Methylenetetrahydrofolate reductase gene and coronary artery disease

Polymorphisms C677T and A1298C of MTHFR Gene: Homocysteine Levels and Prothrombotic Biomarkers in Coronary and Pulmonary Thromboembolic Disease

The activity of the enzyme methylenetetrahydrofolate reductase (MTHFR) determines homocysteine (Hcy) levels, and polymorphisms in its gene affect the activity of the enzyme. Changes in the enzyme's activity may lead to a higher susceptibility to develop arterial and venous thromboembolic disease. The aim was to analyze the relationship between the C677T and A1298C polymorphisms of MTHFR, Hcy levels, and prothrombotic biomarkers in pulmonary embolism (PE) and acute myocardial ischemia (AMI). Clinical files of patients with thromboembolic diseases having complete data and whose doctor had requested an assay to determine the polymorphisms of the MTHFR gene, Hcy levels, and prothrombotic biomarkers were studied to search for the correlation between mutations of the MTHFR gene and Hcy levels in the different diseases. We included 334 files: 158 were from women and 176 from men (51 [19 SD] years). Sixty-three percent have had thrombosis, 8% AMI, and 31% PE. Patients with thrombosis had elevated frequency of the C677T polymorphism. The CC genotype was higher than the TT genotype ( P = .003) and CT versus the TT ( P = .009). In patients with PE, the CC genotype was higher than the TT genotype ( P = .038). Pulmonary embolism with massive and submassive events had predominant genotypes 677 TT ( P = .003) and the AA 1298 ( P = .017). Elevated Hcy levels in the presence of the T allele in the C677T gene and of the A allele in the A1298C gene are associated with AMI and massive and submassive PE.

13C Breath Tests in Infections and Beyond

Stable isotope labeled compounds are widely used as diagnostic probes in medicine. These diagnostic stable isotope probes are now being expanded in their scope, to provide precise indications of the presence or absence of etiologically significant change in metabolism due to a specific disease. This concept exploits a labeled tracer probe that is a specifically designed substrate of a “gateway” enzyme in a discrete metabolic pathway, whose turnover can be measured by monitoring unidirectional precursor product mass flow. An example of such a probe is the 13C-urea breath test, where labeled urea is given to patients with H. pylori infection. Another example of this kind of probe is used to study the tripeptide glutathione (glu-cys-gly, GSH), which is the most abundant cellular thiol, and protects cells from the toxic effects of reactive oxygen species. Within the gamma glutamyl cycle, 5-oxoproline (L-pyroglutamic acid) is a metabolite generated during GSH catabolism, and is metabolized to glutamic acid by 5-oxoprolinase. This enzyme can also utilize the substrate L-2-oxothiazolidone-4-carboxylate (OTC), to generate intracellular cysteine, which is beneficial to the cell. Thus, labeled (13C) OTC would, under enzymatic attack yield cysteine and 13CO2, and can thus track the state and capacity of glutathione metabolism. Similarly, stable isotope labeled probes can be used to track the activity of the rate of homocysteine clearance, lymphocyte CD26, and liver CYP (cytochrome P450) enzyme activity. In the future, these applications should be able to titrate, in vivo, the characteristics of various specific enzyme systems in the body and their response to stress or infection as well as to treatment regimes.

High prevalence of factor V Leiden and prothrombin G20101A mutations in Kashmiri patients with venous thromboembolism

AIM

The genetic variants of the factor V (G1691A), prothrombin (G20210A) and MTHFR (C677T) genes have been widely implicated as inherited risk factors for developing venous thrombosis. This study was undertaken to reveal the frequency of these mutations in Kashmiri patients with venous thromboembolism.

METHODOLOGY

A case-control study was designed with 250 VTE patients and 250 healthy controls. The mutations were analysed using ARMS-PCR and PCR-RFLP approach.

RESULT

The factor V Leiden G1691A mutation was found in 17/250 (6.8%) VTE patients and prothrombin G20210A mutation was found in 7/250 (2.8%) VTE patients while no mutation was found in any of the healthy controls. Both the mutations were found to be significantly associated with the increased risk of VTE (p = 0.0001 and 0.0150 respectively) while no association of VTE risk with MTHFR C677T polymorphism was found (p = 0.53).

CONCLUSION

The increased frequency of factor V Leiden G1691A and prothrombin G20210A mutation in VTE patients indicates a significant role of these mutations in the development of VTE in our population. We therefore suggest the routine screening of these two mutations as thrombophilic markers in Kashmiri patients with venous thromboembolism.

MTHFR gene methylation is associated with perceived stress in healthy young adults

BACKGROUND

Epigenetic factors have been identified in the past years as interesting candidates for psychiatric disorders and related endophenotypes. It has been found that the methylenetetrahydrofolate reductase (MTHFR) gene is associated with major depressive disorder, and the aim of the current study was to examine the possible association between perceived stress and MTHFR methylation, taking into account depressive symptoms as a covariate.

PARTICIPANTS AND METHODS

Seventy-eight healthy Colombian participants (mean age=20.9 years; SD=3.0) were evaluated with the Perceived Stress Scale and with the Patient Health Questionnaire-9 for depressive symptomatology. MTHFR methylation levels were measured with a methylation-sensitive high-resolution melting method. A multiple regression analysis (adjusting for age, sex, and depressive symptoms) was carried out to assess the association between MTHFR methylation and perceived stress scores.

RESULTS

We found a significant inverse correlation between MTHFR methylation levels and perceived stress scores (r=-0.502; P=5.9×10(-5)), which remained significant after being adjusted for age, sex, and depressive symptomatology.

CONCLUSION

To our knowledge, this is the first study that reports an association between perceived stress and MTHFR methylation levels. This report adds evidence to the emerging role of epigenetic changes in endophenotypes related to affective disorders.

Recurrent unprovoked venous thromboembolism in a young female patient with high levels of homocysteine

Hyperhomocysteinemia is a rare condition which predisposes to atherothrombosis. Recurrent venous thromboembolism (VTE) with hyperhomocysteinemia is known but extremely uncommon. Homocysteine levels of more than 22 umol/L can predispose to VTE in a middle-aged women. We describe a case of a middle-aged woman, community ambulant with recurrent VTE with intermediately high homocysteine levels. She had no other risk factors for recurrent venous thrombosis. In our article, we also discuss hyperhomocysteinemia and its link to VTE.

