: Subjects (n=190) were free of cardiovascular diseases and were not on hemodialysis. Retinopathy was assessed according to fundamental differentiation; nephropathy was determined according to urinary albumin level; and MTHFR genotype was determined by polymerase chain reaction-restriction fragment length polymorphism. We also analyzed how hyperglycemia affected these three conditions in 131 patients with glycosylated hemoglobin > or =6.5% and fasting blood sugar > or =110 mg/dl. RESULTS: The frequency of 677T/677T homozygous subjects with retinopathy was higher than the frequencies of the other two genotypes, and a significant difference was observed in the distribution of the genotypes (677C/677C, 41.9%; 677C/677T, 31.1%; 677T/677T, 61.5%; P<.05). The susceptibility of 677T/677T homozygote to retinopathy approached significance [odds ratio (OR)=2.17; 95% confidence interval (95% CI)=0.87-5.42]. However, in the population with hyperglycemia, the 677T/677T homozygote modified the risk for retinopathy (OR=4.30; 95% CI=1.42-13.1), especially the risk for nonproliferative retinopathy. In contrast, the 677T/677T homozygote did not affect the risk for nephropathy (OR=1.17; 95% CI=0.45-3.05), even in subjects with hyperglycemia (OR=1.50; 95% CI=0.50-4.48). CONCLUSIONS: Our results are highly suggestive of an important role for MTHFR genotype in susceptibility to retinopathy under hyperglycemia, but not to nephropathy. Preventive therapies based on MTHFR polymorphism could delay the onset of retinopathy in type 2 diabetic patients.     

The association between 5, 10 – methylenetetrahydrofolate reductase and the risk of unexplained recurrent pregnancy loss in China: A Meta-analysis

Backgroud:To analyze the correlation between gene polymorphisms of 5,10- methylenetetrahydrofolate reductase (MTHFR) and risk of unexplained recurrent pregnancy loss (URPL) in Chinese women.Methods:Eligible studies were searched in Pubmed, Embase, Web of Science, Wanfang, and China National Knowledge Infrastructure (CNKI) databases. Established inclusion criteria were used to screening articles, subsequently evaluate the quality of the included studies, Stata 16.0 PM and RevMan 5.3 software were conducted for meta-analysis. The pooled odds ratio (OR) with 95% confidence interval (CI) was determined to assess the relationship between MTHFR and risk of URPL in Chinese women.Results:For MTHFR C677T, fifty studies were included, involving 6677 URPL cases and 8111 controls. The overall results showed that MTHFR C677T was significantly correlated with URPL risk, especially in the homozygous model (TT vs CC; OR 3.06; 95% CI 2.56–3.66). For MTHFR A1298C, twenty-first studies were included, involving 3439 URPL cases and 3155 controls. The results showed that MTHFR A1298C was also significantly correlated with URPL risk in recessive (CC vs AC + AA; OR 1.55; 95% CI 1.25–1.93) and homozygous (CC vs AA; OR 1.53; 95% CI 1.22–1.91) models. In addition, sub-group results showed that no significant difference between north and south China populations in the MTHFR gene polymorphisms and URPL risk. Of note, the patients carrying MTHFR C677T and MTHFR A1298C joint mutants had no synergistic effect (OR 2.71; 95% CI 0.84–8.70) on the occurrence of URPL compared with the wild-type homozygous genotype (MTHFR 677CC/ MTHFR 1298AA).Conclusion:Studies included in this meta-analysis suggested that MTHFR 677T allele and 677TT genotype and MTHFR 1298CC genotype were both associated with URPL; testing MTHFR C677T gene polymorphism was a more appropriate target compared with other mutations in the prediction of URPL.     

Maternal MTHFR 677C>T is a risk factor for congenital heart defects: effect modification by periconceptional folate supplementation.

