Increase In tHcy Levels Research Articles

Impact of MTHFR (C677T) gene polymorphism on antiepileptic drug monotherapy in North Indian epileptic population.

BACKGROUND AND OBJECTIVESAntiepileptic drugs (AEDs) are known to interfere with homocysteine metabolism. Hyperhomocysteinemia may be a risk factor associated in the long-term treatment with AEDs. Both genetic and non-genetic factors are responsible for hyperhomocysteinemia. MTHFR C677T. Polymorphism leads to the reduction in enzyme activity and subsequent elevation of plasma homocysteine. This study aimed to investigate the role of MTHFR C677T polymorphism in epileptic patients receiving AEDs as monotherapy (phenytoin, carbamazepine, and sodium valproate) and showing toxicity and non-toxicity, and the impact of AEDs on hyperhomocysteinemia in North Indian population.DESIGN AND SETTINGSBlood samples for this case-control study were collected from the outpatient department and wards of the Department of Neurosciences at the All India Institute of Medical Sciences, New Delhi, India, between July 2008 and May 2010.PATIENTS AND METHODSIn this study, 200 epileptic patients and 100 normal controls were assessed for total homocysteine (tHcy), vitamin B12, and folate levels using enhanced chemiluminescence enzyme immunoassay method (ImmuliteR, 1000 systems, DPC, United States); genotyping of MTHFR C677T was done using polymerase chain reaction-restriction fragment length polymorphism method.RESULTSThe results showed a significant increase in tHcy levels in epileptic patients with toxicity and non-toxicity than in normal controls (P<.005). The allelic and genotypic distributions were found to be statistically significant in toxicity and non-toxicity groups (P<.05).CONCLUSIONThe result confirmed that hyperhomocysteinemia is common in adults receiving AED treatment for epilepsy with toxicity and non-toxicity groups. This increase in tHcy is mainly related to low folate and vitamin B12 levels, which are the main determinants for tHcy.

Folic acid deficiency induces premature hearing loss through mechanisms involving cochlear oxidative stress and impairment of homocysteine metabolism.

Nutritional imbalance is emerging as a causative factor of hearing loss. Epidemiologic studies have linked hearing loss to elevated plasma total homocysteine (tHcy) and folate deficiency, and have shown that folate supplementation lowers tHcy levels potentially ameliorating age-related hearing loss. The purpose of this study was to address the impact of folate deficiency on hearing loss and to examine the underlying mechanisms. For this purpose, 2-mo-old C57BL/6J mice (Animalia Chordata Mus musculus) were randomly divided into 2 groups (n = 65 each) that were fed folate-deficient (FD) or standard diets for 8 wk. HPLC analysis demonstrated a 7-fold decline in serum folate and a 3-fold increase in tHcy levels. FD mice exhibited severe hearing loss measured by auditory brainstem recordings and TUNEL-positive-apoptotic cochlear cells. RT-quantitative PCR and Western blotting showed reduced levels of enzymes catalyzing homocysteine (Hcy) production and recycling, together with a 30% increase in protein homocysteinylation. Redox stress was demonstrated by decreased expression of catalase, glutathione peroxidase 4, and glutathione synthetase genes, increased levels of manganese superoxide dismutase, and NADPH oxidase-complex adaptor cytochrome b-245, α-polypeptide (p22phox) proteins, and elevated concentrations of glutathione species. Altogether, our findings demonstrate, for the first time, that the relationship between hyperhomocysteinemia induced by folate deficiency and premature hearing loss involves impairment of cochlear Hcy metabolism and associated oxidative stress.

Bioavailability ofS-Adenosyl Methionine and Impact on Response in a Randomized, Double-Blind, Placebo-Controlled Trial in Major Depressive Disorder