Renal insufficiency in non-diabetic subjects: relationship of MTHFR C677t gene polymorphism and left ventricular hypertrophy

BACKGROUND

Association of methylenetetrahydrofolate reductase (MTHFR) 677C>T gene polymorphism with hyperhomocysteinemia, renal failure, and cardiovascular events is controversial. We investigated the relationship of MTHFR 677C>T polymorphisms with left ventricular hypertrophy (LVH) and renal insufficiency.

METHODS

Glomerular filtration rate (GFR) and left myocardial ventricular mass/m2 were assessed in 138 non-diabetic subjects (age, 50.93 ± 14.85 years; body mass index, 27.95 ± 5.98 kg/m(2)), 38 no-mutation wild MTHFR C677CC, 52 heterozygous MTHFR C677CT, and 48 homozygous MTHFR C677TT, all with adequate adherence to current international healthy dietary guidelines. Serum homocysteine, insulin resistance, high-sensitivity C-reactive-protein (hsCRP), parathyroid hormone, and renal artery resistive index (RRI) were challenged by odds ratio analysis and multiple linear regression models.

RESULTS

MTHFR 677C>T polymorphism showed higher GFR (73.8 ± 27.99 vs. 58.64 ± 29.95; p= 0.001) and lower renal failure odds (OR, 0.443; 95% confidence interval, 0.141-1.387) in comparison with wild MTHFR genotype. A favorable effect on GFR of MTHFR polymorphism is presented independently by the negative effects of LVH, increased intra-renal arterial resistance, and hyperparathyroidism; GFR is the significant predictive factor to LVH.

CONCLUSIONS

Renal insufficiency in non-diabetic subjects is explained by interactions of MTHFR C677T polymorphism mutation with LVH, hsCRP, intact parathyroid hormone (iPTH), and RRI. Sign of these predictive effects is opposite: subjects with MTHFR 677C>T polymorphism have lower likelihood of renal insufficiency; differently, wild-type MTHFR genotype subjects have lower GFR and greater hsCRP, iPTH, RRI, and LVH.

Elevated homocysteine is associated with poorer self-perceived physical health in older men: the Health in Men Study

OBJECTIVES

To determine the relationship between high total homocysteine (tHcy) and self-perceived physical health, by investigating the associations between tHcy, the methylenetetrahydrofolate reductase (MTHFR) 677T polymorphism and physical health-related quality of life (HRQOL).

STUDY DESIGN

We conducted a cross-sectional study using a cohort of 4248 community-dwelling men aged 70-88 years.

MAIN OUTCOME MEASURES

In addition to clinical determinants of physical health, tHcy was measured by immunoassay, the MTHFR 677T polymorphism was detected by a polymerase chain reaction (PCR)-based method, and physical HRQOL were assessed with the SF-36 Health Survey.

RESULTS

In multiple regression analyses, the odds of being in the lowest quartile of the physical component summary (PCS) scores (i.e. <35) was 1.47 (95% CI 1.21-1.78) for men with high tHcy (≥15 μmol/l), after adjusting for age, smoking, history of hazardous alcohol use, polypharmacy, prevalent falls and weighted Charlson co-morbidity index. When history of hypertension, heart disease, stroke, arthritis and osteoporosis were included in place of the Charlson's index, the result was unchanged (OR 1.45, 95% CI 1.20-1.75). Men with the MTHFR TT homozygosity had significantly higher tHcy concentration than those with the CC genotype (mean difference of 1.38 μmol/l, 95% CI 0.77-1.99). However, there was no apparent association between the MTHFR polymorphism and PCS.

CONCLUSION

Elevated tHcy is associated with poorer self-perceived physical health in community-dwelling older men. The results of this study support further longitudinal investigations to assess this relationship prospectively.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism and cognitive impairment: the health in men study

High total plasma homocysteine (tHcy) has been associated with cognitive impairment in later life, but it is unclear if this association is causal or is due to confounding. The C677T polymorphism of the 5,10 methylenetetrahydrofolate reductase gene (MTHFR) increases basal tHcy, but its contribution to cognitive impairment has not been established. We designed this study to determine if tHcy is causally related to cognitive impairment in later life by investigating its association with high tHcy and the MTHFR-C677T polymorphism. We recruited 1778 older men from the Health in Men Study cohort and established caseness on the basis of the participants' scores on a Telephone Interview for Cognitive Status score 27 in 2008. Exposure to tHcy, gene status and other variables of interest were obtained from assessments 4-7 years earlier. Multivariate logistic regression showed that the odds of cognitive impairment increased with a doubling of tHcy (adjusted odds ratio, OR 1.36; 95% confidence interval, 95% CI 1.02-1.82). Compared with the wild CC genotype, participants with the MTHFR-TT genotype had 46% greater odds of cognitive impairment (OR 1.46, 95% CI 1.01-2.11, P=0.043). The results of this study are consistent with, but do not prove the hypothesis that high tHcy causes cognitive impairment in later life.

Polymorphisms of methylenetetrahydrofolate reductase are not a risk factor for Kawasaki disease in the Korean population

PURPOSE

Hyperhomocysteinemia is known as a risk factor for atherosclerosis. Preclinical arteriosclerosis is noted and premature atherosclerosis is known to be accelerated in Kawasaki disease (KD) patients. Genetic polymorphisms in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene result in elevated plasma homocysteine concentrations and are known to be associated with the development of coronary artery disease. Our hypothesis is that single nucleotide polymorphisms (SNPs) of the MTHFR gene are related to the development of KD and coronary artery lesions (CALs).

METHODS

For this study, we selected 3 candidate single nucleotide polymorphisms (SNPs) (rs2274976, rs1801131, and rs1801133) of MTHFR. These SNPs are located on chromosome 1p36.3. We included 101 KD patients and 306 healthy adults as controls in this study. CALs were seen in 38 patients. Genotypes of the selected SNPs were determined by direct sequencing and analyzed with SNPAlyze.

RESULTS

The genetic distribution and allelic frequency of the 3 MTHFR SNPs (rs2274976, rs1801131, and rs1801133) were not significantly different in patients with KD compared to the control group (P=0.71, 0.17, and 0.96, respectively). There was no difference in the genetic distribution of the MTHFR SNPs between the normal control group and the CAL group (P=0.43, 0.39, 0.52 respectively).

