Asymmetric dimethylarginine increases mononuclear cell adhesiveness in hypercholesterolemic humans

Do Antiepileptic Drugs Change the Levels of Arginine Derivatives in Epileptic Children Treated with Polytherapy? The Results of a Case–Control Study

Previously, a relation between therapy with antiepileptic drugs (AEDs) and the levels of biochemical parameters was observed in adult patients suffering from epilepsy. Among these biochemical factors, arginine derivatives are often analyzed, i.e., asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and homoarginine (hArg) as they may be linked with increased risk for cardiovascular disease (CVD). Since the levels of arginine derivatives may increase during therapy, and the treatment of epilepsy often lasts many years, patients may experience CVD faster. The aim of the present study was to analyze the levels of arginine derivatives in children with epilepsy who were treated with multiple AEDs to answer the question whether pediatric patients may be at increased risk of CVD in the future. We prospectively analyzed 21 children suffering from epilepsy who took ≥2 AEDs for at least 6 months and 22 children without epilepsy (reference group). The levels of the arginine derivatives, e.g., ADMA, SDMA, and hArg, were determined in the blood serum using the HPLC method. No differences in both the mean levels of ADMA and SDMA, as well as in the mean values of the arginine derivative ratios, were observed between the groups. The tendency toward a lower level of hArg was found in epileptic patients more than in the reference group (p = 0.091). Epileptic children receiving three or more AEDs had significantly lower concentrations of hArg and values of the hArg/ADMA ratio than the reference group (p = 0.023 and p = 0.006, respectively). In turn, the mean hArg/ADMA ratio was lower in children receiving three or more AEDs compared to children receiving two AEDs (p = 0.002). There was also a positive correlation between the hArg and ADMA concentrations in children with epilepsy taking two AEDs; the higher the level of hArg, the greater the level of ADMA on average (r = 0.650, p = 0.022). Taking three or more AEDs by epileptic children resulted in lower levels of both hArg and the value of the hArg/ADMA ratio.

The Potential of L-Arginine in Prevention and Treatment of Disturbed Carbohydrate and Lipid Metabolism—A Review

L-arginine, an endogenous amino acid, is a safe substance that can be found in food. The compound is involved in synthesis of various products responsible for regulatory functions in the body. Particularly noteworthy is, among others, nitric oxide, a signaling molecule regulating carbohydrate and lipid metabolism. The increasing experimental and clinical data indicate that L-arginine supplementation may be helpful in managing disturbed metabolism in obesity, regulate arterial blood pressure or alleviate type 2 diabetes symptoms, but the mechanisms underlying these effects have not been sufficiently elucidated. This review aims to present the up-to-date information regarding the current uses and health-promoting potential of L-arginine, its effects on nitric oxide, carbohydrate and lipid metabolisms, based on the results of in vivo, in vitro studies, and clinical human trials. Available literature suggests that L-arginine may have beneficial effects on human health. However, some studies found that higher dietary L-arginine is associated with worsening of an existing disease or may be potential risk factor for development of some diseases. The mechanisms of regulatory effects of L-arginine on carbohydrate and lipid metabolism have not been fully understood and are currently under investigation.

Effect of calcium and vitamin D supplementation on the clinical, hormonal, and metabolic profile in non-obese women with polycystic ovary syndrome

BACKGROUND

In this study, we investigated the effect of calcium and vitamin D (Ca/Vit D) supplementation on the clinical, hormonal, and metabolic profile of patients with low vitamin D levels. In addition, we investigated the effect of Ca/Vit D supplementation on asymmetric dimethylarginine (ADMA) level in patients with polycystic ovary syndrome (PCOS).

METHODS

In total, 75 patients aged 19-35 years, with a normal body mass index and a diagnosis of PCOS and Vit D deficiency/insufficiency, were included in the study. Patients received 50,000 IU of vitamin D3 once a week for 8 weeks. Afterward, 2500 mg calcium carbonate equivalent to 1000 mg calcium ion and 9.68 mg cholecalciferol equivalent to 880 IU vitamin D3 were administered orally as a maintenance treatment once a day.

RESULTS

The mean age of the patients was 21.7 ± 3.5. After Ca/Vit D supplementation, Vit D levels significantly increased compared to baseline (8.6 ng/ml) levels. An increase in SHBG levels (p < 0.001), a decrease in total testosterone, FAI (p = 0.042), and ADMA levels (p < 0.001) were observed in the first and third months compared to the onset. Significant improvement compared to baseline was observed in menstrual irregularity and median mFG score.

CONCLUSION

Ca/Vit D supplementation can improve PCOS symptoms such as menstrual dysfunction, hirsutism, and hyperandrogenism. It may be effective in reducing the risk of cardiovascular disease in patients with PCOS later in life by decreasing ADMA levels, which is an indicator of endothelial dysfunction.

Asymmetric Dimethylarginine: a Key Player in the Pathophysiology of Endothelial Dysfunction, Vascular Inflammation and Atherosclerosis in Rheumatoid Arthritis?

Patients with rheumatoid arthritis (RA), a chronic and disabling autoimmune condition that is characterized by articular and extra-articular manifestations and a pro-inflammatory and pro-oxidant state, suffer from premature atherosclerosis and excessive cardiovascular disease burden. A key step in the pathogenesis of atherosclerosis is impaired synthesis of the endogenous messenger nitric oxide (NO) by endothelial cells which, in turn, alters local homeostatic mechanisms and favors vascular damage and plaque deposition. While the exact mechanisms of endothelial dysfunction in RA remain to be established, there is good evidence that RA patients have relatively high circulating concentrations of the methylated arginine asymmetric dimethylarginine (ADMA), a potent endogenous inhibitor of endothelial NO synthase (eNOS). This review discusses the biological and pathophysiological role of ADMA, the interplay between ADMA, inflammation and oxidative stress, and the available evidence on the adverse impact of ADMA on endothelial function and atherosclerosis and potential ADMA-lowering therapies in RA patients.