To characterize the impact of S-adenosyl methionine (SAMe) on homocysteine and potential risk of adverse cardiovascular effects by examining plasma levels of SAMe, S-adenosyl homocysteine (SAH), total homocysteine (tHCY), methionine (MET), and 5-methyltetrahydrofolate (5-MTHF) in 35 of 73 patients from a 6-week randomized double-blind, placebo-controlled trial of SAMe augmentation in serotonin reuptake inhibitor partial responders with DSM-IV major depressive disorder (MDD), published in 2010.Subjects were randomized from June 4, 2004, until August 8, 2008, to adjunctive placebo or SAMe 800-1600 mg/d for 6 weeks. Primary outcome measures included changes in one-carbon cycle intermediates within each treatment arm (by paired t test) and between treatment arms (by independent samples t test). Univariate analysis of variance and Fisher Protected Least Significant Difference were carried out to compare posttreatment levels of each one-carbon cycle intermediate. Secondary outcome measures included associations between clinical improvement and change in plasma intermediate levels, examined by linear regression (for change in Hamilton Depression Rating Scale scores) and logistic regression (for response or remission).We found significant differences in pretreatment plasma levels of tHCY (P = .03) between the SAMe and placebo arms. Following 6 weeks of treatment, plasma SAMe (P = .002) and SAH (P < .0001) levels increased significantly in the SAMe arm; no intermediates in the placebo group changed significantly. Posttreatment plasma SAMe (P = .0035), SAH (P < .0001), and tHCY (P = .0016) levels differed significantly between the SAMe and placebo groups. No significant associations were found between plasma intermediate levels and clinical improvement, response, or remission.Despite concerns about the impact that SAMe therapy may have on homocysteine levels and risk of adverse cardiovascular effects, the lack of significant increase in tHCY levels after treatment suggests that no toxic effects from SAMe should be expected. Our findings, however, have some significant limitations and should be interpreted with caution.ClinicalTrials.gov identifier: NCT00093847.

Effect of fenofibrate-mediated increase in plasma homocysteine on the progression of coronary artery disease in type 2 diabetes mellitus

The Diabetes Atherosclerosis Intervention Study (DAIS) examined the effects of fenofibrate or placebo on the progression of coronary artery disease (CAD) in 418 type 2 diabetic subjects with dyslipidemia. Fenofibrate use was associated with a 6% increase in high-density lipoprotein cholesterol, a 28% decrease in triglycerides, a 5% decrease in low-density lipoprotein cholesterol, and a 55% increase in plasma homocysteine (tHcy). The purpose of the present study was to determine whether this increase in tHcy in the fenofibrate group was associated with CAD progression or with clinical events. The increase in tHcy with fenofibrate (n = 207) was not related to changes in factors known to modulate tHcy levels (serum levels of Vitamin B 12, folate, or renal function). CAD was quantified by angiography at baseline and after a minimum of 3 years of therapy with fenofibrate or placebo. The primary end point was change in mean segment diameter (MSD), minimal lumen diameter, and percent stenosis. Baseline tHcy level was correlated with percent diameter stenosis (r = 0.111, p = 0.028). Baseline, but not end-of-study elevated tHcy levels, decreased the beneficial effect of fenofibrate. Unexpectedly, the final tHcy levels correlated negatively with CAD progression (r = −0.111, p = 0.031) in the overall group. In the fenofibrate group, there was no significant correlation between tHcy and minimal lumen diameter (r = −0.135, p = 0.069), or percent stenosis. An increase in tHcy levels was not correlated with adverse clinical events in the fenofibrate group. This analysis of the the DAIS reveals that the fenofibrate-mediated increase in tHcy levels does not attenuate the beneficial effects of fenofibrate on CAD progression or clinical events.

Serum homocysteine concentrations, gemfibrozil treatment, and progression of coronary atherosclerosis

The present study aimed to assess the effect of gemfibrozil on serum total homocysteine (tHcy) concentration and to evaluate the influence of tHcy on the angiographically determined progression of coronary atherosclerosis in a randomised, placebo-controlled trial of 395 post-coronary bypass men with low HDL cholesterol levels. The baseline levels of tHcy and those after 16 months of randomised therapy were measured by high-pressure liquid chromatography. Patients were genotyped for the thermolabile variant of N 5, N 10-methylenetetrahydrofolate reductase (MTHFR) (677C>T substitution). Gemfibrozil therapy was associated with a median 18% increase in tHcy levels ( P<0.001). In the gemfibrozil group increases in tHcy and HDL cholesterol were related ( r=0.217, P=0.004), but changes in tHcy and triglycerides were not. Levels of tHCy were not associated with baseline extent or progression of coronary-artery disease. Subjects homozygous for the rare MTHFR T allele had 34% higher median tHcy concentrations than CC homozygotes or CT heterozygotes, but responses to gemfibrozil did not differ significantly among genotypes. The MTHFR genotype was not associated with extent or progression of coronary atherosclerosis. We conclude that gemfibrozil causes a significant elevation in tHcy levels, but the clinical relevance of this is unknown at present.

