Methylenetetrahydrofolate Reductase C677T Mutation and Nonalcoholic Fatty Liver Disease

A mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is known as one of the causes of hyperhomocyteinemia. The oxidation products of homocysteine can initiate lipid peroxidation, which has a central role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). We aimed to assess the possible role of the MTHFR C677T mutation in the progression of simple steatosis to an advanced form of NAFLD. Thirty-four patients with NAFLD diagnosed by histologic analysis and 282 healthy controls were included in the study. The discrimination of nonalcoholic steatohepatitis (NASH) from another NAFLD was made by NAFLD activity score (NAS), and a NAS≥5 was considered NASH. Patients with either NASH or nonalcoholic fatty liver (NAFL) and controls were evaluated for frequency of the MTHFR C677T mutation. The frequency of the MTHFR C677T mutation was 53.5% (CT, 44.7%; TT, 8.9%) in controls and 41.5% (CT, 37.7%; TT, 3.8%) in patients (odds ratio [OR], 0.62; 95% confidence interval [CI], 0.34–1.12). There was no statistical difference in the frequency of this genotype between patients with NAFL and those with NASH (36% [CT, 28%; TT, 8%] vs 46.4% [CT, 46.4; TT, 0%]; OR, 0.65; 95% CI, 0.22–1.96). According to this study, the MTHFR C677T mutation does not seem to be a risk factor for the progression of NAFL to NASH.     

The MTHFR CT polymorphism confers a high risk for stroke in both homozygous and heterozygous T allele carriers with Type 2 diabetes.

OBJECTIVE: Individuals with Type 2 diabetes are at increased risk of stroke. Plasma homocysteine (tHcy) is an independent risk factor for cardiovascular (CV) disease. The methylene-tetrahydrofolate reductase (MTHFR) gene polymorphism (thermolabile variant C(677)T) is associated with CV risk, partly as a result of increased Hcy, especially in homozygous subjects. AIM: To relate the occurrence of the MTHFR polymorphism with stroke prevalence by examining allelic frequency and genotype distribution in 165 subjects with Type 2 diabetes studied for the presence of thermolabile C(677)T MTHFR mutation. RESULTS: Mean age was 67.7 years, and tHcy 18.2 micromol/l. T allele frequency was 38.5%. MTHFR genotypes were: normal (CC) 40%; heterozygous (CT) 43%; homozygous (TT) 17%. Serum levels of folic acid and B12 vitamin were within normal limits. Stroke prevalence was 14%. Sixty-four per cent of stroke-free subjects had the normal C allele vs. 46% in stroke subjects. The frequencies of genotypes (CC-CT-TT) were (%): 44-41-15 in stroke-free vs. 17-57-26 in stroke patients. Coronary (CAD) and peripheral artery disease (PAD) were common in all groups, with no differences according to genotypes. Stroke prevalence was markedly higher in genotypes CT and TT (18 and 21%) compared with CC (6%). Mean tHcy levels were higher in TT subjects. CONCLUSION: The allelic frequency of C(677)T MTHFR mutation in Type 2 diabetes subjects with stroke is markedly different from that of subjects without stroke. Genotypic characteristics suggest that C(677)T MTHFR mutation confers a higher risk for stroke to both homozygous and heterozygous T allele carriers that cannot be ascribed solely to raised tHcy and/or lower folate status in CT subjects, nor to phenotypic expression of conventional risk factors for stroke. The impact of the MTHFR polymorphism on stroke may result from T allele-linked deleterious effects, or C allele-linked protection. Confirmatory studies are warranted, as this cohort was not randomly selected, and a type 1 error cannot be ruled out.     

