Plasma Total Hcy Research Articles

Alzheimer's disease in Brazilian elderly has a relation with homocysteine but not with MTHFR polymorphisms

To investigate the association between total plasma homocysteine concentration, C677T and A1298C polymorphisms in MTHFR gene and Alzheimer's disease (AD) development. Forty-three patients with probable (63%) and possible (37%) AD and 50 non-demented controls were evaluated. Groups did not differ as to gender, age, scholar years, diabetes, alcohol and coffee intake and physical activity. Total plasma homocysteine (Hcy) levels were determined by HPLC and genotyping for MTHFR by PCR/RFLP. Mann-Whitney "U" test was used to compare quantitative variable, Fisher-Freeman-Halton test to compare genotypes and allele proportions and Chi-square test to other qualitative variables. AD patients presented higher total plasma Hcy levels than controls and the difference was statistically significant. No differences in the C677T and A1298C MTHFR polymorphisms distributions were found between patients and controls. Plasma homocysteine concentration did not change with MTHFR genotypes. Our data confirms the association between increased plasma Hcy concentration and AD and suggests that neither C677T nor A1298C MTHFR polymorphisms contributed to genetic susceptibility for AD in elderly individuals in the Northeast of Brazil.

No association between MTHFR A1298C and MTRR A66G polymorphisms, and MS in an Australian cohort

Multiple sclerosis (MS) is a complex neurological disease that affects the central nervous system (CNS) resulting in debilitating neuropathology. Pathogenesis is primarily defined by CNS inflammation and demyelination of nerve axons. Methionine synthase reductase (MTRR) is an enzyme that catalyzes the remethylation of homocysteine (Hcy) to methionine via cobalamin and folate dependant reactions. Cobalamin acts as an intermediate methyl carrier between methylenetetrahydrofolate reductase (MTHFR) and Hcy. MTRR plays a critical role in maintaining cobalamin in an active form and is consequently an important determinant of total plasma Hcy (pHcy) concentrations. Elevated intracellular pHcy levels have been suggested to play a role in CNS dysfunction, neurodegenerative, and cerebrovascular diseases. Our investigation entailed the genotyping of a cohort of 140 cases and matched controls for MTRR and MTHFR, by restriction length polymorphism (RFLP) techniques. Two polymorphisms: MTRR A66G and MTHFR A1298C were investigated in an Australian age and gender matched case-control study. No significant allelic frequency difference was observed between cases and controls at the α = 0.05 level (MTRR χ 2 = 0.005, P = 0.95, MTHFR χ 2 = 1.15, P = 0.28). Our preliminary findings suggest no association between the MTRR A66G and MTHFR A1298C polymorphisms and MS.

Association of Homocysteine and Asymmetric Dimethylarginine With Atherosclerosis and Cardiovascular Events in Maintenance Hemodialysis Patients

Homocysteine (Hcy) and asymmetric dimethylarginine (ADMA) recently were recognized as potential risk factors for atherosclerosis in the general population, and the metabolism of each of these substances seems to be closely related. This study investigates the association between these substances and whether elevated serum Hcy and ADMA levels are related to high risk for atherosclerosis and cardiovascular events in maintenance hemodialysis (HD) patients. A study was made of 197 HD patients (132 men, 65 women; mean age, 56.9 +/- 8.6 years) for the correlation between plasma total Hcy (tHcy) and ADMA concentrations and the association of these substances with atherosclerotic indices of cervical intima-media thickness, plaque diameter, aortic calcification index, and aortic elongation. Cardiovascular events were followed up for 5 years in these patients. Mean plasma tHcy (37.3 +/- 25.8 micromol/L) and ADMA (0.77 +/- 0.16 micromol/L) levels were significantly greater in HD patients than in healthy subjects. Plasma tHcy level did not correlate with plasma ADMA level (r = -0.1; P = not significant). Although ADMA level was associated significantly with atherosclerotic indices from a simple regression analysis, this association was less from multiple regression analysis. When patients were classified into 3 groups according to ADMA level, cardiovascular events during 5 years were significantly greater in the group with the highest ADMA levels than in the other groups, confirmed by using a Cox proportional hazard model. However, no association was found between tHcy levels and atherosclerotic indices or cardiovascular events. ADMA level emerged as a potential risk factor for cardiovascular events that might be mediated in part by atherosclerosis in HD patients. Conversely, neither high nor low plasma tHcy levels were associated with atherosclerotic indices and cardiovascular events. This result for our HD patients does not fulfill the terms of traditional epidemiology and paradoxical reverse epidemiology of Hcy.

