The methionine synthase reductase (MTRR) A66G polymorphism is a novel genetic determinant of plasma homocysteine concentrations

Recent data suggest that infections, inflammation and the immune system are involved in the process of atherosclerosis. The aim of the present study was to analyze the association of coronary heart disease (CHD) with three inflammation markers, C-reactive protein (CRP), serum amyloid-A (SAA) and plasma fibrinogen. The cross-sectional study included 1400 men aged 45-74 years, who participated in a cardiovascular risk factor survey in Finland in 1997. Participants with prevalent CHD had markedly higher CRP, SAA and fibrinogen levels than participants without CHD. In logistic regression models, the age, smoking, serum cholesterol and systolic blood pressure adjusted odds ratios (2nd, 3rd and 4th quartile as compared with the 1st quartile) of CHD increased gradually with increasing quartile of CRP (1.90, 2.27, 2.64), SAA (1.68, 1.83, 2.41), and fibrinogen (1.60, 1.95, 2.14). The associations weakened somewhat after further adjustment for indicators of obesity, particularly waist hip-ratio. CRP, SAA and fibrinogen levels were markedly lower among CHD patients using cholesterol-lowering medication as compared to non-users. In conclusion, CRP, SAA and fibrinogen, which are markers of inflammation, were positively and significantly associated with prevalent CHD. Central obesity needs to be considered as a confounding factor in the observed associations. These findings support the hypothesis that cholesterol-lowering drugs have an anti-inflammatory effect.     

Methylenetetrahydrofolate reductase 677C>T and methionine synthase 2756A>G mutations: no impact on survival, cognitive functioning, or cognitive decline in nonagenarians

BACKGROUND: Several reports have shown an association between homocysteine, cognitive functioning, and survival among the oldest-old. Two common polymorphisms in the genes coding for methylenetetrahydrofolate reductase (MTHFR 677C>T) and methionine synthase (MTR 2756A>G) have an impact on plasma homocysteine level. METHODS: We examined the effect of the MTHFR 677C>T and MTR 2756A>G genotypes on baseline cognitive functioning, cognitive decline over 5 years measured in three assessments, and survival in a population-based cohort of 1581 nonagenarians. Cognitive functioning was assessed by using the Mini-Mental State Examination (MMSE) and five brief cognitive tests (cognitive composite). RESULTS: There are no differences in MMSE score (p =.83) or in cognitive composite (p =.56) at intake as a function of genotype tested by analysis of variance, whereas sex and social group have a impact on MMSE (p < or =.03), and social group on the cognitive composite (p <.01). The mean MMSE was lower for women than for men. However, considering the group participating in all three assessments, there were no sex-related differences in MMSE (p =.34). The cognitive decline in the group participating in all three assessments was investigated using regression models for the relationship between cognitive performance and genotype, age, sex, and social group and revealed no significant difference. Furthermore, the MTHFR 677T and MTR 2756A heterozygous and homozygous genotype had no significant impact on survival, with hazard ratios of 1.05 (95% confidence interval [CI], 0.93-1.17), 0.93 (95% CI, 0.77-1.14), 1.05 (95% CI, 0.94-1.18), and 0.97 (95% CI, 0.74-1.28). CONCLUSIONS: MTHFR and MTR genotypes are not associated with cognitive functioning, cognitive decline, or survival among nonagenarians.     

Influence of methionine synthase (A2756G) and methionine synthase reductase (A66G) polymorphisms on plasma homocysteine levels and relation to risk of coronary artery disease

