Homocysteine and coronary atherosclerosis

Preeclampsia and the future risk of hypertension: the pregnant evidence

Cardiovascular death rates continue to rise for women under age 55, underlying the importance of focusing on female-specific conditions that may increase cardiovascular risk, including pregnancy-related disorders. Hypertension complicates about 5-10 % of pregnancies. Preeclampsia, a pregnancy-specific condition, is characterized by hypertension and proteinuria after 20 weeks of gestation and remains one of the major causes of maternal deaths in the United States. In addition, preeclampsia may have an impact on women's health beyond their pregnancies, and has been associated with increased risks for future hypertension and cardiovascular disease, such as coronary heart disease and stroke. In this review, we discuss the evidence supporting the association between preeclampsia and future hypertension; possible mechanisms that underlie this association; current approach to women with a history of preeclampsia; and future research that is needed in this field in order to deliver optimal and timely medical care to the affected women.

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.

The beneficial effect of folate-enriched egg on the folate and homocysteine levels in rats fed a folate- and choline-deficient diet

We investigated the effects of folate-enriched egg yolk powder on folate and homocysteine levels in plasma and liver of rats fed the folate- and choline-deficient diet to determine bioavailability in vivo. Three-wk-old Wistar rats were fed (1) the pteroylglutamate (PteGlu), (2) the choline, (3) the PteGlu and choline, (4) the folate-enriched egg yolk powder diet for 4 wk after having been fed the folate- and choline-deficient diet. The hepatic folate level in the folate-enriched egg yolk powder group was significantly higher than that in the folate- and choline-deficient or the control groups. The homocysteine concentration in plasma and liver of the folate-enriched egg yolk powder group was significantly lower than that of the folate- and choline-deficient or the PteGlu groups. The S-adenosyl-methionine (SAM)/S-adenosyl-homocysteine (SAH) ratio in the folate-enriched egg yolk powder group was significantly higher than that in the folate- and choline-deficient group. These effects were similar in the PteGlu and choline, but not the PteGlu or the choline groups. These data suggest that the intake of folate-enriched eggs, as well as of both folate and choline, induced the beneficial effects on folate and homocysteine metabolism. Thus, folate-enriched eggs could be used as beneficial source of folate with a high bioavailability.

Differences in metabolites of different tongue coatings in patients with chronic hepatitis B

Tongue coating is one of the important foundations of tongue diagnosis in traditional Chinese medicine (TCM) and plays an important role in reflecting the occurrence, development, and prognosis of the disease. However, its material basis is still poorly understood. In this study, a urinary metabonomic method based on gas chromatography coupled to mass spectrometry (GC/MS) was developed. The distinct clustering in metabolic profile was observed from Group A (thick yellow coating in patients with chronic hepatitis B), Group B (thick white coating in patients with chronic hepatitis B), and Group C (thin white coating with healthy humans) using orthogonal projections to latent structures (OPLS). Based on the variable of importance in the project (VIP) values, some significantly changed metabolites have been identified. These changes were related to the disturbance in energy metabolism, amino acid metabolism, nucleotide metabolism, and gut microflora, which were helpful to understand the material basis leading to the formation of tongue coating. This study demonstrated that tongue coating may have an objective material basis.

Risk prediction-Homocysteine in Coronary Heart Disease

Majority of patients who experience a Coronary Heart disease event have one or more of the conventional risk factors for atherosclerosis and so do many people who have not yet experienced such an event. Thus predictive models based on conventional risk factors have lower than the desired accuracy, providing a stimulus to search for new factors to predict accurately the risk of CHD. In this regard newer risk factors like homocysteine, Lp(a), insulin resistances are the important ones and are called as 'novel risk factors'. The study was undertaken to find the prediction of CHD risk by homocysteine in comparison with other conventional risk factors. The data obtained suggests a very high sensitivity, specificity and accuracy with above 90% positive prediction value for homocysteine in CHD patients when compared to commonest conventional risk factors.

Studies on homocysteine demonstrating its significance as a possible tool for differential diagnosis in occlusive vascular disease

Homocysteine (Hcy) is a non-protein forming amino-acid, whose metabolism is at the intersection of two metabolic pathways: remethylation and transsulfuration which are dependent on the vitamins folic acid, B(12) and B(6), and the enzymes methylenetetrahydrofolate reductase and cystathionine-β-synthetase. A deficiency of any of these vitamins or enzymes results in hyperhomocysteinemia. This causes oxidative and other damage to blood vessels, thus affecting various organ systems of the body. As part of our ongoing research on cardiovascular risk factors, we have studied the Hcy levels in the plasma of normal controls and those suffering from vascular diseases. It was observed that Hcy is significantly higher in patients of vascular diseases (21.59±1.28 μmol/L, mean±SEM), as compared to normal controls (11.33±0.18 μmol/L). This significance, was more pronounced in cases of venous thrombosis (26.77±2.43 μmol/L) as opposed to cases of arterial block (17.27±0.84 μmol/L). This signifies that Hcy estimation would be beneficial in obtaining a differential diagnosis in addition to being a modifiable vascular risk factor.

