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.     

The 5,10-methylenetetrahydrofolate reductase C677T polymorphism interacts with smoking to increase homocysteine

Elevated homocysteine is a risk marker for several human pathologies. Risk factors for elevated homocysteine include low folate and homozygosity for the T allele of the 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism. Because nitric oxide may inhibit folate catabolism and endothelial nitric oxide synthase activity is reduced in smokers, we postulated that smoking status might modify the impact of the MTHFR C677T polymorphism on homocysteine (tHcy) concentrations. We tested this hypothesis in a healthy young adult population for which MTHFR C677T genotypes and tHcy concentrations were previously reported. The MTHFR 677TT genotype was significantly associated with elevated tHcy concentrations in smokers (P = 0.001) but not in non-smokers (P = 0.36). Among smokers, the MTHFR 677TT genotype was significantly associated with high tHcy in heavy smokers (P = 0.003) but not light smokers (P = 0.09), in men (P = 0.003) but not women (P = 0.11), and in subjects from the lowest serum folate quartile (P = 0.49) but not from folate quartiles 2-4 (P = 0.49). After adjustment for nutritional variables, interactions between MTHFR C677T genotype and NOS3 G894T genotype, and between MTHFR genotype, smoking status and gender were statistically significant. We propose that hyperhomocysteinemia in MTHFR 677TT homozygote smokers is the consequence of mild intracellular folate deficiency caused by a smoking-related reduction of NOS3 activity that is exacerbated when serum folate is low.     

No association between the common MTHFR 677C->T polymorphism and venous thrombosis: results from the MEGA study

BACKGROUND: Increased homocysteine levels are related to the occurrence of venous thrombosis, but whether this relation is causal is unclear. The T-variant of the common methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism mildly increases homocysteine levels. Meta-analyses have demonstrated a weak effect of the MTHFR 677TT genotype on risk but are sensitive to selective publication of positive results. The aim of the present study was to evaluate the effect of the MTHFR genotype on the risk of venous thrombosis, overall and in subgroups of known risk factors, in a single large study. METHODS: In the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA Study), a population-based case-control study, we collected DNA from 4375 patients with a first deep vein thrombosis of the leg or pulmonary embolism and from 4856 control subjects. Information about risk factors for venous thrombosis was obtained from questionnaires. RESULTS: MTHFR 677C-->T was not associated with the risk of venous thrombosis (odds ratio [95% confidence interval], 0.99 [0.91-1.08] for the CT genotype and 0.94 [0.81-1.08] for the TT genotype). Stratification by known risk factors for venous thrombosis provided no evidence of an association in specific groups. CONCLUSIONS: In a single large study, MTHFR 677C-->T was not associated with the risk of venous thrombosis, and the narrow confidence interval excludes even a small effect. Therefore, mildly elevated homocysteine levels as a result of MTHFR 677TT do not seem to cause venous thrombosis. There is no rationale for measuring the MTHFR 677C-->T variant for clinical purposes.     

Methylenetetrahydrofolate reductase polymorphism (C677T), hyperhomocysteinemia, and risk of ischemic cardiovascular disease and venous thromboembolism: prospective and case-control studies from the Copenhagen City Heart Study

Hyperhomocysteinemia is associated with ischemic cardiovascular disease (ICD) and venous thromboembolism (VTE). We tested the hypothesis that methylenetetrahydrofolate reductase (MTHFR) C677T homozygosity with hyperhomocysteinemia is associated with ICD and VTE. First, 9238 randomly selected whites from the general population were followed for 23 years. Second, 2125 whites with ischemic heart disease and 836 whites with ischemic cerebrovascular disease were compared with 7568 controls from the general population. Plasma homocysteine was elevated 25% in homozygotes versus noncarriers (P < .001) and 19% in ICD/VTE cases versus controls (P < .001). In prospective studies adjusted hazard ratios for ICD and VTE for homozygotes versus noncarriers did not differ from 1.0. Furthermore, MTHFR C677T homozygosity was not associated with increased risk of ICD or VTE in subgroups after stratification for sex, age, cholesterol, high-density lipoprotein cholesterol, lipoprotein(a), fibrinogen, triglycerides, body mass index, smoking, diabetes mellitus, hypertension, and factor V Leiden genotype. Finally, in case-control studies odds ratios for ischemic heart disease and ischemic cerebrovascular disease in homozygotes versus noncarriers did not differ from 1.0. In conclusion, MTHFR C677T homozygosity with hyperhomocysteinemia is not associated with ICD or VTE; however, ICD/VTE is associated with hyperhomocysteinemia. Therefore, ICD and VTE may cause hyperhomocysteinemia, rather than vice versa.     