AIMS: Periconceptional folate supplementation prevents neural tube defects and possibly congenital heart defects (CHD) as well. The search for candidate genes involved in the folate metabolism includes the methylenetetrahydrofolate reductase (MTHFR) 677C > T polymorphism. We studied the association between MTHFR 677C > T variants and CHD risk. The interaction with periconceptional folate supplementation was also investigated. METHODS AND RESULTS: A case-control study and a family-based transmission disequilibrium test (TDT) were conducted to explore this association. In 133 triads, the TDT revealed no association of the fetal 677T allele with the development of a heart defect. In 158 mothers with a CHD-affected child, the maternal MTHFR 677CT and TT genotypes in combination with no use of periconceptional folate supplements were associated with, respectively, a three-fold (OR 3.3 95% CI 1.46-7.32) and six-fold (OR 6.3 95% CI 2.32-17.27) increased risk for conotruncal heart defects in offspring. In a case-only study, the interaction between periconceptional folate supplementation and maternal MTHFR genotype was significant (P = 0.012). CONCLUSION: The maternal MTHFR 677C > T variants are a risk factor for CHD in offspring, confined to conotruncal heart defects. A gene-environment interaction between maternal MTFHR 677CT and TT genotypes with periconceptional folate supplementation was observed. These findings provide a mechanism of the protective role of folate and support the thesis that periconceptional folate supplementation might prevent CHD.     

Prevalence of methylenetetrahydrofolate reductase C677T and its association with arterial and venous thrombosis in the Chinese population

Moderate hyperhomocysteinaemia (MHH) is associated with arterial and venous thrombosis. A main genetic defect related to MHH is a C to T substitution at nucleotide 677 of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene. A prothrombin 20210A mutation was recently identified as a risk factor for arterial and venous thrombosis. However, studies on the prevalence of mutant MTHFR C677T and prothrombin G20210A and their association with thrombosis were controversial and seldom reported in the Chinese population. We investigated the prevalence of MTHFR C677T and prothrombin G20210A genotypes by polymerase chain reaction (PCR) followed by restriction enzyme digestion in 420 Chinese subjects: 53 with deep venous thrombosis (DVT); 145 with cerebrovascular disease [115 cerebral infarction, 30 cerebral haemorrhage (CH)]; 100 with coronary artery disease (CAD); and 122 control subjects. The prevalence of the mutated MTHFR 677TT genotype and the 677T allele in normal controls was 12.3% and 30.7% respectively, similar to that in Caucasians and Japanese. The mutant 677T homozygotes and alleles were more frequent in patients with DVT than in controls (18.9% vs. 12.3%, 0.01 < P < 0. 025; 48.1% vs. 30.7%, P < 0.005). The relative risk of DVT among the carriers of 677TT and 677T were significantly increased [odds ratios: 3.4, 95% confidence interval (CI) 1.3-9.5, and 3.6, 95% CI 1. 7-7.7, respectively). The mutant MTHFR heterozygous 677C/T carriers were increased in patients with cerebral infarction compared with controls (53.9% vs. 36.9%, 0.01 < P < 0.025). Relative risk of cerebral infarction was 0.96 (95% CI 0.4-2.3) for 677TT homozygotes and 1.99 (95% CI 1.2-3.4) for 677C/T heterozygotes. However, the distribution of the MTHFR TT genotype was less frequent in patients with CAD with coronary artery stenosis of > 50% than in controls (2. 8% vs. 12.3%, 0.025 < P < 0.05). Relative risk of CAD was not increased among the carriers of 677TT and 677T (odds ratios: 0.2, 95% CI 0-1.1, and 0.97, 95% CI 0.5-1.8, respectively). There were no differences in the distribution of the MTHFR genotypes among CH, CAD with coronary artery stenosis of < 50% and controls. The prothrombin 20210A mutation was not found in any patients or controls. These results demonstrated that MTHFR 677T was associated with DVT and cerebral infarction but was less associated with CAD in the Chinese population.     

Hyperhomocysteinemia increases the risk of venous thrombosis independent of the C677T mutation of the methylenetetrahydrofolate reductase gene in selected Brazilian patients.