CONCLUSION

The genetic distribution of the MTHFR SNPs (rs2274976, rs1801131, and rs1801133) was not different in the KD group compared to the control group. In addition, the genetic distribution of these SNPs was not different in the CAL group compared to the control group in the Korean population.

Creatine kinase MM TaqI and methylenetetrahydrofolate reductase C677T and A1298C gene polymorphisms influence exercise-induced C-reactive protein levels

Physical training induces beneficial adaptations, but exhausting exercise increases reactive oxygen species, which can cause muscular injuries with consequent inflammatory processes, implying jeopardized performance and possibly overtraining. Acute strenuous exercise almost certainly exceeds the benefits of physical activity; it can compromise performance and may contribute to increased future risk of cardiovascular disease (CVD) in athletes. Polymorphisms in the muscle-type creatine kinase (CK-MM) gene may influence performance and adaptation to training, while many potentially significant genetic variants are reported as risk factors for CVD. Therefore, we investigated the influence of polymorphisms in CK-MM TaqI and NcoI, methylenetetrahydrofolate reductase (MTHFR C677T and A1298C) and C-reactive protein (CRP G1059C) genes on exercise-induced damage and inflammation markers. Blood samples were taken immediately after a race (of at least 4 km) that took place outdoors on flat tracks, and were submitted to genotyping and biochemical evaluation of aspartate aminotransferase (AST), CK, CRP and high-sensitivity CRP (hs-CRP). CK-MM TaqI polymorphism significantly influenced results of AST, CK and hs-CRP, and an association between MTHFR C677T and A1298C with CRP level was found, although these levels did not exceed reference values. Results indicate that these polymorphisms can indirectly influence performance, contribute to higher susceptibility to exercise-induced inflammation or protection against it, and perhaps affect future risks of CVD in athletes.

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.

Atherothrombosis in 2 Vascular Territories in a Young Woman: Importance of Thrombophilia Testing

The diagnosis and management of complex and multiple inherited thrombophilias is still a challenge for the clinicians involved in this field, clinical events being the result of the interaction between genes, environmental or other acquired factors, and age. Moreover, various clinical manifestations as regards severity or type of event (venous or arterial thrombotic event, obstetrical complications) are cited in these patients. We present the case of a 20-year-old woman, with a 2-month history of third-generation contraceptive use and with recently diagnosed hypercholesterolemia, who presented ischemic events in 2 arterial territories: acute left lower limb ischemia and silent myocardial infarction. Screening tests for thrombophilia, including genetic testing, showed moderate hyperhomocysteinemia and 2 inherited thrombophilic defects. Invasive investigation of the coronary arteries showed the presence of advanced atherosclerotic disease. Management of this complex thrombophilia includes lifetime oral anticoagulation as well as a homocysteine-lowering strategy comprising lifestyle modification and group B (folic acid, B6, B12) vitamin supplementing.

The B-VITAGE trial: a randomized trial of homocysteine lowering treatment of depression in later life

Background

Depression is a leading cause of disability worldwide and depressive symptoms are common in later life. Observational evidence suggests that depression is more prevalent among people with high plasma homocysteine (tHcy), but the results of randomized trials to date have been unable to show that lowering tHcy through the supplementation of vitamins B₆, B₁₂ and folate benefits depressive symptoms. We designed the B-VITAGE trial to determine whether adjunctive treatment with vitamins B₆, B₁₂ and folate increases the efficacy of standard antidepressant treatment.

Methods/Design

The B-VITAGE trial is a 12-month randomized, double-blind, placebo-controlled trial of daily citalopram (20 to 40 mg) plus B₁₂(0.4 mg), B₆ (25 mg) and folic acid (2 mg) or citalopram (20 to 40 mg) plus placebo for the treatment of depression in later life. The trial aims to recruit over 300 older adults with major depression (DSM-IV) and has been powered to detect the impact of an intervention associated with moderate effect size. Depressive symptoms will be rated with the Montgomery-Åsberg Depression Rating Scale (MADRS). The trial has two main outcomes of interest: a reduction of 50% or more in the MADRS total score between baseline and week 12 and the remission of the depressive episode at weeks 12, 26 and 52 according to DSM-IV criteria. We hypothesize that subjects randomly allocated to the vitamin arm of the study will be more likely to show a clinically significant improvement and achieve and maintain remission of symptoms at 12, 26 and 52 weeks. Secondary outcomes of interest include compliance with treatment, reduction in the severity of depressive symptoms, switching to different antidepressants, the use of non-pharmacological antidepressant treatments, response to treatment according to MTHFRC677T genotype, and changes in cognitive function over 52 weeks.

Conclusions

The results of this trial will clarify whether the systematic use of B-vitamins improves the response of older adults to standard antidepressant treatment. We anticipate that our findings will have implications for clinical practice and health policy development.

Trial Registration

The trial is registered with the Australian Clinical Trials Registry, trial number (())ACTRN12609000256279.

Impact of homocysteine-lowering vitamin therapy on long-term outcome of patients with coronary artery disease

Elevated homocysteine levels are associated with increased risk for mortality in patients with coronary artery disease (CAD). However, the benefit of homocysteine-lowering therapy remains controversial. The aim of this study was to examine the impact of homocysteine-lowering therapy on the long-term outcomes of patients with CAD and its interaction with the methylenetetrahydrofolate reductase genotype. The study sample included 492 patients with early-onset CAD who were genotyped for the C677T mutation in the methylenetetrahydrofolate reductase gene or screened for elevated homocysteine from January 1997 to December 2002. Folic acid > or =400 microg/day with or without additional B vitamins was administered at the attending physicians' discretion. There was no difference between treated (n = 140) and untreated patients in age, gender, or prevalence of coronary risk factors. Forty-six patients (9%) died during a median follow-up period of 115 months. Treatment was associated with significantly lower all-cause mortality in patients with homocysteine levels >15 micromol/L (4% vs 32%, p <0.001) but not in patients with lower levels (5% vs 7%, p >0.05). On Cox regression analysis, the following factors were independently associated with all-cause mortality: vitamin therapy (hazard ratio 0.33, 95% confidence interval 0.11 to 0.98, p = 0.046), elevated homocysteine level (hazard ratio 3.5, 95% confidence interval 1.31 to 9.43, p = 0.013), and older age (hazard ratio 1.1, 95% confidence interval 1.04 to 1.14, p <0.0001 for an increment of 5 years). The methylenetetrahydrofolate reductase genotype was not associated with outcomes. In conclusion, long-term folate-based vitamin therapy was independently associated with lower all-cause mortality in patients with CAD and elevated homocysteine levels. This association was not observed in patients with lower homocysteine levels.

