Homocysteine and risk of premature coronary heart disease. Evidence for a common gene mutation

H2S Prodrug, SG-1002, Protects against Myocardial Oxidative Damage and Hypertrophy In Vitro via Induction of Cystathionine β-Synthase and Antioxidant Proteins

Endogenously produced hydrogen sulfide (H₂S) is critical for cardiovascular homeostasis. Therapeutic strategies aimed at increasing H₂S levels have proven cardioprotective in models of acute myocardial infarction (MI) and heart failure (HF). The present study was undertaken to investigate the effects of a novel H₂S prodrug, SG-1002, on stress induced hypertrophic signaling in murine HL-1 cardiac muscle cells. Treatment of HL-1 cells with SG-1002 under serum starvation without or with H₂O₂ increased the levels of H₂S, H₂S producing enzyme, and cystathionine β-synthase (CBS), as well as antioxidant protein levels, such as super oxide dismutase1 (SOD1) and catalase, and additionally decreased oxidative stress. SG-1002 also decreased the expression of hypertrophic/HF protein markers such as atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), galectin-3, TIMP1, collagen type III, and TGF-β1 in stressed HL-1 cells. Treatment with SG-1002 caused a significant induction of cell viability and a marked reduction of cellular cytotoxicity in HL-1 cells under serum starvation incubated without or with H₂O₂. Experimental results of this study suggest that SG-1002 attenuates myocardial cellular oxidative damage and/or hypertrophic signaling via increasing H₂S levels or H₂S producing enzymes, CBS, and antioxidant proteins.

Methylenetetrahydrofolate reductase polymorphisms as risk factors for retinal venous occlusive disease: A literature review

The role of polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene in retinal vein occlusion (RVO) is a theme of discussion since the first reports of RVO in patients with MTHFR C677T mutation and without classic acquired risk factors for retinal vascular disease. The association between MTHFR polymorphisms and RVO has been studied over the last 20 years producing conflicting results. This review aims to summarize the literature concerning the role MTHFR polymorphisms as risk factors for RVO.

Potential Links between Impaired One-Carbon Metabolism Due to Polymorphisms, Inadequate B-Vitamin Status, and the Development of Alzheimer's Disease

Alzheimer's disease (AD) is the major cause of dementia and no preventive or effective treatment has been established to date. The etiology of AD is poorly understood, but genetic and environmental factors seem to play a role in its onset and progression. In particular, factors affecting the one-carbon metabolism (OCM) are thought to be important and elevated homocysteine (Hcy) levels, indicating impaired OCM, have been associated with AD. We aimed at evaluating the role of polymorphisms of key OCM enzymes in the etiology of AD, particularly when intakes of relevant B-vitamins are inadequate. Our review indicates that a range of compensatory mechanisms exist to maintain a metabolic balance. However, these become overwhelmed if the activity of more than one enzyme is reduced due to genetic factors or insufficient folate, riboflavin, vitamin B6 and/or vitamin B12 levels. Consequences include increased Hcy levels and reduced capacity to synthetize, methylate and repair DNA, and/or modulated neurotransmission. This seems to favor the development of hallmarks of AD particularly when combined with increased oxidative stress e.g., in apolipoprotein E (ApoE) ε4 carriers. However, as these effects can be compensated at least partially by adequate intakes of B-vitamins, achieving optimal B-vitamin status for the general population should be a public health priority.

Hypercoagulable States

The hypercoagulable states consist of a group of prothrombotic clinical disorders associated with an increased risk for thromboembolic events. The abnormalities lead to inappropriate thrombus formation. After a review of the coagulation process, inherited disorders (including antithrombin-III deficiency, protein CS system deficiencies, disorders of plasmin generation, dysfibrinogenemias, and homocysteinuria) and acquired disorders (including responses to surgery, cancer, drugs, and the antiphospholipid syndrome) are described. Screening and management methods are discussed. Copyright © 1997 by W. B. Saunders Company.

A novel hydrogen sulfide prodrug, SG1002, promotes hydrogen sulfide and nitric oxide bioavailability in heart failure patients

Recent studies demonstrate robust molecular cross talk and signaling between hydrogen sulfide (H2 S) and nitric oxide (NO). Heart failure (HF) patients are deficient in both H2 S and NO, two molecules that are critical for cardiovascular homeostasis. A phase I clinical trial of a novel H2 S prodrug (SG1002) was designed to assess safety and changes in H2 S and NO bioavailability in healthy and HF subjects. Healthy subjects (n = 7) and heart failure patients (n = 8) received oral SG1002 treatment in escalating dosages of 200, 400, and 800 mg twice daily for 7 days for each dose. Safety and tolerability were assessed by physical examination, vital signs, and ECG analysis. Plasma samples were collected during a 24-h period each week for H2 S and NO analysis. BNP and glutathione levels were analyzed as markers of cardiac health and redox status. Administration of SG1002 resulted in increased H2 S levels in healthy subjects. We also observed increased H2 S levels in HF subjects following 400 mg SG1002. Nitrite, a metabolite of NO, was increased in both healthy and HF patients receiving 400 mg and 800 mg SG1002. HF subjects treated with SG1002 displayed stable drug levels over the course of the trial. SG1002 was safe and well tolerated at all doses in both healthy and HF subjects. These data suggest that SG1002 increases blood H2 S levels and circulating NO bioavailability. The finding that SG1002 attenuates increases in BNP in HF patients suggests that this novel agent warrants further study in a larger clinical study.