亚甲基四氢叶酸还原酶基因 C677 T多态性与中国山东地区汉族人群缺血性卒中、高尿酸血症的相关性

目的：探讨亚甲基四氢叶酸还原酶（methylenetetrahydrofolatereductase,MTHFR）基因C677 T 多态性与中国山东地区汉族人群缺血性卒中、高尿酸血症的相关性。方法纳入山东地区汉族急性缺血性卒中患者和年龄、性别相匹配的对照者。采用聚合酶链反应扩增和芯片杂交显色技术检测MTHFR基因C677T 多态性,并测定血清尿酸浓度。结果共纳入山东地区汉族急性缺血性卒中患者145例和年龄、性别相匹配的对照者145名。缺血性卒中组糖尿病构成比（26.90％对6.89％;χ2=20.653,P<0.001）以及空腹血糖[（5.56±1.57）mmol/L对（5.01±1.11）mmol/L;t=－3.390, P=0.001]、高半胱氨酸[中位数,四分位数间距：18.2（16.30~22.55）μmol/L对15.20（12.10~17.85）μmol/L;Z=－6.323,P<0.001]和尿酸[43.0（361.60~490.45）μmol/L对285.9（267.00~346.25）μm o l/L;Z=－10.360, P<0.001]水平均显著高于对照组;缺血性卒中组 T T 基因型（42.07％对15.17％;χ2=25.673, P<0.001）和 T 等位基因（58.28％对34.48％;χ2=33.008, P<0.001）分布频率均显著高于对照组。多变量logistic回归分析显示,尿酸[优势比（ odds ratio, OR）1.018,95％可信区间（confidence interval, CI）1.013~1.024;P<0.001]、TT 基因型（对CT 基因型, OR 6.774,95％CI 1.779~25.507;P=0.005）、高血压（ OR 1.919,95％CI 1.013~3.636;P=0.045）、高半胱氨酸（ OR 1.153,95％CI 1.059~1.258;P=0.001）为缺血性卒中的独立危险因素。将缺血性卒中组与对照组合并,共101例存在高尿酸血症,189例尿酸正常。高尿酸血症组糖尿病患者构成比（32.67％对11.64％;χ2=23.749, P<0.001）以及总胆固醇[（5.67±1.56）mmol/L对（5.10±1.33）mmol/L;t=－3.255,P<0.001]和高半胱氨酸[19.50（17.10~24.70）μmol/L对15.40（12.60~18.05）μmol/L;Z=－7.236,P<0.001]水平显著高于尿酸正常组,TT 基因型（55.45％对13.76％;χ2=56.409,P<0.001）和T等位基因（71.79％对32.54％;χ2=79.561,P<0.001）分布频率显著高于尿酸正常组。多变量logistic回归分析显示,TT 基因型（对CC 基因型,OR 6.434,95％CI 2.334~17.736;P<0.001）、CT 基因型（对CC基因型,OR 2.234,95％CI 1.019~4.898;P=0.045）、高半胱氨酸（OR 1.081,95％CI 1.010~1.157;P=0.024）、总胆固醇（OR 1.363,95％CI 1.123~1.653;P=0.002）为高尿酸血症的独立危险因素。结论 MTHFR基因C677T TT 基因型和血清尿酸水平是中国山东地区汉族人群缺血性卒中的独立危险因素,MTHFR基因C677T TT 基因型亦为该人群高尿酸血症的独立危险因素,调整饮食习惯可能对山东地区汉族人群缺血性卒中的预防具有积极意义。     

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.     

Increased prevalence of methylenetetrahydrofolate reductase C677T variant in patients with inflammatory bowel disease, and its clinical implications

BACKGROUND: Inflammatory bowel disease (IBD) is associated with an increased incidence of thromboembolic disease. Hyperhomocysteinaemia (hyper-tHcy), a condition associated with the C677T variant of 5, 10-methylenetetrahydrofolate reductase (MTHFR), is linked with an increased incidence of thromboembolic disease. Hyper-tHcy has been reported in patients with IBD. AIMS: To assess the prevalence of the C677T MTHFR genotype and the contribution of this genotype to hyper-tHcy in patients with IBD. METHODS: Patients with established IBD (n=174) and healthy controls (n=273) were studied. DNA samples were genotyped for the MTHFR (C677T) mutation. Subjects were categorised as homozygous for the thermolabile variant (TT), heterozygous for wild type and variant (CT), or homozygous for the wild type (CC). RESULTS: Plasma homocysteine concentrations were significantly higher in patients with IBD than in healthy controls. A total of 17.5% of ulcerative colitis and 16.8% of Crohn's disease patients were homozygous for the C677T variant compared with 7.3% of controls. Homozygosity (TT) for the variant was associated with higher plasma tHcy levels in patients with IBD and in healthy controls. When all subjects who were TT for the variant were excluded, median plasma tHcy was still significantly higher in IBD than controls. Plasma vitamin B(12) levels were lower in patients with IBD irrespective of MTHFR genotype. CONCLUSIONS: There is an association between the thermolabile MTHFR C677T variant and IBD. This accounts in part for the raised plasma tHcy found in patients with IBD and may contribute to the increased incidence of thromboembolic complications. All patients with IBD should receive low dose folic acid and vitamin B(12) therapy to protect against the thromboembolic complications of raised tHcy.     