Effect of isotretinoin treatment on plasma holotranscobalamin, vitamin B12, folic acid, and homocysteine levels: non-controlled study

Isotretinoin (Iso) has been used for the treatment of acne. Some previous studies reported elevated homocysteine (Hcy) levels after treatment with Iso. Some side effects have clinical presentations similar to vitamin B12, folic acid deficiencies, and hyperhomocysteinemia. In the present study we evaluated the plasma Hcy levels, the vitamins involved in its metabolism (vitamin B12 and folic acid), and holotranscobalamin (HoloTC), a transport system for vitamin B12 absorption in patients receiving Iso treatment for acne vulgaris. A total of 66 patients with acne vulgaris between the ages of 18 and 40 years were included. Screening for hemoglobin, creatinine, SGOT, SGPT, total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and very low-density lipoprotein cholesterol (VLDL-C), folic acid, vitamin B12, Hcy, and HoloTC were done just before initiation (pretreatment) and after four months of Iso treatment (posttreatment). Posttreatment vitamin B12, folic acid, and HoloTC levels were significantly lower while Hcy levels were significantly higher compared with initial values. Posttreatment total cholesterol, LDL-C, triglycerides, VLDL-C, SGPT, and SGOT levels were also higher, and HDL-C levels were lower compared with initial values while there was no change in hemoglobin levels during Iso treatment. We found that Iso usage might cause decreased vitamin B12, folic acid, and HoloTC. These Iso side effects might contribute to the missing link between Iso usage, hyperhomocysteinemia, and neuropsychiatric disorders. Trials may be made with the aim of demonstrating (clearly) if starting vitamin B12 and folic acid replacement therapies with Iso treatment initialization could be useful for preventing hyperhomocysteinemia and possibly related disorders.

The basis of differential responses to folic acid supplementation

BACKGROUND/AIMS

Elevated levels of total homocysteine (tHcy) are associated with an increased risk of many common diseases. Supplementation with folic acid has been shown to significantly reduce tHcy levels. We used the classical twin model to partition the variability in changes in plasma tHcy levels through folic acid supplementation into genetic, environmental, and confounding epidemiological factors.

METHODS

We carried out an intervention study of folic acid using 101 healthy, female, identical and non-identical twins aged 50-80 years. Each twin was administered folic acid (0.8 mg/day) for 6 weeks. Total plasma folate, cobalamin and tHcy were measured at both baseline and after dosing. We calculated the heritability and tested for associations between the MTHFR C677T functional variant and response to folic acid supplementation.

RESULTS

Supplementation with folic acid led to a significant reduction in tHcy levels. The mean tHcy changed from 12.14 to 10.42 μmol/l after supplementation (p < 10(-5)). Moreover, the change in tHcy levels was highly heritable (64%), not associated with the C677T functional variant at MTHFR and not confounded by age, BMI or diet.

CONCLUSIONS

Our results highlight the need to identify genetic factors associated with biomarkers of response to folate supplementation.

Lipid profiles and oxidative stress parameters in male and female hemodialysis patients

To study atherogenesis markers in patients with stage 5D chronic kidney disease (CKD-5D) on hemodialysis to determine which parameters are modified and whether their behavior differ between male and female patients of similar age. Total cholesterol, triglycerides, glucose, total proteins, HDL-cholesterol, LDL-cholesterol, oxidative modification of low-density lipoprotein-cholesterol, autoantibodies against oxidized low-density lipoproteins-cholesterol, homocysteine (Hcy), folate, and vitamin B12 were measured in male and female controls and CKD-5D patients on hemodialysis for >6 months. The CKD-5D patients had significantly lower cholesterol, LDL-c and ox-LDL levels and significantly higher ox-LDL-AB and Hcy levels versus their respective controls. The reduction in ox-LDL in CKD patients does not imply a lower risk of atherosclerosis. In fact, the risk may be higher due to a greater capture of ox-LDL by macrophage scavenger receptors, which are increased in these patients. Elevated Hcy levels may also be a risk factor for atherosclerosis in male and female CKD-5D patients.

Carbamylated LDL

Nonenzymatic modification of protein by cyanate, that is, carbamylation, has received new attention due to its apparent relevance in atherosclerosis. For example, carbamylation of low-density lipoprotein (LDL) is an important mechanism that potentially impacts high-risk atherosclerotic individuals with increased urea (renal insufficiency) or thiocyanate (tobacco smoking). Carbamylated LDL (cLDL) is increased in patients with end-stage kidney disease, especially those with atherosclerosis. In addition, cLDL exhibits distinct cytotoxic effects when tested in vitro on endothelial cells, induces the expression of adhesion molecules, and aggravates the monocyte adhesion to endothelial cells. It also facilitates the proliferation of vascular smooth-muscle cell (VSMC). Studies of potential pharmacological interruption of these processes in vivo may lead to discoveries of novel therapies for atherosclerosis.

