A mutation in the methylenetetrahydrofolate reductase gene is not associated with increased risk for coronary artery disease or myocardial infarction

MTHFR gene polymorphisms and susceptibility to myocardial infarction: Evidence from meta-analysis and trial sequential analysis

Background

This meta-analysis aimed to provide a comprehensive assessment of the association between Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms, specifically C677T and A1298C, and the susceptibility to myocardial infarction (MI).

Methods

A systematic literature search was conducted in MEDLINE, Web of Science, and Scopus until April 2023 to identify studies investigating the relationship between MTHFR gene polymorphisms (C677T and A1298C) and the risk of MI.

Results

The analysis included 66 studies involving 16,860 cases and 20,403 controls for the C677T polymorphism and 18 studies comprising 3162 cases and 3632 controls for the A1298C polymorphism. Significant associations were observed between the C677T polymorphism and MI risk in various genetic models: dominant (OR = 1.16, 95 % CI = 1.06-1.28, P = 0.008), recessive (OR = 1.20, 95 % CI = 1.12-1.28, P < 0.001), allelic (OR = 1.13, 95 % CI = 1.06-1.21, P < 0.001), TT vs. CC (OR = 1.19, 95 % CI = 1.05-1.36, P < 0.001), and CT vs. CC (OR = 1.11, 95 % CI = 1.02-1.21, P = 0.01). Furthermore, an overall analysis indicated a marginally significant association between the A1298C polymorphism and MI risk in the recessive model (OR = 1.27, 95 % CI = 1.06-1.51, P = 0.008), allelic model (OR = 1.18, 95 % CI = 1.01-1.39, P = 0.03), and CC vs. AA model (OR = 1.22, 95 % CI = 1.01-1.47, P = 0.04). Meta-regression analysis revealed that none of the potential factors contributed to the observed heterogeneity.

Conclusions

This meta-analysis revealed an association between MTHFR gene C677T and A1298C polymorphisms and the risk of MI.

The Effects of Resistin Gene Polymorphism on Pain Thresholds and Postoperative Sufentanil Consumption in Gastric Cancer Patients

Purpose

As an adipocyte-secreted hormone, resistin is linked to inflammation, insulin resistance and atherosclerosis. Currently, resistin is proposed as a novel biomarker for postoperative pain intensity. However, due to the various types of surgery and limited numbers of studies, previous conclusions should be validated. This study aimed to explore the effect of resistin polymorphism (rs3745367) on pain thresholds and sufentanil consumption in gastric cancer patients.

Patients and Methods

A total of 148 gastric cancer patients enrolled in this study had their pain thresholds measured before surgery. After the exclusion of 16 patients, the characteristics of demography and clinic, numerical rating scale (NRS) and sufentanil consumption of 132 patients were recorded. Rs3745367 of resistin was identified by Sanger sequencing. Multivariate linear regression analysis was performed for sufentanil consumption and mechanical pain threshold.

Results

The distributions of the GG, AG, and AA genotypes of rs3745367 among the participants were 54 (40.9%), 65 (49.2%), and 13 (9.9%), respectively. The mechanical pain threshold (P=0.04) and postoperative sufentanil consumption in the 1st 24 h (P=0.03) were significantly different among GG, AG, and AA genotype carriers. There was no significant difference among the three genotypes for the heat pain threshold and cold pain threshold. Regarding the NRS, no statistically significant difference among the three different genotypes was found 24 h postoperatively.

Conclusion

Rs3745367 of resistin is associated with the mechanical pain threshold and postoperative sufentanil consumption in gastric cancer patients. Patients with the AA genotype of rs3745367 present an increased mechanical pain threshold and decreased postoperative sufentanil consumption.

The role of MTHFR C677T and ALDH2 Glu504Lys polymorphism in acute coronary syndrome in a Hakka population in southern China

Background

Acute coronary syndrome (ACS) is the most serious type of coronary heart disease and is a global medical burden. The pathogenesis of ACS is very complex and still poorly understood. Epidemiologic studies have revealed that the manifestation of ACS are the results of the interactions between multiple environmental and genetic factors. The present study aimed to investigate the role of polymorphisms of MTHFR C677T and ALDH2 Glu504Lys as risk factors for ACS in a Hakka population in southern China.

Methods

Between September 1, 2015 and October 31, 2017, a total of 1957 individuals, including 860 ACS patients and 1097 controls were recruited. Blood samples were collected and genotypes were determined by DNA microarray chip method and direct sequencing method.

Results

For the MTHFR C677T polymorphism, frequencies of CC, CT, and TT genotypes were 53.60% versus 55.33, 39.53% versus 38.65 and 6.86% versus 6.02% in patients with ACS versus controls, respectively(p > 0.05). The differences in genotype frequencies between the ACS patients and controls in the three genetic model were not statistically significant. For the ALDH2 Glu504Lys polymorphism, the frequencies of ALDH2*1*1, ALDH2*1*2, and ALDH2*2*2 genotypes were 48.72, 42.67 and 8.6% in the ACS patients, respectively, while these were 53.33, 39.11 and 7.57% in the controls, respectively, showing no significant difference in the distribution of the ALDH2 genotype between the groups. Using the wild genotype ALDH2*1*1 as reference, relative risk analysis revealed a slightly increased risk for ACS in individuals with the ALDH2*1*2 plus ALDH2*2*2 genotypes (odds ratio (OR) = 1.203, 95% confidence interval (CI) = 1.006–1.438, p = 0.043). In a multivariate logistic regression model, even after adjusting for potential covariates, the association between ALDH2 *2 allele and ACS remained significant (OR = 1.242, 95% CI = 1.045–1.561, p = 0.038).

Conclusions

We present findings regarding the possible clinical impact of the ALDH2*2 variant on ACS patients in a Hakka population in southern China and our findings might help to stratify the high-risk ACS patients and implement appropriate strategies for this genetic subpopulation to ultimately guide the precision preventive procedures in the future.

Uncertain thrombophilia markers

The development of venous thromboembolism (VTE), which includes deep-vein thrombosis and pulmonary embolism, may be associated with inherited or acquired risk factors that can be measured in plasma or DNA testing. The main inherited thrombophilias include the plasma deficiencies of the natural anticoagulants antithrombin, protein C and S; the gain-of-function mutations factor V Leiden and prothrombin G20210A; some dysfibrinogenaemias and high plasma levels of coagulation factor VIII. Besides these established biomarkers, which usually represent the first-level laboratory tests for thrombophilia screening, a number of additional abnormalities have been less consistently associated with an increased VTE risk. These uncertain causes of thrombophilias will be discussed in this narrative review, focusing on their clinical impact and the underlying pathogenetic mechanisms. Currently, there is insufficient ground to recommend their inclusion within the framework of conventional thrombophilia testing.

C667T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene and susceptibility to myocardial infarction: A systematic review and meta-analysis

MTHFR C677T and A1298C polymorphisms have been reported to be associated with the risk of myocardial infarction (MI), although the results of previous studies have been inconsistent. The aim of this study was to explore whether these polymorphisms play a role in the genetic susceptibility to MI. A comprehensive search of MEDLINE and EMBASE databases was conducted for studies evaluating the association between the C667T and A1298C polymorphisms and MI risk. Odds ratios (OR) with 95% confidence intervals (CIs) were calculated to assess the strength of association in the dominant model, recessive model, allelic model, and genotypes contrast. A total of 47 studies were finally included in this meta-analysis. Overall, the results showed no statistically significant association between C667T and A1298C polymorphisms and MI risk. However, in subgroup analysis by ethnicity, the T allele of C677T polymorphism was associated with a 63% increased risk of MI compared with the C allele (T vs. C, OR=1. 63, 95%CI=1.15-2.10, fixed effects) in African populations, while compared to wild homozygote genotype, CT genotype was associated with a decreased risk of MI in North American populations (CT vs. CC, OR=0.81, 95%CI=0.64-0.98, fixed effects). Moreover, C677T polymorphism had a protective effect against MI risk under the dominant model (OR=0.93, 945%CI=0.87-0.99, fixed effects) in elderly (≥50) population. The A1298C polymorphism was not significantly associated with MI risk. Unlike A1298C polymorphism, C677T polymorphism was associated with risk of MI in African, North American, and elderly populations.