ADMA: A Key Player in the Relationship between Vascular Dysfunction and Inflammation in Atherosclerosis

Atherosclerosis is a chronic cardiovascular disease which increases risk of major cardiovascular events including myocardial infarction and stroke. Elevated plasma concentrations of asymmetric dimethylarginine (ADMA) have long been recognised as a hallmark of cardiovascular disease and are associated with cardiovascular risk factors including hypertension, obesity and hypertriglyceridemia. In this review, we discuss the clinical literature that link ADMA concentrations to increased risk of the development of atherosclerosis. The formation of atherosclerotic lesions relies on the interplay between vascular dysfunction, leading to endothelial activation and the accumulation of inflammatory cells, particularly macrophages, within the vessel wall. Here, we review the mechanisms through which elevated ADMA contributes to endothelial dysfunction, activation and reactive oxygen species (ROS) production; how ADMA may affect vascular smooth muscle phenotype; and finally whether ADMA plays a regulatory role in the inflammatory processes occurring within the vessel wall.

The Bovine Metabolome

From an animal health perspective, relatively little is known about the typical or healthy ranges of concentrations for many metabolites in bovine biofluids and tissues. Here, we describe the results of a comprehensive, quantitative metabolomic characterization of six bovine biofluids and tissues, including serum, ruminal fluid, liver, Longissimus thoracis (LT) muscle, semimembranosus (SM) muscle, and testis tissues. Using nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography–tandem mass spectrometry (LC–MS/MS), and inductively coupled plasma–mass spectrometry (ICP–MS), we were able to identify and quantify more than 145 metabolites in each of these biofluids/tissues. Combining these results with previous work done by our team on other bovine biofluids, as well as previously published literature values for other bovine tissues and biofluids, we were able to generate quantitative reference concentration data for 2100 unique metabolites across five different bovine biofluids and seven different tissues. These experimental data were combined with computer-aided, genome-scale metabolite inference techniques to add another 48,628 unique metabolites that are biochemically expected to be in bovine tissues or biofluids. Altogether, 51,801 unique metabolites were identified in this study. Detailed information on these 51,801 unique metabolites has been placed in a publicly available database called the Bovine Metabolome Database.

Concentrations of the Selected Biomarkers of Endothelial Dysfunction in Response to Antiepileptic Drugs: A Literature Review

Epilepsy is a disease arising from morphological and metabolic changes in the brain. Approximately 60% of patients with seizures can be controlled with 1 antiepileptic drug (AED), while in others, polytherapy is required. The AED treatment affects a number of biochemical processes in the body, including increasing the risk of cardiovascular diseases (CVDs). It is indicated that the duration of AED therapy with some AEDs significantly accelerates the process of atherosclerosis. Most of AEDs increase levels of homocysteine (HCys) as well as may affect concentrations of new, nonclassical risk factors for atherosclerosis, that is, asymmetric dimethylarginine (ADMA) and homoarginine (hArg). Because of the role of these parameters in the pathogenesis of CVD, knowledge of HCys, ADMA, and hArg concentrations in patients with epilepsia treated with AED, both pediatric and adult, appears to be of significant importance.

Association of serum asymmetric dimethyl-arginine and troponin I levels as a risk of myocardial infarction in thalassemia

BACKGROUND

The current study evaluated level of serum asymmetric dimethylarginine (ADMA) and its association to cardiac biomarkers in thalassemia patients for early diagnosis of abnormality in myocardial infarction.

SUBJECTS AND METHODS

This study was conducted on 80 subjects divided into four groups each with 20 subjects. Group I: Control: healthy subjects. Group II: Myocardial infarction: Patients with elevated serum troponin T. Group III: thalassemia patients. Group IV: thalassemia with myocardial infarction patients: Included 20 thalassemia patients with Myocardial infarction. Serum samples were subjected for assay of creatine kinase (CK:MB), Lactate dehydrogenase, troponin I, ADMA, Serum MDA level was determined.

RESULTS

Data obtained showed that serum CKMB, LDH1, AST, Troponin T and ADMA levels were significant elevated in MI with or without Thalassemia compared with control groups. Serum MDA was statistically significantly elevated in MI with or without Thalassemia compared with control groups. The serum level of troponin T showed an area under curve (AUC) of 0.92, (sensitivity 91.0 % and specificity, 88%). Also, the ADMA supported the diagnostic profile, showing an AUC of 0.85 with (sensitivity, 92.0%; specificity, 91,9%).

CONCLUSION

Serum ADMA is sensitive marker for incidence of MI in thalassemia patients.

Asymmetric dimethylarginine (ADMA) and cardiovascular disease: insights from prospective clinical trials

Evidence has accumulated that asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase. ADMA inhibits vascular NO production at concentrations found in pathophysiological conditions; it also causes local vasoconstriction when infused intra-arterially. ADMA is increased in the plasma of humans with hypercholesterolemia, atherosclerosis, hypertension, chronic renal failure, chronic heart failure, and other clinical conditions. Increased ADMA levels are associated with reduced NO synthesis as assessed by impaired endothelium-dependent vasodilation or reduced NO metabolite levels. In several prospective and cross-sectional studies, ADMA has evolved as a marker of cardiovascular risk. Moreover, prospective clinical studies have suggested that it may play a role as a novel cardiovascular risk factor. Zoccali and coworkers were the first to show that elevated ADMA is associated with a three-fold increased risk of future severe cardiovascular events and mortality in patients undergoing hemodialysis. Valkonen and coworkers demonstrated in a nested case-control study that elevated ADMA was associated with a four-fold increased risk for acute coronary events in clinically healthy, nonsmoking men. In patients with stable angina pectoris, preinterventional ADMA indicates the risk of developing restenosis or severe clinical events after coronary intervention. Furthermore, in humans with no underlying cardiovascular disease who are undergoing intensive care unit treatment, ADMA is a marker of the mortality risk. A number of additional prospective clinical trials are currently under way in diverse patient populations, among them individuals with congestive heart failure, cardiac transplantation patients, and patients with pulmonary hypertension.