Association of the MTHFR rs1801131 and rs1801133 variants in sporadic Parkinson's disease patients

Parkinson's disease (PD) is a common age-dependent neurodegenerative movement disorder related to multiple factors, and genetic factors play an important role in the pathogenesis of PD. Variants in the methylenetetrahydrofolate reductase gene (MTHFR), a gene encoding a folate-dependent enzyme that is involved in homocysteine metabolism, have been reported to be associated with PD. To explore the role of the MTHFR gene in the development of PD in Chinese Han population, we analyzed two MTHFR variants (rs1801131 and rs1801133) in a patient cohort consisting of 512 patients with PD from mainland China and a control cohort consisting of 512 age, gender and ethnicity matched normal subjects. Statistically significant differences in genotypic and allelic frequencies were detected in the MTHFR variant rs1801133 (P=0.022 and 0.007, respectively; odds ratio=0.780, 95% confidence interval=0.651-0.934). In addition, the A-T haplotype of rs1801131-rs1801133 showed a protective role against PD development (P=0.007, odds ratio=0.779, 95% confidence interval=0.650-0.933). Our results suggested that the T allele of rs1801133 variant and A-T haplotype of rs1801131-rs1801133 in the MTHFR gene may decrease the risk of developing PD in Chinese Han population from mainland China.

Genetic polymorphism of MTHFR C677T and premature coronary artery disease susceptibility: A meta-analysis

The association between 5, 10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism and premature coronary artery disease (PCAD) is controversial. To explore a more precise estimation of the association, a meta-analysis was conducted in the present study. The relevant studies were identified by searching PubMed, EMBASE, the Web of Science, Cochrane Collaboration Database, Chinese National Knowledge Infrastructure, Wanfang Database and China Biological Medicine up to November, 2014. The meta-analysis was performed by STATA 11. 21 studies with a total of 6912 subjects, including 2972 PCAD patients and 3940 controls. The pooled analysis showed that MTHFR C677T gene polymorphism was probably associated with PCAD (CT vs. CC: OR=1.13, 95% CI=1.01-1.27; dominant model: OR=1.16, 95% CI=1.04-1.29; recessive model: OR=1.19, 95% CI=1.00-1.40; allele analysis: OR=1.17, 95% CI=1.01-1.34). Subgroup analysis by plasma homocysteine concentration showed a significant association in the homocysteine >15μmol/L subgroup (CT vs. CC: OR=1.44, 95% CI=1.10-1.88; TT vs. CC: OR=2.51, 95% CI=1.12-5.63; dominant model: OR=1.51, 95% CI=1.16-1.96; recessive model: OR=2.33, 95% CI=1.05-5.20; allele analysis: OR=1.48, 95% CI=1.18-1.87). Subgroup analysis by continent displayed a significant association among the Asian population (CT vs. CC: OR=1.51, 95% CI=1.23-1.86; TT vs. CC: OR=2.81, 95% CI=1.87-4.23; dominant model: OR=1.65, 95% CI=1.35-2.01; recessive model: OR=2.22, 95% CI=1.53-3.21; allele analysis: OR=1.61, 95% CI=1.37-1.89). The statistical stability and reliability was demonstrated by sensitivity analysis and publication bias outcomes. In conclusion, the meta-analysis suggests that MTHFR C677T gene polymorphism may be associated with PCAD.

Higher incidence of C677T polymorphism of the MTHFR gene in North Indian patients with vascular disease

Homocysteine is a sulfur-containing amino acid, which is derived from dietary methionine. Hyperhomocysteinemia has been implicated in vascular disease for over a decade now, and can be treated with B vitamins. Among its causes is polymorphism of the MTHFR gene, the most common being the cytidine to thymidine at position 677 (MTHFR C677T), which gives rise to three genotypes - normal homozygous CC, heterozygous CT and homozygous variant TT. An attempt was made to ascertain the prevalence of this MTHFR C677T in our population so that preventive measures may accordingly be instituted. Blood samples from 70 patients with vascular disease and 70 healthy controls were analyzed for plasma homocysteine levels (chemiluminescent immunoassay) and for the presence of MTHFR C677T (polymerase chain reaction analysis). Homocysteine was higher in the homozygous subjects (TT genotype) than in the heterozygous (CT genotype). In patients, the frequency of the C allele was significantly lower, and that of the T allele was significantly higher than the corresponding frequencies in controls. In conclusion, the North Indian urban population has higher homocysteine levels associated with the TT genotype. Hence, instituting measures towards reduction of homocysteine levels in the population would probably reduce the incidence and morbidity of vascular disease in our population.

Nutrigenetic impact of daily folate intake on plasma homocysteine and folate levels in patients with different methylenetetrahydrofolate reductase genotypes

BACKGROUND

Elevated plasma homocysteine level is associated with coronary artery disease (CAD). Homozygosity for the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is typically but inconsistently associated with hyperhomocysteinemia. We examined the impact of daily intake of folate, a co-factor in homocysteine metabolism, on plasma homocysteine and folate levels in CAD patients in relation with MTHFR genotypes.

METHODS

Daily folate intake was assessed from 3-day food records in 99 patients with CAD: 35 with the T/T (homozygous mutant) genotype and 64 with the C/C or C/T (non-T/T) genotypes.

RESULTS

Patients with the T/T genotype had higher fasting plasma homocysteine levels (18.4±1.9 vs. 12.6±0.6 μmol/l, P=0.01) and lower plasma folate levels (17.8±1.7 vs. 20.8±1.0 nmol/l, P=0.02). There were no differences between the genotype groups in energy-adjusted folate intake. In patients with the non-T/T genotypes, higher folate intake was associated with higher plasma folate levels and lower plasma homocysteine levels. In T/T homozygotes this association was weaker. Linear regression analysis showed that folate intake, the MTHFR genotype, plasma vitamin B12 levels, and the interaction between plasma folate level and MTHFR genotype, predicted homocysteine elevation. (folate intake, P=0.04, MTHFR genotype, P=0.03, plasma folate, P=0.02, and plasma B12 level, P=0.004). The model explained only 29% of the variance in log-transformed plasma homocysteine levels.