Chronic treatment with cyclosporine affects systemic purinergic parameters, homocysteine levels and vascular disturbances in rats

Vascular disease is a major cause of morbidity and mortality among transplanted recipients and cyclosporine (CsA) treatment has been consistently implicated in this event. In this study we assessed total blood homocysteine levels (tHcy), ecto-nucleotidase activities and adenine nucleotide/nucleoside levels searching for parameters related to the mechanisms of vascular damage induced by chronic CsA treatment in non-transplanted rats. Thirty male Wistar rats were divided in three groups: control group treated with corn oil, CsA 5mg/kg and CsA 15 mg/kg, administered by daily gastric gavage during 8 weeks. CsA 15 mg/kg treatment increased blood levels of tHcy. Both CsA treatments (5mg/kg and 15 mg/kg) decreased adenine nucleotides hydrolysis by ecto-nucleotidases in serum, which negatively correlated with tHcy levels (r: -0.74, r: -0.63 and r: -0.63, p<0.004, for ATP, ADP and AMP, respectively). CsA 15mg/kg induced a statistically significant increase in ADP and decrease in adenosine (ADO) plasma levels compared to control group. THcy levels were positively correlated with plasma ADP levels and negatively correlated with ADO levels (r: 0.84, p<0.0001 and r: -0.68, p<0.0001, respectively). Rats under CsA 15 mg/kg treatment presented cell injury and inflammatory responses in the endothelium and intima layer of the aorta artery. In conclusion, blood ecto-nucleotidases activity, tHcy, and ADP and ADO levels may be implicated in vascular injury induced by CsA treatment.

Diabetes and obesity: therapeutic targeting and risk reduction - a complex interplay

Obesity is a major risk factor for the development of diabetes and predisposes individuals to hypertension and dyslipidaemia. Together these pathologies increase the risk for cardiovascular disease (CVD), the major cause of morbidity and mortality in type 2 diabetes mellitus (T2DM). Worsening trends in obesity and T2DM raise a serious conundrum, namely, how to control blood glucose, blood pressure, and lipids when many antidiabetic agents cause weight gain and thereby exacerbate other cardiovascular risk factors associated with T2DM. Further, evidence suggests that some established antihypertensive agents may worsen glucose intolerance. Many patients who are obese, hypertensive, and/or hyperlipidaemic fail to achieve blood pressure, lipid and glycaemic goals, and this failure may in part be explained by physician reluctance to utilize complex combination regimens for fear of off-target effects. Thus, a clear need exists for clinicians to understand the risks and benefits of different pharmacologic, and indeed non-pharmacologic, options in order to maximize treatment outcomes. While intensive lifestyle modification remains an elusive gold standard, newer diabetes targets, including the incretin axis, may offer greater cardiovascular risk reduction than other antidiabetes therapies, although definitive clinical trial data are needed. The glucagon-like peptide-1 (GLP-1) receptor agonists exenatide and liraglutide and the dipeptidyl peptidase-4 (DPP-4) inhibitors sitagliptin and vildagliptin effectively lower HbA1c; exenatide and liraglutide reduce weight and blood pressure and improve lipid profiles. Sitagliptin and vildagliptin are weight neutral but also appear to improve lipid profiles. Integration of incretin therapies into the therapeutic armamentarium is a promising approach to improving outcomes in T2DM, and perhaps even in reducing complications of T2DM, such as co-morbid hypertension and dyslipidaemia. Additional long-term studies, including CVD end-point studies, will be necessary to determine the appropriate places for incretin-based therapies in treatment algorithms.

[Use of nitrous oxide in Uruguay]

BACKGROUND

Nitrous oxide (N2O) is a medicinal gas that has been used for anesthesia for over a century and a half. As evidence of the adverse effects of N2O have been contrasted with the good safety profiles of new anesthetic agents, use of the older gas has declined.

OBJECTIVE

To describe and analyze the use of N2O for anesthesia in the Eastern Republic of Uruguay. To describe the use of other drugs for general anesthesia.

METHODS

The study had 2 phases. In the first phase, information on the use of N2O and other drugs for general anesthesia was obtained from the medical records of a sample of patients who underwent surgery between November 2007 and November 2008 at nationally important hospitals. In the second phase 80 physician anesthesiologists were surveyed to obtain information on their reported use of N2O for general anesthesia. The respondents were found working during the first half of 2008.

RESULTS

A total of 104 patients' records were read and 80 anesthesiologists were surveyed. We found that 31 (29.8%) patients received N2O during anesthesia. The survey showed that 62 (77.5%) of the anesthesiologists had used N2O in the last 6 months. Nine (50%) of the anesthesiologists who had not used N2O said their reason was that it was unavailable. The other 9 referred either to the risk of postoperative nausea and/or vomiting (n = 6) or the fact of having better alternatives (n = 9).

CONCLUSION

This study shows that N2O is little used in current anesthesia practice. The tendency in Uruguay continues to be toward declining use.

Genome-wide significant predictors of metabolites in the one-carbon metabolism pathway

Low plasma B-vitamin levels and elevated homocysteine have been associated with cancer, cardiovascular disease and neurodegenerative disorders. Common variants in FUT2 on chromosome 19q13 were associated with plasma vitamin B12 levels among women in a genome-wide association study in the Nurses' Health Study (NHS) NCI-Cancer Genetic Markers of Susceptibility (CGEMS) project. To identify additional loci associated with plasma vitamin B12, homocysteine, folate and vitamin B6 (active form pyridoxal 5'-phosphate, PLP), we conducted a meta-analysis of three GWA scans (total n = 4763, consisting of 1658 women in NHS-CGEMS, 1647 women in Framingham-SNP-Health Association Resource (SHARe) and 1458 men in SHARe). On chromosome 19q13, we confirm the association of plasma vitamin B12 with rs602662 and rs492602 (P-value = 1.83 x 10(-15) and 1.30 x 10(-14), respectively) in strong linkage disequilibrium (LD) with rs601338 (P = 6.92 x 10(-15)), the FUT2 W143X nonsense mutation. We identified additional genome-wide significant loci for plasma vitamin B12 on chromosomes 6p21 (P = 4.05 x 10(-08)), 10p12 (P-value=2.87 x 10(-9)) and 11q11 (P-value=2.25 x 10(-10)) in genes with biological relevance. We confirm the association of the well-studied functional candidate SNP 5,10-methylene tetrahydrofolate reductase (MTHFR) Ala222Val (dbSNP ID: rs1801133; P-value=1.27 x 10(-8)), on chromosome 1p36 with plasma homocysteine and identify an additional genome-wide significant locus on chromosome 9q22 (P-value=2.06 x 10(-8)) associated with plasma homocysteine. We also identified genome-wide associations with variants on chromosome 1p36 with plasma PLP (P-value=1.40 x 10(-15)). Genome-wide significant loci were not identified for plasma folate. These data reveal new biological candidates and confirm prior candidate genes for plasma homocysteine, plasma vitamin B12 and plasma PLP.