Effect of raloxifene, estrogen, and hormone replacement therapy on serum homocysteine levels in postmenopausal women

Homocysteine (Hcy) is a sulfur-containing amino acid involved in the remethylation and transulfuration metabolic pathways (1). Genetic mutations and the deficiency in nutrients and micronutrients may disrupt Hcy metabolism and result in elevated serum levels. Furthermore, total Hcy (tHcy) levels may be determined by demographics, lifestyle, and state of health factors (1–4). Although tHcy levels are reported to be lower in premenopausal women compared with postmenopausal women (5), there is no consensus on whether they increase after menopause (5, 6). Furthermore, it is unclear whether the menopause-associated increase is related to age (2, 7) or to estrogen depletion (2, 5). In a previous study, we reported that the increase in tHcy levels among postmenopausal women appears to be age related (7).

Plasma homocysteine levels, cerebrovascular risk factors, and cerebral white matter changes (leukoaraiosis) in patients with Alzheimer disease.

The pathogenesis of leukoaraiosis on computed tomographic (CT) scanning is unknown, but cerebrovascular risk factors for leukoaraiosis show overlap with those for Alzheimer disease (AD). To investigate the contribution of cerebrovascular risk factors, in particular plasma total homocysteine (tHcy), to leukoaraiosis in patients with AD and controls. Cross-sectional case-control study. Referral population to a hospital clinic and community volunteers from the Oxfordshire region in England seen between July 1, 1988, and July 1, 2000. One hundred thirty-seven AD cases (104 confirmed post mortem) and 277 controls matched for age (mean +/- SD, 73 +/- 8 years) and sex. Cerebrovascular risk factors and leukoaraiosis on CT scans of cases and controls; the odds ratio (OR) of having moderate to severe leukoaraiosis with higher levels of plasma tHcy and cerebrovascular risk factors such as age, sex, systolic blood pressure, smoking, diabetes mellitus, and apolipoprotein E epsilon4 genotype. Leukoaraiosis was more prevalent in AD cases. For a 5-micromol/L increase in tHcy levels, the OR for leukoaraiosis was 1.40 (95% confidence interval, 1.02-1.91) independent of other risk factors. The distribution pattern of leukoaraiosis was more marked in the deep white matter than in the periventricular area in individuals with elevated tHcy levels, particularly in patients with AD. Higher tHcy levels are an independent risk factor for moderate to severe leukoaraiosis in individuals with AD and of leukoaraiosis of the deep white matter in particular. The nature of the relationship between tHcy levels and leukoaraiosis in AD requires further longitudinal and intervention studies.

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

Epidemiological evidence has revealed that an elevated plasma homocysteine level (hyperhomocysteinemia) confers an increased risk of cardiovascular disease and neural tube defects. Hyperhomocysteinemia is caused by both nutritional (e.g. folate, vitamins B 6 and B 12) and genetic factors, including functional polymorphisms of key enzymes involved in homocysteine metabolism. One such enzyme, methionine synthase reductase (MTRR), maintains adequate levels of methylcob(III)alamin, the activated cofactor for methionine synthase, which catalyzes the remethylation of homocysteine to methionine. A common MTRR polymorphism, i.e. a 66 A→G substitution specifying an isoleucine to methionine substitution (I22M), was recently identified. To assess the influence of this polymorphism on total plasma homocysteine (tHcy), we undertook a genotype/phenotype analysis in a study population of 601 Northern-Irish men, aged 30–49, for which biochemical and genetic data relevant to folate/homocysteine metabolism had already been acquired. The 66AA genotype has a frequency of 29% in this population. We established that there was a significant influence of MTRR genotype on tHcy ranking ( P=0.004) and that the 66AA genotype contributes to a moderate increase in tHcy levels across the distribution [OR 1.59 (95% CI: 1.10–2.25) for the 66AA genotype to be in the upper half of the tHcy distribution, P=0.03]. The homocysteine-elevating effect of the 66AA genotype is independent of serum folate, vitamin B 12 and vitamin B 6 levels. Based on published estimates of the enhanced cardiovascular disease risk conferred by defined increments of plasma tHcy, we estimate that 66AA homozygotes have, on average, an approximately 4% increase in cardiovascular disease risk compared to 66GG homozygotes. This study provides the first evidence that the MTRR A66G polymorphism significantly influences the circulating tHcy concentration.