Genetic risk factors of bronchopulmonary dysplasia

The aim of the study was to assess the association between bronchopulmonary dysplasia (BPD) and polymorphisms of genes coding for vascular endothelial growth factor (VEGF), transforming growth factor (TGF-[beta]1), insulin-like growth factor (IGF-1), and 5,10-methylenetetrahydrofolate reductase (MTHFR). A sample of 181 newborns with mean gestational age of 28 wk was prospectively evaluated. Molecular analysis of TGF-[beta]1 -800G>A, -509C>T, 10T>C, 25G>C, VEGF -460T>C and 405G>C and MTHFR 677C>T polymorphisms were performed and the number of CA repeats in the promoter region of IGF-1 gene was assessed. The frequency of all TGF-[beta]1, IGF-1, and MTHFR polymorphisms, as well as the frequency of VEGF 405G>C polymorphism was similar in all groups. The newborns with -460TT and -460CT genotypes were significantly overrepresented in the BPD groups compared with the no BPD group. Multivariate analysis revealed that carrying T allele increased the risk of BPD by 9% (95%CI: 2-14%) above the baseline risk established for given gestational age, length of oxygen therapy, and sex. Based on our data from a single center, we propose that VEGF -460T>C polymorphism may influence the risk of BPD.

Association of methylenetetrahydrofolate reductase (MTHFR-677 and MTHFR-1298) genetic polymorphisms with occlusive artery disease and deep venous thrombosis in Macedonians

AIM

To analyze the association of methylenetetrahydrofolate reductase polymorphisms (MTHFR-677 and MTHFR-1298) with occlusive artery disease and deep venous thrombosis in Macedonians.

METHODS

We examined 83 healthy respondents, 76 patients with occlusive artery disease, and 67 patients with deep venous thrombosis. Blood samples were collected and DNA was isolated from peripheral blood leukocytes. Identification of MTHFR mutations was done with CVD StripAssay (ViennaLab, Labordiagnostika GmbH, Vienna, Austria) and the population genetics analysis package, PyPop, was used for the analysis. Pearson P values, crude odds ratio, and Wald's 95% confidence intervals were calculated.

RESULTS

The frequency of C alleles of MTHFR-677 was 0.575 in patients with deep venous thrombosis, 0.612 in patients with occlusive artery disease, and 0.645 in healthy participants. The frequency of T allele of MTHFR-677 was lower in healthy participants (0.355) than in patients with occlusive artery disease (0.388) and deep venous thrombosis (0.425). The frequency of A allele for MTHFR-1298 was 0.729 in healthy participants, 0.770 in patients with occlusive artery disease, and 0.746 in patients with deep venous thrombosis. The frequency of C allele of MTHFR-1298 was 0.271 in healthy participants, 0.230 in patients with occlusive artery disease, and 0.425 in patients with deep venous thrombosis. No association of MTHFR-677 and MTHFR-1289 polymorphisms with occlusive artery disease and deep venous thrombosis was found, except for the protective effect of MTHFR/CA:CC diplotype for occlusive artery disease.

CONCLUSION

We could not confirm a significant association of MTHFR-677 and MTHFR-1289 polymorphisms with occlusive artery disease or deep venous thrombosis in Macedonians, except for the protective effect of MTHFR/CA:CC diplotype against occlusive artery disease.

Homocysteine as a risk factor for cardiovascular and related disease: nutritional implications

The objectives were firstly to assess the evidence that homocysteine is a significant and independent risk factor for vascular disease with special reference to cardiovascular disease, and secondly to evaluate the evidence that a food staple fortified with folic acid will reduce this problem on a population basis.

The structure of plasma homocysteine (tHcy) is described. Homocysteine, a highly reactive compound, is synthesized from the amino acid, methionine, and is metabolized by two pathways, the catabolic transsulphuration routeviacystathionine β-synthase (EC 4.2.1.22) and the remethylation path using 5-methyltetrahy-drofolate polyglutamate, the product of 5,10-methylenetetrahydrofolate reductase (MTHFR; EC 1.1.1.171),viathe cobalamin dependent enzyme, methionine synthase (MS; EC 2.1.1.13).

The mechanisms whereby hyper-tHcy is produced include both increased rates of synthesis and decreased metabolism. The latter may occur owing to nutritional deficiency of the vitamin cofactors which are necessary for the normal function of the metabolic enzymes. In particular, folate is required for methylene reductase, pyridoxal phosphate for cystathionine synthase and cobalamin for methionine synthase. When these vitamins are deficient hyper-tHcy is induced and this occurs especially in the elderly. Alternatively, a variant form of methylene reductase has recently been described which occurs in nearly 10% of the normal population. This variant is associated with hyper-tHcy, especially in situations associated with a low folate nutritional status.

Meta-analysis of both retrospective case-control studies, nested prospective case-control surveys and a secondary trial of mortality in postmyocardial infarct patients have shown that the association of hyper-tHcy with vascular disease is beyond doubt. This has been further supported by direct assessments of the degree of vascular disease in the carotid brachial and aortic arteries in relation to tHcy levels. Furthermore, treatment with a cocktail of the vitamin cofactors has produced lowering of tHcy levels and regression of the vascular disease in the carotid arteries of affected individuals.

Suggested pathogenic mechanisms in vascular disease induced by hyper-tHcy include vascular endothelial cell dysfunction, smooth muscle proliferation and derangements of normal intravascular regulation mechanisms. A variety of clinical conditions are known to be associated with a high incidence of thromboembolic complications. Some of these are associated with hyper-tHcy.

Low physiological doses of folic acid, as well as pharmocological doses, lower tHcy. However, because of the poor bioavailability of food folate (50%) and the considerable chemical instability of the naturally occurring reduced forms of folate, in most people it would require unacceptably high consumption of green vegetables to accomplish the necessary increase in intracellular folate and reduction in tHcy. Accordingly, folic acid, the nonreduced synthetic form of the vitamin, which is 100% bioavailable and chemically extremely stable, should be added to a food staple such as flour to ensure maximum protection for most of the population.