In summary, an increasing number of prospective clinical trials have shown that the association between elevated ADMA levels and major cardiovascular events and total mortality is robust and extends to diverse patient populations. However, we need to define more clearly in the future who will profit from ADMA determination, in order to use this novel risk marker as a more specific diagnostic tool.

Endothelial cell metabolism: A novel player in atherosclerosis? Basic principles and therapeutic opportunities

Atherosclerosis is a leading cause of morbidity and mortality in Western society. Despite improved insight into disease pathogenesis and therapeutic options, additional treatment strategies are required. Emerging evidence highlights the relevance of endothelial cell (EC) metabolism for angiogenesis, and indicates that EC metabolism is perturbed when ECs become dysfunctional to promote atherogenesis. In this review, we overview the latest insights on EC metabolism and discuss current knowledge on how atherosclerosis deregulates EC metabolism, and how maladaptation of deregulated EC metabolism can contribute to atherosclerosis progression. We will also highlight possible therapeutic avenues, based on targeting EC metabolism.

Effects of L-thyroxine treatment on early markers of atherosclerotic disease in children with subclinical hypothyroidism

OBJECTIVE

To investigate the effect of levothyroxine (L-T4) treatment on early markers of atherosclerotic disease in children with mild idiopathic subclinical hypothyroidism (SH).

DESIGN

Two-year, open, case-control prospective study.

METHODS

A total of 39 children, aged 9.18±3.56 years, with SH and 39 healthy controls were enrolled in the study. Waist-to-height ratio (WHtR), blood pressure, triglycerides, total cholesterol (total-C), HDL-C, LDL-C, non-HDL-C, triglycerides/HDL-C, atherogenic index (AI), homocysteine (Hcy), asymmetric dimethylarginine (ADMA), flow-mediated dilation (FMD) and intima-media thickness (IMT) were evaluated at baseline and after 2 years of L-T4 treatment in SH children and after 2 years of follow-up in controls.

RESULTS

At study entry WHtR was higher in SH subjects compared with controls (0.56±0.08 vs 0.49±0.07, P=0.04) and significantly decreased after 2 years of treatment (0.50±0.06, P<0.0001). Mean HDL-C levels (50.47±11.43 vs 61.06±13.83mg/dL, P=0.002) were lower, while triglycerides/HDL-C (1.63±1.07 vs 1.19±0.69, P=0.05), AI (3.32±0.90 vs 2.78±0.68, P=0.005), and Hcy (9.35±2.61 vs 7.71±1.94μmol/L, P=0.01) were higher in SH subjects compared with controls and improved after 2 years of treatment (HDL-C 56.26±13.76mg/dL, P<0.0001; triglycerides/HDL-C 1.23±0.78, P=0.006; AI 2.82±0.68, P<0.0001; and Hcy 8.25±2.09μmol/L, P=0.06). ADMA concentrations at baseline were higher in SH subjects compared with controls (0.77±0.21 vs 0.60±0.16μmol/L, P=0.001) and decreased after therapy (0.58±0.13μmol/L, P<0.0001). FMD, IMT and other metabolic parameters were not different among SH subjects and controls at baseline and after 2 years.

CONCLUSIONS

Children with SH may have subtle pro-atherogenic abnormalities. Although L-T4 treatment exerts some beneficial effects, the long-term impact of therapy on metabolic outcomes in SH children still remains unclear.

Association between endothelial and platelet function markers and adiponectin in renal transplanted recipients on cyclosporine and tacrolimus immunosuppression based therapy

AIM

Coagulation abnormalities, endothelial dysfunction and arteriosclerosis play a key role in cardiovascular disease state observed in transplanted patients. Plasma adiponectin levels are lower following kidney transplantation. However, there is still a debate about this topic in the literature. This study evaluated, adiponectin levels associated with markers of endothelial dysfunction and platelet function in renal transplant patients.

METHODS

Sixty-six renal transplant patients were studied. Patients were grouped according to immunosuppression regimen. Group 1 (n = 36) were treated with cyclosporine A based regimes and group 2 (n = 30) were treated with tacrolimus based regimes. Plasma adiponectin, asymmetric dimethyl arginine (ADMA), sP-selectin levels and platelet aggregation tests were studied and were compared with those in control group (n = 15, group 3).

RESULTS

Adiponectin, sP-selectin and ADMA levels were higher in group 1 and statistically significant differences were observed compared with those of group 2 and group 3, respectively (P < 0.001, P < 0.05, P < 0.05). Platelet aggregation values induced by agonists were lower in group 1 than group 2 and group 3, but the difference did not reach statistical significance (P > 0.05).

CONCLUSION

Adiponectin levels are elevated in line with ADMA and sP-selectin levels. Since CsA induces higher adiponectin levels, platelet activation and endothelial dysfunction. These changes may be responsible for the increased risk of post-transplant cardiovascular events in renal transplant patients.

Plasmodium Infection Is Associated with Impaired Hepatic Dimethylarginine Dimethylaminohydrolase Activity and Disruption of Nitric Oxide Synthase Inhibitor/Substrate Homeostasis

Inhibition of nitric oxide (NO) signaling may contribute to pathological activation of the vascular endothelium during severe malaria infection. Dimethylarginine dimethylaminohydrolase (DDAH) regulates endothelial NO synthesis by maintaining homeostasis between asymmetric dimethylarginine (ADMA), an endogenous NO synthase (NOS) inhibitor, and arginine, the NOS substrate. We carried out a community-based case-control study of Gambian children to determine whether ADMA and arginine homeostasis is disrupted during severe or uncomplicated malaria infections. Circulating plasma levels of ADMA and arginine were determined at initial presentation and 28 days later. Plasma ADMA/arginine ratios were elevated in children with acute severe malaria compared to 28-day follow-up values and compared to children with uncomplicated malaria or healthy children (p<0.0001 for each comparison). To test the hypothesis that DDAH1 is inactivated during Plasmodium infection, we examined DDAH1 in a mouse model of severe malaria. Plasmodium berghei ANKA infection inactivated hepatic DDAH1 via a post-transcriptional mechanism as evidenced by stable mRNA transcript number, decreased DDAH1 protein concentration, decreased enzyme activity, elevated tissue ADMA, elevated ADMA/arginine ratio in plasma, and decreased whole blood nitrite concentration. Loss of hepatic DDAH1 activity and disruption of ADMA/arginine homeostasis may contribute to severe malaria pathogenesis by inhibiting NO synthesis.