Factors Affecting S-Homocysteinylation of LDL Apoprotein B

Hyperhomocysteinemia is an important risk factor for vascular disease and atherosclerosis, but the mechanisms by which homocysteine exerts its deleterious effects are not known. Because oxidation and/or homocysteinylation may increase atherogenicity of LDL, we investigated S-homocysteinylation of LDL as a possible contributor to atherosclerosis pathogenesis. We used capillary electrophoresis to measure LDL-bound thiols [homocysteine, cysteine (Cys), cysteinylglycine, glutathione, and glutamylcysteine] in 104 healthy study participants We also assessed total plasma thiol concentrations and lipid profiles. Our data suggest that apoprotein B (apoB)-cysteinylglycine (CysGly), apoB-Hcy, and apoB-Cys concentrations are markedly higher in men than in women. The percentage of CysGly and glutathione on apoB was higher than that of the same thiols in plasma, whereas the other thiols were markedly less prevalent in lipoprotein than in plasma. Pearson correlation showed that among all thiols, only total plasma Hcy is related to apoB-Hcy concentrations. Multiple correlation analysis confirmed that total Hcy was the most important determinant of apoB-Hcy. Age and LDL cholesterol also showed positive associations, but Cys and, mainly, CysGly were negatively associated with apoB-Hcy concentrations. apoB-Hcy derivative formation is mainly dependent on total homocysteine concentration. Increased cholesterol concentrations are related to increased apoB-Hcy. CysGly seems to compete with Hcy for binding to LDL apoprotein, suggesting that CysGly may protect against atherosclerosis by decreasing the concentrations of Hcy transferred by LDL from plasma to endothelial and subendothelial spaces.

Influence of PON1 Polymorphisms on the Association between Serum Paraoxonase 1 and Homocysteinemia in a General Population

Homocysteine (Hcy)-induced vascular impairment may be partially mediated by the production of Hcy thiolactone (HTL). This compound acylates side-chain lysine groups in proteins and alters protein structure and function. HTL is formed under conditions of high Hcy resulting from insufficient remethylation of Hcy to methionine; however, HTL is not a reliable marker of plasma total Hcy (tHcy). In healthy volunteers, it contributes only 0.14%–0.28% of tHcy, has a half-life of 1 h, and is below the detection limit in approximately one half of volunteers (1). Paraoxonase 1 (PON1) is a hydrolase associated with HDL that is thought to degrade lipid peroxides and HTL (2). Decreased PON1 activity has been associated with atherosclerosis (3). Hepatic expression of the PON1 gene is down-regulated in hyperhomocysteinemic mice (4); it is plausible, therefore, that the proatherogenic effects of Hcy may involve diminished serum PON1 activity, leading to impaired antioxidant function and …

Effect of Homocysteine Lowering by 5-Methyltetrahydrofolate on Redox Status in Hyperhomocysteinemia