Methylenetetrahydrofolate reductase C677T polymorphism is associated with increased risk of coronary artery disease in young South African Indians

Methylenetetrahydrofolate reductase (MTHFR) reduces 5',10'-methylenetetrahydrofolate to 5'-methyltetrahydrofolate, and is involved in remethylation of homocysteine to methionine, two important reactions involved in folate metabolism and methylation pathways. The common MTHFR C677T single nucleotide polymorphism (SNP) (rs1801133) has been associated with raised levels of homocysteine, a well known risk factor for coronary artery disease (CAD). CAD is a major cause of mortality worldwide. The age of onset of this chronic disorder is on the decline, particularly in the Indian population. Indians in South Africa (SA) have a higher prevalence of premature CAD compared to Black South Africans. The MTHFR C677T SNP has not been investigated in the SA Indian population. The present study therefore investigated the MTHFR C677T SNP in young SA Indian males with CAD compared to young Indian and Black male controls. A total of 290 subjects were recruited into this study which included 106 CAD patients (diagnosed on angiography, mean age 37.5, range 24-45 years), 100 Indian male controls (mean age 37.5, range 28-45 years), and 84 Black male controls (mean age 36.4, range 25-45). Polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) was used to genotype CAD patients and healthy controls. Data for clinical markers were obtained from pathology reports. There was a significant association between the 677 MTHFR variant (T) allele and CAD patients compared to the healthy Indian controls (p=0.0353, OR=2.105 95% CI 1.077-4.114). Indian controls presented with a higher frequency of the variant allele compared to Black controls (7% vs. 2% respectively, p=0.0515 OR=3.086 95% CI 0.9958-9.564). The MTHFR C677T SNP did not influence levels of total cholesterol, LDL, HDL, triglycerides, fasting glucose, fasting insulin, HbA1c or hsCRP. The higher frequency of the MTHFR 677 variant allele in South African Indians may be a contributing factor to the higher risk profile for the development of premature CAD in Indians.

Comparison of homocysteinemia and MTHFR 677CT polymorphism with Framingham Coronary Heart Risk Score

OBJECTIVE

The Framingham Coronary Heart Disease Risk Score is an important clinical tool. The aim of this cross-sectional study was to compare plasma homocysteine levels and polymorphism 677CT MTHFR with this score to determine the utility of these new biomarkers in clinical practice.

METHODS

Plasma homocysteine levels determined by chemiluminescence and polymorphism 677CT MTHFR, detected by PCR-RFLP, were compared with Framingham coronary risk score in a cross-sectional survey on 68 men and 165 women.

RESULTS

Coronary heart disease risk augmented with an increase in the quartile of plasma homocysteine. In the 2nd, 3rd and 4th quartile of plasma homocysteine, men showed significantly (P<0.001) higher risk than women. For the highest quartile of plasma homocysteine, OR of high-risk (10-year risk≥20%) compared with the lowest quartile was 17.45 (95% CI: 5.79-52.01). Frequencies of CT and TT genotype and T allele were not over-represented in the individuals with score≥10%. The higher plasma homocysteine concentrations in individuals with score≥10% with respect to those with low risk (P<0.005 and P<0.001) were not due to the presence of T allele. The T allele (CT+TT genotypes) of the MTHFR C677T polymorphism was not significantly associated with an increased risk of coronary disease (OR=1.09, 95% CI=0.50-2.39, P=0.844).

CONCLUSIONS

The present study demonstrated an association between plasma homocysteine levels and the severity of coronary heart disease estimated with the Framingham coronary risk score, and this association appeared to be independent on the genotype of MTHFR. We postulate that plasma homocysteine is effective enough, considered even in isolation.

Association of homocysteine and methylene tetrahydrofolate reductase (MTHFR C677T) gene polymorphism with coronary artery disease (CAD) in the population of North India

The implications of the methylene tetrahydrofolate reductase (MTHFR) gene and the level of homocysteine in the pathogenesis of coronary artery disease (CAD) have been extensively studied in various ethnic groups. Our aim was to discover the association of MTHFR (C677T) polymorphism and homocysteine level with CAD in north Indian subjects. The study group consisted of 329 angiographically proven CAD patients, and 331 age and sex matched healthy individuals as controls. MTHFR (C677T) gene polymorphism was detected based on the polymerase chain reaction and restriction digestion with HinfI. Total homocysteine plasma concentration was measured using immunoassay. T allele frequency was found to be significantly higher in patients than in the control group. We found significantly elevated levels of mean homocysteine in the patient group when compared to the control group (p = 0.00). Traditional risk factors such as diabetes, hypertension, smoking habits, a positive family history and lipid profiles (triglyceride, total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol), were found significantly associated through univariate analysis. Furthermore, multivariable logistics regression analysis revealed that CAD is significantly and variably associated with diabetes, hypertension, smoking, triglycerides and HDL-cholesterol. Our findings showed that MTHFR C677T polymorphism and homocysteine levels were associated with coronary artery disease in the selected population.

Methylenetetrahydrofolate reductase gene polymorphism and risk of premature myocardial infarction

BACKGROUND

Elevated plasma homocysteine level is an independent risk factor for cardiovascular disease. A common mutation (nucleotid 677C-T) in the gene coding for methylenetetrahydrofolate reductase (MTHFR) has been reported to reduce the enzymatic activity of MTHFR and is associated with elevated plasma levels of homocysteine, especially in subjects with low folate intake.

HYPOTHESIS

Methylenetetrahydrofolate reductase T/T genotype may be a risk factor for premature MI in Turkish population who are known to have low folate levels.

METHODS

The study group was comprised of 96 men (aged <45 years) with premature myocardial infarction (MI) and 100 age- and gender-matched controls who had no history or clinical evidence of coronary artery disease (CAD) and/or MI. DNA was extracted from peripheral blood and genotypes were determined by polymerase chain reaction, restriction mapping with HinfI, and gel electrophoresis. Conventional risk factors for CAD were prospectively documented.

RESULTS

Allele and genotype frequencies among cases and control subjects were compatible with Hardy-Weinberg equilibrium. The frequencies of T/T, C/T, and C/C genotypes among patients with MI and control subjects were 15.6, 40.6, and 43.8%, and 5, 35, and 60%, respectively. Multivariate analyses identified smoking, MTHFR C/T polymorphism, diabetes mellitus, family history of CAD, and hypertension as the independent predictors of premature MI. Defining patients with non-T/T genotype (C/C and C/T combined) as reference, the relative risk of MI for subjects with T/T genotype was 5.94 (95% confidence interval: 1.96-18.02, p = 0.0016).