During a malaria infection, the vascular endothelium becomes more adhesive, permeable, and prone to trigger blood clotting. These changes help the parasite adhere to blood vessels, but endanger the host by obstructing blood flow through small vessels. Endothelial nitric oxide (NO) would normally counteract these pathological changes, but NO signalling is diminished malaria. NO synthesis is inhibited by asymmetric dimethylarginine (ADMA), a methylated derivative of arginine that is released during normal protein turnover. We found the ratio of ADMA to arginine to be elevated in Gambian children with severe malaria, a metabolic disturbance known to inhibit NO synthesis. ADMA was associated with markers of endothelial activation and impaired tissue perfusion. In parallel experiments using mice, the enzyme responsible for metabolizing ADMA, dimethylarginine dimethylaminohydrolase (DDAH), was inactivated after infection with a rodent malaria. Based on these studies, we propose that decreased metabolism of ADMA by DDAH might contribute to the elevated ADMA/arginine ratio observed during an acute episode of malaria. Strategies to preserve or increase DDAH activity might improve NO synthesis and help to prevent the vascular manifestations of severe malaria.

Left ventricular diastolic dysfunction and plasma asymmetric dimethylarginine concentration in persons with essential hypertension

INTRODUCTION

The study aimed to evaluate the relationship between plasma asymmetric dimethylarginine (ADMA) concentration and development of left ventricular diastolic dysfunction (LVDD) in patients with essential hypertension (EH). Moreover, an attempt was made to define independent risk factors of LVDD in patients with EH.

MATERIAL AND METHODS

A group of 106 individuals with EH was obtained (mean age: 47.18 ±11.76 years). Two groups of patients were distinguished: group I - individuals with EH with LVDD (n = 57); group II - persons with EH without LVDD (n = 49). Echocardiographic examination was conducted by the transthoracic technique. High-performance liquid chromatography was used to measure dimethylarginine concentrations.

RESULTS

In the group suffering from EH with LVDD, mean ADMA concentration was significantly higher and the ratio of arginine to ADMA was significantly lower than in patients with EH without LVDD. No significant differences were detected between mean concentrations of plasma symmetric dimethylarginine concentration (SDMA) and arginine or in arginine/SDMA ratios in the studied groups. Independent factors of LVDD risk in the study group included higher plasma ADMA concentration, higher serum low-density lipoprotein (LDL) concentration, higher values of body mass index (BMI), higher values of left ventricular mass index (LVMI) and higher values of mean blood pressure (mBP) (ORADMA = 1.731; ORLDL = 1.188; ORBMI = 1.056; ORLVMI = 1.062; ORmBP = 1.014; p < 0.05).

CONCLUSIONS

The results of this study showed that ADMA concentration may be of prognostic value in relation to manifestation of LVDD in patients with EH.

Asymmetric dimethylarginine and cardiovascular risk: systematic review and meta-analysis of 22 prospective studies

BACKGROUND

Asymmetric dimethylarginine (ADMA) inhibits the production of nitric oxide, a key regulator of the vascular tone, and may be important in the development of cardiovascular disease (CVD). Our aim was to reliably quantify the association of ADMA and its isomer symmetric dimethylarginine (SDMA) with the risk of CVD outcomes in long-term cohort studies.

METHODS AND RESULTS

Data were collated from 22 prospective studies involving a total of 19 842 participants, which have recorded 2339 CVD, 997 coronary heart disease, and 467 stroke outcomes during a mean follow-up of 7.1 years. In a comparison of individuals in the top with those in the bottom third of baseline ADMA values, the combined risk ratios were 1.42 (95% confidence interval: 1.29 to 1.56) for CVD, 1.39 for coronary heart disease (1.19 to 1.62), and 1.60 for stroke (1.33 to 1.91). Broadly similar results were observed according to participants' baseline disease status (risk ratios for CVD: 1.35 [1.18 to 1.54] in general populations; 1.47 [1.16 to 1.87] in individuals with pre-existing CVD; and 1.52 [1.26 to 1.84] in individuals with pre-existing kidney disease) and by different study characteristics, including geographical location, sample type, assay method, number of incident outcomes, and level of statistical adjustment (all P values>0.05). In contrast, in 8 prospective studies involving 9070 participants and 848 outcomes, the corresponding estimate for SDMA concentration was 1.32 (0.92 to 1.90) for CVD.

CONCLUSIONS

Available prospective studies suggest associations between circulating ADMA concentration and CVD outcomes under a broad range of circumstances. Further research is needed to better clarify these associations, particularly in large general population studies.