The 677 C/T MTHFR polymorphism is associated with essential hypertension, coronary artery disease, and higher homocysteine levels

BACKGROUND

Essential hypertension (EH) and cardiovascular disease are common, multifactorial disorders likely to be influenced by multiple genes of modest effect. The C677T methylenetetrahydrofolate reductase (MTHFR) gene polymorphism is related to MTHFR enzyme activity and to plasma homocysteine (Hcy) concentration. This study was designed to investigate an association of this polymorphism with coronary artery disease (CAD), EH, and healthy subjects.

METHODS

In this study, we measured serum folate, serum vitamin B12, and plasma homocysteine and determined the MTHFR C677T genotype of 78 patients with essential hypertension, 100 patients with coronary artery disease, and 100 healthy subjects. MTHFR genotypes were assessed by real-time polymerase chain reaction.

RESULTS

CC, CT, and TT genotype frequencies were 52, 44.0, and 4.0% in patients with CAD, respectively. In patients with essential hypertension, the CC, CT, and TT genotype frequencies were 46.2, 41.0, and 12.8%, respectively. In control subjects, the CC, CT, and TT genotype frequencies were 72.0, 26.0, and 2.0%, respectively. The C allele was significantly more frequent in controls compared with patients with EH (p<0.05), and CC genotypes were more frequent in controls compared to patients with EH and CAD. Homocysteine level was higher in TT genotypes in CAD patients compared with CC and CT genotypes (p<0.01). MTHFR gene polymorphism is an independent risk factor for EH but not for CAD.

CONCLUSIONS

The TT genotype of the 677C/T MTHFR polymorphism is associated with EH and CAD. In addition, TT genotypes had higher plasma Hcy levels in CAD patients compared with CC and CT genotypes. MTHFR gene polymorphism is an independent risk factor for EH but not for CAD.

Association of cardiovascular risk factors and disease with depression in later life

OBJECTIVE

The objective of this study is to determine the association between established cardiovascular risk factors and depression among older men.

METHODS

The authors conducted a cross-sectional study of a community-representative sample of 5,439 men aged 71-89 years. Cardiovascular disease and risk factors assessed included history of diabetes, hypertension, angina, myocardial infarction, and stroke; current smoking; total cholesterol and fractions; triglycerides; total plasma homocysteine; and MTHFR677 genotype. Depression was defined by a Geriatric Depression Scale 15 items score of 7 or greater.

RESULTS

A complete data set was available for 4,204 men, of whom 212 were depressed (5%). Men who were depressed reported higher frequency of diabetes (23.1% versus 13.2%), angina (30.2% versus 20.4%), myocardial infarction (26.2% versus 16.0%), and stroke (23.6% versus 9.1%) than nondepressed men. Participants with depression were also more likely to have plasma homocysteine above 15 mumol/L (39.1% versus 25.5%) and high triglycerides (32.1% versus 20.9%) than nondepressed subjects. Depressed older men were also more likely to be active smokers (9.9% versus 4.8%). The other factors measured in the study were not significantly associated with depression. Estimation of the population-attributable fraction (PAF) after logistic regression showed that high plasma homocysteine had the highest PAF for depression (PAF:15%, 95% confidence interval [95% CI]: 5%-23%) followed by high triglycerides (PAF: 11%, 95% CI: 2%-18%), angina (PAF: 9%, 95% CI: 2%-15%), stroke (PAF: 8%, 95% CI: 3%-13%), diabetes (PAF: 7%, 95% CI: 1%-13%), myocardial infarction (PAF: 5%, 95% CI: 0%-11%), and smoking (PAF: 5%, 95% CI: 1%-9%).

CONCLUSIONS

High plasma homocysteine and triglycerides appear to account for a considerable proportion of cases of depression in older men. The successful management of these risk factors may contribute to decrease the prevalence of depression in later life.

Hyperhomocysteinemia in patients with arterial occlusive disease

PURPOSE

Hyperhomocysteinemia (HHCA) is defined as an independent risk factor for atherothrombotic vascular disease; therefore, screening for HHCA is recommended. However, the incidence and characteristics of HHCA in patients with vascular disease remain unclear. We conducted this study in an attempt to resolve these issues.

METHODS

This nonrandomized prospective study included 56 patients who were admitted with occlusive arterial disease (group I), and 39 control patients without occlusive arterial disease (group II). We recorded all the demographic data of both groups and collected blood samples for fasting homocysteine, vitamin B(12), and folic acid. All of the patients were followed up and the results were compared.

RESULTS

The mean concentration of homocysteine was 12.69 +/- 3.82 micromol/l in group I and 10.46 +/- 5.08 micromol/l in group II (P = 0.00048). In group I, the mean homocysteine levels for patients aged > or =70 years and those aged <70 years were 13.74 +/- 3.02 and 11.55 +/- 4.15 micromol/l, respectively (P = 0.021). There was no significant difference in mortality between the patients with HHCA and those with normal homocysteine levels during follow-up.

CONCLUSION

The incidence of hyperhomocysteinemia was higher in the patients with occlusive vascular disease than in the control patients. More evidence of the association with vitamins B(12) and folate and the benefits of homocysteine-lowering therapy is needed since we found no relationship between these vitamins and homocysteine in this study.

Methylenetetrahydrofolate reductase gene polymorphism, homocysteine and risk of macroangiopathy in Type 2 diabetes mellitus

OBJECTIVE

A polymorphism in the gene for methylenetetrahydrofolate reductase (MTHFR) has been reported to be associated with hyperhomocysteinemia and risk for atherosclerotic vascular diseases. In this case-control study, we examined the distribution of the MTHFR genotypes in the Chinese population and clarified the relationship between the gene polymorphism for MTHFR and macroangiopathy in Chinese Type 2 diabetes mellitus.

METHODS

Two hundred and sixteen unrelated patients with Type 2 diabetes mellitus, 112 of whom had macroangiopathy, and 114 healthy control subjects, were recruited. The MTHFR C677T genotype was analyzed by polymerase chain reaction-restriction fragment length polymorphism. Plasma total homocysteine levels were measured using high-performance liquid chromatography (HPLC) with fluorescence detection.

RESULTS

In 114 healthy control subjects, the frequency of the mutant T allele was 31.1%. The genotype distribution did not differ between control subjects and Type 2 diabetic patients (chi2=3.03, p=0.220). Genotypic analysis revealed that the MTHFR genotype was different between diabetic patients with and without macroangiopathy (chi2=12.42, p=0.002). Type 2 diabetic patients with macroangiopathy displayed a greater prevalence of T allele than Type 2 diabetic patients without macroangiopathy (44.6 vs 29.3%; chi2=10.82, p=0.001). The odds ratio for macroangiopathy in Type 2 diabetic patients in presence of T allele was 1.94 [confidence interval (CI) 95%: 1.31-2.89]. Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype.