A cardiologic approach to non-insulin antidiabetic pharmacotherapy in patients with heart disease

Classical non-insulin antihyperglycemic drugs currently approved for the treatment of type 2 diabetes mellitus (T2DM) comprise five groups: biguanides, sulfonylureas, meglitinides, glitazones and alpha-glucosidase inhibitors. Novel compounds are represented by the incretin mimetic drugs like glucagon like peptide-1 (GLP-1), the dipeptidyl peptidase 4 (DPP-4) inhibitors, dual peroxisome proliferator-activated receptors (PPAR) agonists (glitazars) and amylin mimetic drugs. We review the cardiovascular effects of these drugs in an attempt to improve knowledge regarding their potential risks when treating T2DM in cardiac patients. Metformin may lead to lethal lactic acidosis, especially in patients with clinical conditions that predispose to this complication, such as recent myocardial infarction, heart or renal failure. Sulfonylureas exert their effect by closing the ATP-dependent potassium channels. This prevents the opening of these channels during myocardial ischemia, impeding the necessary hyperpolarization that protects the cell. The combined sulfonylurea/metformin therapy reveals additive effects on mortality in patients with coronary artery disease (CAD). Meglitinides effects are similar to those of sulfonylureas, due to their almost analogous mechanism of action. Glitazones lower leptin levels, leading to weight gain and are unsafe in NYHA class III or IV. The long-term effects of alpha-glucosidase inhibitors on morbidity and mortality rates is yet unknown. The incretin GLP-1 is associated with reductions in body weight and appears to present positive inotropic effects. DPP-4 inhibitors influences on the cardiovascular system seem to be neutral and patients do not gain weight. The future of glitazars is presently uncertain following concerns about their safety. The amylin mimetic drug paramlintide, while a satisfactory adjuvant medication in insulin-dependent diabetes, is unlikely to play a major role in the management of T2DM. Summarizing the present information it can be stated that 1. Four out the five classical oral antidiabetic drug groups present proven or potential cardiac hazards; 2. These hazards are not mere 'side effects', but biochemical phenomena which are deeply rooted in the drugs' mechanism of action; 3. Current data indicate that the combined glibenclamide/metformin therapy seems to present special risk and should be avoided in the long-term management of T2DM with proven CAD; 4. Glitazones should be avoided in patients with overt heart failure; 5, The novel incretin mimetic drugs and DPP-4 inhibitors--while usually inadequate as monotherapy--appear to be satisfactory adjuvant drugs due to the lack of known undesirable cardiovascular effects; 6. Customized antihyperglycemic pharmacological approaches should be implemented for the achievement of optimal treatment of T2DM patients with heart disease. In this context, it should be carefully taken into consideration whether the leading clinical status is CAD or heart failure.

Stroke: roles of B vitamins, homocysteine and antioxidants

In the present review concerning stroke, we evaluate the roles of B vitamins, homocysteine and antioxidant vitamins. Stroke is a leading cause of death in developed countries. However, current therapeutic strategies for stroke have been largely unsuccessful. Several studies have reported important benefits on reducing the risk of stroke and improving the post-stroke-associated functional declines in patients who ate foods rich in micronutrients, including B vitamins and antioxidant vitamins E and C. Folic acid, vitamin B6and vitamin B12are all cofactors in homocysteine metabolism. Growing interest has been paid to hyperhomocysteinaemia as a risk factor for CVD. Hyperhomocysteinaemia has been linked to inadequate intake of vitamins, particularly to B-group vitamins and therefore may be amenable to nutritional intervention. Hence, poor dietary intake of folate, vitamin B6and vitamin B12are associated with increased risk of stroke. Elevated consumption of fruits and vegetables appears to protect against stroke. Antioxidant nutrients have important roles in cell function and have been implicated in processes associated with ageing, including vascular, inflammatory and neurological damage. Plasma vitamin E and C concentrations may serve as a biological marker of lifestyle or other factors associated with reduced stroke risk and may be useful in identifying those at high risk of stroke. After reviewing the observational and intervention studies, there is an incomplete understanding of mechanisms and some conflicting findings; therefore the available evidence is insufficient to recommend the routine use of B vitamins, vitamin E and vitamin C for the prevention of stroke. A better understanding of mechanisms, along with well-designed controlled clinical trials will allow further progress in this area.