CONCLUSIONS

Our findings suggest that C677T transition in the MTHFR gene may be a risk factor for premature MI in Turkish men.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Thermolabile methylenetetrahydrofolate reductase C677T polymorphism and homocysteine are risk factors for coronary artery disease in Moroccan population

Increased plasma total homocysteine (tHcy) levels have been shown to be a risk factor for coronary artery disease (CAD). The common methylenetetrahydrofolate reductase C677T (MTHFR C677T) polymorphism has been reported to be a strong predictor of mild hyperhomocysteinaemia (HHcy). We assessed whether this mutation was associated with increased risk of CAD and plasma levels of tHcy. We also evaluated interactions between this polymorphism, mild elevated tHcy levels and conventional risk factors of CAD. Method. Using PCR-RFLP analysis, we studied the frequency of the C677T genotypes and its effect on CAD and on tHcy concentrations in 400 subjects without and with CAD angiographically confirmed. There were 210 subjects with CAD and 190 subjects without CAD. Results. The frequencies of the C677T genotypes were 53% (59.5% in controls versus 48.1% in cases), 34.8% (32.1 in controls versus 37.1 in cases), and 11.8% (8.4% in controls versus 14.8% in cases), respectively, for 677CC, 677CT, and 677TT. The genotype frequencies were significantly different between case and control groups (P < .05). The 677T allele enhances the risk of CAD associated to HHcy (P < .01). In multivariate analysis models, MTHFR C677T polymorphism effect on CAD was masked by other risk factors. HHcy was only and independently influenced by MTHFR polymorphism and smoking habits, and it is a strong predictor of CAD independently of conventional risk factors. Conclusion. Our data suggest that HHcy is strongly and independently associated to CAD risk increase; and MTHFR C677T polymorphism and smoking habits were the main predictors of tHcy levels. The CAD risk increase is mainly associated with mild HHcy in 677TT, whereas in 677CT and 677CC it is mainly associated with the conventional risk factors.

G1793A polymorphisms in the methyl- enetetrahydrofolate gene: Effect of folic acid on homocysteine levels

Mutations or polymorphisms in the gene of the enzyme methylenetetrahydrofolate (MTHFR) are associated with hyperhomocysteinemia and possibly with an elevated risk for vascular diseases. A study was conducted on 83 individuals with type 2 diabetes in order to determine the allelic and genotypic frequencies of the G1793A mutation and to assess the effect of folic acid supplementation on plasma homocysteine concentrations. The patients were attended by the Diabetes and Hypertension Program--Balneario Camboriu/SC and received daily supplements containing 1 mg of folic acid for 3 months. DNA was previously extracted from leukocytes and the G1793A mutation was detected by PCR-RFLP. Blood samples were collected during the basal period and after supplementation for the determination of homocysteine by HPLC, and of folic acid and vitamin B(12) by RIA. The allele frequency for the G1793A mutation was 3.01% and no homozygous individuals with mutant alleles were detected. Hyperhomocysteinemia was diagnosed in 27.71% of the patients, folic acid deficiency in 15.66%, and vitamin B(12) deficiency in 7.23%. Plasma homocysteine concentrations were inversely correlated with folic acid (r = -0.27, p = 0.01) and vitamin B(12) (r = -0.21; p = 0.05) concentrations. The individuals with a heterozygous genotype for the G1793A mutation showed borderlines or deficient values in folic acid and vitamin B(12) concentrations compared to individuals with a normal genotype. Hyperhomocysteinemia and the vitamin deficiencies presented by type 2 diabetic individuals, included with a heterozygous genotype for the G1793A mutation in the MTHFR gene, reached normal values by daily folic acid supplementation.

Candidate gene susceptibility variants predict intermediate end points but not angiographic coronary artery disease

BACKGROUND

Moderate-sized studies have suggested that variants of candidate genes can influence laboratory markers of coronary artery disease (CAD), but whether they predict parallel changes in clinical CAD risk is unknown.

METHODS

We studied a single nucleotide polymorphism (SNP) from each of the 5 candidate genes for intermediate (laboratory) and clinical (angiographic CAD) end points in a large cohort of patients. The 5 gene SNPs were cholesteryl ester transfer protein (CETP) TaqIB (N = 3219), ATP-binding cassette (ABCA1) G596A (N = 3302), lipoprotein lipase (LPL) HindIII (N = 909), plasminogen activator inhibitor, type 1 (PAI1), 4G/5G (N = 1142), and hepatic lipase (HL) C-541T (N = 4704). Intermediate outcomes were high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs). Cases had 1- to 3-vessel CAD (> or = 70% stenosis); controls had angiographically normal coronaries.

RESULTS

Cholesteryl ester transfer protein predicted HDL (mean, B1B1 35.0 mg/dL, B2B2 38.6 mg/dL; P < .001) but not CAD (B1B1 74%, B2B2 70%; adjusted P = .35, odds ratio [OR] = 0.89). ABCA1 predicted HDL (mean, GG = 36.4 mg/dL, AA = 39.2 mg/dL; P = .02) but not CAD (GG 74%, AA 75%; adjusted P = .96, OR = 0.99). HL predicted HDL (CC 37.1 mg/dL, TT 40.9 mg/dL; P = .002) but not CAD (CC 71%, TT 68%, adjusted P = .66, OR = 0.94). LPL predicted TG (median: [++] 134, [--] 98 mg/dL; P < .001) but not CAD ([++] 79%, [--] 79%; adjusted P = .99, OR = 1.00). PAI1 predicted TG (median, 4G4G 130 mg/dL, 5G5G 148 mg/dL; P = .16), but not CAD (4G4G 77%, 5G5G 76%; adjusted P = .62, OR = 1.11).

CONCLUSIONS

Five SNPs predicted differences in risk-related lipids but not angiographic CAD. These discrepancies suggest that genetic determinants of CAD are complex and intermediate phenotypes are poor surrogates. These findings have important implications for future directions in genetic research.

Lack of association of methylenetetrahydrofolate reductase 677C>T mutation with coronary artery disease in a Pakistani population

Pakistanis belong to the South Asian population which has the highest known rate of coronary artery disease. Folic acid deficiency also appears to be highly prevalent in this population. Methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism decreases the activity of this enzyme and can be associated with mild to moderate hyperhomocysteinemia in homozygotes, particularly when there is folic acid deficiency, as well as with coronary artery disease. To assess the value of genotyping the MTHFR 677C>T dimorphism, we carried out a case-control study of dimorphism 677C>T for putative association with myocardial infarction (MI) among Pakistani nationals. We investigated a sample population of 622 Pakistanis consisting of 225 controls and 397 patients with clinical diagnosis of acute MI (AMI). MTHFR C677T alleles were determined by assays based on polymerase chain reaction and restriction endonuclease analysis. Frequencies of C alleles were 0.87 among controls and 0.86 among AMI patients. The MTHFR 677C>T dimorphism showed no association with MI (χ² = 0.25, 1df, P=0.62), serum levels of folate and vitamin B12 and plasma level of vitamin B6. A significant association, however, was found between homozygous 677T genotype and plasma levels of homocysteine. Multivariate analysis of the data showed that in case of log homocysteine, age and MTHFR genotypes were significantly different (P<0.001). In case of B12, smoking and age were found to be statistically significant (P<0.001), while in case of serum folate only smoking was found to be significant (P<0.001). The results indicate that MTHFR 677C>T polymorphism, though associated with homocysteine levels, confers no significant risk of coronary artery disease in the Pakistani population investigated here. We suggest that the higher incidence of AMI in South Asia occurs through mechanisms other than the MTHFR related pathways.

C677T mutation of methylenetetrahydrofolate reductase gene and serum homocysteine levels in Turkish patients with coronary artery disease

Elevated levels of homocysteine is a risk factor for coronary artery disease. The C677T transition in methylenetetrahydrofolate reductase (MTHFR) is associated with increased homocysteine levels in the general population. We analysed the association between the MTHFR C677T polymorphism and serum homocysteine concentrations in patients with coronary artery disease (CAD). Allele frequencies for the 'C' (wild-type) and 'T' alleles were 0.71 and 0.29 in CAD patients and 0.70 and 0.30 in controls, respectively. There was no difference in the distribution of MTHFR genotypes between patients with CAD and control subjects (p > 0.05). In the patient group, homocysteine levels were higher than controls but not significantly (13.99 +/- 7.44 vs. 11.77 +/- 5.18 micromol l(-1); p > 0.05). Serum homocysteine concentration was significantly higher in the TT genotype with respect to CC and CT genotypes in both the control group (p < 0.01) and patient group (p < 0.01). Systolic and diastolic blood pressures in subjects with different MTHFR genotypes did not differ significantly. In conclusion, MTHFR C677T mutation was significantly related to hyperhomocysteinemia. In spite of the clear effect of the MTHFR polymorphism on elevated homocysteine levels, we did not observe any associations among the MTHFR genotypes with a the risk of CAD in the Turkish population.