BACKGROUND: Elevated plasma total homocysteine (tHcy) is increasingly being recognized as a risk factor for coronary artery disease (CAD) and other defects. Recent genetic studies have characterized molecular determinants contributing to altered homocysteine metabolism. Our objectives were therefore to confirm the relationship of tHcy with CAD and to examine the importance of genetic influence on tHcy in the coronary angiograms and conventional cardiovascular risk factors recorded in 230 subjects. We also determined the genotype frequencies distribution of the A2756G transition of the B12-dependent methionine synthase (MTR) gene and the A66G mutation of the methionine synthase reductase (MTRR) gene. RESULTS: Patients with CAD (n=151) had significantly higher tHcy concentrations than control subjects (15.49 +/- 2.75 micromol/l vs. 11.21 +/- 3.54 micromol/l, P < 0.001). Hyperhomocysteinaemia (tHcy > or =15 micromol/l) was a risk factor for CAD [RR = 4.07, 95% CI: 2.21 - 7.47, P < 0.001]. The homocysteine concentrations were significantly different between smokers and non-smokers, at 15.63 +/- 3.10 vs. 12.45 +/- 3.84 micromol/l, P < 0.05. In addition, smokers with hyperhomocysteinaemia demonstrated a markedly increased risk of CAD (OR = 2.50, 95% CI: 1.67 - 3.32, P < 0.05) compared with non-smokers with normal homocysteine.The 2756G and the 66G allele contribute to a moderate increase in homocysteine levels (P = 0.008 and P = 0.007, respectively), but not to CAD (P > 0.05). Combined MTR and MTRR polymorphisms, the 2756AG + 66AG and the 2756AG + 66GG were the combined genotypes that were a significant risk factor for having hyperhomocysteinaemia (14.4 +/- 2.8 micromol/l, OR = 2.75, IC 95% = 1.21 - 6.24, P=0.016 and 17.9 +/- 4.1 micromol/l, OR = 6.28, IC 95% = 1.46 - 12.1, P = 0.021, respectively). Statistic analysis using the UniANOVA test shows that these two polymorphisms have an interactive effect circulating homocysteine levels (P < 0.05). CONCLUSION: Our data suggest that moderately elevated tHcy levels are prevalent in our population and are associated with an increased risk for CAD. This study provides evidence that the MTR A2756G and MTRR A66G polymorphisms significantly influence the circulating homocysteine concentration. In addition, the MTR and MTRR genes may interact to increase the risk for having hyperhomocysteinaemia.     

Methylenetetrahydrofolate reductase (MTHFR) polymorphism (C677T) in relation to homocysteine concentration in overweight and obese Thais

We analyzed the association between MTHFR (C677T) gene polymorphism with serum concentrations of homocysteine, folate, and vitamin B12 in 37 male and 112 female overweight/ obese Thai volunteers (BMI > or = 25.00 kg/m2), and compared them with 23 male and 90 female control subjects (BMI = 18.5-24.99 kg/m2). Statistically significant higher levels of serum homocysteine were found in the overweight/obese subjects than the control subjects (p < 0.05). Serum folic acid levels in the overweight/obese subjects were significantly lower than the control subjects (p < 0.05). When the data were grouped according to homocysteine concentration and MTHFR gene polymorphism, there were significantly higher homocysteine concentrations in the overweight/obese subjects than the control subjects in wild type gene polymorphism (CC) in the hyperhomocysteine group (homocysteine >10.0 mmol/l) (p < 0.05), but in genotype polymorphism (CC, CT, TT) there were lower folic acid and vitamin B12 concentrations in the overweight/obese subjects than in the control subjects. In the hyperhomocysteine groups, there was no significant difference in the frequencies of MTHFR (C677T) gene polymorphism between the overweight/obese subjects and the control subjects. Folic acid and gene polymorphism were found to be significantly related to the overweight/ obese and control groups in logistic regression analysis (p < 0.05). The results support the supposition that folic acid is more important than vitamin B12.     

Lack of association between plasma homocysteine and angiographic coronary artery disease in the era of fortification of cereal grain flour with folic acid

Homocysteine is associated with coronary disease (CAD). However, the strength of the association after accounting for traditional and emerging risk factors is unclear, particularly since flour fortification with folate was mandated in the USA. We analyzed the association between traditional and emerging risk factors and CAD in 504 patients undergoing clinically-indicated angiography between July 1998 and January 1999. Significant CAD (> or =50% stenosis in > or =1 artery) was present in 271 patients (54%). Mean homocysteine (micromol/l) was 9.36+/-3.07; hyperhomocysteinemia (>13 micromol/l) was present in 7.9% of patients. Mean homocysteine was 9.29+/-3.02 in patients with no disease (no stenoses or stenoses <10%), 9.09+/-2.47 in patients with mild disease (stenoses 10-50%), 9.12+/-2.39 in patients with one vessel disease (VD) (>50% stenosis in one coronary artery), 9.28+/-3.19 in patients with two VD, and 10.1+/-3.89 in patients with three VD (P=0.0793). Multivariate analysis that included age, gender, smoking, LDL, HDL, Lp(a), apo A1, and apo B revealed no independent association between quartile of homocysteine and odds ratio (OR) for CAD. In summary, we found no association between homocysteine and CAD on angiography. The homocysteine-lowering effect of folate-fortified flour, or the inclusion of many traditional and emerging risk factors in multivariate analysis, are potential explanations.     