CONCLUSIONS

The C677T mutation of MTHFR gene is common in the Chinese population. MTHFR C677T gene polymorphism associated with a predisposition to increased plasma homocysteine levels could constitute a useful predictive marker for macroangiopathy in Chinese Type 2 diabetic patients.

Is there a folate-related gene-environment interaction in the etiology of childhood acute lymphoblastic leukemia?

Acute lymphoblastic leukaemia (ALL) is the commonest childhood cancer in developed countries. Little is known about its causes, although its early age at diagnosis has focused interest on maternal and perinatal factors. We have previously observed a protective effect of maternal folate supplementation during pregnancy against ALL, and a number of studies have reported protective effects of some common polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene. One study has suggested that the effect of MTHFR polymorphisms on risk of ALL may depend on folate status. This study aimed to look for evidence of an interaction between maternal folate supplementation and child's genotype among the cases from our previous study. Bone marrow specimens from 82 of 83 case children were available. DNA was extracted and genotyped for MTHFR C677T and A1298C using standard techniques. We used a case-only analysis to estimate the case-only odds ratio (COR) for MTHFR genotype and folate supplementation in association with ALL. None of the CORs indicated a significant departure from a multiplicative model. Adjustment for sex, age or genotype at the other locus had little effect on the results. Other studies of this gene and environment interaction in ALL and other cancers have produced contradictory results, perhaps because of varying definitions of folate exposure. Further research into the interaction of folate intake and genotype in causing ALL and other cancers is needed. We are specifically studying it in an Australian national case-control study of genetic and environmental causes of ALL.

Present status of outcome prediction of invasive coronary treatment by using genetic markers

A growing number of studies suggest that the outcome after invasive coronary treatment may be in part genetically determined. Here, we review the present status of outcome prediction of invasive coronary treatments by using genetic markers. Although some studies found an association between one or another genetic marker with one or another clinical endpoint, many other studies found no such relations; to date, none of the genetic markers that have been investigated in association studies are used in routine clinical practice to prospectively assess the prognosis following invasive coronary treatment or to decide upon therapeutic strategies. Many associations between genetic markers and certain clinical endpoints were initially reported in small studies but could not be confirmed in larger ones. Some of these discrepancies may be explained by publication bias. Some genetic variants may have true effects on clinical endpoints, which, albeit biologically interesting, do not bear much clinical relevance. On the other hand, many-if not most-studies that have been published to date are more or less grossly underpowered and very rarely report on the results of an a priori power analysis. Thus, there is still a need for further high-quality studies designed to investigate the specific contribution of genetic factors to the outcome after invasive coronary interventions.

The John Charnley Award: heritable thrombophilia and development of thromboembolic disease after total hip arthroplasty

We retrospectively assessed whether heritable thrombophilia-hypofibrinolysis was more common in patients developing venous thromboembolism after total hip replacement than among control patients who did not develop venous thromboembolism, as an approach to better identify causes of venous thromboembolism after total hip arthroplasty. Twenty patients with proximal deep venous thrombosis after THA and 23 patients with symptomatic pulmonary embolism were compared with 43 control patients who did not have postoperative venous thromboembolism. Five of 42 patients with venous thromboembolism (12%) and 0 of 43 control patients (0%) had antithrombin III deficiency (< 75%). Nine of 42 patients with venous thromboembolism (21%) and 2 of 43 control patients (4.7%) had protein C deficiency (< 70%). Ten of 43 patients with venous thromboembolism (9 heterozygous, 1 homozygous; 23%) and 1 of 43 control patients (heterozygous; 2%) had the prothrombin gene mutation. Patients who had venous thromboembolism after total hip arthroplasty were more likely than matched control patients to have heritable thrombophilia with antithrombin III or protein C deficiency, or homo-heterozygosity for the prothrombin gene mutation. Screening for these three tests of heritable thrombophilia before total hip arthroplasty should improve the identification of patients with a reduced risk of venous thromboembolism who may need only mild thromboprophylaxis, and of those patients with heritable thrombophilia in whom prophylaxis should be more aggressive.

LEVEL OF EVIDENCE

Prognostic study, Level II-1 (lesser-quality RCT). See the Guidelines for Authors for a complete description of levels of evidence.

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.

[Polymorphisms in cystathionine beta-synthase and methylenetetrahydrofolate reductase genes as risk factors for cerebral vascular disease]

BACKGROUND AND OBJECTIVE

High plasma total homocysteine (tHcy), low dietary intake of folate and other B vitamins, and genetic polymorphisms related to the metabolism of homocysteine may interactively contribute to the risk of cerebral vascular disease (CVD). We explored interrelations between total homocysteine levels and mutations in genes for the two key enzymes in methionine-homocysteine metabolism.

PATIENTS AND METHOD

We analyzed two polymorphisms, C677T in the MTHFR gene and 844ins68 in the CBS gene. We assessed their association with fasting homocysteine in 64 patients with CVD, and in 159 controls.

RESULTS

No differences in CBS and MTHFR genotype frequencies between cases and controls were found (C677T p = 0.87 and 844ins68 p = 0.63), nor was a particular CBS and MTHFR genotype associated with an elevated risk of CVD. None of the genotypes defined by the CBS and MTHFR variants studied showed an association with elevated fasting homocysteine concentrations (C677T p = 0.07 and 844ins68 p = 0.47).

CONCLUSIONS

We did not find any indication that genetic variation in the CBS and MTHFR genes are associated with homocysteine-related risk of CVD, hence needing further investigation. The contributions to total plasma homocysteine levels of the common mutations of genes coding for the enzymes controlling homocysteine metabolism are modest.