Homocysteine levels in men and women of different ethnic and cultural background living in England

This population-based cross-sectional study in South London looks at the total homocysteine (tHcy) levels in groups of different ethnic background and the possible role of environmental factors and the 677C-->T genetic polymorphism of the methylenetetrahydrofolate reductase (MTHFR). Fasting plasma tHcy was measured in 1392 men and women, age 40-59 years; 475 were white, 465 of African origin (of whom 180 were West Africans and 280 Caribbeans) and 452 South Asian (of whom 222 were Hindus and 167 Muslims). The homozygous MTHFR TT variant had observed frequencies of 0.10 in whites, 0.01 in people of African origin and 0.02 in South Asians (P<0.001). tHcy levels were 16% (95% CI 8-26) higher amongst TT than CC. tHcy levels were 25% (21-29) higher in men than women. Levels were significantly higher in South Asians than whites (8% [3-13]). Vegetarians had higher levels than non-vegetarians (25% [18-33]). These differences were present after adjustments for age, sex, smoking, body mass index (BMI), MTHFR 677C-->T polymorphism and socio-economic status. Compared with whites (10.0 [9.7-10.3] micromol/l), and allowing for confounders, Hindus had significantly higher levels of tHcy (12.1 [11.6-12.6] micromol/l). This difference was attenuated by the inclusion of vegetarianism in the model (11.3 [10.8-11.9] micromol/l). In contrast Muslims had similar tHcy levels to whites while both West Africans and Caribbeans had slightly lower levels, though differences were not significant. The reported higher levels of tHcy in South Asians are due to high levels amongst Hindus only. They are in part accounted for by their vegetarianism. These differences in tHcy are large enough to be important contributors to the risk of vascular disease and may be preventable by simple targeted population strategies.     

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.     

Association between plasma homocysteine concentrations and asymptomatic cerebral infarction or leukoaraiosis in elderly diabetic patients

Background: The purpose of the present study was to investigate the possible contribution of plasma homocysteine to asymptomatic cerebral infarction (CI) or leukoaraiosis. Methods: The relationship between plasma homocysteine concentrations and cerebral lesions was investigated in 233 elderly diabetic patients (mean age: 74 years) who were divided into three groups based on the neurological and brain MR findings: asymptomatic cerebral infarction (CI), symptomatic CI, and a control group with no evidence of cerebrovascular disease. Plasma total homocysteine concentrations were measured by high‐performance liquid chromatography. The C677T polymorphism in the methylene tetrahydrofolate reductase (MTHFR) gene was assessed by PCR‐RFLP. The total score of T2 high‐intensity lesions on the brain MR images was summed from the focal T2 high‐intensity scores in 24 areas of the brain. Results: Diabetic patients with asymptomatic or symptomatic CI had significantly higher homocysteine concentrations in plasma than the control group. The plasma homocysteine concentration was more strongly associated with the presence and number of small infarctions or infarction of the putamen, which may explain the association between increased plasma homocysteine concentrations and asymptomatic CI in elderly diabetic patients. In the diabetic patients, high plasma homocysteine concentrations were also significantly associated with high scores of total T2 high‐intensity lesions or focal T2 high‐intensity scores in some periventricular regions. Although there was no significant relationship between the MTHFR TT genotype and CI, a significant association was found between the MTHFR TT genotype and total T2 high‐intensity scores. Conclusion: An elevated plasma homocysteine concentration is independently associated with asymptomatic CI and T2 high‐intensity lesions on brain MR images in elderly patients with diabetes mellitus. The association between the MTHFR TT genotype and periventricular T2 high‐intensity lesions, but not with CI, suggests an important effect of C677T MTHFR gene mutation on leukoaraiosis, independent of hyperhomocysteinemia in elderly diabetic patients.     

亚甲基四氢叶酸还原酶基因多态性与原发性高血压患者合并冠心病的相关性研究

目的探讨N5,10-亚甲基四氢叶酸还原酶(MTHFR)C677T位点突变与河南豫北地区原发性高血压及其合并冠心病发病的关系。方法选择原发性高血压患者405例为高血压组,高血压合并冠心病患者400例为冠心病组,健康体检者400例为对照组。对3组MTHFR基因C677T多态性进行基因分型。结果冠心病组T等位基因频率和TT基因型频率明显高于高血压组和对照组(P<0.05)。冠心病组TT基因型患者TC和血浆同型半胱氨酸水平明显高于CC+CT基因型(P<0.05)。结论 MTHFR基因C677T多态性与原发性高血压患者冠心病的发生相关。     

