Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.5.7.1 (methylenetetrahydrofolate reductase)
 2,116 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alcoholic liver disease is associated with abnormal hepatic methionine metabolism, including increased levels of homocysteine and S-adenosylhomocysteine (SAH) and reduced levels of S-adenosylmethionine (SAM) and glutathione (GSH). The concept that abnormal methionine metabolism is involved in the pathogenesis of alcoholic liver disease was strengthened by our previous findings in a micropig model where combining dietary folate deficiency with chronic ethanol feeding produced maximal changes in these metabolites together with early onset of microscopic steatohepatitis and an eightfold increase in plasma aspartate aminotransferase. The goal of the present study was to determine potential mechanisms for abnormal levels of these methionine metabolites by analyzing the transcripts and activities of transmethylation enzymes in the livers of the same micropigs. Ethanol feeding or folate deficiency, separately or in combination, decreased transcript levels of methylenetetrahydrofolate reductase (MTHFR), methionine adenosyltransferase (MAT1A), glycine-N-methyltransferase (GNMT) and S-adenosylhomocysteine hydrolase (SAHH). Ethanol feeding alone reduced the activities of methionine synthase (MS) and MATIII and increased the activity of GNMT. Each diet, separately or in combination, decreased the activities of MTHFR and SAHH. In conclusion, the observed abnormal levels of methionine metabolites in this animal model of accelerated alcoholic liver injury can be ascribed to specific effects of ethanol with or without folate deficiency on the expressions and activities of hepatic enzymes that regulate transmethylation reactions. These novel effects on transmethylation reactions may be implicated in the pathogenesis of alcoholic liver disease.
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PMID:Hepatic transmethylation reactions in micropigs with alcoholic liver disease. 1512 59

Folate and methionine metabolism is involved in DNA synthesis and methylation processes. Polymorphisms in the genes of folate metabolism enzymes have been associated with some forms of cancer. In a case-control study, we evaluated whether four common polymorphisms in methylenetetrahydrofolate reductase (MTHFR C677T and A1298C), methionine synthase (MS A2756G), and methionine synthase reductase (MTRR A66G) genes may have a role in altering susceptibility to adult acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). We analyzed DNA of 120 adult ALL, 200 NHL, and 257 healthy control subjects. Individual carrying the MTHFR 677TT genotype showed a 3.6-fold decreased ALL risk [odds ratio (OR) 0.28, 95% confidence interval (95% CI) 0.12-0.72] than wild-types. Similarly, MS 2756GG individuals showed a 5.0-fold decreased ALL risk (OR 0.20, 95% CI 0.02-1.45) than wild-types. In combined results, subjects with the MTHFR 677CT/TT and MS 2756AG/GG genotypes revealed a 3.6-fold ALL risk reduction (OR 0.28, 95% CI 0.14-0.58) and those with the MTHFR 677TT and MTRR 66AG genotypes revealed a 4.2-fold ALL risk reduction (OR 0.24, 95% CI 0.06-0.81). Finally, those with the MS 2756AG/GG and MTRR 66AG/GG genotypes revealed a 2.2-fold ALL risk reduction (OR 0.45, 95% CI 0.10-0.85). Single analysis for NHL did not show any significant difference for all the polymorphisms investigated, but in the low-grade NHL subgroup, we found a 2.0-fold risk reduction for the MTRR 66GG homozygous genotype (OR 0.50, 95% CI 0.25-0.99), which was higher (OR 0.37, 95% CI 0.14-0.85) when analyzed in combination with MS 2756AA genotype. These data are in accordance with the hypothesis that polymorphisms in the genes for folate and methionine metabolism might play a greater role in the occurrence of ALL than NHL by influencing DNA synthesis and/or DNA methylation.
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PMID:Common gene polymorphisms in the metabolic folate and methylation pathway and the risk of acute lymphoblastic leukemia and non-Hodgkin's lymphoma in adults. 1515 11