The endothelial dysfunction induced by hyperhomocysteinemia can be reversed by 5-methyltetrahydrofolate (5-MTHF) via homocysteine (Hcy) lowering. An additive antioxidant action of 5-MTHF has been suggested to ameliorate endothelial dysfunction through increased nitric oxide production and superoxide radical scavenging, independent of Hcy lowering. The aim of the study was to assess whether 5-MTHF affects the redox state in hyperhomocysteinemia. We examined the effect of 3 months of oral 5-MTHF treatment (15 mg/day) on the redox pattern in 48 hyperhomocysteinemic subjects compared to 24 untreated hyperhomocysteinemic subjects. By analysis of variance with repeated measures in the 72 subjects, 5-MTHF markedly decreased plasma total Hcy (p-tHcy; P = 0.0001) and blood-total glutathione (GSH; b-tGSH; P = 0.002). By multivariate linear regression in the treated subjects, p-tHcy changes from baseline to 3 months (adjusted by baseline p-tHcy levels) correlated only with changes in reduced cysteinylglycine (P = 0.001). The effects of treatment on Hcy lowering and GSH metabolism were greater in medium than in moderate hyperhomocysteinemia. In conclusion, high-dose 5-MTHF treatment for 3 months ensures marked Hcy lowering to normal values even in subjects with high Hcy levels, and should be the treatment of choice in medium hyperhomocysteinemia. Furthermore, 5-MTHF shows a favorable interaction with GSH metabolism.

Plasma Homocysteine Affects Fibrin Clot Permeability and Resistance to Lysis in Human Subjects

Homocysteine (Hcy) is a risk factor for thrombosis. We investigated a hypothesis that the clot permeability and its resistance to fibrinolysis is associated with plasma total Hcy (tHcy) in human subjects. We studied healthy men not taking any medication (n=76), male patients with advanced coronary artery disease (CAD) taking low-dose aspirin (n=33), men with diabetes mellitus diagnosed recently (median hemoglobin A(1c) 7.65%; n=16), and patients with isolated hypercholesterolemia (>7.0 mmol/L; n=15). We assessed clot permeability and turbidimetric lysis time as the determinants of fibrin clot structure. In a regression model, including age and fibrinogen, plasma tHcy was an independent predictor of clot permeation and fibrinolysis time in healthy subjects (R2=0.88, P<0.0001 and R2=0.54, P<0.0001, respectively). In CAD patients, tHcy and fibrinogen were stronger predictors of the permeation coefficient (R2=0.84; P<0.0001) than was fibrinogen alone (R2=0.66; P<0.0001), whereas tHcy was the only predictor of lysis time (R2=0.69; P<0.0001). Elevated tHcy levels observed after methionine load were not associated with any of the fibrin clot properties. In patients with diabetes or hypercholesterolemia, the influence of Hcy on permeation and, to a lesser extent, on the lysis time was obscured by dominant effects of glucose and cholesterol. In 20 asymptomatic men with hyperhomocysteinemia treated with folic acid, reduction in tHcy levels resulted in increased clot permeability (P=0.0002) and shorter lysis time (P<0.0001). Our results indicate that plasma tHcy predicts clot permeation and susceptibility to fibrinolysis in healthy men and CAD patients. Our data are consistent with a mechanism of thrombosis in hyperhomocysteinemia, which involves modification of fibrinogen by Hcy-thiolactone.

Methionine challenge paradoxically induces a greater activation of the antioxidant defence in subjects with hyper- vs. normohomocysteinemia

To determine whether hyperhomocysteinemia induced post-methionine loading (PML) is associated with different response in the aminothiol redox state and oxidative stress vs. normohomocysteinemia, we assessed PML plasma thiols, vitamins, free malondialdehyde (MDA), and blood reduced glutathione (GSH) in 120 consecutive subjects (50 [35–56] years, 83 males), divided into two groups according to PML plasma total Hcy < 35 μM (Group 1, n = 65) or ≥ 35 μM (Group 2, n = 55).In the group as a whole, plasma reduced cysteine and cysteinylglycine, blood reduced GSH (all p for time = 0.0001) and plasma total GSH (p for time = 0.001) increased from baseline to PML. MDA values were unchanged. Group 1 and 2 differed in blood reduced GSH (p for group = 0.004, higher in Group 2), and MDA levels (p for group = 0.024, lower in Group 2).The oxidative stress induced by methionine challenge seems to be opposed by scavenger molecules activation, namely GSH, and lipid peroxidation does not increase. This mechanism paradoxically appears to be more efficient in hyperhomocysteinemic subjects.