Genetic and environmental influences on total plasma homocysteine and coronary artery disease (CAD) risk among South Indians

BACKGROUND

Hyperhomocysteinemia, a documented risk factor for CAD is highly prevalent in Indians. The rationale behind the current study is to explore the genetic and environmental causes for such high prevalence as there are limited studies in this context.

METHODS

A total of 108 CAD cases and 108 controls were analyzed for tHcy and 4 folate pathway genetic polymorphisms [methylene tetrahydrofolate reductase (MTHFR) C677T, 5-methyltetrahydrofolate homocysteine methyl transferase (MTR) A2756G, methionine synthase reductase (MTRR) A66G and glutamate carboxypeptidase II (GCPII) C1561T] using reverse phase HPLC and PCR-RFLP methods respectively.

RESULTS

MTHFR 677T, MTRR 66A, GCPII 1561T, male gender, alcohol intake, smoking, diabetes, creatinine and hypertension were found to influence tHcy. After controlling for confounding factors, Hyperhomocysteinemia and two of its genetic determinants i.e. MTHFR C677T [OR: 1.96, 95% CI: 1.06-3.61] and GCP II C1561T [OR: 2.09, 95% CI: 1.09-3.97] were found to be associated with risk for CAD. Significant epistatic interactions were observed between MTHFR 677T/MTR 2756G and GCP II 1561T/MTRR 66G. Alcohol intake in subjects with MTR 2756G allele was found to inflate the risk for CAD [OR: 4.15, 95% CI: 1.35-12.69].

CONCLUSION

Hyperhomocysteinemia, C677T MTHFR and C1561T GCPII are risk factors for CAD. Potential gene--gene and gene--environment interactions indicate the need for multi-variate analyses for risk prediction.

Nitrous oxide and perioperative cardiac morbidity (ENIGMA-II) Trial: rationale and design

BACKGROUND

Globally there are >200 million major surgical procedures undertaken annually, and about 20% of these involve patients who have coronary artery disease. Many receive nitrous oxide, which impairs methionine synthase, thus inhibiting folate synthesis and increasing postoperative homocysteine levels. Nitrous oxide anesthesia leads to postoperative endothelial dysfunction, and there is some evidence that it increases myocardial ischemia and, possibly, myocardial infarction. We have initiated the Nitrous oxide and perioperative cardiac morbidity (ENIGMA-II) Trial to test the hypothesis that in inpatients undergoing anesthesia for major noncardiac surgery, avoidance of nitrous oxide will reduce the incidence of death and major cardiovascular events.

METHODS

ENIGMA-II is a 7,000-patient, international randomized trial involving patients at risk of coronary artery disease undergoing noncardiac surgery. The patients, health care providers (except for the anesthesiologists), data collectors, and outcome adjudicators are blinded to whether patients receive nitrous oxide-containing or nitrous oxide-free anesthetic. The primary outcome is a composite of death and major nonfatal events (ie, myocardial infarction, cardiac arrest, pulmonary embolism, and stroke) at 30 days after surgery.

RESULTS

At present, ENIGMA-II has randomized >1,000 patients in 22 hospitals in 5 countries. To date, patients' mean age is 70 years, 66% are men, 38% have a history of coronary artery disease, 19% have a history of cerebrovascular disease, and 84% have a history of hypertension. Most patients have undergone intra-abdominal 28%, vascular 32%, and orthopedic 16% surgery.

CONCLUSIONS

The ENIGMA-II Trial will be the largest study yet conducted to ascertain the benefits and risks of removing nitrous oxide from the gas mixture in anesthesia. The results of this large international trial will guide the clinical care of the hundreds of millions of adults undergoing noncardiac surgery annually.

Possible ethnic differences in plasma homocysteine levels associated with coronary artery disease between south Asian and east Asian immigrants

BACKGROUND

Hyperhomocysteinemia has been identified as a risk factor for coronary artery disease (CAD). South Asians appear to have a high incidence of CAD, while East Asians have a very low incidence.

HYPOTHESIS

The present study was undertaken because the relative association of plasma homocysteine levels (PH) with CAD in South Asians (SA = Indian, Pakistani, Sri Lankan) and East Asians (EA = Chinese, Japanese) is not known.

METHODS

Fasting PH were drawn on all patients with CAD of SA (age 62.4+/-1.1 years, 72 men, 14 women) and EA (age 61.8+/-3.0 years, 13 men, 4 women) descent. These were compared with PH available from Caucasian (CA) patients (age 61.1+/-1.1 years, 89 men, 17 women) with CAD.

RESULTS

The PH in SA, EA, and CA patients were 11.0+/-0.5, 7.6+/-0.5, and 10.8+/-0.6 micromol/l, respectively (p<0.001 between EA and SA/CA). Percentages of SA, EA, and CA with elevated PH (> 12.0 micromol/l) were 33.7, 5.9, and 28.2%, respectively. There were no significant differences in the lipid subfractions between the SA and EA group. History of smoking was significantly higher in the EA (52.9 vs. 26.2%), while hypertension and diabetes mellitus had similar prevalences.

CONCLUSION

Significant differences in PH of SA versus EA patients with CAD exist. The relative contribution of homocysteine in the development of CAD appears to be less in EA immigrants. In contrast, the association between CAD and PH in SA immigrants appears to be similar to that of Caucasians.

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.