Redox Control of Protein Arginine Methyltransferase 1 (PRMT1) Activity

Elevated levels of asymmetric dimethylarginine (ADMA) correlate with risk factors for cardiovascular disease. ADMA is generated by the catabolism of proteins methylated on arginine residues by protein arginine methyltransferases (PRMTs) and is degraded by dimethylarginine dimethylaminohydrolase. Reports have shown that dimethylarginine dimethylaminohydrolase activity is down-regulated and PRMT1 protein expression is up-regulated under oxidative stress conditions, leading many to conclude that ADMA accumulation occurs via increased synthesis by PRMTs and decreased degradation. However, we now report that the methyltransferase activity of PRMT1, the major PRMT isoform in humans, is impaired under oxidative conditions. Oxidized PRMT1 displays decreased activity, which can be rescued by reduction. This oxidation event involves one or more cysteine residues that become oxidized to sulfenic acid (-SOH). We demonstrate a hydrogen peroxide concentration-dependent inhibition of PRMT1 activity that is readily reversed under physiological H2O2 concentrations. Our results challenge the unilateral view that increased PRMT1 expression necessarily results in increased ADMA synthesis and demonstrate that enzymatic activity can be regulated in a redox-sensitive manner.

Endothelial cell metabolism in normal and diseased vasculature

Higher organisms rely on a closed cardiovascular circulatory system with blood vessels supplying vital nutrients and oxygen to distant tissues. Not surprisingly, vascular pathologies rank among the most life-threatening diseases. At the crux of most of these vascular pathologies are (dysfunctional) endothelial cells (ECs), the cells lining the blood vessel lumen. ECs display the remarkable capability to switch rapidly from a quiescent state to a highly migratory and proliferative state during vessel sprouting. This angiogenic switch has long been considered to be dictated by angiogenic growth factors (eg, vascular endothelial growth factor) and other signals (eg, Notch) alone, but recent findings show that it is also driven by a metabolic switch in ECs. Furthermore, these changes in metabolism may even override signals inducing vessel sprouting. Here, we review how EC metabolism differs between the normal and dysfunctional/diseased vasculature and how it relates to or affects the metabolism of other cell types contributing to the pathology. We focus on the biology of ECs in tumor blood vessel and diabetic ECs in atherosclerosis as examples of the role of endothelial metabolism in key pathological processes. Finally, current as well as unexplored EC metabolism-centric therapeutic avenues are discussed.

Asymmetric dimethylarginine is associated with high-sensitivity C-reactive protein and early carotid atherosclerosis in women with previous gestational diabetes mellitus

Asymmetric dimethylarginine (ADMA) is increased in subjects with previous gestational diabetes mellitus (GDM). The aim of this study was to investigate the relationship between serum ADMA levels and early carotid atherosclerosis in women with history of GDM. A total of 42 normoglycemic women with previous GDM and 42 age-matched healthy controls were enrolled. Serum levels of ADMA, lipids, insulin, fasting and 2-h glucose following 75-g oral glucose tolerance test, and high sensitivity C-reactive protein (hsCRP) were measured. Carotid atherosclerosis was evaluated by ultrasonographically determined intima-media thickness (IMT). Serum ADMA and hsCRP were higher in women with previous GDM compared to the healthy controls (0.72 ± 0.16 vs. 0.41 ± 0.15 μmol/L, p < 0.001; 1.81 ± 0.32 vs. 1.05 ± 0.26 mg/L, p < 0.001; respectively). Carotid IMT was also increased in the previous GDM group (0.77 ± 0.14 vs. 0.52 ± 0.13 mm, p < 0.001). In women with previous GDM, ADMA was positively correlated with hsCRP (r = 41, p < 0.001) and carotid IMT (r = 0.38, p < 0.001). Multiple linear regression analysis revealed that ADMA was a significant predictor for elevated carotid IMT in subjects with previous GDM after adjusting for traditional risk factors (β = 0.26, p = 0.017). Our data demonstrated that serum ADMA was associated with hsCRP and carotid IMT in normoglycemic women with previous GDM.

Soluble CD14 is associated with markers of vascular dysfunction in bariatric surgery patients

BACKGROUND

Chronic endotoxemia has been proposed to contribute to obesity-related complications. We aimed to investigate the potential impact of lipopolysaccharide (LPS) and subsequent monocyte activation measured as soluble CD14 (sCD14) on markers of vascular dysfunction in obese subjects undergoing bariatric surgery.

METHODS

This was a prospective study of 49 obese patients and 17 controls, assessed by plasma levels of LPS, sCD14, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA).

RESULTS

Levels of ADMA were increased in obese subjects compared to controls, but were not significantly reduced after bariatric surgery. In obese subjects at baseline, there was a significant trend to increasing levels of ADMA and SDMA through tertiles of sCD14 and decreasing levels of both markers through tertiles of LPS. In models adjusting for age and gender, sCD14 but not LPS remained independently associated with ADMA and SDMA. For every 10% age- and gender-adjusted increase in sCD14, ADMA increased 0.031 μM (5.6%), whereas SDMA increased 0.039 μM (10.8%).

CONCLUSIONS

Our results suggest that monocyte activation as measured by sCD14 is associated with obesity-related vascular dysfunction, whereas potential upstream triggers including microbial products should be investigated in future studies.

Asymmetric dimethylarginine is associated with carotid atherosclerosis in patients with essential hypertension

This study was to assess the relationship between asymmetric dimethylarginine (ADMA) and carotid atherosclerosis in patients with essential hypertension. A total of 182 individuals with never-treated essential hypertension and 182 age-matched healthy controls were studied. Plasma ADMA levels, mean intima-media thickness (IMT) and plaque score were significantly greater in hypertensive patients than normotensive controls. ADMA was positively correlated with mean IMT. On multiple logistic regression analysis, ADMA was a crucial independent predictor of carotid plaque formation (plaque score ≥1.1). Our results suggest that increased levels of ADMA are associated with the development of carotid atherosclerosis in hypertensive patients.