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.     

MTHFR C677T基因多态性与新疆哈族和汉族食管癌易感性的关系

目的:探讨亚甲基四氢叶酸还原酶(MTHFR) 基因C677T多态性与新疆哈族、汉族食管癌易感性的关系．方法:用PCR-RFLP方法检测食管癌患者178 例(哈萨克族94例,汉族84例)和同一地区无肿瘤病史的正常对照者155例(哈萨克族98例,汉族57例)的MTHFR基因C677T基因型分布．结果:新疆哈族食管癌组中MTHFR C677T 3种基因型CC,CT,TT,所占比例分别是 56．4％,36．2％,7．4％,与新疆汉族食管癌组中的32．9％,40．0％,27．1％相比,存在显著差异(X2=1 5．37,P<0．05);哈族正常对照组分别为58．2％,29．6％,12．2％与汉族正常对照组 22．8％,52．6％,24．6％相比,有显著差异(X2= 18．26,P<0．05)．MTHFR 3种基因型在哈族食管癌组中的分布(CC 56．4％,CT 36．2％and TT 7．4％)与对照组中(CC 22．8％,CT 52．6％and TT 24．6％)相比,无显著差异(X2=1．776,P= 0．412)．在汉族食管癌组与对照组间也无显著差异(X2=2．750,P=0．253)．结论:MTHFR C677T基因多态性分布在新疆哈族、汉族正常对照组间存在民族差异,在食管癌间也存在差异．MTHFR C677T基因多态性可能与新疆哈萨克族与汉族食管癌的易感性无关．     

A common mutation in the methylenetetrahydrofolate reductase gene is a determinant of hyperhomocysteinemia in epileptic patients receiving anticonvulsants.

Hyperhomocysteinemia is a condition caused by both genetic and nongenetic factors. To determine whether a common methylenetetrahydrofolate reductase (MTHFR) variant is related to elevated homocysteine concentrations in epileptic patients receiving anticonvulsants, we investigated the plasma total homocysteine (tHcy) level, folate level, and MTHFR 677 C --> T mutation using a polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis with HinfI digestion in 103 patients with epilepsy and 103 normal controls. The prevalence of hyperhomocysteinemia (> or = 11.4 micromol/L, 90th percentile of control group) was higher in patients than in controls (25% v 10.0%, P = .007). The homozygosity for the 677 C --> T mutation of MTHFR was associated with elevated tHcy and low folate levels. The magnitude of hyperhomocysteinemia in MTHFR TT homozygotes was more pronounced in epileptic patients than in controls (18.2 +/- 1.6 v 9.1 +/- 1.2 micromol/L, P = .04). In epileptic patients, hyperhomocysteinemia was more frequent in MTHFR TT genotypes versus CT or CC genotypes (58% v 17% and 16%, P < .001). Multiple logistic regression analysis showed that MTHFR TT genotype was an independent predictor of hyperhomocysteinemia in epileptic patients receiving anticonvulsants (phenytoin and carbamazepine but not valproic acid), suggesting that gene-drug interactions induce hyperhomocysteinemia. These findings indicate that epileptic patients receiving anticonvulsants may have a higher folate requirement to maintain a normal tHcy level, especially homozygotes for MTHFR 677 C --> T mutation.     