Toll-like receptor 4 gene Asp299Gly polymorphism is associated with reductions in vascular inflammation, angiographic coronary artery disease, and clinical diabetes

BACKGROUND

Coronary artery disease (CAD) and, increasingly, diabetes are recognized as having an inflammatory basis. Membrane toll-like receptors (TLRs) activate signaling pathways that up-regulate inflammation. We evaluated whether the Asp299Gly polymorphism in the TLR4 gene, which impairs inflammatory responses, is associated with reduced vascular inflammation (assessed by C-reactive protein [CRP]) and a decreased risk for CAD and diabetes.

METHODS

1894 patients without acute myocardial infarction undergoing coronary angiography were studied. Genotyping was performed by real-time polymerase chain reaction. CAD was defined as >or=70% stenosis. Diabetes was diagnosed by patients' referring physicians. CRP was measured by fluorescence polarization immunoassay. Regression analyses adjusted for traditional cardiac risk factors.

RESULTS

Patients averaged 64 +/- 11 years of age, and 69% were male. Asp299Gly genotype frequencies were: AA = 0.911 (n = 1725), AG = 0.086 (n = 164), and GG = 0.003 (n = 5), in keeping with Hardy-Weinberg equilibrium. CRP was lower among G-allele carriers (median = 1.11 mg/dL) than wild-type (AA) subjects (1.23 mg/dL, adjusted P = .044). G-allele carriers also had a lower prevalence of CAD (65% vs. 73%, OR = 0.67, CI = 0.46-0.99, adjusted P = .048) and diabetes (11% vs. 18%, OR = 0.63, CI = 0.42-0.95, adjusted P = .029), which persisted in multivariate logistic regression analyses. 299Gly carriage did not affect clinical outcomes nor interact with statin therapy.

CONCLUSIONS

The TLR4 299Gly allele was associated with reduced CRP levels and, in parallel, a decreased risk of angiographic CAD and clinical diabetes. These findings suggest that down-regulation of innate immune responsiveness could beneficially modify CAD and diabetes risk and might provide a novel basis for genetic risk stratification and therapeutic targeting.

Hyperhomocysteinemia, enzyme polymorphism and thiobarbituric Acid reactive system in children with high coronary risk family history

OBJECTIVES

To investigate both the frequency and the genetic background of hyperhomocysteinemia and the frequency of increased plasma thiobarbituric acid reactive system (TBARS) levels in children and adolescents whose parents had premature coronary heart disease (CHD).

METHODS

The study was performed on children and adolescents aged 4-18 years (105 offspring of parents with CHD before age 45 and 74 referents from families without any evidence of premature atherosclerosis). Fasting serum total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and total triglyceride (TG) levels were measured by enzymatic methods. Low density lipoprotein cholesterol (LDL-C) level was calculated by the Friedewald formula. Plasma total homocysteine (THCy) level was measured by fluorescence polarisation immunoassay. Plasma TBARS level was determined by fluorimetric method. 5,10-methylenetetrahydrofolate reductase (MTHFR) enzyme polymorphism was analyzed by polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Hyperhomocysteinemia was found in 32 cases and in 4 controls. Increased plasma THCy level was found in 10 children and adolescents from 12 cases homozygous for the C677T polymorphism of the MTHFR gene. No similar high frequency was observed in heterozygous subjects. Elevated fasting plasma TBARS levels were found in 38 cases and in 8 controls. The frequency differences were significant (p < 0.01). Allele frequency of the MTHFR polymorphism among cases and controls was similar. Significant correlation (r = 0.53, p < 0.02) was detected between plasma THCy and TBARS levels. One child had high serum TC level, 5 had low serum HDL-C level and all other children had normal serum TC, LDL-C, HDL-C and TG levels from children with hyperhomocysteinemia and/or high plasma TBARS levels. A significant correlation (r = 0.64, p < 0.01) was observed between plasma THCy levels of parents and children in the case group.

CONCLUSION

The measurement of plasma THCy and TBARS levels may contribute to the detection of the risk of children and adolescents with high CHD risk family history.

A common variant of the AMPD1 gene predicts improved survival in patients with ischemic left ventricular dysfunction

BACKGROUND

A recent retrospective study suggested that the adenosine monophosphate deaminase (AMPD)-1 gene variant C34T predicts outcome in heart failure patients. This variant might lead to ischemic preconditioning by increasing tissue adenosine. We tested whether the survival benefit of C34T occurs preferentially in the setting of ischemic left ventricular dysfunction.

METHODS AND RESULTS

A consecutive cohort of patients (n=390) with left ventricular ejection fraction <40% was evaluated. In the ischemic patient subgroup (n=210) multivariate analysis identified AMPD1 T allele carriage (hazard ratio=0.43, confidence interval=0.20-0.94, P=.035) as an independent predictor of transplant-free cardiovascular survival. No benefit was found in the nonischemic group although the number of events was too small to reliably exclude a benefit by genotype.

CONCLUSION

The AMPD1 C34T polymorphism influences transplant-free cardiovascular survival in the setting of ischemic left ventricular dysfunction.

Correlation between C677T MTHFR gene polymorphism, plasma homocysteine levels and the incidence of CAD

The lesions of coronary atherosclerosis represent the result of a complex, multicellular, inflammatory-healing response in the coronary arterial wall. In vivo and in vitro cellular and molecular studies have suggested a role for tissue homocysteine in endothelial cell injury and adverse extra-cellular matrix remodeling. Gene polymorphisms in relation with numerous risk factors might increase the incidence of coronary artery disease (CAD). In this review we have focused on the correlations between plasma homocysteine levels, the incidence of cardiovascular disease and the cytosine-to-thymidine substitution at nucleotide 677 (C677T) of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, coding for a key enzyme in methionine-homocysteine metabolism. The role of the C677T MTHFR gene polymorphism in the causation of CAD is controversial. We reviewed 12 recent case-control studies comprising 5370 genotyped patients with CAD and 4961 genotyped participants without CAD. There was no significant difference between those with and without CAD in the frequency of the C677T polymorphism (34.9 vs 33.6%). The frequency of homozygous C677T polymorphism in these groups was 10.9 versus 12.8%, respectively, although there were some ethnic differences in the C677T MTHFR polymorphism. In the analysis of the 12 studies, the odds ratio of CAD associated with the TT genotype (homozygous C677T polymorphism) was 1.18. Only slightly higher plasma homocysteine levels were observed in participants with the val/val (TT) genotype (14.4+/-2.9 micro mol/L in TT genotype vs 11.1+/-1.9 and 11.9+/-2 micro mol/L in CC and CT genotype, respectively). In addition, the relation between homocysteine increase after methionine loading and MTHFR genotypes is also controversial. However, hyperhomocysteinemia because of the C677T MTHFR allele may be corrected with oral folic acid therapy. Further investigations on the relationships between MTHFR genotypes and the incidence of CAD should be based on larger samples, paying attention to the differences between various ethnic populations. Individual therapeutic strategies based on single nucleotide polymorphism may become increasingly important for preventive treatment against polygenic CAD.