Homocysteine from endothelial cells promotes LDL nitration and scavenger receptor uptake

We recently reported that methionine-loaded human umbilical vein endothelial cells (HUVECs) exported homocysteine (Hcy) and were associated with hydroxyl radical generation and oxidation of lipids in LDL. Herein we have analysed the Hcy-induced posttranslational modifications (PTMs) of LDL protein. PTMs have been characterised using electrophoretic mobility shift, protein carbonyl ELISA, HPLC with electrochemical detection and Western blotting of 3-nitrotyrosine, and LDL uptake by scavenger receptors on monocyte/macrophages. We have also analysed PTMs in LDL isolated from rheumatoid (RA) and osteo-(OA) arthritis patients with cardiovascular disease (CVD). While reagent Hcy (<50 μM) promoted copper-catalysed LDL protein oxidation, Hcy released from methionine-loaded HUVECs promoted LDL protein nitration. In addition, LDL nitration was associated with enhanced monocyte/macrophage uptake when compared with LDL oxidation. LDL protein nitration and uptake by monocytes, but not carbonyl formation, was elevated in both RA and OA patients with CVD compared with disease-matched patients that had no evidence of CVD. Moreover, a direct correlation between plasma total Hcy (tHcy) and LDL uptake was observed. The present studies suggest that elevated plasma tHcy may promote LDL nitration and increased scavenger receptor uptake, providing a molecular mechanism that may contribute to the clinical link between CVD and elevated plasma tHcy.

Homocysteine metabolism in ZDF (type 2) diabetic rats.

Mild hyperhomocysteinemia is a risk factor for many diseases, including cardiovascular disease. We determined the effects of insulin resistance and of type 2 diabetes on homocysteine (Hcy) metabolism using Zucker diabetic fatty rats (ZDF/Gmi fa/fa and ZDF/Gmi fa/?). Plasma total Hcy was reduced in ZDF fa/fa rats by 24% in the pre-diabetic insulin-resistant stage, while in the frank diabetic stage there was a 59% reduction. Hepatic activities of several enzymes that play a role in the removal of Hcy:cystathionine beta-synthase (CBS), cystathionine gamma-lyase, and betaine:Hcy methyltransferase (BHMT) were increased as was methionine adenosyltransferase. CBS and BHMT mRNA levels and the hepatic level of S-adenosylmethionine were also increased in the ZDF fa/fa rats. Studies with primary hepatocytes showed that Hcy export and the transsulfuration flux in cells from ZDF fa/fa rats were particularly sensitive to betaine. Interestingly, liver betaine concentration was found to be significantly lower in the ZDf fa/fa rats at both 5 and 11 weeks. These results emphasize the importance of betaine metabolism in determining plasma Hcy levels in type 2 diabetes.

Stable-Isotope Dilution Liquid Chromatography–Electrospray Injection Tandem Mass Spectrometry Method for Fast, Selective Measurement of S-Adenosylmethionine and S-Adenosylhomocysteine in Plasma

It has been postulated that changes in S-adenosylhomocysteine (AdoHcy), a potent inhibitor of transmethylation, provide a mechanism by which increased homocysteine causes its detrimental effects. We aimed to develop a rapid and sensitive method to measure AdoHcy and its precursor S-adenosylmethionine (AdoMet). We used stable-isotope dilution liquid chromatography-electrospray injection tandem mass spectrometry (LC-ESI-MS/MS) to measure AdoMet and AdoHcy in plasma. Acetic acid was added to prevent AdoMet degradation. Solid-phase extraction (SPE) columns containing phenylboronic acid were used to bind AdoMet, AdoHcy, and their internal standards and for sample cleanup. An HPLC C(18) column directly coupled to the LC-MS/MS was used for separation and detection. In plasma samples, the interassay CVs for AdoMet and AdoHcy were 3.9% and 8.3%, and the intraassay CVs were 4.2% and 6.7%, respectively. Mean recoveries were 94.5% for AdoMet and 96.8% for AdoHcy. The quantification limits were 2.0 and 1.0 nmol/L for AdoMet and AdoHcy, respectively. Immediate acidification of the plasma samples with acetic acid prevented the observed AdoMet degradation. In a group of controls (mean plasma total Hcy, 11.2 mumol/L), plasma AdoMet and AdoHcy were 94.5 and 12.3 nmol/L, respectively. Stable-isotope dilution LC-ESI-MS/MS allows sensitive and rapid measurement of AdoMet and AdoHcy. The SPE columns enable simple cleanup, and no metabolite derivatization is needed. The instability of AdoMet is a serious problem and can be prevented easily by immediate acidification of samples.