Fasting total homocysteine (tHcy) and the methylenetetrahydrofolate reductase (MTHFR) C677T mutation were evaluated in 91 patients with venous thromboembolism and without acquired thrombophilia, and in 91 age-matched and sex-matched controls. Hyperhomocysteinemia was detected in 11 patients (12.1%) and in two controls (2.2%), yielding an odds ratio (OR) for venous thrombosis of 6.1 [95% confidence interval (CI), 1.3-28.4]. After excluding 21 patients and four controls with other known genetic risk factors for venous thrombosis, the OR was not substantially changed (7.0; 95% CI, 1.5-33.1). The prevalence of the MTHFR 677TT genotype was not significantly different in patients (9.9%) and in controls (5.5%), with an OR for venous thrombosis of 1.8 (95% CI, 0.6-5.8). Subjects with the MTHFR 677TT genotype showed higher levels of tHcy compared with the 677CC genotype in patients (P = 0.010) and in controls (P = 0.030). In conclusion, we found that fasting hyperhomocysteinemia is a risk factor for venous thrombosis in patients without known acquired thrombophilia and other genetic risk factors for venous thrombosis. Although tHcy levels are significantly higher in those homozygous for the MTHFR C677T mutation, this genotype does not increase the thrombotic risk in our study population.     

Hyperhomocysteinemia and the MTHFR C677T mutation in Budd-Chiari syndrome

Hyperhomocysteinemia (HH) is a factor that predisposes individuals to thrombosis, and the C677T mutation in the 5,10-methylenetetrahydrofolate reductase (MTHFR) is known to give increased plasma homocysteine. However, little is known about their roles in Budd-Chiari syndrome (BCS). This study evaluated the roles of HH and the MTHFR C677T mutation in patients with BCS. We compared 41 BCS patients with 80 sex- and age-matched healthy controls. The mean plasma homocysteine level was significantly higher in patients with BCS (20.15 +/- 5.78 micromol/L) compared with normal controls (15.80 +/- 6.58 micromol/L), P < 0.01. HH (>19.5 micromol/L in men and >15.0 micromol/L in women) was detected in 15 (36.59%) patients and in 14 (17.5%) controls (odds ratio [OR], 2.72; 95% confidence internal [CI], 1.17-6.32). The prevalence of the mutated MTHFR 677TT genotype and the 677T allele in normal controls was 10.0% and 31.3%, respectively. The mutant 677T homozygotes and alleles were more frequent in patients with BCS than in controls (22.0% vs. 10.0%, 0.025 < P < 0.05; 45.1% vs. 31.3%, 0.025 < P < 0.05). The relative risk of BCS among the carriers of 677TT was significantly increased (OR, 3.3; 95% CI, 1.1-10.0). The mutant MTHFR heterozygous 677C/T carriers were not significantly increased in patients with BCS compared with controls (46.3% vs. < 2.5%, P > 0.05). The relative risk OR of BCS among carriers of 677C/T was 1.6 (95% CI, 0.7-3.6). This study suggests that both HH and the homozygous C677T mutation in the MTHFR gene are important risk factors of BCS.     

The C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene and vascular dementia

OBJECTIVE: To determine the association between the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene and vascular dementia in Ashkenazi and non-Ashkenazi Jews. DESIGN: A case-control study. SETTING: Nursing homes in Jerusalem, Israel. PARTICIPANTS: Two hundred fifty nine Jewish people of Ashkenazi and non-Ashkenazi origin, older than age 70, who have vascular dementia (VD) (n = 85), Alzheimer's disease (AD) (n = 92), and who are cognitively intact (n = 82) with no clinical evidence of atherosclerotic vascular disease. MEASUREMENTS: The frequencies of the mutant allele (T allele) and homozygotes for the C677T MTHFR mutation (T/T genotype). The total plasma homocysteine (tHCT) level in 75 subjects. RESULTS: There were no significant differences in the frequencies of the T/T genotype or T allele among VD, AD, and cognitively intact older people of the same ethnic origin (0.15, 0.19, 0.25 T/T genotype and 0.42, 0.46, 0.47 T allele in Ashkenazi; 0.08, 0.06, 0.10 T/T genotype and 0.28, 0.32, 0.33 T allele in non-Ashkenazi with VD and AD, and in cognitively intact older people, respectively). The relative risk of VD associated with the T/T genotype versus the C/C genotype was 0.62 (95% CI, 0.19-1.19) in Ashkenazi and 0.65 (95% CI, 0.11-3.7) in non-Ashkenazi, respectively. The relative risk of AD associated with the T/T genotype was 0.85 (95% CI, 0.29-2.45) in Ashkenazi and 0.62 (95% CI, 0.1-4.3) in non-Ashkenazi, respectively. The frequencies of mutant homozygotes and allele were significantly higher in Ashkenazi than in non-Ashkenazi Jews (19.9% vs 7.5% T/T genotype, chi2 = 6.2, P = .01, 0.45 vs 0.31 T allele, chi2 = 9.77, P = .002 in Ashkenazi vs non-Ashkenazi, respectively). There were no differences in mean tHCT concentration among VD, AD, and cognitively intact older people. CONCLUSIONS: The MTHFR C677T is not associated with an increased risk of vascular dementia or Alzheimer's disease. The frequency of the mutation is significantly higher in Ashkenazi compared with non-Ashkenazi Jews.     

