Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.5.1.20 (methylenetetrahydrofolate reductase)
2,134 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

BACKGROUND: Women may be at increased risk for venous thromboembolism (VTE) as compared with men. We studied the effects of genetic and biochemical markers of thrombophilia in women, in conjunction with other established risk factors for VTE. METHOD: The present retrospective case-control study was conducted in a thrombosis treatment programme at a large Toronto hospital. The cases were 129 women aged 16-79 years with objectively confirmed VTE. Age-matched control individuals were women who were free of venous thrombosis. Neither cases nor control individuals had known cardiovascular disease. Participants were interviewed regarding personal risk factors for VTE, including smoking, history of malignancy, pregnancy, and oestrogen or oral contraceptive use. Blood specimens were analyzed for common single nucleotide polymorphisms of prothrombin, factor V and methylenetetrahydrofolate reductase (MTHFR; C677T, A1298C and T1317C), and the A66G polymorphism for methionine synthase reductase (MTRR).Fasting plasma homocysteine was also analyzed. RESULTS: Women with VTE were significantly more likely than female control individuals to carry the prothrombin polymorphism and the factor V polymorphism, or to have fasting hyperhomocysteinaemia. Homozygosity for the C677T MTHFR gene was not a significant risk factor for VTE, or were the A1298C or T1317C MTHFR homozygous variants. Also, the A66G MTRR homozygous state did not confer an increased risk for VTE. CONCLUSION: Prothrombin and factor V polymorphisms increased the risk for VTE in women, independent from other established risk factors. Although hyperhomocysteinaemia also heightens this risk, common polymorphisms in two genes that are responsible for homocysteine remethylation do not. These findings are consistent with previous studies that included both men and women.
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PMID:Genetics University of Toronto Thrombophilia Study in Women (GUTTSI): genetic and other risk factors for venous thromboembolism in women. 1180 87

Polymorphisms in genes encoding the folate metabolizing enzymes methylenetetrahydrofolate reductase (MTHFR C677T) and methionine synthase reductase (MTRR A66G) have been linked to the etiology of Down syndrome. We examined the prevalence of these variant genotypes in mothers who had given birth to a child with Down syndrome (n = 48) and in control mothers (n = 192), and investigated the biochemical factors influenced by the presence of MTRR A66G and MTHFR C677T. The frequency of the MTRR variant genotypes (AG, GG) was significantly higher in mothers of children with Down syndrome compared to controls (P = 0.0028). MTHFR C677T genotype frequencies were not significantly altered in mothers of children with Down syndrome (P = 0.74). However, mothers who had a MTHFR CT or TT genotype and a MTRR GG genotype had a 2.98-fold increased risk of having a child with Down syndrome (P = 0.02). The MTRR polymorphism did not increase plasma homocysteine. Higher homocysteine was found with the presence of the MTHFR T allele. In conclusion, MTRR A66G is significantly more common in mothers of children with Down syndrome but does not appear to increase the risk for Down syndrome by changing homocysteine metabolism. Women who have both the MTRR and MTHFR variant genotypes are also at increased risk of producing offspring with Down syndrome.
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PMID:MTRR and MTHFR polymorphism: link to Down syndrome? 1180 90

The following seven polymorphic marker loci of genes responsible for predisposition to coronary atherosclerosis (CAS) were studied: the ACE locus responsible for angiotensin-converting enzyme insertion/deletion polymorphism for the presence or absence of the Alu insertion in the gene; the F13, PLAT, and APOA1 loci, controlling the clotting factor 13, plasminogen-activating tissue factor, and apolipoprotein A, respectively; the MTHFR and AGT polymorphic loci responsible for point mutations in methylenetetrahydrofolate reductase and those in angiotensinogen, respectively, and the NOS3 locus controlling the number of tandem repeats in the nitric oxide synthase gene. These loci are located on different chromosomes and encode products involved into various metabolic pathways leading to CAS. In the populations studied, significant differences between healthy subjects and patients predisposed to cardiovascular diseases were revealed with regard to the above seven markers. The 174M allele (T174M polymorphism in the ACE gene) was significantly associated with coronary atherosclerosis. It was found that specific gene combinations are involved in the CAS development and determine variation in the pathogenetically important quantitative traits.
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PMID:[Analysis of gene complexes predisposing to coronary atherosclerosis]. 1196 67