Folate metabolism plays an essential role in DNA synthesis and methylation processes. Deviations in the flux of folate due to genetic variation could result in selective growth and genomic instability and affect susceptibility to various cancers including lymphoma. To test this hypothesis, genetic polymorphisms in the folate metabolic pathway were investigated using DNA from a population-based case-control study of non-Hodgkin lymphoma (NHL) conducted in the San Francisco Bay Area between 1988 and 1995. The polymorphisms examined and haplotypes generated included thymidylate synthase (TYMS 28-bp triple repeat [3R]-->double repeat [2R], 1494del6, IVS6 -68C>T, 1122A>G, and 1053C>T); 5,10-methylenetetrahydrofolate reductase (MTHFR 677C>T and 1298A>C); serine hydroxymethyltransferase (SHMT1 C1420T); reduced folate carrier (RFC G80A); and methionine synthase (MTR A2756G), making the present study the largest and most comprehensive to date to evaluate associations between genetic polymorphisms in folatemetabolizing genes and NHL risk. The TYMS 6 base pair (bp)(-)6bp- (homozygous for 6bp deletion), IVS6 -68C>T, and 1053C>T genotypes (all in complete linkage disequilibrium) were all inversely associated with NHL (TYMS; odds ratio [OR] = 0.57; 0.34-0.94), particularly with diffuse large cell lymphoma (DLCL; OR = 0.29; 0.10-0.82). Further, the MTR 2756AG/GG and the MTHFR 677TT genotypes were associated with increased risk for NHL (OR = 1.3; 0.99-1.7) and follicular lymphoma (FL; OR = 1.8; 0.98-3.1), respectively. We did not observe any significant differences in genotype frequencies of the SHMT1 and RFC polymorphisms between the cases and controls. The associations of DLCL and FL with TYMS 1494del6 and MTHFR 677TT genotypes, respectively, suggest that folate metabolism may play an important role in the pathogenesis of specific subtypes of NHL.
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PMID:Polymorphisms and haplotypes in folate-metabolizing genes and risk of non-Hodgkin lymphoma. 1563 15

The role of nutrient-related genetic susceptibility factors for pre-cancerous lesions is gaining attention. We conducted a study to examine associations between polymorphisms in folate pathway coenzymes (methylenetetrahydrofolate reductase [MTHFR] and methionine synthase [MS]) and cervical intraepithelial neoplasia (CIN) 2 or 3 in a population exposed to folic acid by the food fortification program in the United States. Status of MTHFR and MS and circulating concentrations of folate, vitamins B12, A, E, C and total carotene were ascertained in 170 Caucasian and 266 African-American women positive for high-risk human papilloma virus (HR-HPV). Polymorphism status was determined using polymerase chain reaction assays. Micronutrient concentrations were measured using radiobinding assays, high performance liquid chromatography or spectrophotometry. Presence/absence of CIN 2 or 3 was determined on the basis of histology results and the association with risk factors was examined using multivariable analyses. Eighty women had CIN 2 or 3 lesions and they were compared to 356 women who had CIN 1, ASCUS or normal cytology. We found that women polymorphic for MTHFR were less likely to have CIN 2 or 3 (odds ratio [OR] = 0.43, 95% confidence interval [CI] = 0.23-0.79). No associations were seen with MS polymorphism alone (OR = 0.72, 95% CI = 0.43-1.21); however, women polymorphic for both MTHFR and MS were less likely to have CIN 2 or 3 (OR = 0.21, 95% CI = 0.08-0.62). We conclude that these polymorphisms in the folate metabolic pathway were associated with a lower likelihood of CIN 2 or 3 in a population exposed to adequate amounts of folate from exposure to food fortification with folic acid.
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PMID:Women with polymorphisms of methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS) are less likely to have cervical intraepithelial neoplasia (CIN) 2 or 3. 1551 69

Folate and methionine are important nutrients in the "one-carbon" metabolism that is closely associated with DNA synthesis and DNA methylation. Genetic variation in these pathways may change susceptibility to cancer development. We have previously reported associations between lymphoma risk and germline polymorphisms in genes of methylenetetrahydrofolate reductase (MTHFR C677T and A1298C) and methionine synthase (MTR A2756G), finding the genotype other than the MTHFR 677CC/1298AA to confer a half-risk compared to the MTHFR 677CC/1298AA and a 3-fold higher risk with the MTR GG genotype than the AA/AG genotypes. To confirm the association and explore the histological difference, we extended the previous case series. A case-control study was conducted in Japan with a total of 372 lymphoma cases and 500 noncancer controls examined for genotypes. The relative risks were estimated by unconditional logistic regression analysis. In overall analyses, the age-sex adjusted odds ratio (OR) for the subjects harboring MTHFR 677T or 1298C alleles relative to 677CC/1298AA genotype was 0.58 (95% confidence interval: 0.41-0.83, P = 0.002). The MTR GG genotype showed an OR of 1.75 (0.87-3.52, P = 0.114). These findings were validated in separate analyses of the 273 new incident cases. Subgroup analyses according to histological subtype [diffuse large B-cell lymphoma (DLB), follicular lymphoma (FL), low-grade lymphoma of mucosa associated lymphoid tissue (MALT), and others] illustrated similar associations with certain exceptions for FL and MALT. Our data showed an association between the MTHFR polymorphisms and malignant lymphoma risk for all histological subtypes, although the extent of contribution of these polymorphisms may differ somewhat with histological subtype. Lack of association with MTR polymorphism was also confirmed.
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PMID:Methylenetetrahydrofolate reductase gene (MTHFR) polymorphisms and reduced risk of malignant lymphoma. 1555 Dec 85