Relation between Plasma Homocysteine Concentration, the 844ins68 Variant of the Cystathionine β-Synthase Gene, and Pyridoxal-5′-Phosphate Concentration

A moderately elevated plasma total homocysteine (tHcy), whether measured during fasting or post-methionine load (PML), is recognized as a risk factor for coronary artery diseases (CAD). Cystathionine β-synthase (CBS), a key enzyme in the transsulfuration pathway, is important for the metabolism of homocysteine. In recent years, a relatively prevalent mutation, the 844ins68 (68-bp insertion), was found to be carried by about 12% of the general population. In the current investigation, we studied 741 individuals with respect to the effect of the 68-bp insertion of the CBS gene on fasting and PML tHcy, and also determined the level of pyridoxal-5′-phosphate (vitamin B6), a cofactor of the CBS enzyme. Our results showed that the mean fasting and PML increase in tHcy levels were lower in individuals carrying the 844ins68 variant compared to those without the insertion; although only the difference in PML increase in tHcy reached statistical significance (P = 0.02). When these individuals were divided into two groups based on vitamin B6 concentration, the PML increase in tHcy was significantly lower in individuals heterozygous for the insertion compared to those without the insertion only in the group of individuals whose vitamin B6 concentrations were below the sample median (38.0 nmol/L). We speculate that the 68-bp insertion is associated with somewhat higher levels of CBS enzyme activity, and that the effect of this becomes more pronounced in the presence of relatively low concentrations of pyridoxal-5′-phosphate, a cofactor of the CBS enzyme.

Hyperhomocysteinemia and hypofibrinolysis in young adults with ischemic stroke.

Data from epidemiological and case-control studies suggest that increased total homocysteine (tHcy) levels are associated with increased risk for thromboembolic disease. The mechanisms by which hyperhomocysteinemia contributes to thrombogenesis are incompletely understood. The main objectives of this study of young ischemic stroke patients were (1) to examine fasting and post-methionine load levels of tHcy, (2) to ascertain the genotype frequency of the C677CT mutation in the methylenetetrahydrofolate reductase gene (TT genotype), and (3) to study the possible interaction between plasma tHcy levels and fibrinolytic factors. This case-control study was based on 80 consecutive patients aged 18 to 44 years admitted between January 1992 and May 1996 as a result of a first-ever ischemic stroke. Forty-one healthy control subjects were recruited. Measurement of fasting tHcy and post-methionine load levels and evaluation of the fibrinolytic system were undertaken at least 3 months (mean, 5.1+/-1. 9 months) after admission. Genotyping of the methylenetetrahydrofolate reductase gene was performed. Although the increase after methionine loading (ie, postload tHcy minus fasting-level tHcy) was significantly higher among patients, there was no difference in fasting and postload tHcy levels. After adjustment for conventional risk factors, elevated postload increase tHcy levels were associated with a 4.8-fold increased risk of ischemic stroke. There was no difference between patients and control subjects in either TT genotype frequency or T allele frequency. Abnormal response to methionine loading was associated with higher tissue plasminogen activator (tPA) mass concentration, higher plasminogen activator inhibitor-1 levels, and lower tPA activity. After adjustment for age, sex, body mass index, serum cholesterol, and triglycerides, an abnormal increase in postload tHcy levels remained significantly associated with tPA mass concentration levels (P=0.03). A moderately elevated increase in tHcy levels after methionine loading was associated with an increased risk for ischemic stroke in young adults. In contrast, fasting tHcy levels did not differ between patients and controls. A moderately elevated increase in tHcy after methionine loading may provide a additional thrombogenic risk mediated in part by interactions with the fibrinolytic system. In young stroke patients, a methionine loading test to detect hyperhomocysteinemia should always be considered in the convalescent phase of the disease.

Metformin increases total serum homocysteine levels in non-diabetic male patients with coronary heart disease

It is known that the metabolism of homocysteine (Hcy) depends on the vitamins B6, B12 and folate, and furthermore that metformin reduces serum vitamin B12 levels. In order to investigate whether metformin treatment affects serum total Hcy (tHcy) levels we performed an open, prospective, randomised study in 60 non-diabetic male patients with cardiovascular disease. After a 4-week run-in period with lovastatin 40 mg day-1, and diet and lifestyle advice, patients were randomised into two groups, both continuing the run-in treatment. One group received metformin up to 2000 mg day-1, whereas the control group got no additional treatment.After 12 and 40 weeks of metformin treatment, tHcy levels increased moderately but significantly by 7.2% (p<0.05) and 13.8% (p<0.05) in the metformin group relative to the control group, whereas serum vitamin B12 levels decreased by 13.4% (p<0.0005) and 17.7% (p<0.0005), respectively. Serum folate levels did not change after 12 weeks, but decreased by 8.0% after 40 weeks (p=0.061) relative to the control group. Serum levels of total cysteine and methylmalonic acid (MMA) did not change.In conclusion, metformin treatment increased tHcy levels and decreased levels of vitamin B12 and folate. Since MMA levels were unchanged, it remains an open question whether the increase in tHcy levels is secondary to reduced vitamin B12 levels, folate levels or a combination of both.