Physiological Regulation of Phospholipid Methylation Alters Plasma Homocysteine in Mice

Biological methylation reactions and homocysteine (Hcy) metabolism are intimately linked. In previous work, we have shown that phosphatidylethanolamine N-methyltransferase, an enzyme that methylates phosphatidylethanolamine to form phosphatidylcholine, plays a significant role in the regulation of plasma Hcy levels through an effect on methylation demand (Noga, A. A., Stead, L. M., Zhao, Y., Brosnan, M. E., Brosnan, J. T., and Vance, D. E. (2003) J. Biol. Chem. 278, 5952-5955). We have further investigated methylation demand and Hcy metabolism in liver-specific CTP:phosphocholine cytidylyltransferase-alpha (CTalpha) knockout mice, since flux through the phosphatidylethanolamine N-methyltransferase pathway is increased 2-fold to meet hepatic demand for phosphatidylcholine. Our data show that plasma Hcy is elevated by 20-40% in mice lacking hepatic CTalpha. CTalpha-deficient hepatocytes secrete 40% more Hcy into the medium than do control hepatocytes. Liver activity of betaine:homocysteine methyltransferase and methionine adenosyltransferase are elevated in the knockout mice as a mechanism for maintaining normal hepatic S-adenosylmethionine and S-adenosylhomocysteine levels. These data suggest that phospholipid methylation in the liver is a major consumer of AdoMet and a significant source of plasma Hcy.

Homocysteine levels in women with polycystic ovary syndrome treated with metformin versus rosiglitazone: a randomized study

Elevated levels of plasma homocysteine (Hcy) have been implicated as a significant risk factor for cardiovascular disease. Although long-term treatment with metformin can increase Hcy levels in patients with type II diabetes mellitus or coronary heart disease, it is becoming an increasingly accepted and widespread medication in polycystic ovary syndrome (PCOS). In the literature, only one study has demonstrated that metformin increases Hcy levels in PCOS patients, but the effect of other insulin sensitizers on Hcy levels have not been reported previously in women with PCOS. We aimed to assess the effects of metformin and rosiglitazone on plasma Hcy levels in patients with PCOS. Thirty women were randomized to two groups: 15 women in group 1 received 850 mg of metformin twice daily for 3 months. In group 2, 15 women received 4 mg of rosiglitazone for 3 months. In both groups, body mass index, menstrual pattern, and plasma total Hcy, insulin, glucose and lipid metabolism parameters were recorded at baseline and at 3 months. Hcy levels increased from 8.93+/-0.49 to 11.26+/-0.86 micromol/l (P = 0.002) and from 10.70+/-0.86 to 12.36+/-0.81 micromol/l (P = 0.01) in the metformin and rosiglitazone groups, respectively. Apolipoprotein (Apo) A1 levels increased from 127.10+/-6.85 to 145.7+/-7.18 mg/dl (P = 0.018) in the metformin group. Total cholesterol (total-C), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), lipoprotein (a) and Apo B levels decreased in the metformin group, but the change was not significant. Total-C levels decreased from 161.15+/-8.94 to 150.23+/-8.73 mg/dl (P = 0.026), HDL-C decreased from 43.13+/-2.65 to 39.15+/-2.52 mg/dl (P = 0.005) and LDL-C levels decreased from 93.83+/-6.06 to 80.7+/-2.30 mg/dl (P = 0.021) in the rosiglitazone group. Treatment with insulin sensitizers in women with PCOS may lead to increases in Hcy levels.