CONCLUSION

T/T homozygotes are more sensitive to the combination of low folate intake, low plasma folate and vitamin B12 level, than patients with non-T/T genotypes. The variability in plasma homocysteine in T/T homozygotes is only partly explained by these variables.

Survival bias and drug interaction can attenuate cross-sectional case-control comparisons of genes with health outcomes. An example of the kinesin-like protein 6 (KIF6) Trp719Arg polymorphism and coronary heart disease

BACKGROUND

Case-control studies typically exclude fatal endpoints from the case set, which we hypothesize will substantially underestimate risk if survival is genotype-dependent. The loss of fatal cases is particularly nontrivial for studies of coronary heart disease (CHD) because of significantly reduced survival (34% one-year fatality following a coronary attack). A case in point is the KIF6 Trp719Arg polymorphism (rs20455). Whereas six prospective studies have shown that carriers of the KIF6 Trp719Arg risk allele have 20% to 50% greater CHD risk than non-carriers, several cross-sectional case-control studies failed to show that carrier status is related to CHD. Computer simulations were therefore employed to assess the impact of the loss of fatal events on gene associations in cross-sectional case-control studies, using KIF6 Trp719Arg as an example.

RESULTS

Ten replicates of 1,000,000 observations each were generated reflecting Canadian demographics. Cardiovascular disease (CVD) risks were assigned by the Framingham equation and events distributed among KIF6 Trp719Arg genotypes according to published prospective studies. Logistic regression analysis was used to estimate odds ratios between KIF6 genotypes. Results were examined for 33%, 41.5%, and 50% fatality rates for incident CVD.In the absence of any difference in percent fatalities between genotypes, the odds ratios (carriers vs. noncarriers) were unaffected by survival bias, otherwise the odds ratios were increasingly attenuated as the disparity between fatality rates increased between genotypes. Additional simulations demonstrated that statin usage, shown in four clinical trials to substantially reduce the excess CHD risk in the KIF6 719Arg variant, should also attenuate the KIF6 719Arg odds ratio in case-control studies.

CONCLUSIONS

These computer simulations show that exclusions of prior CHD fatalities attenuate odds ratios of case-control studies in proportion to the difference in the percent fatalities between genotypes. Disproportionate CHD survival for KIF6 Trip719Arg carriers is suggested by their 50% greater risk for recurrent myocardial infarction. This, and the attenuation of KIF6 719Arg carrier risk with statin use, may explain the genotype's weak association with CHD in cross-sectional case-control studies. The results may be relevant to the underestimation of risk in cross-sectional case-control studies of other genetic CHD-risk factors affecting survival.

Increased levels of homocysteine in patients with ulcerative colitis

AIM: To investigate serum levels of homocysteine (Hcys) and the risk that altered levels carry for thrombosis development in ulcerative colitis (UC) patients.

METHODS: 55 UC patients and 45 healthy adults were included. Hcys, vitamin B12 and folic acid levels were measured in both groups. Clinical history and thromboembolic events were investigated.

RESULTS: The average Hcys level in the UC patients was 13.3 ± 1.93 μmmol/L (range 4.60-87) and was higher than the average Hcys level of the control group which was 11.2 ± 3.58 μmmol/L (range 4.00-20.8) (P < 0.001). Vitamin B12 and folic acid average values were also lower in the UC group (P < 0.001). When multivariate regression analysis was performed, it was seen that folic acid deficiency was the only risk factor for hyperhomocysteinemia. Frequencies of thromboembolic complications were not statistically significantly different in UC and control groups. When those with and without a thrombosis history in the UC group were compared according to Hcys levels, it was seen that there were no statistically significant differences. A negative linear relationship was found between folic acid levels and Hcys.

CONCLUSION: We could not find any correlations between Hcys levels and history of prior thromboembolic events.

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.

Age-related alteration of risk profile, inflammatory response, and angiographic findings in patients with acute coronary syndrome

Background:

Coronary artery disease (CAD) is a major public health problem which in turn imposes a significant burden on health care systems because of high morbidity and mortality. Although the multifactorial etiology of CAD increases with age, but in recent years, the incidence is increasing among younger age groups.

Objectives:

In this study we aimed to evaluate the effect of age on risk profile, inflammatory response and the angiographic findings in patients with ACS.

Patients and Methods:

The study comprised 253 ACS patients. Seventy six (30%) with UA, 56 (22%) with NSTEMI and 121(48%) with STEMI diagnosis. The value of Hs-CRP, lipid profile, cardiac enzymes, risk factors, EF% and angiographic score were analyzed and compared in different age groups.

Results:

Group 1 (n = 68) with age <45 years, group II (n = 110) with age ≥45–<65 years and group III (n = 75) ≥65 years. Group I had more prevalence of male sex, smoking, family history, hypertriglyceridemia and low levels of HDL (P < 0.01), higher incidence of STEMI (P < 0.01) and lower prevalence of UA (P < 0.01). Diabetes mellitus, hypertension, and female gender were more common in older groups. Hs-CRP was significantly lower in the young age (group I). Group I showed a preponderance of single-vessel disease, lower coronary atherosclerotic score and prevalent left anterior descending artery (LAD) involvement compared with older age groups. Hs-CRP was positively correlated to severity of CAD only in older groups. Stepwise multiple regression analysis showed that age, male gender, cardiac enzymes and EF% were common predictors of multivessel disease. Smoking was independent predictor in young patients <45 years while diabetes and Hs-CRP was the key predictor in older patient groups.