ALOX5AP基因多态2354T/A和MTHFR基因多态677C/T的协同作用显著增加脑梗塞的易患性

目的研究MTHFR多态性和编码5-脂氧合酶激活蛋白的基因ALOX5AP多态性，尤其是基因之间的相互作用，是否与脑卒中的易患性相关。方法采用PCR．RFLP方法，对来自7个临床中心的1823名对照和1832名脑卒中患者检测了基因ALOX5AP和MTHFR的3个多态性，基因分型结果经测序进一步确证。多元logistic回归方法校正了传统危险因素后分析基因多态性与脑卒中的独立相关性。检测7个与脑卒中不相关的微卫星多态标记在病例一对照人群的频率分布以评估人群层化程度。结果MTHFR677TT基因型与男性脑梗塞的发病风险呈弱相关（OR，1．45；95％CI：1．04-2．02；P=0．020），ALOX5AP2354AA基因型也增加男性脑梗塞1．55倍的发病风险（95％CI：1．03．2．35；PP=0．038）。当个体同时携带MTHFR677TT和ALOX5AP2354AA基因型时，男性脑梗塞的相对患病风险率显著增加至3．58倍（（95％CI：1．72-7．43；P=0．001）。微卫星多态性标记的各主要等位基因片段的频率在病例和对照组无显著性差异。结论MTHFR677TT基因型和ALOX5AP2354AA基因型的协同作用与增加的男性脑梗塞患病风险呈显著相关。对于多因素复杂性疾病，综合分析弱效基因的相互作用有助于了解个体易患脑卒中的遗传背景。     

Significance of factor V, prothrombin, MTHFR, and PAI-1 genotypes in childhood cerebral thrombosis.

The aim of this study was to evaluate the significance of factor V (FV) G1691A, prothrombin G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T, and plasminogen activator inhibitor-1 (PAI-1) 4G/5G genotypes in development of childhood cerebral thrombosis (CT). A total of 113 Turkish children with CT were studied and compared with the control group. The carrier frequency of the factor V G1691A mutation was found to be significantly higher in the patient group (17.7%) than controls (7.4%). The presence of this genotype was associated with a 2.7-fold increased risk of developing CT (95% confidence interval [CI], 1.0-7.0). The prevalence of prothrombin G20210A mutation in 110 patients (4.5%) was insignificantly higher than controls (2.3%) (odds ratio, 2.0; 95% CI, 0.4-10.7). A statistically significant increase in the frequency of homozygous MTHFR C677T genotype was observed in 62 patients (11.3%) compared to controls (4.3%), and this genotype was associated with 2.8-fold increased CT risk (95% CI, 1.0-8.0). The incidence of PAI-1 4G/4G genotype in 65 patients (21.5%) was slightly lower than that of controls (26.0%), but the differences did not reach statistical significance (odds ratio, 0.8; 95% CI, 0.4-1.5). The results of this study suggested that factor V G1691A and MTHFR C677T genotypes may be associated with an increased risk of developing CT in Turkish children.     