Homozygosity for the C677T mutation in the methylenetetrahydrofolate reductase ( MTHFR) gene is a risk factor for neural tube defects (NTDs) in many populations, including Italians. Another common mutation on the MTHFR gene, A1298C, has also been described as a risk mutation. Furthermore, several studies have suggested that a defective methionine synthase ( MS) enzyme could be a critical defect in folate-related NTDs. An A-to-G transition at bp 2756 on the MS gene has also been reported. In this case-control study, we studied the frequencies of these two polymorphisms in 203 Italian probands with non-syndromic NTDs: 98 mothers, 67 fathers, and 210 control individuals. Although the A1298C polymorphism is common in the Italian population (0.25), the allelic frequency was significantly higher among NTD cases and their parents. Heterozygous patients and mothers have an odds ratio (OR) of 1.98 and 2.11, respectively. The risk associated with the 1298CC genotype was higher for cases (OR = 3.67), for fathers (OR = 3.28), and, above all, for mothers (OR = 6.23). The prevalence of the A2756G polymorphism of the MS gene was determined (0.15). No increased prevalence of the mutated G allele was found in NTD families. This study shows that the MTHFRA1298C polymorphism is a genetic determinant for NTD risk in Italy. No association between the MSA2756G and NTD susceptibility was found.
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PMID:Study of MTHFR and MS polymorphisms as risk factors for NTD in the Italian population. 1211 80

Many epidemiologic, animal and human studies suggest that folate status modulates carcinogenesis. Although these observations have been made in a number of tissues, the data are clearly most compelling for the colorectum. The mechanism(s) by which this modulation is mediated remains ill defined. Alterations in either genome-wide or gene-specific DNA methylation and/or alterations in DNA stability, resulting from DNA strand breaks or uracil misincorporation, are leading candidates in this regard. Folate has a central role in biological methylation and nucleotide synthesis, and therefore it is not surprising that folate depletion has been observed to alter DNA methylation and diminish DNA stability. The hypothesis that these two pathways are the means by which folate modulates cancer risk is also supported by the epidemiological observation that a common polymorphism in the methylenetetrahydrofolate reductase (MTHFR; EC 1.5.1.20) gene differentially affects the relative risk of colon cancer depending on folate status, because MTHFR catalyzes the reaction that determines whether cellular folate is diverted into biological methylation or nucleotide synthesis. This phenomenon suggests that it is an imbalance between biological methylation and nucleotide synthesis that is responsible for folate-related carcinogenesis. The control of cell proliferation, which also is related to DNA methylation, is another candidate mechanism by which folate status modulates carcinogenesis. In cell culture studies, folate supplementation has been observed to suppress excessive cell proliferation. Understanding the mechanisms by which folate status modulates carcinogenesis is important for advancing insight into cancer biology and for facilitating those efforts to translate research in folate and carcinogenesis into effective and safe public health initiatives.
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PMID:Folate status: effects on pathways of colorectal carcinogenesis. 1216 3

The thymidylate synthase gene ( TYMS or TS) encodes a tightly regulated enzyme that catalyzes the conversion of deoxyuridylate to thymidylate, and contains a tandem repeat polymorphism that affects expression of the enzyme. We have investigated the relationship between TYMS genotype and plasma concentrations of homocysteine and folate in a cohort of 505 Chinese from Singapore. TYMS 3/3 genotype was associated with reduced plasma folate and, among individuals with low dietary folate intake, with elevated plasma homocysteine levels. These associations were independent of the well-established methylenetetrahydrofolate reductase ( MTHFR) C677T genotype effects on plasma folate and homocysteine levels. Our results suggest that TYMS and MTHFR compete for limiting supplies of folate required for the remethylation of homocysteine. These genetic determinants of plasma folate and homocysteine levels may be useful in identifying individuals at increased risk for cardiovascular disease.
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PMID:Thymidylate synthase: a novel genetic determinant of plasma homocysteine and folate levels. 1221 45

Inherited and acquired thrombophilias have been associated with recurrent pregnancy loss. Over recent years our ability to detect protein and genetic abnormalities responsible for thrombotic tendency has improved. We are now left with the task of deciphering which of these thrombophilias carries an increased risk for recurrent pregnancy loss. Acquired thrombophilias including lupus anticoagulant and anticardiolipin antibodies have been linked to recurrent pregnancy loss. However the evidence for the role of inherited thrombophilias such as, heterozygosity for the factor V Leiden, prothrombin G20210A mutation, the methylenetetrahydrofolate reductase (C677T MTHFR) mutation, as well as deficiencies of antithrombin, protein C and protein S is less clear. The methods for diagnosis and the evidence for their associations are discussed in this paper. Treatment modalities independent of those needed to prevent thrombotic events in pregnancy have generally not been studied. Given the present available data, there is insufficient evidence to include inherited thrombophilias in the initial evaluation of RPL. It is important to look for other, more common, causes of recurrent miscarriage in the evaluation of these patients.
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PMID:Thrombophilias and recurrent miscarriage. 1236 98