Conclusion:

Young patients with ACS had different clinical, angiographic and biochemical profile. Hs-CRP peak concentration did not correlate with angiographic findings in young patients that could be attributed to different risk profile and discrete underlying mechanism.

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.

Molecular genetics of myocardial infarction

Myocardial infarction (MI) is an important clinical problem because of its large contribution to mortality. The main causal and treatable risk factors for MI include hypertension, hypercholesterolemia or dyslipidemia, diabetes mellitus, and smoking. In addition to these risk factors, recent studies have shown the importance of genetic factors and interactions between multiple genes and environmental factors. Disease prevention is an important strategy for reducing the overall burden of MI, with the identification of markers for disease risk being key both for risk prediction and for potential intervention to lower the chance of future events. Although genetic linkage analyses of families and sib-pairs as well as candidate gene and genome-wide association studies have implicated several loci and candidate genes in predisposition to coronary heart disease (CHD) or MI, the genes that contribute to genetic susceptibility to these conditions remain to be identified definitively. In this review, we summarize both candidate loci for CHD or MI identified by linkage analyses and candidate genes examined by association studies. We also review in more detail studies that have revealed the association with MI or CHD of polymorphisms in MTHFR, LPL, and APOE by the candidate gene approach and those in LTA and at chromosomal region 9p21.3 by genome-wide scans. Such studies may provide insight into the function of implicated genes as well as into the role of genetic factors in the development of CHD and MI.

Mechanisms and potential therapeutic targets for folic acid in cardiovascular disease

Folic acid (FA) is a member of the B-vitamin family with cardiovascular roles in homocysteine regulation and endothelial nitric oxide synthase (eNOS) activity. Its interaction with eNOS is thought to be due to the enhancement of tetrahydrobiopterin bioavailability, helping maintain eNOS in its coupled state to favor the generation of nitric oxide rather than oxygen free radicals. FA also plays a role in the prevention of several cardiac and noncardiac malformations, has potent direct antioxidant and antithrombotic effects, and can interfere with the production of the endothelial-derived hyperpolarizing factor. These multiple mechanisms of action have led to studies regarding the therapeutic potential of FA in cardiovascular disease. To date, studies have demonstrated that FA ameliorates endothelial dysfunction and nitrate tolerance and can improve pathological features of atherosclerosis. These effects appear to be homocysteine independent but rather related to their role in eNOS function. Given the growing evidence that nitric oxide synthase uncoupling plays a major role in many cardiovascular disorders, the potential of exogenous FA as an inexpensive and safe oral therapy is intriguing and is stimulating ongoing investigations.

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.

Gene polymorphism association studies in dialysis: vascular access

Complications of the vascular access site for hemodialysis are a major cause of morbidity, suboptimal dialysis, and hospitalization. Vascular access for dialysis that is achieved by central venous catheters is associated with complications such as infection and thrombosis. Arteriovenous fistulas and grafts are also at risk for infectious complications. Further, proliferation of the venous wall with secondary thrombosis is a common pathophysiological process that leads to vascular access dysfunction. Genetic polymorphisms that contribute to vascular access failure are found among factors of the coagulation cascade, and host mediators that induce endothelial dysfunction as well as vessel wall proliferation. The two most common mutations of coagulation factors seem to influence the risk of central venous catheter and fistula thrombosis. Indeed, both the single nucleotide polymorphism of the factor V gene at amino acid position 506 (factor V Leiden mutation) and the prothrombin 20210 polymorphism have been associated with thrombotic complications of the vascular access. Among the endothelium-directed factors, a polymorphism of the methylene tetrahydrofolate reductase gene coding for an enzyme that degrades the endothelium toxic product homocysteine, has been associated with fistula failure. While the angiotensin converting enzyme polymorphism does not seem to be associated with vascular access complications, polymorphisms of the profibrogenic cytokine transforming growth factor-beta1 are associated with the prognosis of native arteriovenous fistulae. The role of pro- and anti-inflammatory cytokine gene polymorphisms as prognostic factors for vascular access is yet to be clearly defined.

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.

Genetic mutation analysis by CE with LIF detection using inverse-flow derivatization of DNA fragments

Inverse-flow derivatization is a novel approach to obtain fluorescent DNA derivatives in DNA analysis based on CE with LIF detection. In the present work, we want to explore the feasibility of the application of this method into the mutation detection based on constant denaturant capillary electrophoresis (CDCE) and SSCP analysis. The DNA fragments were first amplified by PCR using a pair of common primers without fluorescent label, and then the mutations were determined by CDCE or SSCP analysis based on CE-LIF with inverse-flow derivatization of DNA fragments. The experimental conditions were investigated systematically, and different labeling modes including inverse-flow derivatization, on-column derivatization and fluorescent labeled primer technique were compared. The inverse-flow derivatization was successfully used in the detection of C677T mutation in the methylenetetrahydrofolate reductase gene by CDCE or SSCP analysis. Our preliminary results demonstrate that inverse-flow derivatization is very simple, inexpensive and sensitive and well suitable for the genetic analysis in clinical diagnosis.

677TT polymorphism of methylenetetrahydrofolate reductase in combination with low serum vitamin B12 is associated with coronary in-stent restenosis

BACKGROUND

Recent studies have shown that a common mutation (nucleotide 677 C-->T) in the methylenetetrahydrofolate reductase (MTHFR) gene may contribute to a mild rise in plasma homocysteine levels and increase the incidence of coronary artery disease. Therefore, this study was designed to further investigate whether the effects of MTHFR 677 C to T mutation, plasma homocysteine, serum vitamin B12, and folate can influence restenosis after successful coronary stenting.