MTHFR C677T polymorphism and its relation to ischemic stroke in the Black Sea Turkish population

The MTHFR C677T mutation has been shown to be associated with venous thrombosis. The role of this mutation in ischemic stroke is unclear. We investigated whether the MTHFR mutation is a risk factor for patients with ischemic stroke in the Black Sea Turkish population or not. We analyzed 30 patients (19 male, 11 female) [median age: 50 years (range: 28-78)] with ischemic stroke who had no known predisposition factors for stroke and 242 (182 male, 60 female) healthy controls [median age: 42 years (range: 18-65)]. Detection of the MTHFR C677T mutation was performed by using commercially available allele-specific PCR-ELISA kits. Prevalence of the MTHFR C677T genotype was 49.1% (CT, 45.8%; TT, 3.3%) in controls and 50% (CT, 43.3%; TT, 6.6%) in patients [OR: 1.03, 95% CI (0.45-2.35]). The prevalence of homozygous gene mutation for MTHFR was higher among patients with stroke than control subjects, but this difference was not statistically significant. The MTHFR gene mutation is not a risk factor for ischemic stroke formation in patients from the Black Sea region in Turkey.     

Methylenetetrahydrofolate reductase C677T gene polymorphism and coronary artery disease in a Chinese Han population: a meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism has been suggested to be associated with increased coronary artery disease (CAD) risk. To explore the relationship between MTHFR C677T gene polymorphism and CAD in the Chinese Han population, a meta-analysis was performed. Fourteen separate studies were included and 2981 subjects were involved in the current meta-analysis. The pooled odds ratio (OR) between CAD size to CAD size and control size (CAD/CAD + control) and the corresponding 95% confidence interval (95% CI) between the CC and TT genotype groups were estimated by a random-effects model. Meta-regression was performed to explore the heterogeneity source. The CAD/CAD + control values were 0.45 for the CC genotype group and 0.62 for the TT genotype group. The pooled OR for the CAD/CAD + control between the CC and TT genotype groups was 0.55 (95% CI, 0.37-0.83; P(heterogeneity) = .0004, I(2) = 64.7%). These results indicated that MTHFR C677T gene polymorphism and CAD were significantly associated (P = .005) in the Chinese Han population. Publication year was detected as the main heterogeneity source. In a stratified analysis by publication year, the pooled OR was 0.76 (95% CI, 0.37-1.57; P(heterogeneity) = .0002; I(2) = 79.6%) in subgroup 1 (publication years 1999-2004). No significant association between gene polymorphism and CAD was found in this subgroup (P = .46). In subgroup 2 (publication years 2005-2011), the pooled OR was 0.39 (95% CI, 0.28-0.55; P(heterogeneity) = .53; I(2) = 0); and the association between gene polymorphism and CAD was significant (P < .00001). In the Chinese Han population, the TT genotype for the MTHFR C677T gene appeared to be associated with increased CAD risk.     

A Case Control Study on the Contribution of Factor V-Leiden,Prothrombin G20210A,and MTHFR C677T Mutations to the Genetic Susceptibility of Deep Venous Thrombosis

Background: Insofar as the inherited prothrombotic single nucleotide polymorphisms (SNPs) factor V G1691A (FV-Leiden), prothrombin (PRT) G20210A, and methylenetetrahydrofolate reductase (MTHFR), C677T are inherited risk factors of venous thromboembolism (VTE), the aim of this study was to determine the prevalence of single and combined SNPs in 198 patients with documented deep venous thrombosis (DVT), and 697 control subjects, and to estimate the associated risks.Methods: Factor V-Leiden, PRT G20210A, and MTHFR C677T were analyzed by PCR and restriction fragment length polymorphism (RFLP).Results: The prevalence of the heterozygote and homozygous variants for FV-Leiden (52.02 vs. 14.78%, RR 6.28), PRT G20210A (19.2 vs. 3.6%; RR 6.38), and to a lesser extent the T/T genotype of MTHFR C677T (20.71 vs. 11.0%; RR 1.49) were higher among DVT patients vs. controls, respectively. Two or more SNPs were detected in 90 of 198 patients (45.5%) and in 60 of 697 controls (8.6%), with odds ratios of 16.754 for joint occurrence of FV-Leiden and PRT G20210A, 10.471 for FV-Leiden and MTHFR C677T, and 6.283 for PRT G20210A SNPs and MTHFR 677T/T. Logistic regression analysis showed a further increased odds for FV-Leiden in combination with PRT G20210A (85.198) or homozygous MTHFR C677T (81.133), and to a lesser extent for PRT G20210A in combination with homozygous MTHFR C677T (20.812).Conclusions: This indicates that FV-Leiden and PRT G20210A, more than MTHFR C677T, are important risk factors for DVT, and that the presence of more than one prothrombotic SNPs was associated with a significant risk of DVT.     