Methylenetetrahydrofolate reductase (MTHFR) C677T genetic polymorphism and late infarct-related coronary artery patency after thrombolysis

In patients with acute myocardial infarction (AMI), a persistently occluded infarct-related artery (IRA) is associated with unfavorable prognosis and genetic factors may be contributing factors to thrombolysis failure. One-hundred and one consecutive patients treated with intravenous thrombolysis during AMI were blind-tested for methylenetetrahydrofolate reductase (MTHFR) and circulating homocysteine levels and underwent protocol angiography 14 ± 6 days after the event. IRA was patent in 61 patients and occluded in 40. Overall MTHFR 677TT frequency was 22%. Patients with MTHFR 677TT homozygosis had higher prevalence of occluded IRA (73%) versus those with MTHFR 677CT/CC genotype (30%, P < 0.001); MTHFR 677TT genotype predicted independently the risk of IRA occlusion with a specificity of 90% (odds ratio 3.8, 95% confidence interval 1.1–9.1; P = 0.03). Moreover, patients with occluded IRA and MTHFR 677TT genotype had the highest homocysteine levels (21 ± 7.6 μmol/l vs. ≤14.9 ± 3.8 μmol/l; P = 0.011). In patients with AMI, MTHFR 677TT homozygosis is independently associated with a persistently occluded IRA after thrombolysis. This finding may have pathophysiological and therapeutic implications for recanalization strategies in patients with AMI.     

老年人亚甲基四氢叶酸还原酶、蛋氨酸合成酶基因多态性及同型半胱氨酸水平与冠心病的关系

目的探讨老年人同型半胱氨酸(Hcy)水平与冠心病的关系,并对亚甲基四氢叶酸还原酶(MTHFR)A1298C基因多态性、蛋氨酸合成酶(MS)A2756G基因多态性与Hcy水平及冠心病的关系进行探讨. 方法 177例老年人为研究对象,其中129例冠状动脉造影证实为冠心病患者(冠心病组),48例冠状动脉造影完全正常(对照组).荧光偏振免疫分析法测定Hcy水平,聚合酶链反应-限制性片段长度多态性方法(PCR-RFLP)分析MTHFR A1298C、MS A2756G基因多态性. 结果冠心病组血Hcy水平显著高于对照组[(16.2±8.6)对(12.7±5.0)μmol/L,P<0.01].MTHFR A1298C基因多态性CC纯合子和AC杂合子血Hcy水平均显著低于AA野生型[(9.1±2.5)、(13.5±6.6)对(16.0±8.3)μmol/L,P<0.01],CC纯合子和AC杂合子间血Hcy水平差异无显著性(P>0.05);MTHFR 1298CC纯合子在冠心病组的分布频率显著低于对照组(3.1%对14.6%,P<0.05).MS A2756G基因多态性GG+AG基因型血Hcy水平显著低于AA野生型[(12.8±6.5)对(15.6±8.1)μmol/L,P<0.05],MS 2756GG+AG基因型在冠心病组的分布频率显著低于对照组(9.3%对20.8%,P<0.05). 结论本研究入选的老年人群中,冠心病患者血Hcy水平升高.MTHFR 1298CC基因型及MS 2756 GG +AG基因型与低血Hcy水平相关,它们可能会通过降低血Hcy水平而减少老年人冠心病的发生.     

Methylenetetrahydrofolate reductase C677T and methionine synthase A2756G gene polymorphisms and associated risk of cardiovascular diseases: A study from Jammu region

AimPotent risk factors at both genetic and non-genetic levels are accountable for susceptibility and instigation of different cardiovascular phenotypes. Recently, homocysteine is being identified as an important predictor for cardiovascular diseases. Homocysteine remethylation plays a key role in the synthesis of methionine and S-adenosine methionine. Methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) genes are known to regulate the homocysteine remethylation reaction and higher homocysteine level is significantly associated with diverse cardiovascular phenotypes. In this context, we aimed to carry out a study on the association of MTHFR (C677T) and MTR (A2756G) gene polymorphism with CVD in population of Jammu region of J&K state.Materials and methodsA total of 435 individuals were enrolled (195 CVD patients and 240 controls) for the case–control study. Genotyping of MTHFR C677T and MTR A2756G gene polymorphism was done by PCR-RFLP technique. Biochemical parameters were estimated by biochemical analyser.ResultsMetabolic variables such as serum LDL-C, TC and TG were significantly higher in patients (p < 0.0001), whereas serum HDL-C was higher in controls. Majority of the patients were having history of hypertension (57.44%; p < 0.0001) as a concomitant condition. The evaluation of genetic association showed that, MTHFR C6877T (OR: 8.89, 95% CI: 2.01–39.40) and MTR A2756G (OR: 1.48, 95% CI: 1.09–2.00) polymorphisms associated with higher risk of CVD.ConclusionThe present study reveals significant differences in nongenetic variables among patients and control as well as association of gene polymorphisms with CVD risk.     