Administration of B-group vitamins reduces circulating homocysteine in polycystic ovarian syndrome patients treated with metformin: a randomized trial

The aim of the current study was to assess the effects of B-group vitamins and folic acid administration on serum levels of homocysteine (Hcy) in patients with polycystic ovarian syndrome (PCOS) on short-term metformin treatment. Patients were randomly assigned to one of three treatment groups. Group 1 patients (n = 20) received metformin (850 mg twice daily); group 2 patients (n = 20) received metformin (850 mg twice daily) and B-group vitamins (vitamin B1, 250 mg; vitamin B6, 250 mg; vitamin B12, 1000 microg twice daily); and group 3 patients (n = 20) received metformin (850 mg twice daily) and folic acid (174 microg twice daily). In all groups, lipid profiles and plasma total Hcy, vitamin B12, folic acid and glucose levels were recorded at baseline and at 3 months. A 26.5% increase in Hcy levels was seen after 12 weeks of metformin therapy, while 21.17 and 8.33% decreases in Hcy levels were detected when B-group vitamins or folic acid plus metformin were given respectively. There were no statistically significant differences recorded in insulin sensitivity using homeostasis model assessment in the three groups. These findings suggest that B-group vitamins and folic acid administration counteract the Hcy-increasing effect seen with metformin therapy.

Urinary Excretion of Homocysteine-Thiolactone in Humans

A metabolite of homocysteine (Hcy), the thioester Hcy-thiolactone, has been implicated in coronary heart disease in humans. Because inadvertent reactions of Hcy-thiolactone with proteins can lead to cell and tissue damage, the ability to detoxify or eliminate Hcy-thiolactone is essential for biological integrity. We examined the hypothesis that the human body eliminates Hcy-thiolactone by urinary excretion. We used a sensitive HPLC method with postcolumn derivatization and fluorescence detection to examine Hcy-thiolactone concentrations in human urine and plasma. We discovered a previously unknown pool of Hcy-thiolactone in human urine. Urinary concentrations of Hcy-thiolactone (11-485 nmol/L; n = 19) were approximately 100-fold higher than those in plasma (<0.1-22.6 nmol/L; n = 20). Urinary Hcy-thiolactone accounted for 2.5-28.3% of urinary total Hcy, whereas plasma Hcy-thiolactone accounted for <0.002-0.29% of plasma total Hcy. Urinary concentrations of Hcy-thiolactone, but not of total Hcy, were negatively correlated with urinary pH. Clearance of Hcy-thiolactone, relative to creatinine, was 0.21-6.96. In contrast, relative clearance of Hcy was 0.001-0.003. The analytical methods described here can be used to quantify Hcy-thiolactone in biological fluids. Using these methods we showed that the human body eliminates Hcy-thiolactone by urinary excretion. Our data also suggest that the protonation status of its amino group affects Hcy-thiolactone excretion.

Physiological variation in plasma total homocysteine concentrations in rats

Hyperhomocysteinemia was initially related to cardiovascular diseases; but homocysteine (Hcy) metabolism disturbances have more recently associated with a wide range of pathophysiological conditions including age-related diseases, disrupted circadian rhythms and gynaecological disorders. Since in many cases we do not know to what extent animal models are physiologically similar to human ones, this study aimed to track spontaneous variations in rat plasma Hcy concentrations during different physiological processes such as life cycle, 24 hours and estrous cycle. Plasma total Hcy concentrations were accessed by HPLC. Plasma Hcy concentration varied with age and newborns had the lowest values (2.94 ± 0.47 μmol/L). Rats aged 10 days presented concentration similar to 3 month old animals (6.87 ± 0.67 and 8.29 ± 1.55 μmol/L respectively). Values decreased to 6.42 ± 1.65 μmol/L at 6 months and 4.87 ± 0.81 μmol/L at 28 months. Concerning circadian variations in Hcy concentration cosinor analysis showed acrophase in young rats at 1:09 pm, but no plasma Hcy circadian variations in aged rats. Female rats showed changes in Hcy concentration during the estrous cycle with higher values during the diestrous I (10.61 ± 1.81 μmol/L) compared with the estrous (8.47 ± 1.86 μmol/L) and diestrous II (7.68 ± 1.58 μmol/L) phases. In conclusion, plasma Hcy concentration varied spontaneously with ontogenic development and during the estrous cycle and presented a circadian rhythm variation in young rats.