Folic acid with or without vitamin B12 for the prevention and treatment of healthy elderly and demented people

BACKGROUND

Folate deficiency can result in congenital neural tube defects and megaloblastic anaemia. Low folate levels may be due to insufficient dietary intake or inefficient absorption, but impaired metabolic utilization also occurs.Because B12 deficiency can produce a similar anaemia to folate deficiency, there is a risk that folate supplementation can delay the diagnosis of B12 deficiency, which can cause irreversible neurological damage. Folic acid supplements may sometimes therefore include vitamin B12 supplements with simultaneous administration of vitamin B12.Lesser degrees of folate inadequacy are associated with high blood levels of the amino acid homocysteine which has been linked with the risk of arterial disease, dementia and Alzheimer's disease. There is therefore interest in whether dietary supplementation can improve cognitive function in the elderly.However, any apparent benefit from folic acid which was given in combination with B12 needs to be "corrected" for any effect of vitamin B12 alone. A separate Cochrane review of vitamin B12 and cognitive function has therefore been published.

OBJECTIVES

To examine the effects of folic acid supplementation, with or without vitamin B12, on elderly healthy or demented people, in preventing cognitive impairment or retarding its progress.

SEARCH STRATEGY

Trials were identified from a search of the Cochrane Dementia and Cognitive Improvement Group's Specialized Register on 10 October 2007 using the terms: folic acid, folate, vitamin B9, leucovorin, methyltetrahydrofolate, vitamin B12, cobalamin and cyanocobalamin. This Register contains references from all major health care databases and many ongoing trials databases. In addition MEDLINE, EMBASE, CINAHL, PsychINFO and LILACS were searched (years 2003-2007) for additional trials of folate with or without vitamin B12 on healthy elderly people.

SELECTION CRITERIA

All double-blind, placebo-controlled, randomized trials, in which supplements of folic acid with or without vitamin B12 were compared with placebo for elderly healthy people or people with any type of dementia or cognitive impairment.

DATA COLLECTION AND ANALYSIS

The reviewers independently applied the selection criteria and assessed study quality. One reviewer extracted and analysed the data. In comparing intervention with placebo, weighted mean differences and standardized mean difference or odds ratios were estimated.

MAIN RESULTS

Eight randomized controlled trials fulfilled the inclusion criteria for this review. Four trials enrolled healthy older people, and four recruited participants with mild to moderate cognitive impairment or dementia with or without diagnosed folate deficiency. Pooling the data was not possible owing to heterogeneity in sample selections, outcomes, trial duration, and dosage. Two studies involved a combination of folic acid and vitamin B12.There is no adequate evidence of benefit from folic acid supplementation with or without vitamin B12 on cognitive function and mood of unselected healthy elderly people. However, in one trial enrolling a selected group of healthy elderly people with high homocysteine levels, 800 mcg/day folic acid supplementation over three years was associated with significant benefit in terms of global functioning (WMD 0.05, 95% CI 0.004 to 0.096, P = 0.033); memory storage (WMD 0.14, 95% CI 0.04 to 0.24, P = 0.006) and information-processing speed (WMD 0.09, 95% CI 0.02 to 0.16, P = 0.016).Four trials involved people with cognitive impairment. In one pilot trial enrolling people with Alzheimer's disease, the overall response to cholinesterase inhibitors significantly improved with folic acid at a dose of 1mg/day (odds ratio: 4.06, 95% CI 1.22 to 13.53; P = 0.02) and there was a significant improvement in scores on the Instrumental Activities of Daily Living and the Social Behaviour subscale of the Nurse's Observation Scale for Geriatric Patients (WMD 4.01, 95% CI 0.50 to 7.52, P = 0.02). Other trials involving people with cognitive impairment did not show any benefit in measures of cognitive function from folic acid, with or without vitamin B12.Folic acid plus vitamin B12 was effective in reducing serum homocysteine concentrations (WMD -5.90, 95% CI -8.43 to -3.37, P < 0.00001). Folic acid was well tolerated and no adverse effects were reported.

AUTHORS' CONCLUSIONS

The small number of studies which have been done provide no consistent evidence either way that folic acid, with or without vitamin B12, has a beneficial effect on cognitive function of unselected healthy or cognitively impaired older people. In a preliminary study, folic acid was associated with improvement in the response of people with Alzheimer's disease to cholinesterase inhibitors. In another, long-term use appeared to improve the cognitive function of healthy older people with high homocysteine levels. More studies are needed on this important issue.

Vascular oxidative stress increases dendritic cell adhesion and transmigration induced by homocysteine

Atherosclerosis is a long-term chronic inflammatory and immunological disease. Endothelial dysfunction and the dendritic cell (DC) immune response are pivotal early events in atherogenesis. This study investigated the effects and possible mechanisms of action of homocysteine (Hcy) on DC adhesion to and transmigration between endothelial cells (ECs), and indicated a novel immunoregulatory mechanism by which Hcy induces atherogenesis. When ECs were stimulated with increasing concentrations of Hcy, immunofluorescence showed that endothelial reactive oxygen species (ROS) generation strikingly increased, while nitrite assay showed that nitric oxide (NO) release markedly decreased. Furthermore, DC adhesion and transmigration were significantly increased when ECs were activated by Hcy. However, pretreatment of ECs with antioxidant before Hcy markedly attenuated the induction of DC adhesion and transmigration, dependent on the intracellular ROS decrease and endothelial NO increase. In conclusion, DC adhesion and transmigration are significantly increased by vascular oxidative stress under conditions of elevated Hcy levels. These findings provide insight into the inflammatory processes and immune responses occurring in atherosclerosis induced by Hcy.