Contribution of the MTHFR gene to the causal pathway for depression, anxiety and cognitive impairment in later life

Homocysteine (Hcy) is harmful to neurons and blood vessels, including the cerebral microvasculature. It is possible that such effects contribute to the cascade of events that leads to cognitive decline, dementia, and depression in later life. Hcy is produced during the metabolism of the essential amino-acid methionine, which also involves a methyl group transfer derived from folate and choline metabolism. Its plasma level can be influenced by factors such as age, vitamin deficiency, renal function, and a common mutation in the methylenetetrahydrofolate reductase (MTHFR) gene, where cytosine is replaced by thymidine (C-->T) at nucleotide position 677. Subjects with the TT genotype have higher homocysteine levels and may be particularly prone to experiencing depression as a result of high plasma Hcy and dysfunction of methylation metabolic pathways critical to the synthesis of noradrenaline and serotonin. We designed the present study to investigate whether older women with the TT genotype would have higher depression and lower cognitive scores than women with CT and CC genotypes. A total of 240 community-dwelling women aged 70 years or over volunteered to take part in the study - 29 carried the TT genotype, 113 the CT and 98 the CC genotype. The Beck Depression Inventory (BDI) score for subjects with the TT genotype was statistically similar to the other groups (P = 0.609). Plasma Hcy showed a modest and significant correlation with BDI scores (r = 0.21) that was independent from age, B12 and folate levels. There was no association between beck anxiety inventory (BAI) scores and MTHFR genotype or homocysteine levels. The cognitive assessment of participants included measures of verbal memory, memory for faces, verbal fluency, visuo-spatial abilities and the cognitive section of the Cambridge Examination For Mental Disorders Of The Elderly (CAMCOG)-MTHFR genotype had no clear association with cognitive scores. These results indicate that, in isolation, the MTHFR C677T gene variation does not play an important role in the modulation of mood and cognitive performance in later life.

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

OBJECTIVE

Epidemiological studies have identified hyperhomocyst(e)inemia as an independent risk factor for atherosclerosis. The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, might play a role in the development of coronary heart disease (CHD). In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and CHD in Chinese type 2 diabetic patients.

METHODS

Two hundred and twenty-eight unrelated patients with type 2 diabetes mellitus (126 with coronary heart disease) and 114 healthy control subjects were recruited. The MTHFR genotype was analyzed by PCR followed by HinfI digestion. Plasma total homocysteine levels were measured using high-performance liquid chromatography (HPLC) with fluorescence detection.

RESULTS

In 114 healthy control subjects, the frequency of the mutant T allele was 38.0%, comparable to that of a Hong Kong (Chinese) population. The genotype distribution did not differ between control subjects and type 2 diabetic patients (chi(2) = 3.67, P > 0.05). Genotypic analysis revealed that type 2 diabetic patients with CHD displayed a greater prevalence of T allele (45.2%) than type 2 diabetic patients without CHD (30.4%) (chi(2) = 8.72, P < 0.005). The odds ratio for CHD in type 2 diabetic patients in presence of T allele was 1.89 (CI 95%, 1.24-2.88). The MTHFR genotype were different between diabetic patients with and without CHD (chi(2) = 11.98, P < 0.005). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype or CC plus CT genotype.

CONCLUSIONS

The C677T mutation of MTHFR gene is common in the Chinese population. MTHFR C677T gene polymorphism associated with a predisposition to increased plasma homocysteine levels could constitute a useful predictive marker for CHD in Chinese type 2 diabetic patients.

Genetic polymorphism of methylenetetrahydrofolate reductase as a risk factor for diabetic nephropathy in Chinese type 2 diabetic patients

OBJECTIVE

Genetic predisposition has been implicated in diabetic nephropathy (DN). The C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene, one of the key enzymes catalyzing remethylation of homocysteine, may play a role in the development of not only vascular disease but also diabetic microangiopathies. In this study, we examined the distribution of the MTHFR genotypes in the Chinese population and the association between the C677T variant and diabetic nephropathy.

METHODS

220 unrelated patients with type 2 diabetes mellitus and 130 controls were recruited. The MTHFR genotype was analyzed by PCR followed by HinfI digestion. Plasma total homocysteine levels were measured using high-performance liquid chromatography (HPLC) with fluorescence detection.

RESULTS

In 130 healthy control subjects, the frequency of the mutant T allele was 30.0%, comparable to that of a Hong Kong (Chinese) population. The distribution of the three genotypes was as follows: TT genotype, 16.9%; CT genotype, 26.2%; and CC genotype, 56.9%. This genotype distribution did not differ between control subjects and type 2 diabetic patients in which 19.1% were TT, 34.5% were CT and 46.4% were CC (2=3.85, P>0.05). The frequency of the mutant T allele was 42.3% in diabetic patients with nephropathy (n=124) versus 28.6% in those without nephropathy (n=96). The genotype frequencies were TT, 21.0%; CT, 42.7%; CC, 36.3% in diabetic patients with nephropathy versus TT, 16.7%; CT, 23.9%; CC, 59.4% in those without nephropathy. The MTHFR genotype and allele frequencies were different between diabetic patients with and without nephropathy (chi2=12.27, P<0.005; chi2=8.77, P<0.005, respectively). Moreover, plasma homocysteine levels were markedly higher in individuals with TT genotype than those with CC or CT genotype.

CONCLUSIONS

The C677T mutation of MTHFR gene is common in the Chinese population. MTHFR C677T gene polymorphism associated with a predisposition to increased plasma homocysteine levels may represent a genetic risk factor for diabetic nephropathy in Chinese type 2 diabetic patients.

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 incidence of hyperhomocysteinaemia in vascular patients

INTRODUCTION

Hyperhomocysteinaemia has recently been identified as an important risk factor for atherosclerotic vascular disease. Screening for hyperhomocysteinaemia has been recommended, however, the incidence of hyperhomocysteinaemia in vascular patients is not known.

AIMS

To determine the incidence of hyperhomocysteinaemia in vascular patients, to determine the relation of hyperhomocysteinaemia with folate, vitamin B12 levels and lipid profiles in vascular patients. To examine if there is a relationship between the degree of vascular injury and homocysteine concentration.

METHODS

New vascular patients at The Queen Elizabeth Hospital were recruited and divided into peripheral, and aneurysmal presentations. Patients demographics were recorded, blood samples were taken for fasting lipid profile, and homocysteine concentration. Samples were also taken for vitamin B12, plasma and red cell folate levels. Sixty age and sex matched controls were included for comparison.

RESULTS

One hundred and twenty-six patients have been recruited, (95 men and 31 women) with a median age of 68 years (61-74 years). The incidence of elevated homocysteine, and cholesterol levels was 33, 47 and 24%. The levels of vitamin B12 and folate were normal in all patients. Homocysteine was elevated in 27% of claudicants, 50% of patients with rest pain and 53% of patients with an aortic aneurysm.