Hyperhomocysteinemia is an accepted risk factor for coronary artery disease, but the determining factors are not fully understood. We investigated hyperhomocysteinemia and vitamin deficiency in Syrian coronary patients and apparently healthy Syrian and German controls. We enrolled 273 Syrian patients with angiographically confirmed stenosis, along with 159 Syrian and 75 German controls. Plasma total homocysteine (HCY), cystathionine, methylmalonic acid (MMA), vitamin B-6, B-12, folate, lipids, apolipoproteins and methylenetetrahydrofolate reductase (C677T-MTHFR) mutation were analysed. There was a very high prevalence of hyperhomocysteinemia (>12 micromol/l) in Syrians (patients 61%, controls 44%, Germans 16%) together with functional vitamin B-12 deficiency diagnosed by elevated MMA (patients 49%, controls 47%, Germans 3%), which was in contrast to the low frequency of decreased serum vitamin B-12 (12% in patients, 7% in Syrian controls). The HCY concentration in German controls was lower than in Syrians, median 8.8 vs. 11.3 micromol/l. The vitamin B-12 deficiency induces folate trapping; higher levels of folate are needed to prevent hyperhomocysteinemia. Germans achieved the HCY level of < or =12 micromol/l at significantly lower folate concentrations > or =4.4 ng/ml, than Syrians with normal MMA (> or =16.7 nmol/l folate) or Syrians with high MMA (> or =23.3 nmol/l folate). Smoking and homozygous state for C677T-MTHFR mutation contributed to hyperhomocysteinemia. We could confirm that the reasons for hyperhomocysteinemia in Syrians were in fact mostly related to a relative folate deficiency, which is due to a vitamin B-12 shortage. Vitamin B-12 deficiency induces folate trapping. Besides lifestyle, other presently unknown factors may contribute to hyperhomocysteinemia and vitamin B-12 deficiency in Syrians.
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PMID:Hyperhomocysteinemia and vitamin B-12 deficiency are more striking in Syrians than in Germans--causes and implications. 1248 61

Common single nucleotide polymorphisms (SNPs; 677C>T and 1298A>C) in the methylenetetrahydrofolate reductase gene ( MTHFR) decrease the activity of the enzyme, leading to hyperhomocysteinemia, particularly in folate-deficient states. We calculate herein the haplotype frequencies of the MTHFR 677 and 1298 polymorphisms in pooled general populations derived from published data. We selected 16 articles that provided reliable data on combined MTHFR genotypes in general populations ( n = 5389). The combined data comprised the following totals for each genotype at nucleotide positions 677 and 1298: 838 CC/AA (i.e., 677CC/1298AA), 1225 CC/AC, 489 CC/CC, 1120 CT/AA, 1093 CT/AC, 8 CT/CC, 606 TT/AA, 10 TT/AC, and 0 TT/CC. The estimated haplotype frequencies, and the fractional contribution of each, were 677C/1298A, 0.37; 677C/1298C, 0.31; 677T/1298A, 0.32; and 677T/1298C, 0.0023 to 0.0034. Thus, a vast majority of 677T alleles and 1298C alleles are associated with 1298A alleles and 677C alleles, respectively. There may be an increased frequency of the very rare cis 677T/1298C haplotype in some parts of the United Kingdom and Canada, possibly due to a founder effect. Further studies on both SNPs are needed to determine their exact role in various clinical settings.
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PMID:Genotype and haplotype distributions of MTHFR677C>T and 1298A>C single nucleotide polymorphisms: a meta-analysis. 1256 Aug 71

Abdominal aortic aneurysm (AAA) presents itself as a progressive dilation of the abdominal aorta, leading--if untreated--to rupture. It is a common disease of the elderly, with a complex etiology. Several genetic, biochemical and environmental factors are recognized as relevant for the pathogenesis of AAA. We determined the polymorphism of the MTHFR (methylenetetrahydrofolate reductase) gene within the fourth exon (C677T) in 63 patients with AAA and compared it to that in 75 subjects of the population sample. The frequencies of the C/C, C/T and T/T genotypes were 65%, 27%, and 8% in the population sample and 33%, 60%, and 6% in the patients. This corresponds to a 4.4-fold greater risk of AAA in subjects who have the 677C/T variant of MTHFR, as compared with those who are 677C/C (p < 0.0001; 95% CI=2.11-9.34). The frequency of allele MTHFR 677T in patients (0.37) was higher than in the population sample (0.21; p < 0.007). This association between the common allele of the MTHFR gene--MTHFR 677T--and the development of AAA suggests that elevated homocysteine (Hcy) may disturb the function of the aortic wall. The disturbance may involve enhancement of elastin degradation, the process enhanced by mild hyperhomocysteinemia in minipigs. The magnitude of this effect, which refers to the AAA patients unselected for familial occurrence, indicates that the disturbance of aortic wall physiology caused by the presence of the MTHFR 677T allele is greater than the effect of the earlier described allele disequilibrium at the polymorphic alleles of the PAI1 (plasminogen activator inhibitor 1) gene seen only in familial cases of AAA.
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PMID:Increased risk of the abdominal aortic aneurysm in carriers of the MTHFR 677T allele. 1259 Jan 85


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