METHODS AND RESULTS

We investigated 260 patients each with a lesion after successful coronary stent placement. All patients received a repeated angiography after 6 months, or earlier if clinically indicated. Angiographic in-stent restenosis (ISR) was defined as >or=50% diameter stenosis at follow-up. Genotyping for MTHFR was based on a polymerase chain reaction technique. Also fasting plasma homocysteine, vitamin B12, and folate levels were measured at the same time. The ISR rate was higher among the patients with the TT genotype than in those with the non-TT genotypes (64.0% versus 32.9%, P=0.002). There was no significant difference in plasma homocysteine levels among patients with the TT genotype and patients with the non-TT genotypes (15.9+/-7.6 versus 15.5+/-6.6 micromol/L, P=0.75). However, among the patients with the TT genotype, those with higher plasma homocysteine levels (>or=12 micromol/L) demonstrated a significantly higher ISR rate (75.0% versus 33.5%, P=0.001). Logistic regression analysis revealed that the combined presence of the MTHFR TT genotype and lower than average serum vitamin B12 (>or=550 pg/mL) resulted in the most significant difference in the risk of ISR (OR=3.57, CI=1.51-8.46, P=0.004; OR=2.36, CI=1.35-4.15, P=0.003).

CONCLUSIONS

MTHFR 677TT polymorphism and low serum vitamin B12 each individually increased the risk of coronary ISR. Furthermore, the combination of these parameters resulted in a greater increase in risk.

Celiac sprue, hyperhomocysteinemia, and MTHFR gene variants

GOALS

To describe the association of untreated celiac disease with hyperhomocysteinemia and variants of the methylenetetrahydrofolicacid reductase (MTHFR) gene found in clinical practice.

STUDY

Case studies with description of associated clinical, biochemical, and genetic findings and review of literature.

RESULTS

Five new cases and 7 additional cases found from literature search of hyperhomocysteinemia with celiac sprue are reported. Treatment with gluten-free diet and folic acid led to the variable improvement in homocysteine levels. MTHFR gene variants were present in the each of the new patients described.

CONCLUSIONS

Untreated celiac disease may be associated with hyperhomocysteinemia caused by a combination of vitamin deficiencies and variants in the MTHFR gene. Abnormalities do not consistently improve with gluten-free diet. The abnormal findings could result from vitamin deficiencies or variant MTHFR status. Possible clinical implications for patients with celiac disease and hyperhomocysteinemia are reviewed.

Hyperhomocysteinemia in ulcerative colitis is related to folate levels

AIM: To study the prevalence and clinical significance of hyperhomocysteinemia (hHcys), an independent factor for arterial and venous thrombosis, in a group of patients with ulcerative colitis (UC).

METHODS: Fasting homocysteine (Hcys), folate, and vitamin B12 serum levels were measured in 40 UC patients and 50 healthy controls. Clinical data regarding UC were gathered.

RESULTS: Median serum Hcys levels in UC patients were similar to those in controls (12.26 µmol/L vs 12.32 µmol/L), but the prevalence of hHcys was higher in UC patients than in controls (30% vs 10%, P = 0.028). UC significantly increased the risk of hHcys (adjusted odds ratio: 4.125; 95%CI: 1.26-13.44). Multivariate regression analysis showed that male sex, folate and vitamin B12 deficiency or lower serum values were significant independent predictors of higher Hcys levels in UC patients (r² = 0.4; P<0.001).

CONCLUSION: hHcys is common in UC patients and it is related to folate and vitamin B12 deficiency or lower serum values. It would be reasonable for patients with UC to receive folate and vitamin B complex supplements as a prophylactic measure.

[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.

Detection of C677T mutation in methylenetetrahydrofolate reductase gene by denaturing high performance liquid chromatography

In this paper, we described an assay for the detection of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene using denaturing high-performance liquid chromatography (DHPLC). The conditions for DHPLC analysis were systematically investigated based on a general HPLC instrument (Prostar VARIAN). A 225 bp DNA fragment covering the 677 site of MTHFR gene was amplified by PCR technology using the purified DNA from whole blood or whole blood as template DNA. PCR products were directly injected without the need for purification. The C677T mutation could be clearly distinguished by DHPLC technology. Our data demonstrated that DHPLC was a powerful and alternative tool for detection of genetic variants and single-nucleotide polymorphisms to electrophoresis technology.

Vascular risk and low serum B12 predict white matter lesions in patients with major depression

BACKGROUND

While patients with depression have been shown to have a greater incidence of vascular risk factors and structural brain changes, any association with dietary co-factors is unclear.

METHODS

Forty-seven patients with major depression (mean age = 52.8 years, SD = 12.6) and 21 healthy volunteers (mean age = 54.7 years, SD = 9.1) underwent high-resolution magnetic resonance imaging scanning. T2-weighted films were scored for deep white matter (DWM), periventricular (PV), and subcortical (SC) hyperintensities.

RESULTS

There was no difference in lesion severity between patients and control subjects. After controlling for age, vitamin B12 levels were predictive of DWM lesions in patients. DWM and SC lesions were associated with histories of hypertension and diabetes.

LIMITATIONS

A relatively small sample of patients were recruited from specialist services and the findings may not represent those observed in larger or community-based cohorts.

CONCLUSIONS

In patients with major depression, vitamin B12 levels and histories of hypertension and/or diabetes are predictive of white matter lesions.

Reduced serum homocysteine levels in type 2 diabetes

OBJECTIVE

To assess the contribution of fasting blood glucose and methylene-tetrahydrofolate reductase (MTHFR) gene polymorphism on fasting serum homocysteine (tHcy) levels in patients with uncomplicated type 2 diabetes compared with healthy subjects.