Risk of cardiovascular diseases in diabetes mellitus and serum concentration of asymmetrical dimethylarginine

Introduction. Asymmetric dimethylarginine (ADMA) is a nonselective nitric oxide (NO) synthase inhibitor associated with cardiovascular and metabolic disorders. ADMA plays an important role in the regulation of vascular tone by acting as an endogenous inhibitor of NO synthesis. Objectives. This study aimed to investigate ADMA with respect to diabetes and its clinical relevance as an independent predictor of CAD (Coronary Artery Disease). Methodology. The present case control study includes two hundred and forty patients selected randomly. Serum ADMA was analyzed by using enzyme immunoassay for the quantitative determination of endogenous ADMA, and serum nitric oxide was estimated by the method of Cortes. Results. Elevated NO level levels was a strong predictor and significantly (t: 9.86, P < 0.001) associated with occurrence of CAD. Increased ADMA level was found to be another strong predictor and associated significantly (t: 8.02, P < 0.001) with CAD. On intra group analysis, the relationship between ADMA and NO in diseased group, is significant negative correlation (r = -0.743). P (0.001) was found between ADMA and NO. Conclusion. ADMA level was found to be one of the strong predictors for CAD. ADMA is an emerging independent risk marker for future CVD (cardiovascular disease) events.

Asymmetric dimethylarginine regulates the lipopolysaccharide-induced nitric oxide production in macrophages by suppressing the activation of NF-kappaB and iNOS expression

Two major effector systems are frequently implicated in the immune and endothelial cell alternations associated with inflammation. They include the enhanced production of reactive oxygen species and diminished bioavailability of nitric oxide (NO). Importantly, these processes can be regulated by endogenously produced methylarginines, inhibitors for NO derived from macrophages and endothelial cells. Therefore, the aim of this study was to show the potential pharmacological intervention of methylarginines (N(G)-methyl-L-arginine, L-NMMA; N(G), N(G)'-dimethyl-L-arginine-symmetric dimethylarginine, SDMA; and N(G), N(G)-dimethyl-L-arginine-asymmetric dimethylarginine, ADMA) in activation of murine peritoneal (RAW 264.7) and alveolar (MHS) macrophages with lipopolysaccharide from Gram-negative bacteria (LPS). The data presented in this study clearly declare that L-NMMA (1-50μM) and ADMA (10-50 μM) significantly inhibited the LPS-induced NO production from macrophages in a concentration-dependent manner. It was demonstrated, for the first time, that the ADMA- and L-NMMA-induced down regulation of NO production was accompanied by reduced expression of mRNA and protein for inducible NO synthase as well as decreased activation of nuclear factor-κB. Importantly, we found a negative correlation between the ADMA-dependent reduction of NO production and ADMA-increased superoxide formation, which indicates that ADMA can negatively affect the balance in LPS-induced macrophage-derived production of reactive mediators. The only effect of SDMA was observed for LPS-triggered superoxide production, which was significantly decreased in its highest concentration (50 μM). In summary, L-NMMA and ADMA can mediate their effects on macrophage activation via regulation of intracellular signaling pathways, which can affect critical functions in activated macrophages.

Asymmetric dimethylarginine and carotid atherosclerosis in Type 2 diabetes mellitus

BACKGROUND

Circulating asymmetric dimethylarginine (ADMA) concentration is elevated in patients with Type 2 diabetes mellitus (T2DM).

AIM

To assess the relationship between plasma ADMA concentration and carotid atherosclerosis in patients with T2DM.

SUBJECTS AND METHODS

A total of 72 newly diagnosed and untreated T2DM individuals and 72 healthy controls were studied. Carotid atherosclerosis was determined by ultrasonographically evaluated intima- media thickness (IMT) and plaque score. Plasma concentration of ADMA was measured by high-performance liquid chromatography.

RESULTS

Plasma ADMA, mean IMT, and plaque score were higher in diabetic patients compared with controls. Univariate and multivariate analyses demonstrated an independent association between ADMA and mean IMT in diabetic patients. On a multiple logistic regression analysis, ADMA was the sole predictor of carotid plaque formation (plaque score ≥1.1) (odds ratio 2.43, 95% confidence interval 1.19 to 4.94, p<0.05).

CONCLUSION

Our results suggest that increased levels of ADMA might be involved in the development of carotid atherosclerosis in T2DM.

The antihypertensive effect of arginine

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at increased risk of stroke, heart disease and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Reducing dietary salt is effective in lowering blood pressure in salt-sensitive individuals. Insulin resistance and altered glucose metabolism are common features of hypertension in humans and animal models, with or without salt sensitivity. Altered glucose metabolism leads to increased formation of advanced glycation end products. Insulin resistance is also linked to oxidative stress, and alterations in the nitric oxide pathway and renin angiotensin system. A diet rich in protein containing the semiessential amino acid, arginine, and arginine treatment, lowers blood pressure in humans and in animal models. This may be due to the ability of arginine to improve insulin resistance, decrease advanced glycation end products formation, increase nitric oxide, and decrease levels of angiotensin II and oxidative stress, with improved endothelial cell function and decreased peripheral vascular resistance. The Dietary Approaches to Stop Hypertension (DASH) study demonstrated that the DASH diet, rich in vegetables, fruits and low-fat dairy products; low in fat; and including whole grains, poultry, fish and nuts, lowered blood pressures even more than a typical North American diet with similar reduced sodium content. The DASH diet is rich in protein; the blood pressure-lowering effect of the DASH diet may be due to its higher arginine-containing protein, higher antioxidants and low salt content.

Endogenous nitric oxide synthase inhibitors in the biology of disease: markers, mediators, and regulators?

The asymmetric methylarginines inhibit nitric oxide synthesis in vivo by competing with L-arginine at the active site of nitric oxide synthase. High circulating levels of asymmetric dimethylarginine predict adverse outcomes, specifically vascular events but there is now increasing experimental and epidemiological evidence that these molecules, and the enzymes that regulate this pathway, play a mechanistic role in cardiovascular diseases. Recent data have provided insight into the impact of altered levels of these amino acids in both humans and rodents, however these reports also suggest a simplistic approach based on measuring, and modulating circulating asymmetric dimethylarginine alone is inadequate. This review outlines the basic biochemistry and physiology of endogenous methylarginines, examines both the experimental and observational evidence for a role in disease pathogenesis, and examines the potential for therapeutic regulation of these molecules.