Vitamin B12 decreases,but does not normalize,homocysteine and methylmalonic acid in end-stage renal disease: a link with glycine metabolism and possible explanation of hyperhomocysteinemia in end-stage renal disease

The genetic and environmental factors influencing catabolism of homocysteine in end-stage renal disease (ESRD) patients remain poorly understood. This study investigated how genetic and nutritional influences affect the response to high-dose vitamin B(12) and folate treatment in ESRD patients with hyperhomocysteinemia. We studied 81 hemodialysis patients with hyperhomocysteinemia (> 16 micromol/L) on varied doses of a multivitamin containing 1 mg of folic acid per day. After screening blood work, all patients were switched to daily multivitamin therapy including 1 mg of folic acid for 4 weeks. Vitamin B(12), 1 mg/d, was added for an additional 4 weeks. Patients were then randomized to receive folic acid or placebo. The influence of the 3 methylenetetrahydrofolate reductase (MTHFR) 677 C-->T genotypes on the efficacy of vitamin therapy was assessed. In addition, we investigated how the metabolic complications of ESRD, including the relationship between methylmalonic acid (MMA) and circulating glycine, may contribute to hyperhomocysteinemia. There was no significant difference in total homocysteine (tHcy) levels between the MTHFR 677 C-->T genotypes during the screening phase of the trial. Treatment with a daily multivitamin containing 1 mg folate significantly lowered tHcy levels in all patients by 19.2%. Further supplementation with 1 mg vitamin B(12) resulted in greater tHcy reduction among subjects with the MTHFR 677 T/T genotype (P<.01, T/T v C/C or C/T) while lowering MMA equally in all MTHFR genotypes. There was a significant positive correlation between plasma glycine levels and MMA (P <.05). High-dose vitamin therapy significantly lowers, but does not normalize, MMA and tHcy levels. The MTHFR genotype, while influencing homocysteine levels, was not responsible for the majority of the elevation in plasma tHcy.     

Homocysteine and methylenetetrahydrofolate reductase genotype: association with risk of coronary heart disease and relation to inflammatory, hemostatic, and lipid parameters

AIM: It has been suggested that homocysteine (tHcy) levels and methylenetetrahydrofolate reductase (MTHFR) genotype are primary risk factors for coronary heart disease (CHD). We performed a case-control study to investigate whether tHcy levels and MTHFR genotype (677 C-->T mutation and 1298 A-->C mutation) are associated with CHD under special consideration of the possibility for confounding. METHODS: German speaking patients aged 40-68 years who underwent coronary angiography at the University of Ulm between April 1996 and November 1997 and who had at least one coronary stenosis greater than 50% were included in the study. Controls were sampled from voluntary blood donors and were matched for sex and age. tHcy levels were measured by high performance liquid chromatography and MTHFR genotype by means of polymerase chain reaction. In addition, C-reactive protein, fibrinogen, plasma viscosity, leukocytes, HDL-cholesterol and Lp(a) were determined. RESULTS: Overall, 312 patients and 479 controls were enrolled in the study (response in patients 78%, in controls 84%). Mean tHcy value was 9.43 micromol/l in CHD patients and 8.91 micromol/l in controls (P=0.145). Prevalence of 677TT-polymorphism was 9.9% in patients and 10.4% in controls (P=0.295). Prevalence of 1298CC-polymorphism was 9.7% in patients and 13.8% in controls (P=0.346). There was a clear association of tHcy-values, but not of 677TT- or 1298CC-genotype with conventional CHD risk factors. After adjustment for these risk factors no increased risk for CHD could be associated with increased tHcy-values, with 677TT or 1298CC-genotype, or with their combination. Also no statistically significant relationships of these parameters to inflammatory, rheologic or hemostatic parameters or lipids were detectable. CONCLUSION: These results do not confirm an independent relationship of tHcy values and MTHFR genotype with risk of CHD in the population studied.     

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.     

Relation of a common methylenetetrahydrofolate reductase mutation and plasma homocysteine with intimal hyperplasia after coronary stenting