亚甲基四氢叶酸还原酶基因C677T多态与肝细胞癌遗传易感性的相关性研究

目的探讨亚甲基四氢叶酸还原酶（MTHFR）基因C677T多态与中国人肝细胞癌（Hcc）遗传易感性的关系。方法采用聚合酶链反应一限制性片段长度多态性（PCR—RFLP）方法，检测508例Hcc与543例对照的MTHFR C677T基因型分布及其差异。结果HCc和对照两组人群的MTHFR C677T基因型分布差异无统计学意义。但与C等位基因携带者（C／C和C／T基因型）相比，T／T基因型携带者患HCC的风险增加0．66倍（95％可信区间为1．08～2．54，P〈0．05）。性别因素分层分析结果显示：T／T基因型女性携带者其HCC的风险是C等位基因女性携带者的2．64倍（95％可信区间为1．19～5．88，P〈0．05）；而男性T／T基因型与C等位基因携带者其HCC的风险差异无统计学意义。结论MTHFR基因C677T多态可能是中国女性患HCC的一个遗传易感因素，而男性HCC发病风险与该多态无明显关系。     

Notch3基因多态、MTHFR基因多态和ALOX5AP基因多态的多位点联合交互作用显著增加血栓性脑卒中的风险

目的研究Notch3基因、MTHFR基因和ALOX5AP基因多态之间的多位点交互作用是否与脑卒中的患病风险相关。方法采用病例对照设计，对来自全国7个临床中心的对照和脑卒中患者检测了Notch3、MTHFR、VKORC1、APOA1和ALOX5AP基因的8个多态性，基因分型结果经测序进一步确证。用Generalized Muhifactor—Dimensionality Reduction（GMDR）方法检测基因与基因之间的交互作用。结果当个体同时携带Notch3 381TT、MTHFR 677TT和ALOX5AP 2354AA基因型时，携带者血栓性脑卒中的相对患病风险率增加至3．72倍（95％CI：1．235～11．209；P〈0．05）。结论Notch 3381TT、MTHFR 677TT和ALOX5AP 2354AA基因型的多位点联合交互作用显著增加血栓性脑卒中患病风险。对基因与基因之间的交互作用的分析，有助于更深入的研究复杂疾病的基因型和表型间的关系。     

Methylenetetrahydrofolate reductase C677T genotype affects promoter methylation of tumor-specific genes in sporadic colorectal cancer through an interaction with folate/vitamin B12 status

AIM： To evaluate joint effects of Methylentetra- hydrofolate reductase （MTHFR） C677Tgenotypes, and serum folate/vitamin B12 concentrations on promoter methylation of tumor-associated genes among Iranian colorectal cancer patients.
METHODS： We examined the associations between MTHFR C677T genotype, and promoter methylation of P16, hMLH1, and hMSH2 tumor-related genes among 151 sporadic colorectal cancer patients. The promoter methylation of tumor-related genes was determined by methylation-specific PCR, Eighty six patients from whom fresh tumor samples were obtained and 81 controls were also examined for serum folate and vitamin B12 concentrations by a commercial radioimmunoassay kit.
RESULTS： We found 29.1% of cases had tumors with at least one methylated gene promoter. In case-case comparison, we did not find a significant association between methylation in tumors and any single genotype. However, in comparison to controls with the CC genotype, an increased risk of tumor methylation was associated with the CT genotype （OR = 2.5; 95% CI, 1.1-5.6）. In case-case comparisons, folate/vitamin B12 levels were positively associated with tumor methylation. Adjusted odds ratios for tumor methylation in cases with high （above median） versus low （below median） serum folate/vitamin B12 levels were 4.9 （95% CI, 1.4-17.7）, and 3.9 （95% CI, 1.1-13.9）, respectively. The frequency of methylated tumors was significantly higher in high methyl donor than low methyl donor group, especially in those with MTHFR CT （P = 0.01）, and CT/TT （P = 0.002） genotypes, but not in those with the CC genotype （P = 1.0）.
CONCLUSION： We conclude that high concentrations of serum folate/vitamin B12 levels are associated with the risk of promoter methylation in tumor-specific genes, and this relationship is modified by MTHFR C677T genotypes.     