Pilot study of the association of the DDAH2 -449G polymorphism with asymmetric dimethylarginine and hemodynamic shock in pediatric sepsis

Background

Genetic variability in the regulation of the nitric oxide (NO) pathway may influence hemodynamic changes in pediatric sepsis. We sought to determine whether functional polymorphisms in DDAH2, which metabolizes the NO synthase inhibitor asymmetric dimethylarginine (ADMA), are associated with susceptibility to sepsis, plasma ADMA, distinct hemodynamic states, and vasopressor requirements in pediatric septic shock.

Methodology/Principal Findings

In a prospective study, blood and buccal swabs were obtained from 82 patients ≤18 years (29 with severe sepsis/septic shock plus 27 febrile and 26 healthy controls). Plasma ADMA was measured using tandem mass spectrometry. DDAH2 gene was partially sequenced to determine the −871 6g/7g insertion/deletion and −449G/C single nucleotide polymorphisms. Shock type (“warm” versus “cold”) was characterized by clinical assessment. The −871 7g allele was more common in septic (17%) then febrile (4%) and healthy (8%) patients, though this was not significant after controlling for sex and race (p = 0.96). ADMA did not differ between −871 6g/7g genotypes. While genotype frequencies also did not vary between groups for the −449G/C SNP (p = 0.75), septic patients with at least one −449G allele had lower ADMA (median, IQR 0.36, 0.30–0.41 µmol/L) than patients with the −449CC genotype (0.55, 0.49–0.64 µmol/L, p = 0.008) and exhibited a higher incidence of “cold” shock (45% versus 0%, p = 0.01). However, after controlling for race, the association with shock type became non-significant (p = 0.32). Neither polymorphism was associated with inotrope score or vasoactive infusion duration.

Conclusions/Significance

The −449G polymorphism in the DDAH2 gene was associated with both low plasma ADMA and an increased likelihood of presenting with “cold” shock in pediatric sepsis, but not with vasopressor requirement. Race, however, was an important confounder. These results support and justify the need for larger studies in racially homogenous populations to further examine whether genotypic differences in NO metabolism contribute to phenotypic variability in sepsis pathophysiology.

Vascular incompetence in dialysis patients--protein-bound uremic toxins and endothelial dysfunction

Patients with chronic kidney disease (CKD) have a much higher risk of cardiovascular diseases than the general population. Endothelial dysfunction, which participates in accelerated atherosclerosis, is a hallmark of CKD. Patients with CKD display impaired endothelium-dependent vasodilatation, elevated soluble biomarkers of endothelial dysfunction, and increased oxidative stress. They also present an imbalance between circulating endothelial populations reflecting endothelial injury (endothelial microparticles and circulating endothelial cells) and repair (endothelial progenitor cells). Endothelial damage induced by a uremic environment suggests an involvement of uremia-specific factors. Several uremic toxins, mostly protein-bound, have been shown to have specific endothelial toxicity: ADMA, homocysteine, AGEs, and more recently, p-cresyl sulfate and indoxyl sulfate. These toxins, all poorly removed by hemodialysis therapies, share mechanisms of endothelial toxicity: they promote pro-oxidant and pro-inflammatory response and inhibit endothelial repair. This article (i) reviews the evidence for endothelial dysfunction in CKD, (ii) specifies the involvement of protein-bound uremic toxins in this dysfunction, and (iii) discusses therapeutic strategies for lowering uremic toxin concentrations or for countering the effects of uremic toxins on the endothelium.

Elevated concentration of asymmetric dimethylarginine (ADMA) in individuals with metabolic syndrome

The metabolic syndrome (MS) is a cluster of pathophysiological alterations that includes the presence of hypertension, insulin resistance, dyslipidemia, and abdominal obesity. MS is associated with increased risk of developing diabetes and cardiovascular diseases. Endothelial dysfunction with impaired nitric oxide (NO) bioavailability has been implicated in insulin resistance and hypertension. NO is synthesized by nitric oxide synthase (NOS) using l-arginine as substrate. Asymmetric dimethyl arginine (ADMA) is a major and potent endogenous NOS inhibitor, associated with cardiovascular and renal diseases. We tested the hypothesis that plasmatic ADMA levels are increased in patients with MS. We studied 85 adult individuals from Talca, Chile, separated in two groups, 48 individuals with MS (according to modified ATP III criteria), and 37 individuals without MS as controls. ADMA levels were significantly increased in the MS group (mean±standard deviation 0.71±0.38 vs. 0.48±0.28μmol/L, p=0.0009). Furthermore, the levels of ADMA were modestly but significantly correlated with waist circumference (p=0.01) but not with the other components of MS (blood pressure, glycemia, triglycerides and high density lipoprotein cholesterol HDL-c). These results suggest a possible link between increased ADMA levels and the MS.

Increased asymmetric dimethylarginine serum levels are associated with acute rejection in kidney transplant recipients

Asymmetric dimethylarginine (ADMA) has been identified as a marker of endothelial dysfunction and an independent risk factor for cardiovascular events in uremic subjects. This study evaluated ADMA plasma levels in kidney transplant recipients. ADMA levels were serially measured during the first year posttransplantation in 41 recipients treated with cyclosporine regimen (CY), sirolimus (SIR), or low-dose cyclosporine plus everolimus (E). Homocysteine, C reactive protein (CRP), nitric oxide (NO), and standard routine laboratory analyses were determined serially. ADMA significantly increased at 6 months posttransplantation, but was significantly lower among patients on SIR or E. NO was only slightly reduced in patients with increased ADMA levels. Interestingly, ADMA was significantly increased during the first 4 days posttransplantation in patients who experienced acute rejection during the first 6 months after transplantation. The same group of patients demonstrated higher levels of CRP and systolic blood pressure before transplantation. Our results demonstrated that ADMA was increased in patients on CY at 6 months. When increased soon after transplantation ADMA may be associated with episodes of acute rejection in kidney transplant recipients. The presence of elevated systolic blood pressure, as well as CRP and ADMA levels, suggested a role for endothelial dysfunction in the development of acute rejection episodes among deceased donor kidney transplant recipients.