Infant methylenetetrahydrofolate reductase 677TT genotype is a risk factor for congenital heart disease

OBJECTIVE: Recently, an association between the homozygous C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in infants with congenital neural tube defects or congenital oral clefts has been shown. However, no data are available so far with respect to the MTHFR 677TT genotype in children with underlying structural congenital heart disease (CHD). METHODS: We investigated the MTHFR genotype in 114 Caucasian CHD patients aged newborn to 16 years (median 0.6 years; 53% male) and in 228 age- and sex-matched healthy controls. RESULTS: In childhood patients with CHD the homozygous MTHFR 677TT genotype was found in 21 out of 114 subjects (18.4%) compared with 21 out of 228 controls (9.2%; odds ratio (OR) 2.2, 95%-confidence interval (CI) 1.2-4.3; P=0.027). In patients with pulmonary valve stenosis, hypoplastic left heart syndrome, coarctation of the aorta, aortic valve stenosis or subaortic stenosis the frequency of the TT genotype varied between 38 and 67% with corresponding ORs from 6.1 (CI, 1.4-27.5; P=0.034) to 20.4 (CI, 1.8-235.0; P=0.025), whereas in other structural CHD the frequency of this genotype was not significantly different from the controls. CONCLUSIONS: With the present study we can show for the first time that the embryonal MTHFR 677TT genotype is significantly associated with the development of structural congenital heart malformations during early pregnancy. It remains to be clarified, whether this genotype is at least a risk marker or a risk factor for structural congenital heart malformations.     

亚甲基四氢叶酸还原酶基因多态性与糖尿病肾病相关性研究

目的：研究亚甲基四氢叶酸还原酶（MTHFR）基因多态性与2型糖尿病肾病的关系。方法：运用聚合酶链反应－限制性片段长度多态性技术（PCR－RFLP）检测85例2型糖尿病患者（其中39例伴糖尿病肾病）及57例正常对照组MTHFR C677T基因型,采用高效液相色谱法测定血浆同型半胱酸水平。结果：糖尿病肾病组MTHFR基因TT纯合基因型,CT杂合基因型及T等位基因频率（分别为38．21％,51．28％,53．85％）均明显高于糖尿病不伴肾病组（分别为19．57％,28．26％,33．70％）及正常对照组（分别为17．54％,28．07％,31．58）,基因型和等位基因频率分布差异均有统计学意义（P＜0．05）,而MTHFR基因该多态性在不伴肾病组与正常对照组之间差异无显著性（P＞0．05）,T等位基因与糖尿病肾病的发生密切相关（OR＝2．30,95％可信区间;1．24－4．26）。糖尿病肾病组,糖尿病不伴肾病组及正常对照组中,MTHFR基因有C677T突变者血浆同型半胱氨酸水平均显著高于无基因突变者。结论：MTHFR基因C677T位碱基突变致血浆同型半胱氨酸水平高是糖尿病肾病发病的重要遗传因素。     

Lipoprotein (a) and genetic polymorphisms of clotting factor V, prothrombin, and methylenetetrahydrofolate reductase are risk factors of spontaneous ischemic stroke in childhood

Ischemic stroke is a rare event in childhood. In approximately one third of cases no obvious underlying cause or disorder can be detected. We investigated the importance of genetic risk factors of venous thromboembolism in childhood or stroke in adulthood as risk factors for spontaneous ischemic stroke in children. One hundred forty-eight Caucasian infants and children (aged 0.5 to 16 years) with stroke and 296 age-matched controls from the same geographic areas as the patients were analyzed for increased lipoprotein (a) [Lp(a)] levels >30 mg/dL; for the presence of the factor V (FV) G1691A mutation, the prothrombin (PT) G20210A variant, and the TT677 genotype of methylenetetrahydrofolate reductase (MTHFR); and deficiencies of protein C, protein S, and antithrombin. The following frequencies (patients v controls), odds ratios (ORs), and confidence intervals (CIs) of single risk factors were found: Lp(a) >30 mg/dL (26.4% v 4.7%; OR/CI, 7.2/3.8 to 13.8; P <.0001), FV G1691A (20.2% v 4%; OR/CI, 6/2.97 to 12.1; P <.0001), protein C deficiency (6% v 0.67%; OR/CI, 9.5/2 to 44.6; P =.001), PT G20210A (6% v 1.3%; OR/CI, 4.7/1.4 to 15.6; P =.01), and the MTHFR TT677 genotype (23.6% v 10.4%; OR/CI, 2.4/1.53 to 4.5; P <.0001). A combination of the heterozygous FV G1691A mutation with increased Lp(a) (n = 11) or the MTHFR TT677 genotype (n = 5) was found in 10. 8% of cases, but only 0.3% of controls (OR/CI, 35.75/4.7 to 272; P <. 0001). Increased Lp (a) levels, the FV G1691A mutation, protein C deficiency, the prothrombin G20210A variant, and the MTHFR TT677 are important risk factors for spontaneous ischemic stroke in childhood.     