Methylenetetrahydrofolate reductase gene C677T and A1298C polymorphisms, plasma homocysteine, folate, and vitamin B12 levels and the extent of coronary artery disease

The question of whether mild hyperhomocysteinemia is a risk factor for coronary artery disease (CAD) has long been debated and is still unclear. We investigated whether there is a link between methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms or plasma homocysteine and CAD. This is a case-control study that included 2,121 consecutive patients (cases) with angiographically proved CAD and 617 patients without CAD (controls). MTHFR gene C677T and A1298C polymorphisms, plasma homocysteine, folate, and vitamin B(12) concentrations were determined and coronary angiography was performed in all subjects. The distribution of MTHFR gene C677T genotypes in patients (or controls) was: CC-genotype in 915 cases, 43.1% (266 controls, 43.1%); CT-genotype in 955 cases, 45.0%, (283 controls, 45.9%); and TT-genotype in 251 cases, 11.9% (68 controls, 11.0%) (p = 0.84). The distribution of MTHFR gene A1298C genotypes in patients (or controls) was: AA-genotype in 973 cases, 45.9% (281 controls, 45.5%); AC-genotype in 905 cases, 42.7% (284 controls, 46.0%); and CC-genotype in 243 cases, 11.4% (52 controls, 8.5%) (p = 0.07). Patients with CAD had higher levels of plasma homocysteine (12.9 +/- 5.1 vs 11.9 +/- 4.5 micromol/L, p <0.001) and lower levels of folate (9.5 +/- 3.1 vs 9.9 +/- 3.8 ng/ml, p = 0.008) than controls. After adjustment for other risk factors for CAD, plasma homocysteine (p = 0.89), MTHFR gene C677T (p = 0.38), or A1298C polymorphisms (p = 0.13) were not independent correlates of CAD. This study demonstrated that MTHFR gene C677T or A1298C polymorphisms are not associated with the presence of angiographic CAD. Although there is an apparent association between elevated levels of homocysteine and CAD, this association is not independent of conventional cardiovascular risk factors.

Association between factor V Leiden, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T mutations and events of the arterial circulatory system: a meta-analysis of published studies

BACKGROUND

The association between the inherited gene mutations of factor V, prothrombin, and homocysteine metabolism and venous thromboembolic events is accepted widely; however, their influence on the arterial circulatory system remains controversial.

METHODS

We performed a MEDLINE search to identify published case-control and cohort studies correlating the factor V Leiden, prothrombin (PT) G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T (TT genotype) mutations with myocardial infarction, ischemic stroke, or peripheral vascular disease. Studies were included only when they adhered to specific diagnostic criteria for ischemic events and met the published methodological criteria. Odds ratios (ORs) with accompanying 95% CIs were calculated for each mutation and clinical end points with a random-effects model (DerSimonian and Laird method).

RESULTS

The association between inherited gene mutations and arterial ischemic events was modest: factor V Leiden mutation (OR, 1.21; 95% CI, 0.99-1.49), PT G20210A mutation (OR, 1.32; 95% CI, 1.03-1.69), and MTHFR TT mutation (OR, 1.20; 95% CI, 1.02-1.41). Subgroup analyses of younger patients (<55 years old) and of women revealed slightly stronger associations overall.

CONCLUSIONS

Genetic abnormalities specific to factor V, prothrombin,and homocysteine metabolism increase the risk for myocardial infarction and ischemic stroke, particularly among younger patients and women. Because the overall association is only modest, screening studies should be limited to carefully selected patient populations. The individual propensity for arterial and venous thrombosis is likely influenced by differing local mechanisms, systemic mechanisms, or both.

The cholesteryl ester transfer protein Taq1B gene polymorphism predicts clinical benefit of statin therapy in patients with significant coronary artery disease

BACKGROUND

Cholesteryl ester transfer protein (CETP) regulates plasma lipid distribution. A polymorphism in the CETP gene (Taq1B) is associated with CETP activity, HDL concentration, atherosclerosis progression, and response to statins, and may influence cardiovascular (CV) events. We studied CETP Taq1B genotype, plasma HDL, and clinical events among all patients and patients stratified by statin treatment.

METHODS

Consenting patients (n = 2531) with significant coronary artery disease (> or =1 lesion of > or =70% stenosis) undergoing coronary arteriography were genotyped, grouped by statin prescription at hospital discharge, and prospectively followed-up for the outcomes of all-cause mortality and myocardial infarction.

RESULTS

CETP Taq1B genotype frequencies were: B1B1, 32.9%; B1B2, 50.3%; and B2B2 16.8%. Plasma HDL was reduced for B1B1 patients (33 +/- 12 mg/dL, vs 36 +/- 13 mg/dL and 36 +/- 13 mg/dL for B1B2 and B2B2, respectively, P for trend =.003). Overall, event rates did not differ between genotypes. Event rates were similar among untreated (24.8%) and statin-treated (24.2%) B1 homozygotes (P = NS); statins significantly reduced events for B1B2 subjects (28.0% vs 21.0%, P =.009) and for B2B2 subjects (26.4% vs 17.4%, P =.048). Therapeutic benefit for B2 carriers remained after adjustment for covariates, and regression interaction analysis showed that B2 carriers experienced reduced events (relative risk [RR] 0.62, 95% CI 0.45-0.86), but statins did not benefit those with B1B1 (RR 1.09, 95% CI 0.70-1.7; P for interaction =.02). Findings were similar for the end point of death alone, although a modest benefit was seen in B1B1 patients (RR 0.67, P =.10), in addition to the strong benefit for B1B2 (RR 0.53, P =.001) and B2B2 (RR 0.28, P =.001).

CONCLUSIONS

The CETP Taq1B polymorphism is associated with differential HDL levels but no significant differential in CV risk in the absence of treatment. Importantly, however, CV event reduction by statin therapy is substantially enhanced in the presence of a B2 allele. Our findings suggest, for the first time, the potential of CETP Taq1B genotyping to enable more effective, pharmacogenetically directed therapy.

Thermolabile methylenetetrahydrofolate reductase, homocysteine, and cardiovascular disease risk: the European Concerted Action Project

BACKGROUND

Homozygotes for the thermolabile mutation (TT genotype) of the methylenetetrahydrofolate reductase (MTHFR; EC 1.5.1.20) enzyme have elevated plasma concentrations of the cardiovascular disease risk factor homocysteine, particularly if folate depleted.

OBJECTIVE

We examined the relations between thermolabile MTHFR, plasma homocysteine, plasma folate, and vascular disease risk.

DESIGN

This was a case-control comparison in 711 vascular disease cases and 747 controls from 9 European countries.

RESULTS

The TT genotype was associated with higher homocysteine and lower plasma folate than the CC and CT genotypes in both cases and controls and a nonsignificant increase in vascular disease risk (1.26; 95% CI: 0.88, 1.81; P = 0.20). The frequency of the TT genotype in cases was not significantly different from that in controls (12.8% compared with 10.8%). After adjustment for traditional risk factors, the TT genotype was associated with an odds ratio of 1.48 (1.0, 2.20) for risk of vascular disease. This risk was attenuated after further adjustment for homocysteine. In subgroups with homocysteine concentrations >or= 9 micro mol/L, risk tended to be higher in CC than in TT subjects. However, CC subjects were characterized by a higher prevalence of the conventional risk factors associated with both elevated plasma homocysteine and serum creatinine. After adjustment, the risk of vascular disease associated with each genotype was not significantly different.

CONCLUSIONS

There was a strong graded association between homocysteine and vascular risk in all genotypes. MTHFR genotype is a key determinant of plasma total homocysteine concentrations. The initially nonsignificant risk estimate associated with the TT genotype was strengthened after adjustment for conventional cardiovascular disease risk factors but was attenuated after adjustment for plasma folate and total homocysteine. The modest risk increase conferred by the TT genotype is mediated mainly by increased total homocysteine and low plasma folate concentrations.

Impact of renal failure on the risk of myocardial infarction and death

BACKGROUND

It is unclear whether pre-existing cardiovascular disease or predisposition of the uremic state leads to the high cardiovascular morbidity and mortality associated with renal failure. We examined whether renal failure independently increases the risk of myocardial infarction and death.

METHODS

A total of 8600 patients with variable glomerular filtration rate (GFR) at the time of coronary angiography participated in the Intermountain Heart Study. Coronary disease was defined as >or=70% stenosis. Modification of Diet in Renal Disease formula was used to calculate glomerular filtration rate (GFR). Cox regression models were used to compare outcomes.