Preeclampsia and future cardiovascular risk: formal risk factor or failed stress test?

It is estimated that 10% of pregnancies are affected by hypertension worldwide. Approximately one-half of all hypertensive pregnancy disorders are due to preeclampsia, a pregnancy-specific disorder, its distinctive feature being either sudden onset, or worsening of pre-existing proteinuria. It has become increasingly recognized that women with a history of preeclampsia are at increased risk for future cardiovascular disease (CVD), but the mechanisms of this increase in risk are unclear. One possible explanation is that these two conditions share several common metabolic abnormalities as risk factors, including obesity, insulin resistance, and lipid abnormalities that may lead to preeclampsia and CVD at different times of a woman's life. Recent studies have revealed that, similar to CVD, several mediators of endothelial cell dysfunction are up-regulated in preeclampsia. Free radical derived oxidative stress, various inflammatory markers, including neutrophil response, C-reactive protein, and leukocyte adhesion, may contribute to endothelial dysfunction in both preeclampsia and coronary atherosclerosis. Alternatively, preeclampsia itself may induce metabolic and vascular changes that may increase the overall future risk for CVD in affected women. Therefore, at present, it remains unclear whether preeclampsia is a formal risk factor for CVD, or identifies women at increased risk for CVD later in life. Pending large-scale studies aiming to examine the causality of this association, women with a history of preeclampsia should be counseled regarding their increased risks for hypertension and other cardiovascular sequelae later in life, followed closely and treated aggressively for modifiable CVD risk factors.

Elevated plasma homocysteine and low vitamin B-6 status in nonsupplementing older women with rheumatoid arthritis

OBJECTIVE

The purpose of this study was to determine if nonsupplementing older women (aged >or=55 years) with rheumatoid arthritis had higher plasma homocysteine and lower B-vitamin status compared to healthy controls. Elevated plasma homocysteine, a risk factor for cardiovascular disease, may help explain why individuals with rheumatoid arthritis have an increased risk of cardiovascular disease.

METHODS

Older, free-living women were classified as rheumatoid arthritis (n=18) or healthy control (n=33). Participants were not using B-vitamin supplements. Fasting blood samples were measured for pyridoxal 5'phosphate (PLP) (the metabolically active coenzyme form of vitamin B-6), folate, red blood cell folate, vitamin B-12, transcobalamin II, homocysteine, C-reactive protein, and lipid concentrations. Participants completed 7-day weighed food records, the Stanford Health Assessment Questionnaire (HAQ), and a visual analog pain scale.

RESULTS

PLP concentrations were lower in the rheumatoid arthritis vs healthy control participants (4.93+/-3.85 vs 11.35+/-7.11 ng/mL [20+/-16 vs 46+/-29 nmol/L]; P<0.01) whereas plasma homocysteine was higher in the rheumatoid arthritis group (1.63+/-0.74 vs 1.15+/-0.38 mg/L [12.1+/-5.5 vs 8.5+/-2.8 micromol/L]; P=0.02). Red blood cell folate concentrations were lower in the rheumatoid arthritis vs healthy control participants [414+/-141 vs 525+/-172 ng/mL [938+/-320 vs 1,190+/-390 nmol/L]; P=0.02). No significant differences were found for plasma folate, vitamin B-12, and transcobalamin II. An inverse correlation was found between PLP concentrations and the HAQ disability index (r=-0.37; P<0.01). A positive correlation was found between homocysteine concentrations and the HAQ disability index (r=0.36; P=0.01). Total cholesterol and low-density lipoprotein cholesterol levels were lower in the rheumatoid arthritis group (cholesterol 191+/-43 vs 218+/-33 mg/dL [4.95+/-1.11 vs 5.65+/-0.85 mmol/L]; P=0.02; low-density lipoprotein cholesterol 110+/-36 vs 137+/-29 mg/dL [2.85+/-0.93 vs 3.55+/-0.75 mmol/L]; P<0.01). No significant differences were seen between groups for protein (g/day), fat (g/day), cholesterol (mg/day), folate (microg/day), vitamin B-12 (microg/day), and vitamin B-6 (mg/day) dietary intakes.

CONCLUSIONS

Poor vitamin B-6 status and elevated plasma homocysteine concentrations were seen in older women with rheumatoid arthritis compared to healthy controls and may contribute to their increased risk of cardiovascular disease.

Effects of C-reactive Protein and Homocysteine on Cytokine Production: Modulation by Pravastatin