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.     

Genetic polymorphism of methylenetetrahydrofolate reductase as a risk factor for diabetic nephropathy in Chinese type 2 diabetic patients

OBJECTIVE: Genetic predisposition has been implicated in diabetic nephropathy (DN). The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, may play a role in the development of not only vascular disease but also diabetic microangiopathies. In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and diabetic nephropathy. METHODS: 220 unrelated patients with type 2 diabetes mellitus and 130 controls were recruited. The MTHFR genotype was analyzed by PCR followed by HinfI digestion. Plasma total homocysteine levels were measured using high-performance liquid chromatography (HPLC) with fluorescence detection. RESULTS: In 130 healthy control subjects, the frequency of the mutant T allele was 30.0%, comparable to that of a Hong Kong (Chinese) population. The distribution of the three genotypes was as follows: TT genotype, 16.9%; CT genotype, 26.2%; and CC genotype, 56.9%. This genotype distribution did not differ between control subjects and type 2 diabetic patients in which 19.1% were TT, 34.5% were CT and 46.4% were CC (2=3.85, P>0.05). The frequency of the mutant T allele was 42.3% in diabetic patients with nephropathy (n=124) versus 28.6% in those without nephropathy (n=96). The genotype frequencies were TT, 21.0%; CT, 42.7%; CC, 36.3% in diabetic patients with nephropathy versus TT, 16.7%; CT, 23.9%; CC, 59.4% in those without nephropathy. The MTHFR genotype and allele frequencies were different between diabetic patients with and without nephropathy (chi2=12.27, P<0.005; chi2=8.77, P<0.005, respectively). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype. CONCLUSIONS: The C677T mutation of MTHFR gene is common in the Chinese population. MTHFR C677T gene polymorphism associated with a predisposition to increased plasma homocysteine levels may represent a genetic risk factor for diabetic nephropathy in Chinese type 2 diabetic patients.     

The MTHFR 677TT and 677CT/1298AC genotypes in Cypriot patients may be predisposing to hypertensive nephrosclerosis and chronic renal failure.

AIM: The homozygous 677TT mutation of the MTHFR gene has been linked to deep vein thrombosis and to arterial atherosclerotic events of the coronary, carotid and peripheral arteries. Its putative association with renal arteriosclerosis and chronic renal failure (CRF) in the presence of hypertensive nephrosclerosis is yet to be investigated. METHODS: Two hundred and twenty-one Greek-Cypriot patients with CRF from one single renal unit in Cyprus were divided into 6 diagnostic categories: 49 due to chronic glomerulonephritis (22.2%), 43 due to diabetes mellitus (19.4%), 26 due to autosomal dominant polycystic kidney disease (11.8%), 30 due to essential hypertension leading to nephrosclerosis (13.6%), including 4 patients with primary malignant hypertension, 32 with other rarer causes of CRF (14.5%) and 41 of uncertain etiology (18.5%). These 221 CRF patients had their MTHFR C677T and A1298C genotypes analyzed by the polymerase chain reaction and agarose gel electrophoresis after restriction enzyme digestion. The frequency of the homozygous states 677TT and 1298CC and the double heterozygous 677CT/1298AC were compared to those of 210 unrelated normal local controls. RESULTS: A statistically significant increase in the frequency of the 677TT genotype compared to controls was only found in the hypertensive nephrosclerosis CRF sub-group of patients. The prevalence rate of the 677TT genotype was 46.7% (controls 17.6%, P=0.0007). Combined together the homozygous 677TT and the double heterozygous 677CT/1298AC genotypes were found in 86.7% of the hypertensive nephrosclerotic CRF patients, compared to 46.6% in normal controls (P=0.0001). CONCLUSIONS: The findings support the hypothesis that Caucasian patients with essential hypertension, homozygous for 677TT or doubly heterozygous for 677CT/1298AC genotypes, are predisposed to develop hypertensive nephrosclerosis and CRF.     