RESULTS

The mean GFR was 71 +/- 24 mL/min. There were 1320 (15%) deaths, 657 (9%) myocardial infarctions and 1776 (21%) death or myocardial infarctions over 3.2 +/- 1.9 years. Compared to the highest GFR quartile, the lowest GFR quartile (mean GFR 41 +/- 14 mL/min) was associated with higher risk for myocardial infarction (RR 1.43, 95% CI 1.15 to 1.78), death (RR 2.77, 95% CI 2.32 to 3.30) and death/myocardial infarction (RR 2.13, 95% CI 1.85 to 2.45) in multivariable models adjusted for age, sex, hypertension, hyperlipidemia, smoking, family history of coronary disease and diabetes. Even after further adjustment for coronary angiographic data and the choice of initial therapy, lowest GFR quartile was associated with increased risk of myocardial infarction (RR 1.51, 95% CI 1.21 to 1.88), death (RR 2.60, 95% CI 2.18 to 3.10) and death/myocardial infarction (RR 2.08, 95% CI 1.80 to 2.39).

CONCLUSIONS

Even moderate renal failure increases the risk of myocardial infarction and death independent of clinical variables, baseline angiographic evidence of coronary disease and therapy.

The role of hyperhomocysteinemia and methylenetetrahydrofolate reductase (MTHFR) C677T mutation in patients with retinal artery occlusion

PURPOSE

Hyperhomocysteinemia has been established as an important risk factor for cardiovascular diseases. The aim of the present study was to investigate whether hyperhomocysteinemia and/or homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation are associated with an increased risk for retinal artery occlusion (RAO).

DESIGN

Retrospective case-control study.

METHODS

We studied 105 consecutive patients with retinal artery occlusion and 105 age and sex-matched control subjects. Fasting plasma homocysteine levels were determined by high-performance liquid chromatography, while genotypes of the MTHFR C677T mutation were determined by polymerase chain reaction.

RESULTS

Mean plasma homocysteine levels were significantly higher in patients with RAO compared with control subjects (12.2 +/- 4.8 micromol/l vs 10.3 +/- 3.4 micromol/l; P =.003). Hyperhomocysteinemia was defined by the 95th percentile of control plasma homocysteine levels as 15.8 micromol/l. Twenty (19.1%) patients with RAO exceeded this level and were therefore classified as hyperhomocysteinemic compared with 5 (4.8%) control subjects (P =.003). The odds ratio for these patients was calculated at 4.7 (95% confidence interval [CI], 1.5-15.1). Mean plasma folate levels were significantly lower in patients than in the control group (5.6 +/- 2.3 ng/ml vs. 6.3 +/- 2.5 ng/ml; P =.04). The prevalence of the homozygous genotype of methylenetetrahydrofolate reductase C677T mutation did not significantly differ between patients and controls.

CONCLUSIONS

Our results suggest that hyperhomocysteinemia, but not homozygosity, for the MTHFR C677T mutation is associated with RAO.

Hyperhomocyst(e)inemia, but not methylenetetrahydrofolate reductase C677T mutation, as a risk factor in branch retinal vein occlusion

OBJECTIVE

To determine whether hyperhomocyst(e)inemia and methylenetetrahydrofolate reductase (MTHFR) C677T mutation are associated with branch retinal vein occlusion (BRVO).

DESIGN

Retrospective, case-control study.

PARTICIPANTS

The study cohort consisted of 84 consecutive patients with branch retinal vein occlusion and 84 controls, matched for age and gender.

MAIN OUTCOME MEASURES

Fasting plasma homocyst(e)ine, folate, and vitamin B(12) levels, MTHFR C677T genotypes.

RESULTS

Mean plasma homocyst(e)ine levels were significantly higher in patients than in controls (11.4 +/- 4.3 micromol/l vs. 9.9 +/- 2.8 micromol/l; P = 0.002). An increase of plasma homocyst(e)ine level by 1 micromol/l was associated with an odds ratio of 1.19 (95% confidence interval 1.06-1.34; P = 0.004). Mean plasma folate levels were significantly lower in patients than in the control group (4.5 +/- 2.1 ng/ml vs. 5.6 +/- 2.1 ng/ml; P = 0.007). The prevalence of the homozygous genotype of the MTHFR C677T mutation did not differ significantly between patients and controls.

CONCLUSIONS

Our results suggest that hyperhomocyst(e)inemia, but not homozygosity for the MTHFR C677T mutation, is associated with BRVO. Increased plasma homocyst(e)ine levels in our study are not the result of an increased prevalence of the homozygous genotype of MTHFR C677T mutation.

Folates and cardiovascular disease

It is increasingly recognized that folates may play a role in the prevention of cardiovascular disease. Over the last few years, several studies have reported beneficial effects of folates on endothelial function, a surrogate end point for cardiovascular risk. Consistently, observational studies have demonstrated an association between folate levels and cardiovascular morbidity and mortality. The exact mechanisms underlying the ameliorative effects of folates on the endothelium remain to be elucidated. Thus far, most studies have focused on the homocysteine-lowering effects of folates. However, recently, benefits of folates independent of homocysteine lowering have also been reported. Potential mechanisms include antioxidant actions, effects on cofactor availability, or direct interactions with the enzyme endothelial NO synthase. Obviously, beneficial effects of folates on cardiovascular risk would have important clinical and dietary consequences. However, for definite conclusions, the completion of ongoing randomized controlled trials will have to be awaited.

The associations among thoracic aortic atherosclerosis, coronary atherosclerosis and the function of high density lipoprotein

We sought to determine the associations among thoracic aortic atherosclerosis, coronary atherosclerosis and the function of high density lipoprotein (HDL) in a case-control study. The function of HDL can be assessed by the fractional esterification rate of cholesterol in low density lipoprotein (LDL)- and very low density lipoprotein (VLDL)-depleted plasma (FER(HDL)), which reflects a balance of cholesterol uptake by HDL and cholesterol ester (CE) transport in the reverse cholesterol transport (RCT) system in humans. Cases (n=51, age: 64.3+/-8.0 years) and controls (n=51, age: 58.7+/-13.1 years) were defined as subjects with/without angiographically proven coronary artery disease (CAD), respectively and examined for thoracic aortic atherosclerosis (TAA) by transesophageal echocardiography. The severity of TAA was determined by the ratio of average sclerotic areas (ASA) and average sclerotic lengths (ASL). The cases had significantly (P<0.05) higher values of ASA (0.22+/-0.18 vs. 0.10+/-0.11), ASL (0.82+/-0.56 vs. 0.48+/-0.45), ASA/ASL ratio (0.23+/-0.08 vs. 0.17+/-0.09) and FER(HDL) (10.3+/-3.8 vs. 8.3+/-3.5% per hour) and lower HDL-C and apolipoprotein A-I levels than the controls. A receiver operating characteristic (ROC) curve analysis showed that ASA/ASL and FER(HDL) had moderate discriminating ability for CAD and the diagnostic accuracy of ASA/ASL was better than that of FER(HDL) (area under ROC curve: 0.703 and 0.656, respectively). Multivariate logistic regression analysis indicated that ASA/ASL and FER(HDL) were independent indicators for CAD [odds ratio (95% CI): 7.5 (2.4-27), P<0.01 and 4.0 (1.2-15), P<0.05] after adjusting for age, gender and other conventional risk factors, and that a high FER(HDL) value greatly increased the relative risk of CAD associated with a high ASA/ASL. The function of HDL, as assessed by FER(HDL), enhances the ability of TAA to predict CAD.

MTHFR 677 C-->T mutation: a predictor of early-onset coronary artery disease risk

The atherosclerotic potential of the methyenetetrahydrofolate reductase (MTHFR) gene mutation 677 C --> T substitution remains controversial. In this study, we describe the association of this mutation in a Southern Texan patient population of multiracial ethnic background with risk and extent of coronary artery disease (CAD) as measured by luminal narrowing. Sixty nine patients who were 50 years or younger composed our population. Chi-square analysis was used to analyze the data and found a significant association between CAD and this mutation (P value=0.03). In addition, in the small number of patients in this study who had diabetes, those who had mutation have more severe disease than those without the mutation. This study highlights the potential cardiovascular prognostic significance of the MTHFR 677 C --> T in the studied population.