CONCLUSION

There is a high rate of hyperhomocysteinaemia in vascular patients with a higher incidence in patients with rest pain. There was also a high incidence of elevated homocysteine levels in patients with an abdominal aortic aneurysm. The rate of growth of these aneurysms is currently under review. Low folate or B12 concentrations is not the cause of raised homocysteine levels.

Elevated plasma homocysteine as risk factor for peripheral arterial disease--what is the evidence?

There is abundant evidence that elevated plasma homocysteine (HC) is independently associated with presence of atherosclerotic disease. There is credible evidence from a number of prospective studies that elevated HC is independently associated with progression of atherosclerotic disease. All studies to date agree that vitamin therapy, primarily folate, results in reliable decreases in HC, without recognized toxicity or side effects. Two small, randomized clinical trials have demonstrated clinically relevant benefit from folate treatment, which reduced HC in patients, compared to placebo. The results of multiple large scale clinical trials will be available within 2 to 5 years, and these have sufficient power to determine whether vitamin therapy intended to lower plasma HC will be established as the first effective therapy for atherosclerosis that does not involve expensive medication with toxic side effects and/or difficult changes in habits or lifestyle.

[Atherosclerosis and uremia: signifance of non-traditional risk factors]

Arteriosclerosis, atherosclerosis and vascular calcification are causally related to the high morbidity and mortality of patients with chronic renal failure. Oxidative stress and carbonyl stress of uremia, dialysis procedure and/or intravenous iron therapy result in AGE (advanced glycation end-product), ALE (advanced lipoxidation end-product) and AOPP (advanced oxidation protein product) formation, favouring together with elevated CRP (C-reactive protein) levels the development of cardiovascular and cerebrovascular complications. Enhanced plasma levels of homocysteine and ADMA (asymmetric dimethylarginine) contribute to this process. In addition, in chronic renal insufficiency hyperphosphatemia and an enhanced calcium x phosphorus ion product are associated with the morbidity and mortality of the patients, particularly in the presence of fetuin deficiency. Phosphorus, AGEs and AOPPs, beside other factors, catalyze the conversion of vascular smooth muscle cells to osteoblast--like cells (particularly in the presence of monocytes/macrophages), resulting in bone matrix protein formation. Other risk factors, such as age, male sex, smoking, hypertension, diabetes, chronic inflammation, insulin resistance or dyslipidemia (enhanced non-HDL-cholesterol) also contribute to the atherosclerotic risk profile of the patient with chronic renal insufficiency. While there is growing understanding of the mechanisms involved in arteriosclerosis, atherosclerosis and vascular calcification in uremia, we are still missing effective therapeutic maneuvers for reduction of excess mortality in uremic patients.

Genetic determinants of fasting and post-methionine hyperhomocysteinemia in patients with retinal vein occlusion

INTRODUCTION

Moderate hyperhomocysteinemia is considered a risk factor for both venous and arterial thrombosis. A prevalence of up to 30% of fasting hyperhomocysteinemia has been recently reported in patients with retinal vein occlusion (RVO) whereas conflicting data exist on the role of C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene as a risk factor for RVO. No report has been published on cystathionine beta-synthase (CBS) 844ins68 polymorphism (another genetic determinant of blood Hcy levels) in RVO patients. Moreover, scarce information is available on the usefulness of measuring homocysteine also after methionine loading to increase the diagnostic efficacy of hyperhomocysteinemia in RVO patients.

MATERIALS AND METHODS

In 55 consecutive patients with diagnosis of RVO and 65 matched controls, plasma fasting total homocysteine (Hcy) levels and CBS and MTHFR polymorphisms were evaluated. In patients with normal fasting Hcy levels, post-methionine Hcy levels were determined.

RESULTS

Moderate fasting hyperhomocysteinemia was detected in 18/55 patients (32.7%). In the remaining 37 patients, Hcy was measured again post-methionine loading (PML). Only 3/37 (8.1%) patients had PML hyperhomocysteinemia. Thus, the total prevalence of moderate hyperhomocysteinemia in this cohort of RVO patients was 21/55 (38.2%). The prevalence of homozygosity for C677T MTHFR genotype, but not that of heterozygosity for CBS844ins68, was significantly higher in RVO patients than in controls.

CONCLUSIONS

Differently from what has been reported for arterial and/or venous thrombosis, a single fasting Hcy measurement is able to detect most of RVO patients (85.7%) with moderate hyperhomocysteinemia. C677T MTHFR, but not CBS 844ins68, genotype may play a role as risk factor for RVO.

Genetic testing for coronary heart disease: the approaching frontier

The prospect for genetic testing to better delineate the risk for coronary heart disease will become a reality in the next decade. Advances in this area will follow the accelerated trajectory in our ability to dissect the genetics of complex diseases including coronary heart disease. A brief overview of the present state of knowledge will follow the discussion of present approaches in discovering these genetic predispositions. The key issues that will likely shape the field in the near future will also be presented.

Homocysteine levels and C677T polymorphism of methylenetetrahydrofolate reductase in women with polycystic ovary syndrome

The aim of this study was to investigate the homocysteine (Hcy) levels and the C677T polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR), a crucial factor of the Hcy metabolism in young women with polycystic ovary syndrome (PCOS). Seventy young women with PCOS and another 70 healthy women with low folate intake were enrolled. Cases and controls were matched for age, body mass index, and allele frequency. Hcy, vitamin B(12), and folate levels were measured, and a genetic analysis of 5,10-MTHFR at nucleotide 677 was performed in all subjects. No difference in mean Hcy levels was observed between PCOS women in comparison to the control group. Considering the different MTHFR polymorphism, no significant difference was found in serum Hcy levels between subjects with PCOS and controls showing CC (10.4 +/- 3.1 vs. 9.7 +/- 2.9 micromol/liter +/- SD) and CT genotypes (10.9 +/- 3.8 vs. 11.0 +/- 3.2 micromol/liter +/- SD). In subjects with a TT homozygous state, a significant (P < 0.05) difference was observed between PCOS and control women (11.5 +/- 3.9 vs. 22.0 +/- 7.8 micromol/liter +/- SD). In conclusion, our data show that in PCOS women, the serum Hcy levels are normal, and the C677T polymorphism of MTHFR does not influence the Hcy levels like in controls.

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.