OBJECTIVE: C-reactive protein (CRP) and homocysteine are markers of cardiovascular risk that may have inflammatory effects. HMG coenzyme A reductase inhibitors (statins) have anti-inflammatory effects in vitro, but it is not clear if such responses in vivo are secondary to lipid lowering. We examined the hypothesis that CRP and homocysteine would stimulate cytokine release in human whole blood and that short-term treatment with a statin would inhibit it. METHODS: The time course of IL-6 and MCP-1 production was determined in whole blood incubated with saline, 1 microg/mL lipopolysaccaride (LPS), 50 and 100 microM/L DL-homocysteine, and 5 microg/mL human recombinant CRP for 24 hours at 37 degrees C under 5% CO(2) atmosphere. Cytokine responses were determined in blood drawn from 15 healthy volunteers before and after administration of pravastatin 40 mg daily for 2 days. RESULTS: Both human recombinant CRP and LPS significantly increased the production of IL-6 and MCP-1 in whole blood samples more than 4-fold (P < 0.001) but homocysteine did not. Oral administration of pravastatin, 40mg daily for 2 days, decreased CRP-stimulated IL-6 production by approximately 20% (P = 0.02) 6 hours after incubation, but did not affect MCP-1 production (P = 0.69). Pravastatin treatment did not affect LPS-stimulated MCP-1 but increased IL-6 modestly. CONCLUSIONS: CRP stimulated the production of the proatherogenic mediators MCP-1 and IL-6 in human whole blood, but homocysteine did not. CRP-stimulated production of IL-6, but not MCP-1, was modestly attenuated by short-term treatment with pravastatin.

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.

General anesthesia and methylenetetrahydrofolate reductase deficiency

Methylenetetrahydrofolate reductase (MTHFR) deficiency is an autosomal recessive disorder with a spectrum of manifestations including neurological symptoms, premature arteriosclerosis, and venous and arterial thrombosis. Most patients are heterozygous for multiple MTHFR substitutions; small minorities are homozygous for mutations at this locus. Among these mutations, the C677T polymorphism is the most deleterious. Nitrous oxide use in anesthesia leads to significant increases in plasma homocysteine. We present a patient undergoing urgent surgery with a preoperative diagnosis of homozygous MTHFR deficiency.

Homocysteine at pathophysiological concentrations enhances binding of dendritic cells to endothelial cells mediated by DC-SIGN

Elevated plasma homocysteine (Hcy) is an independent risk factor for atherosclerosis, which is recognized as inflammatory and immune responses. The purpose of this study was to investigate the effect of Hcy on the interaction between dendritic cells (DCs) and endothelial cells (ECs) by upregulating the expression of DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) in cultured DCs. The immunophenotype of Hcy-treated DCs was monitored by flow cytometry. Then, they were coincubated with cultured human umbilical vein endothelial cells, and adhesion of DCs to ECs, and migration of DCs through an endothelial monolayer growing on the insert of a transwell plate, were assessed using a confocal microscope and a multi-detection microplate reader. The expression of DC-SIGN on Hcy-stimulated DCs was assessed by Western blot and immunofluorescence staining. The presence of Hcy did not change the phenotype of immature and mature DCs. Hcy promoted adhesion of DCs to ECs and migration in a concentration-dependent fashion. This effect was inhibited by an anti-DC-SIGN monoclonal antibody. The expression of DC-SIGN on DCs was significantly upregulated by Hcy in a concentration-dependent manner. Taken together, our results show for the first time that Hcy can potentiate the adhesion of DCs to ECs and migration by upregulating the expression of DC-SIGN on DCs, suggesting a novel role of Hcy in the pathogenesis of human vascular disease.

The influence of homocysteine levels on endothelial function and their relation with microvascular complications in T2DM patients without macrovascular disease

The aim of this study was to investigate the influence of homocysteine (hcy) levels on endothelial function by the method of brachial artery ultrasonography and their relation with microvascular complications in type 2 diabetes mellitus (T2DM) patients without macrovascular disease. Fifty-nine T2DM patients with a mean age of 53.4+/-8.6 years and diabetes duration of 8.1+/-6.2 years and 16 healthy controls with a mean age of 47+/-14.5 years were included in the study. Endothelialdependent and endothelium-independent flow-mediated dilatation (FMD) were evaluated via brachial artery ultrasonography. Fasting plasma glucose (FPG), glycosylated haemoglobin (A1c), lipid profile, hcy, B12 and folic acid levels were measured. Diabetic patients and control group individuals were compared with regard to the laboratory values and brachial artery vascular reactivity. Factors influencing endothelium-dependent FMD were investigated with linear regression analysis. Age, gender, body mass index, lipid profiles and hcy levels were similar in both groups (p>0.05). Endothelium-dependent FMD percentages were significantly lower in diabetics than in the control group (7.7+/-5.9 vs. 11.7+/-7.1%, p<0.05). Endothelial-independent FMD percentage was similar for both groups (p>0.05). The upper limit of the reference hcy value was found to be 12.6 micromol/l in the control group. In the diabetic group, hcy levels were high in 33 patients and normal in 26 patients. No difference was detected between the patients with high hcy levels and those with a normal level with regard to endothelium-dependent and endothelium-independent FMD values (p>0.05). Mean hcy levels were 16+/-1.7 and 13.3+/-4.3 micromol/l in T2DM patients with microvascular complication and those with no microvascular complication, respectively (p<0.05). Regression analysis revealed that the main factors influencing the endothelial-dependent FMD were FPG, total cholesterol (TC), triglycerides (TG) and high-density lipoprotein (HDL-C) levels (p<0.05, p=0.05, p=0.05, p=0.02, respectively). Hcy, folic acid and B12 values did not influence endothelium-dependent FMD (p>0.05). Diabetes duration and A1c levels were close to being significant although they did not reach statistical significance (p=0.07 and p=0.08 respectively). Hcy levels have no effect on endothelium-dependent and endothelium-independent FMD in T2DM patients without macrovascular complications. The influence of classical atherogenic factors (such as FPG, TC, TG and HDL-C levels) on endothelium functions, detected with endothelium-dependent FMD, is greater.