Oral nutritional supplements and heart disease: a review

The use of nutritional supplements in the treatment of cardiovascular disease is rapidly growing in the United States. Many substances are marketed with anecdotal claims of efficacy. Most have not been scientifically studied. Excitement exists in the lay press about the homocysteine hypothesis of coronary artery disease and vitamin cures. A MEDLINE search and review of papers covering the study of popular nutritional supplements were undertaken. The papers were limited to peer-review journals using patient series reports, double-blinded prospective studies, and population studies. A compendium of the available data was obtained and an analysis of each paper's methodology was done. A review of the most popular and most studied oral nutritional supplements for the treatment of heart disease demonstrated relatively few well-founded indications for the widespread application of substances with the exception of the bioflavonoids. Some modest effects for endothelial dysfunction were noted for vitamins C and E. Red wines and beers were also noted to be beneficial. The majority of substances either had no effect or were deleterious.

Hyperhomocyst(e)inaemia, but not MTHFR C677T mutation, as a risk factor for non-arteritic ischaemic optic neuropathy

BACKGROUND/AIMS

Hyperhomocyst(e)inaemia has been identified as a strong risk factor for stroke, myocardial infarction, and deep vein thrombosis. A point mutation of methylene tetrahydrofolate reductase (MTHFR C677T) has been associated with increased plasma homocyst(e)ine levels. To investigate whether hyperhomocyst(e)inaemia and/or MTHFR C677T mutation are associated with non-arteritic ischaemic optic neuropathy (NAION), a case-control study including 59 consecutive patients with NAION and 59 controls matched for age and sex was performed.

METHODS

Fasting plasma homocyst(e)ine levels, MTHFR C677T genotypes, and plasma levels of folate and vitamin B-12 were determined.

RESULTS

Mean plasma homocyst(e)ine levels were significantly higher in patients than in controls (11.8 (SD 5.7) micromol/l v 9.8 (2.5) micromol/l, p = 0.02). The odds ratio for patients with homocyst(e)ine levels exceeding the 95th percentile of control homocyst(e)ine levels was 5.8 (95% CI 1.5-21.4). Mean plasma folate levels were significantly lower in patients than in controls (4.3 (1.7) ng/ml v 5.5 (1.9) ng/ml, p = 0.001), whereas plasma vitamin B-12 levels did not differ significantly. Prevalence of the MTHFR C677T mutation was not significantly increased in patients with NAION compared with controls.

CONCLUSION

These results suggest that hyperhomocyst(e)inaemia, but not MTHFR C677T mutation is associated with NAION. Determination of plasma homocyst(e)ine levels might be of diagnostic value in patients with NAION.

Correlation of polymorphisms to coagulation and biochemical risk factors for cardiovascular diseases

Currently, the established risk factors for cardiovascular disease (CVD) are largely environmental in nature. Conflicting studies have suggested that mutations in specific coagulation genes may also provide a genetic basis for CVD risk. We reviewed clinical studies that examined the role of single nucleotide polymorphisms in coagulation and platelet factors, and a biochemical factor to determine if specific genotypes are correlated with patients with a history of arterial thrombotic diseases (acute coronary syndromes or stroke). A meta-analysis was performed on studies for factors II (G20210A variant), V Leiden (G1691A), VII (R353Q), glycoprotein (GP) IIIa receptor (PI(A1/A2)), and methylenetetrahydrofolate reductase (MTHFR, C677T). There was no correlation for factor II or factor V polymorphisms to coronary artery disease (CAD) in 5,607 and 5,431 patients studied, respectively. There was also no correlation for factor II variants and stroke in 3,451 patients studied. For factor V, statistical significance was achieved for the G1691A variant on 3,399 patients with stroke (odds ratio [OR] 1.43, 95% confidence intervals [CI] 1.03 to 1.97). The GP IIIa PI(A1/A2) genotype was associated with increased risk for CAD in 7,920 patients (OR 1.12, 95% CI 1.01 to 1.24), but not for 1,855 patients who had a stroke (OR 0.80, 95% CI 0.62 to 1.04). The combined RQ and RR genotypes of factor VII R353Q were correlated to a reduced risk for CVD in 2,574 patients (OR 0.78, 95% CI 0.65 to 0.93), whereas the QQ genotype had offered more protection (OR 0.53, 95% CI 0.27 to 1.03). The TT homozygous variant of MTHFR was associated with CAD risk in 5,644 patients studied (OR 1.30, 95% CI 1.11 to 1.52) but not for 3,075 patients with stroke. This study shows that for some genes, further studies are unnecessary, whereas for others, no more enrollments are needed. The impact of certain genotypes must be examined in relation to other established risk factors and potentially new therapeutic strategies.

Genetics of arterial prothrombotic risk states

Coronary artery disease is a leading cause of death worldwide and the largest killer of men and women in the United States. The pathophysiology of myocardial infarction is multifactorial, and numerous physiologic systems converge to dictate the formation of the two fundamental lesions, thrombosis and atherosclerosis. In this review we address genetic aspects of arterial thrombosis and the key thrombotic factors that have been associated with the increased risk for its development. Specifically, we consider components of coagulation, fibrinolysis, and platelet adhesive receptors, and we review the genetic epidemiology and in vitro laboratory data regarding their risk for the acute coronary syndromes. In combination with traditional risk factor assessment, in the near future these inherited markers can be used to manage patients with vascular disease through a better utilization of invasive or expensive diagnostic testing, as well as pharmacologic intervention.

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.

The methylenetetrahydrofolate reductase gene polymorphism in Koreans with coronary artery disease

Hyperhomocysteinemia is a known risk factor of cardiovascular diseases. Methylenetetrahydrofolate reductase (MTHFR), involved in folate-dependant metabolism, is associated with homocysteine levels. We studied the associations among MTHFR genotypes, coronary artery disease (CAD), and homocysteine levels in 85 patients with CAD and 152 healthy subjects. The MTHFR genotypes and plasma homocysteine levels were determined. No significant difference in mutation of the MTHFR gene between two groups was observed (P>0.05). While the homozygous mutant genotype (V/V) had the highest homocysteine levels compared to wild (A/A) and heterozygous mutant (A/V) genotypes, there were no significant differences in homocysteine levels among the MTHFR genotype groups. Homocysteine was significantly and inversely related to folate levels, the significant association in V/V genotype (beta coefficient=-1.954, P=0.04). Our data suggested that MTHFR polymorphism was not associated with homocysteine levels, implying no association between gene polymorphism and CAD in Koreans.

Homozygosity for the C677-->T mutation of 5,10-methylenetetrahydrofolate reductase and total plasma homocyst(e) ine are not associated with greater than normal risk of a first myocardial infarction in northern Sweden

BACKGROUND

Results of several case-control studies have shown elevated total plasma homocyst(e)ine (TPH) and homozygosity for the point mutation C677-->T in the gene for 5,10-methylenetetrahydrofolate reductase (MTHFR) to be associated with a greater than normal risk of atherosclerotic vascular disease. However, there have been few epidemiologic studies and the interpretation of the results is not clear-cut.

OBJECTIVE

To elucidate whether homozygosity for the point mutation C677-->T in the gene for MTHFR, and TPH are risk factors for a first myocardial infarction.

DESIGN

A prospective nested case-control study in Northern Sweden.

METHODS

Among more than 36000 persons screened, 78 cases satisfied the inclusion criterion of having developed, after sampling, a first myocardial infarction. For each case, two controls matched for sex and age were randomly selected.