BACKGROUND: Hyperhomocysteinemia has been identified as an independent risk factor for coronary artery disease. Recent studies have shown that a common mutation (nucleotide 677 C-->T) in the methylenetetrahydrofolate reductase (MTHFR) gene may contribute to mild hyperhomocysteinemia and, therefore, to the incidence of coronary artery disease. No information exists, however, regarding the association between the mutation of the MTHFR gene or plasma homocysteine levels and morphological analysis of coronary atherosclerosis using intravascular ultrasound. METHODS AND RESULTS: To examine the potential influence of MTHFR genotype and homocysteine on coronaryarteries morphologically, we screened 62 patients with 65 lesions that were treated with 93 Palmaz-Schatz stents. The plasma homocysteine levels in the patients with the TT genotype were not significantly higher than those in the patients with non-TT (CC+CT) genotypes (13.1 +/- 5.5 versus 11.5 +/- 3.1 mmol/L, P=0.16). Angiographic analysis showed that the percent diameter stenosis in the patients with the TT genotype was significantly greater than that in those with non-TT genotypes (43.7 +/- 17.8% versus 29.0 +/- 22.0%, P=0.015). Intravascular ultrasound analysis showed that the TT genotype was significantly associated with greater intimal hyperplasia area (5.70 +/- 1.94 versus 3.72 +/- 1.38 mm2, P=0.001). In multiple stepwise regression analysis, the number of the T alleles was the only independent predictor of intimal hyperplasia after intervention (r2=0.21, P=0.004). CONCLUSIONS: The homozygous mutant genotype of the MTHFR gene may increase the risk of in-stent restenosis more than does the normal homozygous or heterozygous genotype.     

Homocysteine and carotid intima-media thickness: a critical appraisal of the evidence

This review examines the relationship between hyperhomocysteinemia, a risk factor for vascular disease, and carotid intima-media thickness (CIMT), a valid marker of generalized atherosclerosis and future vascular disease risk. The relationship between two important determinants of hyperhomocysteinemia in the general population-folate status and the 677C --> T methylenetetrahydrofolate reductase (MTHFR) polymorphism-and CIMT is also covered. METHODS: We searched literature databases for articles examining homocysteine and CIMT published before September 2003. RESULTS: We identified 54 studies. Observational studies generally failed to demonstrate a relationship between homocysteine and CIMT in homocystinuric, uremic, hypercholesterolemic or non-insulin-dependent diabetes mellitus patients or in subjects with insulin insensitivity. Weak associations, but usually only in certain sub-populations were found in vascular disease patients and in population-based studies. B vitamins reduce the progression of CIMT in renal transplant recipients and vascular disease patients as demonstrated by two trials. The majority of studies demonstrated increased CIMT in individuals with the MTHFR 677TT genotype. Folate status showed no relation to CIMT. DISCUSSION: In non-patient populations, hyperhomocysteinemia is weakly associated with CIMT. The association of the 677 C--> T MTHFR polymorphism with CIMT further supports this finding. Lastly, folate levels may need to reach a critically low status before an association can be found between folate and CIMT. Larger trials in various population types are needed to determine whether folate alone or in combination with Vitamins B6 and B12 will slow down or even reverse atherosclerotic progression.     

Methylenetetrahydrofolate reductase polymorphism associated with susceptibility to coronary heart disease in Chinese type 2 diabetic patients

OBJECTIVE: Epidemiological studies have identified hyperhomocyst(e)inemia as an independent risk factor for atherosclerosis. The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, might play a role in the development of coronary heart disease (CHD). In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and CHD in Chinese type 2 diabetic patients. METHODS: Two hundred and twenty-eight unrelated patients with type 2 diabetes mellitus (126 with coronary heart disease) and 114 healthy control subjects 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 114 healthy control subjects, the frequency of the mutant T allele was 38.0%, comparable to that of a Hong Kong (Chinese) population. The genotype distribution did not differ between control subjects and type 2 diabetic patients (chi(2) = 3.67, P > 0.05). Genotypic analysis revealed that type 2 diabetic patients with CHD displayed a greater prevalence of T allele (45.2%) than type 2 diabetic patients without CHD (30.4%) (chi(2) = 8.72, P < 0.005). The odds ratio for CHD in type 2 diabetic patients in presence of T allele was 1.89 (CI 95%, 1.24-2.88). The MTHFR genotype were different between diabetic patients with and without CHD (chi(2) = 11.98, P < 0.005). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype or CC plus 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 could constitute a useful predictive marker for CHD in Chinese type 2 diabetic patients.     

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.     

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.     

Hyperhomocysteinemia and the compound heterozygous state for methylene tetrahydrofolate reductase are independent risk factors for deep vein thrombosis among South Indians.