亚甲基四氢叶酸还原酶基因C677T突变与高尿酸血症的相关性研究

目的探讨高尿酸血症（HUM）与亚甲基四氢叶酸还原酶（MTHFR）基因C677T突变及高血糖、肥胖和高血压等的相关性。方法从青岛地区糖尿病流行病学调查数据库中，随机选取HUM＋T2DM患者79例、HUM无T2DM患者（HUM组）90例、并选取T2DM无HUA患者（DM组）90例和健康对照（NC）91例。采用聚合酶链反应-限制性片段长度多态性技术检测MTHFR基因突变。结果HUM组和HUM＋T2DM组MTHFR677T等位基因频率分别为46．7％和51．3％，TT基因型频率分别为23．3％和26．6％，两组差异无统计学意义（P〉0．05）；T等位基因和TT基因型频率在NC组和DM组间差异无统计学意义（P〉0．05）；而HUM组和HUM＋T2DM组MTHFR677T等位基因型频率和TT基因型频率均分别高于NC组和DM组（P〈0．005）。CT和TT基因型患者平均血尿酸水平（分别为394．2μmol／L和465．8μmol／L）明显高于CC基因型者（347．3μmol／L）（P〈0．05）。多因素logistic回归分析表明，调整BMI、SBP、TG、TC及饮酒等因素后显示，MTHFR基因型是HUM患病的独立危险因素。结论MTHFR基因C677T突变是青岛地区人群发生HUM的独立危险因素。     

Methylenetetrahydrofolate reductase mutation (677C-->T) negatively influences plasma homocysteine response to marginal folate intake in elderly women

Individuals who are homozygous for the methylenetetrahydrofolate reductase (MTHFR) 677C --> T mutation have depressed serum folate (SF) and elevated plasma total homocysteine (tHcy) concentrations, which may affect folate requirements and increase the risk for coronary artery disease. A controlled metabolic study (14 weeks) using a depletion/repletion protocol was performed in women (aged 60 to 85 years, N = 33) to provide age-specific data on the effects of the MTHFR mutation on SF and tHcy status. Subjects consumed a moderately folate-deplete diet (118 microg/d) for 7 weeks, followed by 7 weeks of folate repletion with 200 or 415 microg/d provided as two different treatments. Following folate depletion, the mean SF concentration was lower for homozygous (P = .017) versus heterozygous subjects. Homozygotes for the 677C --> T mutation showed a higher (P = .015) percent increase in plasma tHcy (44%) than heterozygous (20%) or normal (15%) subjects. At week 7, the mean plasma tHcy concentration was higher in homozygous subjects (12.5 +/- 5.3 micromol/L, mean +/- SD) versus the heterozygous (10.8 +/- 3.8 micromol/L, P = .008) or normal (11.3 +/- 2.7 micromol/L, P = .001) genotype groups. Following folate repletion, plasma tHcy concentrations were not different between genotype groups, despite a higher (P < .016) SF concentration in subjects with the homozygous genotype. These data suggest that older women who are homozygous for the MTHFR 677C --> T mutation may be at risk for greater elevations in plasma tHcy in response to moderately low folate intake as compared with individuals with the normal or heterozygous genotypes.     

Methionine synthase reductase MTRR 66A > G has no effect on total homocysteine, folate, and Vitamin B12 concentrations in renal transplant patients

The association of variants of the gene encoding methionine synthase reductase (MTRR) with hyperhomocysteinemia, folate and Vitamin B(12) status in kidney graft recipients is unknown. We examined two mutations in MTRR in a cross-sectional study of 733 kidney graft recipients. The allele frequency of MTRR 66G was 0.55. 369 patients (50.3%) were heterozygous and 219 patients (29.9%) were homozygous for the mutation. None of the patients showed the 997C > G mutation. The allelic variants of MTRR 66A > G showed no significant association with total homocysteine (tHcy) levels, both in univariate analyses, and in a multivariate model controlling for age, gender, body mass index, renal function, time since transplantation, underlying kidney disease, as well as the MTHFR 677C > T/1298A > C genotypes. Similarly, no significant associations between the MTRR 66A > Ggenotypes and plasma folate or Vitamin B(12) levels were found. In conclusion, MTRR 66A > G has no major effect on tHcy, folate, or Vitamin B(12) plasma concentrations in kidney graft recipients.     