METHODS AND RESULTS

We studied 105 type 2 diabetic patients without cardiovascular complications or diabetic nephropathy (55 males, 50 females, mean age 53+/-10 years, mean duration of diabetes 11.4+/-8 years) and 120 age- and sex-matched control subjects (65 males, 55 females, mean age 52+/-8 years). tHcy and other biochemical variables were measured. The C677T MTHFR gene polymorphism was determined by analysis of HinfI restriction fragment length polymorphism tHcy levels were significantly lower in diabetic patients compared with control subjects (7.7 +/- 2.2 vs. 11.8 +/- 4.5 micromol/l, P < 0.0001). In both patients and control subjects, homocysteinemia was higher in men than in women (8.4+/-2.6 vs. 7.3+/-2.0 micromol/l, P < 0.03, and 13.0+/-5.3 vs. 10.4+/-2.6 micromol/l, P < 0.0001, respectively). Levels were slightly higher in subjects with the mutated Val/Val genotype compared with the Ala/Val plus Ala/Ala genotypes in both diabetic patients (P < 0.02) and control subjects (P < 0.003). On simple regression analysis, tHcy was inversely related with blood glucose levels (P < 0.02) and directly with sex (P < 0.04) in diabetic patients, and with sex (P < 0.0001), age (P < 0.02), BMI (P < 0.03), systolic and diastolic blood pressure (P < 0.0004 and P < 0.0002), uric acid and creatinine (P < 0.0001 and P < 0.0003) in control subjects. On multiple regression, tHcy levels were associated with sex (P < 0.03) and glucose levels (P < 0.04) in diabetic patients, and with uric acid (P < 0.002) and MTHFR genotype (P < 0.03) in control subjects.

CONCLUSION

In type 2 diabetic patients without nephropathy, basal levels of tHcy were 35% lower compared with healthy controls. Chronic hyperglycemia may control tHcy by affecting its renal excretion, or accelerate hepatic trans-sulfuration secondary to insulin disorders.

The effect of hormone therapy on plasma homocysteine levels: a randomized clinical trial*

OBJECTIVE

An elevated plasma homocysteine level is a risk factor for cardiovascular diseases. Hormone therapy (HT) may reduce fasting plasma homocysteine levels. We studied 80 postmenopausal women to determine the effect of medroxyprogesterone acetate (MPA) combined with conjugated equine estrogens (CEE) on fasting plasma homocysteine levels.

DESIGN

In a randomized, double blind, prospective, placebo-controlled study, we randomly assigned 80 healthy postmenopausal women between CEE 0.625 mg/d combined with MPA 2.5 mg/d (n = 20), CEE 0.625 mg/d combined with MPA 5 mg/d (n = 20), unopposed CEE 0.625 mg/d (n = 20), and placebo (n = 20) all given for a duration of 6 months. Fasting plasma homocysteine levels were measured before and at the end of the treatment.

RESULTS

Before treatment, plasma homocysteine concentrations were similar in all groups. After 6 months of unopposed CEE, the mean fasting plasma homocysteine levels decreased by 19.02% when compared with baseline levels (P < 0.05). The mean fasting plasma homocysteine concentrations decreased by 17.63% and 19.56% from baseline in both the CEE plus MPA 2.5 mg/d and CEE plus MPA 5 mg/d groups, respectively (P < 0.05 for each group). In contrast, plasma homocysteine levels increased by 11.66% in the placebo group. The homocysteine lowering effect did not differ significantly among the three groups of women receiving unopposed CEE alone and CEE plus MPA at two different doses.

CONCLUSION

Six months of estrogen therapy (ET) and combined estrogen-progestogen therapy (EPT) significantly lower fasting plasma homocysteine levels in healthy postmenopausal women with equal efficacy.

MTHFR C677T gene mutation as a risk factor for arterial stroke: a hospital based study

Elevated homocysteine level is an independent risk factor for ischemic stroke, thrombotic and cardiovascular diseases. The enzyme methylenetetrahydrofolate reductase (MTHFR) plays a crucial role in regulating the levels of homocysteine. A C677T mutation in this gene results in reduced activity. Sixty-nine patients with arterial stroke, six patients with venous stroke (confirmed by computed tomography and/or magnetic resonance imaging) with hyperhomocysteinemia were selected for the study. Forty-nine subjects with no past history of stroke served as controls. MTHFR genotypes were determined by PCR using specific primers, followed by restriction digestion and gel analysis. The prevalence of the mutated homozygous and heterozygous C677T MTHFR genotype in the patients with arterial stroke was 1.4% (one of 69) and 31.88% (21 of 69), respectively. There frequency was 16.6% (one of six) and 33.3% (two of six) in venous stroke. The genotyping results from controls showed that there was only one heterozygote out of the 49 studied (2.08%). There was a significant difference between the control and the patient groups. Odds ratio for the probability of the C677T MTHFR gene mutation in the patients versus control group was 22.29 (95% CI 4.89-98.8). This indicates that C677T MTHFR mutation is strongly associated with arterial stroke especially in young adults. MTHFR allele evaluation will help in preventing/reducing morbidity caused by stroke.

C677T polymorphism of the methylenetetrahydrofolate reductase gene is a risk factor of adverse events after coronary revascularization

BACKGROUND

A common point mutation (C677T) in the gene for 5,10-methylenetetrahydrofolate reductase (MTHFR) is associated with hyperhomocysteinemia, an independent risk factor and a strong predictor of mortality in patients with coronary artery disease (CAD). The aim of this study was to investigate whether C677T polymorphism can be a predictor of major adverse cardiac events after myocardial revascularization.

METHODS

We determined MTHFR genotype in 159 patients with CAD undergoing myocardial revascularization [72 percutaneous transluminal coronary angioplasty (PTCA) and 87 coronary artery bypass graft (CABG)]. Recurrent angina, nonfatal myocardial infarction (MI), target vessel revascularization, heart failure and cardiac death were considered major adverse cardiac events that occurred after discharge from index hospitalization.