To investigate the role of methylene tetrahydrofolate reductase (MTHFR) (677 C-->T and 1298 A-->C), factor V (1691 G-->A), factor II (20210 G-->A) genetic polymorphisms and hyperhomocysteinemia in the aetiology of deep vein thrombosis (DVT) in 163 cases and 163 controls. Polymerase chain reaction-restriction fragment length polymorphism was used for genotyping, reverse-phase high-performance liquid chromatography for plasma homocysteine, and Student's t-test and Fisher exact tests were used for statistical analysis. Elevated mean plasma homocysteine levels were observed in DVT cases irrespective of gender differences. Homocysteine elevation above the 95th percentile of the control group associated with 9.4-fold and 7.6-fold increased risk for DVT in men and women, respectively. Genotyping showed the MTHFR 677CT/1298AC genotype (i.e. compound heterozygosity) is associated with 3.5-fold risk for thrombosis. The factor V Leiden mutation frequency was higher in DVT cases, but not statistically significant; however, genetic predisposition to this mutation was associated with early age of DVT onset. Factor II mutation was absent in cases and controls. Co-segregation of two or more risk factors was associated with 11.7-fold increased risk for thrombosis. This study projects that hyperhomocysteinemia and compound heterozygous state for MTHFR are independent risk factors for DVT among South Indians.     

Methylenetetrahydrofolate reductase genotypes and predisposition to atherothrombotic disease; evidence that all three MTHFR C677T genotypes confer different levels of risk.

AIMS: Elevated plasma homocysteine is an independent risk factor for atherothrombotic disease. Individuals homozygous for the methylenetetrahydrofolate reductase (MTHFR) 677C allele exclusively accumulate 5methyltetrahydrofolate, the methyl donor for homocysteine remethylation, in their red blood cells; this contrasts with 677 TT homozygotes who also accumulate significant levels of non-methylated folate derivatives. Those with the MTHFR 677 TT, CT and CC genotypes may therefore differ qualitatively with respect to folate utilization and hence their capacity to remethylate homocysteine. This study was consequently designed to establish whether all three genotypes confer different levels of atherothrombotic risk. METHODS AND RESULTS: The risk of atherothrombotic disease conferred by the MTHFR 677 CT and 677 CC genotypes was assessed using a 'restricted' meta-analysis approach applied to subjects from the first ten studies reporting a significantly increased risk conferred by the 677 TT genotype. The defined risk of the TT genotype in each of these ten studies was judged by us to denote 'genetic vulnerability' in the populations from which subjects were drawn. After proportional adjustment for the greater number of case TT homozygotes, the CT and CC frequencies observed in cases were compared with expectations based on the frequencies of these genotypes in controls. The observed CT frequency among cases was higher than expected in eight of the ten studies. In the meta-analysis, which included 1857 cases and 2942 controls, 847 (45.6%) cases, instead of the 777 (41.8%) expected, had the MTHFR CT genotype (P=0.010). CONCLUSIONS: Our findings suggest that the three MTHFR C677T genotypes confer different levels of atherothrombotic risk in 'genetically vulnerable' populations: CT heterozygotes have an elevated risk over CC homozygotes. One explanation is that the CT genotype actively confers atherothrombotic risk. An alternative interpretation however, for which a biologically plausible mechanism is proposed, is that CC is a protective genotype.     

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.     

Methylenetetrahydrofolate reductase gene polymorphisms in essential hypertension relation: with the development of hypertensive end-stage renal disease

BACKGROUND: The pathogenesis of hypertensive nephropathy is multifactoral and in addition to BP, other factors contribute to the development of this renal pathology and its progression to end-stage renal disease. These include genetic predisposition and increased pleasure level of homocysteine-intermediate protein catabolism product known to induce kidney injury. The 677C --> T polymorphism in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene is associated with elevated homocysteine level in the general population, and therefore it has been hypothesized to be a risk factor for the development of renal failure in the course of essential hypertension. METHODS: In this case-control, cross-sectional study the frequency of the MTHFR 677C --> T and the 1298A --> C polymorphism was compared between patients with hypertension-related chronic renal failure (n = 90), patients with essential hypertension without kidney injury (n = 90), and healthy individuals (n = 90) who were matched for age and gender. In addition, the influence of these polymorphisms on homocysteine concentration in individuals with essential hypertension was examined. RESULTS: The frequency of the MTHFR 677 TT genotype did not differ between groups (4.5%, 12.3%, and 11.1%, respectively). Patients with hypertension and the 677TT genotype showed significantly higher homocysteine levels as compared to individuals having CC and CT. In the multivariate correlation analysis the MTHFR 677TT genotype (P < .01; beta = 0.27), age (P < .001; beta = 0.33), and body mass index (P < .01; beta = 0.3) were independent predictors for total homocysteine level. CONCLUSIONS: Plasma homocysteine levels in individuals with essential hypertension is affected by the MTHFR 677C --> T polymorphism. However, we did not prove the hypothesis that MTHFR 677C --> T influences the risk of development of renal failure in the course of hypertension.