Polymorphisms in genes involved in the metabolism of folate and methyl groups have been implicated with risk of colorectal cancer. We evaluated the relation between the polymorphisms 677C --> T of the methylenetetrahydrofolate reductase (MTHFR) and 2756A --> G of the methionine synthase (MTR) genes and risk of colorectal cancer. From the Norwegian JANUS cohort of 309,000 subjects, 2,179 cases were identified and a similar number of controls were selected. The controls were matched for age, gender, time, and place of serum donation. Genotypes were obtained from 2,168 case-control pairs by real-time PCR of serum samples. Risk of colorectal cancer was estimated with conditional and unconditional logistic regression. Median age at diagnosis was 60 years and mean follow-up 13 years. The odds ratio for MTHFR TT versus CC was 0.73 [95% confidence interval (95% CI), 0.58-0.92] and for MTR GG versus AA was 0.65 (95% CI, 0.47-0.90). No interaction between the polymorphisms was found. Relative risk estimates were similar for men and women, and for young and old age at diagnosis. For the MTR GG genotype, risk reduction was observed at the two most distal sites (sigmoideum and rectum) only (P = 0.003). The folate marker, serum total homocysteine (tHcy), was measured in 1,837 subjects. Odds ratio for the upper versus the lower tertile of tHcy was 1.32 (95% CI, 1.04-1.68). No significant effect modification by tHcy levels was detected for either polymorphism. In summary, we found significantly reduced risk of colorectal cancer in subjects with the MTHFR 677 TT and MTR 2756 GG genotypes. No interaction between the polymorphisms, or of either polymorphism with tHcy, was detected.
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PMID:Colorectal cancer and the methylenetetrahydrofolate reductase 677C -> T and methionine synthase 2756A -> G polymorphisms: a study of 2,168 case-control pairs from the JANUS cohort. 1559 77

Genetic determinants for high homocysteine (Hcy) levels are now well known. We studied several single nucleotide polymorphisms (SNP) in Hcy-regulating genes [methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C; methionine synthase (MS) A2756G; methionine synthase reductase (MTRR) A66G] in relation to total plasma Hcy levels, transplant coronary artery disease and thromboembolic episodes in 84 heart transplant patients, and we compared the incidence of these polymorphisms with those in a healthy adult controls. At least one copy of the G allele of the MTRR A66G SNP was found in a significantly greater proportion of cardiac transplant (CTX) recipients compared with controls (94.0% vs. 79.9% respectively). None of the SNP analyzed were correlated with total Hcy plasma levels or the presence of transplant coronary artery disease. However, MS A2756G was significantly associated with cobalamin levels (AA genotype: 290 +/- 122 pmol/l; AG: 381 +/- 151 pmol/l and GG: 415 +/- 100 pmol/l), as was MTRR A66G (AA: 478 +/- 219 pmol/l, AG: 306 +/- 124 pmol/l and GG: 306 +/- 123 pmol/l). MTRR A66G was also correlated with serum folate. No association was found with thromboembolic events. In conclusion, there was a significant difference in the frequency of the G allele genotype of the MTRR A66G in CTX patients versus controls. Differences in cobalamin and folate levels with the MTRR A66G and MS A2756G polymorphisms were noted. Thus, SNP in Hcy-regulating genes may be important determinants of vitamin metabolism in CTX, raising the question of increased vitamin requirements to minimize increased plasma Hcy in this high-risk group.
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PMID:Genetic polymorphisms predisposing to hyperhomocysteinemia in cardiac transplant patients. 1561 80