The 1298A-->C polymorphism in methylenetetrahydrofolate reductase (MTHFR): in vitro expression and association with homocysteine

A common mutation in methylenetetrahydrofolate reductase (MTHFR), 677C-->T, is associated with reduced enzyme activity, a thermolabile enzyme and mild hyperhomocysteinemia, a risk factor for vascular disease. Recently, a second common mutation (1298A-->C; glutamate to alanine) was reported, but this mutation was suggested to increase homocysteine only in individuals who carried the bp677 variant. To evaluate the functional consequences of this mutation, we performed site-directed mutagenesis and in vitro expression. For in vivo assessment of clinical impact, we examined the 1298A-->C genotypes and plasma homocysteine in 198 individuals from the NHLBI Family Heart Study that had previously been assessed for the 677 substitution. Site-directed mutagenesis of the human cDNA was performed to generate enzymes containing each of the two mutations, as well as an enzyme containing both substitutions. Enzyme activity and thermolability were assessed in bacterial extracts. The activity of the wild-type cDNA was designated as 100%; mutant enzymes containing the 1298 and 677 mutations separately had 68% (+/-5.0) and 45% (+/-10.8), respectively, of control activity while the enzyme containing both mutations had 41% (+/-12.8) of control activity. The 1298 mutation was not associated with a thermolabile enzyme. In the Family Heart Study, fasting homocysteine was significantly higher (P<0.05) in individuals heterozygous for both substitutions, compared to individuals who carried only the 677C-->T variant. This study suggests that two variants in MTHFR should be assessed as genetic risk factors for hyperhomocysteinemia.     

Identification of six methylenetetrahydrofolate reductase (MTHFR) genotypes resulting from common polymorphisms: impact on plasma homocysteine levels and development of coronary artery disease

Although three common MTHFR polymorphisms (C677T, A1298C, T1317C) have been reported, only polymorphism C677T has been investigated intensively as a risk factor for coronary artery disease (CAD). We investigated polymorphism frequencies, allelic associations and the effect of the resulting MTHFR genotypes on total plasma homocysteine (tHcy) levels and on coronary risk in a case-control study with 1000 angiographically confirmed Middle-European CAD patients and 1000 matched controls. Three out of four theoretically possible MTHFR haplotypes were detected: *1 (677C, 1298A), *2 (677T, 1298A), and *3 (677C, 1298C). The frequencies were *1: 36.4 and 34.4%; *2: 30.8 and 32.3%; and *3: 32.8 and 33.3%, in cases and controls, respectively. Only one patient was heterozygous for 1317C. None of the six resulting genotypes showed significant influence on tHcy levels. Moreover, there was no significant association with CAD risk or with disease severity or early disease manifestation. In the subgroup presenting with acute coronary syndromes, MTHFR genotypes *2/*3 and *3/*3 were surprisingly underrepresented (relative risk of *3/*3, 0.40; 95% confidence interval 0.20-0.79, P=0.009). We conclude from our genotype-based analysis that, in this well-fed Middle-European population, the observed common allelic variants of the MTHFR gene have no significant influence on tHcy levels or on the chronic process of CAD development.     

The 19-bp deletion of dihydrofolate reductase (DHFR), methylenetetrahydrofolate reductase (MTHFR) C677T, Factor V Leiden, prothrombin G20210A polymorphisms in cancer patients with and without thrombosis

Venous thromboembolism (VTE) is a common complication in cancer patients. Several genetic risk factors related to thrombophilia are known; however, their contributions to thrombotic tendency in cancer patients have conflicting results. In the present study, we have focused on the prevalence of methylenetetrahydrofolate reductase (MTHFR) C677T, dihydrofolate reductase (DHFR) 19-bp deletion within intron 1, factor V Leiden (FVL), and prothrombin (PT) G20210A polymorphisms in cancer patients with and without VTE. The study consisted of 63 cancer patients with VTE (group 1) and 124 cancer patients who had no evidence of VTE (group 2). Four gene polymorphisms were determined by the method of polymerase-chain-reaction-based DNA analysis. The prevalence of DHFR 19-bp deletion and MTHFR C677T polymorphisms was similar in two groups (p > 0.05). The frequency of FVL was significantly higher in group1 compared with group 2 (31.7% vs. 1.6%, p < 0.0001), but PT G20210A polymorphism was not associated with VTE. Cancer patients with thrombosis should be evaluated for FVL, but routine screening for PT G20210A, MTHFR C677T and DHFR 19-bp deletion polymorphisms is not suggested.