RESULTS

During the follow-up (6.9+/-0.3 months, mean+/-S.E.M.), the composite endpoint accounted for 25.9%, 11.4% and 4.3% for TT, CT and CC genotype (log-rank statistic 5.2, p=0.02), respectively. Subjects with mutant TT genotype had a threefold increase of any cardiac event (hazard ratio [HR]=3.0; 95% [CI], 1.1-8.1). In multiple-variable regression Cox, predictors of events were TT genotype (HR=2.8; 95% CI, 1.01-7.62, p=0.047), low-ejection fraction<40% (HR=4.5; 95% CI, 1.62-12.6, p=0.004) and revascularization procedure (HR=6.1; 95% CI, 1.86-20.34, p=0.003).

CONCLUSIONS

These data indicate that the TT genotype seems to be significantly associated with major adverse cardiac events after myocardial revascularization in CAD patients, suggesting a potential pathological influence of homocysteine in the clinical outcome.

Homocysteine and markers of coagulation and endothelial cell activation

OBJECTIVES

In vitro studies suggest an influence of hyperhomocysteinemia on the coagulation system, but the influence of mild hyperhomocysteinemia in vivo is unclear.

METHODS AND RESULTS

We studied the relation between homocysteine and markers of coagulation activation and endothelial cell activation in 279 patients with established atherosclerotic disease. In addition, we performed an investigator-blinded placebo-controlled cross-over study to investigate the influence of acute hyperhomocysteinemia by oral methionine load on these markers in 20 healthy volunteers. In the atherosclerotic patients prothrombin fragment F1+2 and soluble thrombomodulin (sTM) were associated with homocysteine in univariate analyses (P = 0.003 and P = 0.001, respectively), but not in multivariate analyses. Age, creatinine and MTHFR C677T polymorphism were major determinants of homocysteine concentration. MTHFR C677T polymorphism status was not associated with F1+2 and sTM. Median homocysteine concentrations increased in the healthy volunteers after methione load. However, after methionine load or after placebo, we did not observe different plasma concentrations of F1+2 (0.9 nmol L-1 vs. 0.9 nmol L-1, P = 0.39), d-dimer (153 micro g L-1 vs. 151 micro g L-1, P = 0.63) and von Willebrand factor (103% vs. 107%, P = 1.00).

CONCLUSIONS

These results provide evidence against a major effect of mild hyperhomocysteinemia on activation of the coagulation system and endothelial cell activation in vivo.

Folate, homocysteine levels, methylenetetrahydrofolate reductase (MTHFR) 677C --> T variant, and the risk of myocardial infarction in young women: effect of female hormones on homocysteine levels

In young women data are limited about the association between myocardial infarction (MI) and hyperhomocysteinemia, low folate or methylenetetrahydrofolate reductase (MTHFR) genotypes. The effect of oral contraceptive (OC) use on plasma homocysteine levels is not clear. We assessed the association between hyperhomocysteinemia, low folate, MTHFR 677TT mutation and risk of MI, and we investigated the effect of OC use on homocysteine levels in controls. In 181 patients with a first MI and 601 controls 18-49 years of age from a population-based case-control study, non-fasting blood samples were available. The homozygote mutant allele (TT) was detected in 12% of the patients and in 10% of controls. The odds ratio (OR) for MI in TT patients compared with the wild-type (CC) controls was 1.3 [95% confidence interval (CI) 0.8, 2.3]. For all MTHFR genotypes combined, the OR for MI in the lowest quartile of folate (<5.4 nmol L-1) compared with the highest quartile (>10.4 nmol L-1) was 3.0 (95% CI 1.7, 5.1). A 2-fold increased risk of MI was found in women with the TT genotype who had folate levels below the median of 7.4 nmol L-1 compared with CC genotype and folate levels above the median (OR = 2.0; 95% CI 1.0, 3.7). Mean homocysteine levels were 12.2 micromol L-1 in OC users and 12.3 micromol L-1 in non-users. Only at the 97.5 percentile (cut-off 21.0 micromol L-1) was the adjusted OR for higher vs. lower homocysteine levels increased by 2.8-fold (95% CI 1.2, 6.8). Low folate is a risk factor for MI, particularly in women with the MTHFR 677TT genotype. Homocysteine levels were not influenced by OC use.

Meta-analysis of plasma homocysteine, serum folate, serum vitamin B12, and thermolabile MTHFR genotype as risk factors for retinal vascular occlusive disease

PURPOSE

To assess the role of plasma total homocysteine (tHcy) levels, serum folate and vitamin B(12)levels, and homozygosity for the thermolabile methylenetetrahydrofolate reductase genotype (TT) as risk factors for retinal vascular occlusive disease.

DESIGN

Meta-analysis of literature.

METHODS

A MEDLINE search was performed to identify all published case-control studies of plasma tHcy levels, serum folate and vitamin B(12) levels, and TT genotype in persons with retinal vascular occlusive disease. Main outcome measures included calculation of plasma tHcy, serum folate, and serum vitamin B(12) standard differences and odds ratios (OR) of TT genotype between cases and controls.

RESULTS

In total, 614 patients with all types of retinal vein occlusion had higher plasma tHcy levels than 762 control subjects (standard difference, 0.867; 95% confidence interval [CI] = 0.735, 0.999; P <.001). Plasma tHcy levels were also higher in 154 patients with retinal artery occlusion compared with 358 control subjects (standard difference 1.174; 95% CI = 0.947, 1.402; P <.001). Serum folates, but not vitamin B(12) levels, were lower in 287 patients with retinal vascular occlusion than in the same number of control subjects (standard difference, 0.508; 95% CI = 0.340, 0.675; P <.001; and -0.060; 95% CI = -0.024, 0.104; P =.474, respectively). Similar proportions of 690 patients with retinal vein occlusion and 2754 control subjects demonstrated the TT genotype (OR = 1.332; 95% CI = 0.995, 1.783; P =.054) as did 152 patients with retinal artery occlusions and 435 control subjects (OR = 1.716; 95% CI = 0.977, 3.014; P =.060).