Homocyst(e)ine-Lowering Therapy Does Not Affect Plasma Asymmetrical Dimethylarginine Concentrations in Patients with Peripheral Artery Disease

Elevated plasma asymmetrical dimethylarginine (ADMA) is suggested to contribute to hyperhomocyst(e)ine-related vascular dysfunction in patients with peripheral artery disease (PAD). The present trial investigated whether homocyst(e)ine (Hcy)-lowering therapy with vitamin-B (vit-B) and folic acid affects plasma concentrations of ADMA in patients with PAD and hyperhomocyst(e)inemia. Forty-nine subjects (15 women, 34 men) with PAD and fasting plasma total Hcy concentrations greater than 15 micromol/liter were randomized to receive either oral vit-B and folic acid therapy (n = 27) or placebo (n = 22) for 6 wk. Fasting venous blood samples were monitored for plasma total Hcy, vit-B12 and folate, ADMA, symmetric dimethylarginine, L-arginine, and high-sensitivity C-reactive protein. After 6 wk, plasma Hcy concentrations were decreased, and concentrations of vit-B12 and folate were elevated in patients with vitamin supplementation (all P < 0.05 vs. baseline) and unchanged in the placebo group. Dimethylarginine plasma concentrations were not affected by treatment. High-sensitivity C-reactive protein correlated with ADMA plasma concentrations (r = 0.29; P < 0.01). The lack of vit-B and folic acid therapy on plasma concentrations of ADMA renders a role of extracellular methylarginines unlikely to be involved in the pathophysiology of hyperhomocyst(e)inemia and its complications.

Antibodies to N-homocysteinylated albumin as a marker for earlyonset coronary artery disease in men

N-homocysteinylated (Nepsilon-Hcy) proteins and corresponding antibodies have recently been discovered in humans and animals. Increased autoimmune response to Nepsilon-Hcy-proteins has been reported in stroke patients. The aim of the present study was to investigate whether antibodies against N-homocysteinylated albumin are associated with coronary artery disease (CAD). We studied 88 male patients aged 50 years or under with angiographically documented CAD and 100 age-matched apparently healthy men as controls. Serum levels of IgG antibodies against Nepsilon-Hcy-albumin were determined using an enzymelinked immunosorbent assay. Seropositivity to anti-Nepsilon-Hcy-albumin antibodies was 5-fold more frequent in CAD patients than in controls (52.3% vs 10.0%; p<0.0001). Plasma Hcy levels in CAD patients were also significantly higher in the former than in the latter group (medians, 13.0 microM vs 12.1 microM; p=0.026). Importantly, 41.2% of subjects with plasma total Hcy >14.5 mM were seropositive compared with 25.5% of normohomocysteinemic individuals (p=0.048). There was a weak correlation between anti-Nepsilon-Hcy-albumin antibodies and Hcy levels (r=0.16; p=0.03). By multivariate logistic regression analysis, seropositivity to anti-Nepsilon-Hcy-albumin antibodies was an independent predictor of early CAD (OR, 14.82; 95% CI, 4.47 to 49.19; p=0.00002). Interestingly, anti-Nepsilon-Hcy-albumin antibodies were associated with C-reactive protein levels (r=0.24; p=0.002). Seropositivity to anti-Nepsilon-Hcy-albumin antibodies showed no association with the MTHFR C677T polymorphism. Our results suggest that seropositivity to antibodies against Nepsilon-homocysteinylated albumin is associated with early-onset CAD. An autoimmune response to Nepsilon-Hcy-albumin may represent a novel mechanism involved in the early development of CAD.