Associations between maternal methylenetetrahydrofolate reductase polymorphisms and adverse outcomes of pregnancy: the Hordaland Homocysteine Study

PURPOSE: Methylenetetrahydrofolate reductase (MTHFR) is involved in the metabolism of folate and homocysteine; a polymorphism in the MTHFR gene (677C-->T) has been associated with adverse outcomes of pregnancy. We studied whether two polymorphisms in the MTHFR gene (677C-->T and 1298A-->C) are associated with pregnancy complications, adverse outcomes, and birth defects. METHODS: MTHFR polymorphisms were determined in blood collected in 1992 and 1993 from 5883 women aged 40 to 42 years, and linked with 14,492 pregnancies in the same women recorded in the Medical Birth Registry of Norway from 1967 to 1996. RESULTS: The 677TT genotype in mothers was associated with increased risk of placental abruption (odds ratio [OR] = 2.6; 95% confidence interval [CI]: 1.4 to 4.8) compared with the CC variant. The risk of intrauterine growth restriction increased with number of T alleles (P for trend = 0.04). Compared with the 1298AA variant, the CC variant was associated with a reduced risk of very low birth weight infants (OR = 0.4; 95% CI: 0.2 to 0.8). No significant associations were found between MTHFR polymorphisms and birth defects. CONCLUSION: The maternal MTHFR 677C-->T polymorphism was a risk factor for placental abruption. The unexpected protective effect of the 1298A-->C polymorphism on very low birth weight needs further study.     

Associations of plasma homocysteine and the methylenetetrahydrofolate reductase C677T polymorphism with carotid intima media thickness among South Asian, Chinese and European Canadians

BACKGROUND: Few studies have evaluated the associations of plasma homocysteine concentration, the methylenetetrahydrofolate reductase (MTHFR) C677T genotype and B vitamin concentration with intima media thickness (IMT) in multiethnic populations. METHODS: In the Study of Health Assessment and Risk in Ethnic groups (SHARE), we measured carotid IMT, fasting serum folate, serum B12, plasma pyridoxal-5'-phosphate (PLP) and plasma homocysteine and determined the MTHFR C677T genotype in a cross-sectional study of 818 South Asian, Chinese and European Canadians without previous history of CVD, cancer or diabetes during 1996-1998. RESULTS: Plasma homocysteine was inversely related to serum folate, serum B12, plasma PLP, B vitamin supplement use and Chinese ethnicity, and was positively associated with hypertension, smoking, IMT, MTHFR 677T/T genotype and South Asian ethnicity. Although ethnicity was not a statistically significant modifier, among carriers of the MTHFR 677T/T genotype with serum folate < or =14 nmol/L compared to >14 nmol/L, plasma homocysteine was significantly higher among South Asians (50.9% increase, P < 0.001) and Europeans (52.4% increase, P < 0.001) but not Chinese (11.0% increase, P > 0.05). Plasma homocysteine > 11.7 micromol/L was associated with a 5.9% (95% CI: 1.9%, 10.0%) increase in IMT (approximately 0.04 mm) in the pooled-data analyses with similar increases noted in the ethnic-specific analyses. The 677T/T genotype was not associated with a significant change in IMT in the pooled-data analyses (2.7%; 95% CI: -1.7%, 7.2%) nor in ethnic-specific analyses compared to other genotypes, although there were only 63 677T/T homozygotes. CONCLUSION: The combination of lower serum folate and the MTHFR 677T/T genotype is associated with increased plasma homocysteine among South Asians and Europeans, but the association is not evident among Chinese possibly because their serum folate may not have been low enough to compromise MTHFR activity. Plasma homocysteine > 11.7 micromol/L appears to be associated with a clinically important increase in IMT.