CONCLUSIONS

Retinal vascular occlusion is associated with elevated plasma tHcy levels and low serum folate levels, but not serum vitamin B(12) levels and TT genotype. Until a prospective multicenter trial is undertaken, plasma tHcy levels and serum folate levels should be determined in patients with retinal vascular occlusions, and dietary supplementation with low doses of folate and vitamin B(12) should be considered for affected persons.

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.

Large volume donor plasmapheresis in inherited thrombophilia implicated in arterial thrombosis

BACKGROUND

Life-threatening complications following apheresis are rare, and include venous thrombosis. Arterial thrombosis following apheresis has not been reported.

CASE REPORT

A 48 year old donor had cerebral infarction following large volume plasma donation. The outcome was fatal. He was found to be heterozygous for both methylene tetrahydrofolate reductase (MTHFR) 677C-T mutation and Prothrombin 20210G-A allele.

CONCLUSION

This case suggests that large volume plasma donation may trigger arterial thrombotic events in inherited thrombophilia. Therefore, the effects of plasmapheresis on coagulation system should be studied thoroughly.

Homocysteine and hemostatic disorder as a risk factor for myocardial infarction at a young age

INTRODUCTION

Hyperhomocysteinemia is a coronary risk factor, but its pathophysiologic mechanism remains unclear.

MATERIALS AND METHODS

The importance of hyperhomocysteinemia in the pathogenesis of early myocardial infarction, was determined in case-control study of 127 men with a first early myocardial infarction <or=45 years and 150 age-matched male controls. We measured plasma concentrations of homocysteine, fibrinogen, antithrombin, tissue factor, tissue factor pathway inhibitor, tissue plasminogen activator, plasminogen activator inhibitor-I, plasminogen, alpha(2)-antiplasmin, lipoprotein(a), protein C, protein S, factor VII, and activated factor VII.

RESULTS

Homocysteine concentrations were higher in patients with early myocardial infarction than in controls (11.2+/-5.3 and 8.3+/-5.0 micromol/l, respectively, P<0.001). Hyperhomocysteinemia was associated with early myocardial infarction (odds ratio=2.22, P<0.001) by multivariate logistic regression analysis. Tissue factor, antithrombin, plasminogen, tissue plasminogen activator, plasminogen activator inhibitor-I, lipoprotein(a), diabetes, and smoking also had associations. In a stepwise logistic regression analysis, hyperhomocysteinemia was the strongest predictor of early myocardial infarction (R(2)=0.19, P<0.001). Hyperhomocysteinemia also had positive correlations with tissue factor (rho=0.26, P=0.009), tissue factor pathway inhibitor (rho=0.23, P=0.020), and tissue plasminogen activator (rho=0.25, P=0.011) in patients with early myocardial infarction, but not in controls.

CONCLUSIONS

Hyperhomocysteinemia is an independent risk factor for early myocardial infarction, and is associated with a hypercoagulable state mediated by the extrinsic coagulation cascade.

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.

Coronary atherosclerosis and somatic mutations: an overview of the contributive factors for oxidative DNA damage

Coronary artery disease (CAD) is a multifactorial process that appears to be caused by the interaction of environmental risk factors with multiple predisposing genes. Genetic research on CAD has traditionally focused on investigation aimed at identifying disease-susceptibility genes. Recent evidence suggests that somatically acquired DNA mutations may also contribute significantly to the pathogenesis of the disease, underlining the similarity between atherosclerotic and carcinogenic processes. The generation of oxidative stress has been emphasized as an important cause of DNA damage in atherosclerosis. This review highlights some of the major atherogenic risk factors as likely mediators in the oxidative modification of DNA. It also examines the hypothesis that an increase in oxidative stress may derive from "oxidatively" damaged mitochondria. Accordingly, further research in this field should be given high priority, since increased somatic DNA damage could be an important pathogenic factor and an additional prognostic predictor, as well as a potential target for therapeutic strategies in coronary artery disease.

Cystathionine beta-synthase polymorphisms and hyperhomocysteinaemia: an association study

Hyperhomocysteinaemia is generally accepted as an independent and graded risk factor for both arterial occlusive disease and venous thrombosis. The only way of homocysteine degradation is conversion to cysteine in the transsulfuration pathway in which the regulating step is catalysed by cystathionine beta-synthase (CBS). Mild impairment of CBS function could therefore affect homocysteine concentration, in particular after methionine loading, and consequently cardiovascular disease (CVD) risk. We analysed two silent polymorphisms and one short tandem repeat in the CBS gene (ie 699C-->T, 1080C-->T and -5697 (GT) STR) as genetic markers potentially in linkage disequilibrium with a functional polymorphism. We assessed their association with fasting and post-methionine load homocysteine in 190 patients with arterial occlusive disease, and in 381 controls. No differences in CBS genotype frequencies between cases and controls were found, nor was a particular CBS genotype associated with an elevated risk of arterial occlusive disease. Although we did find a high rate of linkage disequilibrium between the two single nucleotide polymorphisms and the GT STR, none of the genotypes defined by the three CBS variants studied showed an association with elevated fasting, post-load or increase upon methionine loading homocysteine concentrations. In conclusion, we did not find any indication that genetic variation in the CBS gene is associated with increased homocysteine concentrations.