Genetic polymorphisms predisposing to hyperhomocysteinemia in cardiac transplant patients

Genetic determinants for high homocysteine (Hcy) levels are now well known. We studied several single nucleotide polymorphisms (SNP) in Hcy-regulating genes [methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C; methionine synthase (MS) A2756G; methionine synthase reductase (MTRR) A66G] in relation to total plasma Hcy levels, transplant coronary artery disease and thromboembolic episodes in 84 heart transplant patients, and we compared the incidence of these polymorphisms with those in a healthy adult controls. At least one copy of the G allele of the MTRR A66G SNP was found in a significantly greater proportion of cardiac transplant (CTX) recipients compared with controls (94.0% vs. 79.9% respectively). None of the SNP analyzed were correlated with total Hcy plasma levels or the presence of transplant coronary artery disease. However, MS A2756G was significantly associated with cobalamin levels (AA genotype: 290 +/- 122 pmol/l; AG: 381 +/- 151 pmol/l and GG: 415 +/- 100 pmol/l), as was MTRR A66G (AA: 478 +/- 219 pmol/l, AG: 306 +/- 124 pmol/l and GG: 306 +/- 123 pmol/l). MTRR A66G was also correlated with serum folate. No association was found with thromboembolic events. In conclusion, there was a significant difference in the frequency of the G allele genotype of the MTRR A66G in CTX patients versus controls. Differences in cobalamin and folate levels with the MTRR A66G and MS A2756G polymorphisms were noted. Thus, SNP in Hcy-regulating genes may be important determinants of vitamin metabolism in CTX, raising the question of increased vitamin requirements to minimize increased plasma Hcy in this high-risk group.

Factors associated with increased plasma homocysteine in patients using an amino acid peritoneal dialysis fluid

Although amino acid peritoneal dialysate (AAPD) substitution is thought to improve protein-energy malnutrition in patients undergoing peritoneal dialysis (PD), it may also increase plasma homocysteine (Hcy) levels due to the methionine load in the dialysate. However, it is still unclear which factors are important for elevating Hcy in patients treated with AAPD. Sixteen malnourished PD patients (age 48+/-18 years) were treated daily with one exchange of 1.1% AAPD for 3 months. The effects of AAPD on nutrition, Hcy, methionine, leptin and insulin resistance were studied. We also analysed factors that influenced plasma Hcy levels. We found a transient increase in serum albumin (P<0.01) after 1 month treatment, especially in patients with serum albumin < or = 3.5 g/dl. Total plasma Hcy increased markedly after AAPD (the peak at month 2, P<0.001) and returned to baseline after ceasing AAPD, despite no changes in dietary methionine intake and serum methionine levels. Eight patients with Hcy increments >5.65 microM (the median) had lesser dietary intakes of protein (P = 0.01) and methionine (P = 0.028), lower body fat mass (P = 0.05) and lower aspartate transaminase (AST) (P = 0.008) before AAPD treatment than patients with lower increments. DeltaHcy was inversely correlated with baseline dietary methionine intake (r = -0.61), protein intake (r = -0.54) and AST (r = -0.51) (all P<0.05). There was no change in leptin or insulin resistance. AAPD treatment significantly increased Kt/Vurea (P<0.001), weekly creatinine clearance (P<0.05) and peritoneal glucose transport (P<0.05). Treatment with 1.1% AAPD transiently increased serum albumin in malnourished PD patients. However, the methionine load from the dialysate in this study significantly elevated plasma Hcy levels, especially in patients with lower protein and methionine intakes, and lower AST levels. Further long-term studies will be needed to clarify potential nutritional benefits and adverse effects of AAPD.