MTHFR基因多态性及Hcy与房颤伴卒中的关系

目的探讨MTHFR基因突变引起Hcy水平升高与中国人种房颤对缺血性卒中的发生是否存在相互关系。方法纳入非瓣膜性房颤和房颤伴缺血性卒中的患者及正常对照组，采用PCR——RFLP的方法研究MTHFR基因677位点上C／T碱基的突变情况。两组计量资料用t检验，多组计量资料用方差分析进行整体比较。结果（1）房颤、房颤伴卒中患者MTHFR基因多态性与血浆Hcy有关，1Tr型Hcy水平（21．38±18．75μmoVL）明显高于CT（14．46±4．70μmol／L），CC（14．33±5．09μmol/L）型；（2）房颤伴卒中组血浆Hcy水平（18．15±13．74μmol/L）较房颤组（13．76±5．12μmol/L）升高明显。结论（1）房颤伴卒中患者血浆Hcy水平明显升高，高Hcy水平可能是非瓣膜性房颤发生卒中的危险因素；（2）MTHFR基因C677T位点突变纯合基因型TT型较CT基因型、CC基因型血浆Hcy升高明显，示TT基因型MTHFR酶活性最低；（3）MTHFR基因C677T位点多态性与房颤伴卒中无关。     

Mutations C677T and A1298C of the 5,10-methylenetetrahydrofolate reductase gene and fasting plasma homocysteine levels are not associated with the increased risk of venous thromboembolic disease.

Mild hyperhomocysteinemia is associated with homozygosity for the thermolabile variant of 5,10-methylenetetrahydrofolate reductase (MTHFR) and could increase the risk of venous thromboembolic disease (VTD). Recently, the second A1298C mutation of the MTHFR gene was described. The present study aimed to analyze both mutations of the MTHFR gene and plasma homocysteine levels in subjects with VTD. The study groups comprised 146 patients with VTD and 100 healthy subjects. There were no statistical differences in carrier frequency and allelic frequency for both A1298C and C677T mutations, nor were there any differences encountered between subjects with VTD and controls in either plasma homocysteine levels or according to C677T or A1298C genotypes of MTHFR. In our VTD patients and controls, neither MTHFR 677CT/1298CC nor MTHFR 677TT/1298CC combined genotypes were observed; double heterozygotes (A1298C/C677T) were represented only in 11% of VTD patients, and in 15% of the controls. In conclusion, the polymorphisms C677T and A1298C of MTHFR and fasting plasma homocysteine levels do not seem to be significant risk factors for venous thromboembolic disease.     

Genetic risk factors in young adults with 'cryptogenic' ischemic cerebrovascular disease.

Mutations such as factor V Leiden G1691A (FVL), prothrombin G20210A (FIIM), methylenetetrahydrofolate reductase (MTHFR) C677T, cystathionine beta-synthase (CBS) 844ins68 and endothelial cell protein C receptor (EPCR) 4031ins23 are risk factors for thromboembolism. To assess the role of these mutations in young adults with cerebral ischemia of otherwise undetermined etiology, 93 patients younger than 50 years old with thromboembolic strokes or transient ischemic attacks were studied. One hundred and eighty-six healthy age-matched and sex-matched blood donors served as controls. The FVL mutation was detected in 15/93 patients and 13/186 controls. After adjustment for smoking, arterial hypertension, and hyperlipidemia, the association of the FVL mutation with cerebral ischemia [odds ratio (OR), 3.19; 95% confidence interval (CI), 1.38-7.39] remained significant. One of 93 patients and 6/186 controls were carriers of FIIM (OR, 0.33; 95% CI, 0.04-2.75). We detected the MTHFR TT677 genotype in 9/93 patients and 26/186 controls (OR, 0.66; 95% CI, 0.30-1.47), a CBS 844ins68 mutation in 12/93 patients and 19/186 controls (OR, 1.30; 95% CI, 0.60-2.81), and an EPCR 4031ins23 mutation in 1/93 patients and in no control individual (P = 0.33). In conclusion, in younger adults the FVL mutation is a risk factor for cerebrovascular disease. FIIM, the MTHFR TT677 genotype and the CBS 844ins68 mutation did not contribute to the risk in this group of patients. The EPCR 4031ins23 mutation is very rare, its possible role needs further investigation.     