Drought is a major abiotic stress affecting all levels of plant organization and, in particular, leaf elongation. Several experiments were designed to study the effect of water deficits on maize (Zea mays) leaves at the protein level by taking into account the reduction of leaf elongation. Proteomic analyses of growing maize leaves allowed us to show that two isoforms of caffeic acid/5-hydroxyferulic 3-O-methyltransferase (COMT) accumulated mostly at 10 to 20 cm from the leaf point of insertion and that drought resulted in a shift of this region of maximal accumulation toward basal regions. We showed that this shift was due to the combined effect of reductions in growth and in total amounts of COMT. Several other enzymes involved in lignin and/or flavonoid synthesis (caffeoyl-CoA 3-O-methyltransferase, phenylalanine ammonia lyase, methylenetetrahydrofolate reductase, and several isoforms of S-adenosyl-l-methionine synthase and methionine synthase) were highly correlated with COMT, reinforcing the hypothesis that the zone of maximal accumulation corresponds to a zone of lignification. According to the accumulation profiles of the enzymes, lignification increases in leaves of control plants when their growth decreases before reaching their final size. Lignin levels analyzed by thioacidolysis confirmed that lignin is synthesized in the region where we observed the maximal accumulation of these enzymes. Consistent with the levels of these enzymes, we found that the lignin level was lower in leaves of plants subjected to water deficit than in those of well-watered plants.
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PMID:Water deficits affect caffeate O-methyltransferase, lignification, and related enzymes in maize leaves. A proteomic investigation. 1572 45

We studied whether common polymorphisms in genes involved in folate metabolism affect methotrexate (MTX) sensitivity. Ex vivo MTX sensitivity of lymphoblasts obtained from pediatric patients with acute lymphoblastic leukemia (ALL; n = 157) was determined by the in situ thymidylate synthase inhibition assay after either continuous (21 hours; TSI(50, cont)) or short-term (3 hours; TSI(50, short)) MTX exposure. DNA was isolated from lymphoblasts obtained from cytospin slides. Polymorphisms in methylenetetrahydrofolate reductase (MTHFR 677C>T, MTHFR 1298A>C), methionine synthase (MTR 2756A>G), methionine synthase reductase (MTRR 66A>G), methylenetetrahydrofolate dehydrogenase (MTHFD1 1958G>A), serine hydroxymethyl transferase (SHMT1 1420C>T), thymidylate synthase (TS 2R3R), and the reduced folate carrier (RFC 80G>A) were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or real-time PCR. Patients with the MTHFR 1298AC variant or the MTRR 66 G-allele showed decreased in vitro MTX sensitivity measured under both test conditions. SHMT1 1420TT homozygotes only showed decreased MTX sensitivity in the TSI(50, cont). In conclusion, polymorphisms in the folate-related genes MTHFR, MTRR, and SHMT1 are related to MTX resistance in pediatric patients with ALL.
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PMID:Effect of polymorphisms in folate-related genes on in vitro methotrexate sensitivity in pediatric acute lymphoblastic leukemia. 1579 93

The present review focuses on the B-vitamins, i.e. folate, vitamin B12, vitamin B6 and riboflavin, that are involved in homocysteine metabolism. Homocysteine is a S-containing amino acid and its plasma concentrations can be raised by various constitutive, genetic and lifestyle factors, by inadequate nutrient status and as a result of systemic disease and various drugs. Hyperhomocysteinaemia is a modest independent predictor of CVD and stroke, but causality and the precise pathophysiological mechanism(s) of homocysteine action remain unproven. The predominant nutritional cause of raised plasma homocysteine in most healthy populations is folate insufficiency. Vitamin B12 and, to a lesser extent, vitamin B6 are also effective at lowering plasma homocysteine, especially after homocysteine lowering by folic acid in those individuals presenting with raised plasma homocysteine. However, riboflavin supplementation appears to be effective at lowering plasma homocysteine only in those individuals homozygous for the T allele of the C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene. This gene codes for the MTHFR enzyme that produces methyltetrahydrofolate, which, in turn, is a substrate for the remethylation of homocysteine by the vitamin B12-dependent enzyme methionine synthase. Individuals with the MTHFR 677TT genotype are genetically predisposed to elevated plasma homocysteine, and in most populations have a markedly higher risk of CVD.
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PMID:B-vitamins, homocysteine metabolism and CVD. 1583 Nov 32


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