RESULTS

We found no statistically significant difference among the prevalences of the three possible MTHFR genotypes -/- (no mutation), +/+ (both alleles have the mutation), and +/- among cases and controls in univariate conditional logistic regression analysis. Mean levels of TPH in patients and controls were 12.2+/-4.9 and 12.2+/-3.5 micromol/l (means +/- SD), respectively (NS).

CONCLUSIONS

In this study neither homozygosity for the point mutation C677-->T in the gene for MTHFR nor TPH was related to a greater than normal risk of a first myocardial infarction for members of the population of northern Sweden. Further research is needed in order to show whether TPH is an independent risk factor for a first myocardial infarction.

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.

Genetic, dietary, and other lifestyle determinants of plasma homocysteine concentrations in middle-aged and older Chinese men and women in Singapore

BACKGROUND

Epidemiologic studies have identified the plasma homocysteine concentration as a risk factor for atherothrombotic vascular disease. There is little information on the distributions and determinants of homocysteine concentrations in Asian populations.

OBJECTIVE

The present study was designed to examine the relations between genetic and lifestyle factors and plasma homocysteine concentrations among Chinese in Singapore.

DESIGN

Plasma total homocysteine, folate, vitamin B-12, and vitamin B-6 concentrations and genetic variation at the methylenetetrahydrofolate reductase (MTHFR) locus were measured in 486 Chinese men and women aged 45-74 y in Singapore. Data on dietary and other lifestyle factors were collected in face-to-face interviews.

RESULTS

Men had higher plasma concentrations of total homocysteine than women (P = 0.0001). Age was positively associated with plasma homocysteine in both sexes (P for trend = 0.0001). Plasma concentrations of folate, vitamin B-12, and vitamin B-6 were inversely associated with homocysteine concentrations. Among individuals with low plasma folate, those possessing 2 copies of MTHFR mutant alleles had significantly higher homocysteine concentrations than did those with > or = 1 copy of the wild-type allele. Cigarette smoking, daily coffee consumption, and physical inactivity were positively related to plasma homocysteine concentrations in both sexes (P < 0.05). However, these associations disappeared after adjustment for plasma folate concentrations.

CONCLUSIONS

Age, sex, plasma folate, vitamin B-12 and B-6 concentrations, and MTHFR genotype are independent determinants of plasma homocysteine in middle-aged and older Chinese in Singapore. These factors combined could account for up to 40% of the total variation in homocysteine concentrations in this Asian population.

Thermolabile MTHFR genotype and retinal vascular occlusive disease

BACKGROUND

Raised levels of total plasma homocysteine (tHcy) are associated with an increased risk of retinal vascular occlusive disease. A thermolabile form of a pivotal enzyme in homocysteine metabolism, methylenetetrahydrofolate reductase (MTHFR), has been associated with vascular occlusive disease and raised tHcy levels. The relation between thermolabile MTHFR genotype, tHcy, and retinal vascular occlusive disease has not been determined.

METHODS

A retrospective case-control study involving hospital based controls and cases with retinal vascular occlusions in whom tHcy levels had been determined was undertaken. Genotyping for the MTHFR 677 C-T mutation that specifies the thermolabile form of the enzyme was performed by established methods in all subjects. The relation between homozygosity for thermolabile MTHFR genotype (TT), raised tHcy levels, and risk of retinal vascular occlusive disease was examined.

RESULTS

87 cases of retinal vascular occlusive disease (mean age 68.7 years) comprising 26 cases of retinal artery occlusion and 61 of retinal vein occlusion were compared with 87 controls (mean age 70.2 years). The TT genotype did not confer a significantly increased risk of retinal vascular occlusive disease. The mean tHcy level was significantly higher in the cases than in the controls (p<0.0001). Overall, and in both the cases and controls, the frequency of the TT genotype was higher in those with normal tHcy levels than in those with increased levels of tHcy. However, the TT genotype did not significantly alter the risk of increased tHcy levels in these patients.

CONCLUSIONS

The TT genotype is not associated with an increased risk of retinal vascular occlusive disease or increased tHcy levels in this group of elderly patients. In older patients, nutritional rather than genetic factors may be more important in increasing tHcy levels, a known risk factor for retinal vascular occlusive disease.

The methylenetetrahydrofolate reductase gene is associated with increased cardiovascular risk in Japan, but not in other populations

The methylenetetrahydrofolate reductase (MTHFR) gene has been associated with increased risk for cardiovascular disease in some, but not all studies. Our data sources included a MEDLINE search of the literature published before December 1998, a bibliography review, and expert consultation. Of 23 studies initially identified, 18 (9855 persons) met the inclusion criteria. Information on sample size, study design, Hardy-Weinberg equilibrium, method of genotype determination, plasma folate and homocysteine were abstracted by two reviewers using a standardized protocol. The overall odds ratio of the MTHFR gene on cardiovascular disease was estimated using the Mantel-Haenzel method. From 12 studies with angiographically-confirmed coronary artery disease (CAD), the overall odds ratio (OR) for CAD among those with heterozygous (V/A) was 1.3 (95% CI, 1.1-1.5), while it was 1.4 (1.2-1.6) for the homozygous mutant (V/V) compared to those with homozygous normal (A/A). However, the overall odds ratio for CAD among those with the V/V genotype versus A/A genotype was not statistically significant (OR: 1.1; 95% CI: 0.9-1.3) after excluding three Japanese studies. The corresponding OR for the three Japanese studies was 2.0 (1.6-2.7). For six studies with myocardial infarction (MI), the overall OR of MI was 1.0 (0.8-1.1) for those with the V/A genotype and 0.9 (0.7-1.1) for those with the V/V genotype, respectively; none of these ORs for MI was statistically significant. The MTHFR gene is associated with increased risk for CAD in Japan, but not in other populations.

Methylenetetrahydrofolate reductase 677 C-->T mutation and coronary heart disease risk in UK Indian Asians

Plasma homocysteine concentrations are elevated in UK Indian Asians and may contribute to twice as many coronary heart disease (CHD) deaths in this group compared with European whites. The mechanisms underlying elevated homocysteine concentrations among Indian Asians are not well understood. In this study, we have investigated the extent to which the methylenetetrahydrofolate reductase (MTHFR) 677 C-->T mutation accounts for elevated plasma homocysteine and increased CHD risk in Indian Asians compared with European whites. We investigated 454 male cases (with myocardial infarction or angiographically proven CHD: 224 Indian Asians, 230 European whites) and 805 healthy male controls (381 Indian Asians, 424 European whites). Fasting homocysteine concentrations, MTHFR 677 C-->T genotype, and conventional CHD risk factors were measured. The prevalence of homozygous MTHFR 677T in Indian Asian controls was less than one third that in European white controls (3.1% versus 9. 7%, P<0.001). In Indian Asians, the TT MTHFR genotype was not associated with homocysteine concentrations and was not present in any of the Asian controls with hyperhomocysteinemia (>15 micromol/L). In contrast, among European whites, the TT MTHFR genotype was strongly related to elevated plasma homocysteine concentrations and was found in 27% of the European controls with hyperhomocysteinemia. Elevated homocysteine in Indian Asian compared with European white controls was accounted for by their reduced levels of B vitamins but not by the MTHFR 677T genotype. However, neither the TT MTHFR genotype nor B vitamin levels explained the elevated homocysteine concentrations in CHD cases compared with controls. TT MTHFR was not a risk factor for early-onset CHD in Indian Asians (odds ratio, 0.5; 95% confidence interval, 0.1 to 2.4; P=0.39), unlike in European whites (odds ratio, 2.1; 95% confidence interval, 1.1 to 4. 1; P=0.02). We conclude that the MTHFR 677T: mutation does not contribute to elevated plasma homocysteine concentrations or increased CHD risk in Indian Asians compared with European whites. Our results suggest that novel genetic defects and/or environmental factors influence homocysteine metabolism in Indian Asians residing in the United Kingdom.