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.     

Cost-effectiveness analysis of MTHFR polymorphism screening by polymerase chain reaction in Korean patients with rheumatoid arthritis receiving methotrexate

OBJECTIVE: To determine whether a strategy based on methylenetetrahydrofolate reductase (MTHFR) genotype screening is more cost-effective than the conventional strategy in reducing the risk of methotrexate (MTX)-related toxicity in patients with rheumatoid arthritis (RA). METHODS: We consecutively enrolled 385 patients with RA (355 female, 30 male) who had received MTX and identified toxicity associated with MTHFR C677T genotypes. We designed a hypothetical decision model to compare the genotype-based strategy with the conventional strategy. The time horizon was set as 1 year, and direct medical costs were used. The measured outcomes were the total expected cost, the effectiveness, and the incremental cost-effectiveness ratio. RESULTS: MTHFR genotype distribution revealed 133 patients (34.6%) with 677CC, 193 (50.1%) with 677CT, and 59 (15.3%) with 677TT. A total of 154 patients (40.0%) exhibited MTX-related toxicity. Compared to RA patients with the CC genotype, the odds ratio (95% confidence interval) for risk of toxicity was 3.8 (2.29-6.33) for the CT genotype, and 4.7 (2.40-9.04) for the TT genotype. In the base-case model, the total expected cost and the probability of continuing MTX medication for the conventional and genotype-based strategies were 851,415 Korean won (710 US dollars) and 788,664 Korean won (658 US dollars), and 94.03% and 95.58%, respectively. CONCLUSION: The MTHFR C677T polymorphism may be an important predictor of MTX-related toxicity in patients with RA. The cost-effectiveness analysis suggests that the genotype-based strategy is both less costly and more effective than the conventional strategy for MTX therapy.     

类风湿关节炎亚甲基四氢叶酸还原酶基因多态性与甲氨蝶呤疗效和不良反应的关系

目的 探讨类风湿关节炎(RA)患者亚甲基四氢叶酸还原酶(MTHFR)基因677CDT[rs1801133)、1298A/C(rs1801131)单核苷酸多态性(SNP)及其与甲氨蝶呤(MTX)治疗的疗效和不良反应相关性.方法 收集RA患者184例.分为单用MTX组、MTX联用其他改善病情抗风湿药(DMARD)组、非MTX的DMARD组,于治疗前及治疗后24周检查临床及实验室指标,评价疗效及不良反应.采用实时荧光定量聚合酶链反应(FQ-PCR)方法检测RA患者及100名健康对照组的MTHFR基因677C/T及1298A/C多态性,比较两组间基因型分布及等位基因频率.结果 677CC/CT/TT基因型分布在RA组(19%、67%、14%)与健康对照组(27%、56%、17%)基因型分布频率差异无统计学意义(P>0.05);1298AA/AC/CC基因型分布在RA组(66%、31%、3%)健康对照组(70%、30%、0%)基因型分布频率差异无统计学意义(P>0.05).677CC/CT/TT基因型分布在RA有心血管并发症组(6%、75%、19%)与正常对照组(27%、56%、17%)差异有统计学意义(P<0.05).在单用MTX治疗者巾,1298AA/AC/CC在MTX治疗有效组(54%、44%、2%)和无效组(90%、10%、O%)中差异有统计学意义(P<0.05),677CC/CT/TT在MTX有不良反应组(13%、71%、16%)和无不良反应组(48%、48%、4%)中差异有统计学意义(P<0.05).在MTX联用其他DMARD组,677CC/CT/TT在有不良反应组(9%、78%、13%)和无不良反应组(35%、50%、15%)中差异有统计学意义(P<0.05).结论 MTHFR基因677C/T及1298A/C多态性与RA发病无关;677 C/T多态性与RA心血管并发症的出现有关、与MTX治疗后的不良反应相关,1298 A/C多态性与MTX的疗效相关.