A study of endothelial function and circulating asymmetric dimethylarginine levels in people with Type 1 diabetes without macrovascular disease or microalbuminuria

Background

Asymmetric dimethylarginine (ADMA) is a competitive inhibitor of endothelial nitric oxide synthase (eNOS) that is associated with endothelial dysfunction, and is a risk marker for cardiovascular disease, a significant problem in Type 1 diabetes. The aim of the present study was to measure circulating ADMA, and define its association with endothelial dysfunction and endothelial markers in people with Type 1 diabetes with low likelihood of macrovascular disease.

Methods

Sixty-one young people with Type 1 diabetes without macrovascular disease or nephropathy and 62 healthy volunteers underwent brachial artery flow-mediated dilatation (FMD) and assay of plasma ADMA and adhesion molecules.

Results

Age, gender, BMI, lipid profile and renal function were similar in the two groups. People with Type 1 diabetes had impaired FMD compared to healthy controls (5.0 ± 0.4 vs 8.9 ± 0.4%; p < 0.001). Plasma ADMA levels were significantly lower in the people with diabetes compared to healthy controls (0.52 ± 0.12 vs 0.66 ± 0.20 μmol/l, p < 0.001). Plasma ICAM-1, E-selectin and PAI-1 levels were significantly higher in people with diabetes compared to healthy controls (median 201 (IQR 172–226) vs 180 (156–216) μg/l, p = 0.027; 44.2 (32.6–60.9) vs. 33.1 (22.4–51.0) μg/l; p = 0.003 and 70.8 (33.3–85.5) vs 46.3 (23.9–76.8) μg/l, p = 0.035). Plasma ADMA and VCAM-1 levels were positively correlated (r = 0.37, p = 0.003) in people with diabetes. There was no correlation between the plasma ADMA and FMD.

Conclusion

ADMA levels are not associated with endothelial dysfunction in young adults with Type 1 diabetes without microalbuminuria or known macrovascular disease. This suggests that the impaired endothelial function in these individuals is not a result of eNOS inhibition by ADMA.

The complexity of neurobiological processes in acute ischemic stroke

There is an urgent need for improved diagnostics and therapeutics for acute ischemic stroke. This is the focus of numerous research projects involving in vitro studies, animal models and clinical trials, all of which are based on current knowledge of disease mechanisms underlying acute focal cerebral ischemia. Insight in the chain of events occurring during acute ischemic injury is essential for understanding current and future diagnostic and therapeutic approaches. In this review, we summarize the actual knowledge on the pathophysiology of acute ischemic stroke. We focus on the ischemic cascade, which is a complex series of neurochemical processes that are unleashed by transient or permanent focal cerebral ischemia and involves cellular bioenergetic failure, excitotoxicity, oxidative stress, blood-brain barrier dysfunction, microvascular injury, hemostatic activation, post-ischemic inflammation and finally cell death of neurons, glial and endothelial cells.

Biomarkers of oxidative stress and endothelial dysfunction in glucose intolerance and diabetes mellitus

OBJECTIVES

To evaluate biomarkers of endothelial dysfunction and oxidative stress in glucose intolerance (GI) compared to overt diabetes (DM2).

DESIGN AND METHODS

140 volunteers including 96 with DM2, 32 with GI and 12 controls (C) were studied. (*)NO metabolites, (*)NO synthase inhibitors, thiols and N-acetyl-beta-glucosaminidase (NAGase) activity were analyzed by chemiluminescence, capillary electrophoresis, ELISA and colorimetric assay, respectively.

RESULTS

(*)NO metabolites were higher in GI (NOx: p=0.03; S-nitrosothiols: p=0.001) and DM2 (p=0.006; p=0.0006) groups in relation to group C, while nitrotyrosine was higher only in the DM2 group in comparison to the other groups. NAGase activity was elevated in GI (p=0.003) and DM2 (p=0.0004) groups in relation to group C, as well as, ADMA (p=0.01; p=0.003) and GSSG (p=0.01; p=0.002).

CONCLUSIONS

(*)NO metabolites, (*)NO synthase inhibitors, thiols and NAGase are biomarkers suitable to indicate endothelial dysfunction and oxidative stress in the early stages of impaired response to insulin.

Elevated asymmetric dimethylarginine alters lung function and induces collagen deposition in mice

Increasing evidence suggests that lung mechanics and structure are maintained in part by an intimate balance between the L-arginine-metabolizing enzymes nitric oxide synthase (NOS) and arginase. Asymmetric dimethylarginine (ADMA) is a competitive endogenous inhibitor of NOS. The role of ADMA in the regulation of NOS and arginase in the airways has not yet been explored. Our objective was to investigate the role of ADMA in lung physiology. A murine model of continuous subcutaneous ADMA infusion via osmotic minipump was used for assessment of elevated ADMA in vivo, and primary lung fibroblasts were used for in vitro assessments. Two weeks after minipump placement, animals were anesthetized and mechanically ventilated, and lung mechanical responses were evaluated. Lungs were assessed histologically and biochemically for collagen content, arginase activity, and arginase protein levels. Lung lavage fluid was assessed for cellularity, nitrite, urea, and cytokine concentrations. ADMA infusion resulted in significantly enhanced lung resistance and decreased dynamic compliance in response to methacholine. These physiologic changes were associated with significantly increased lung collagen content in the absence of inflammation. Significant decreases in lung fluid nitrite were accompanied by elevated lung fluid urea and arginase activity in lung homogenates. These changes were reversed in mice 4 weeks after completion of ADMA administration. In addition, treatment of primary mouse lung fibroblasts with ADMA stimulated arginase activity and collagen formation in vitro. These data support the idea that ADMA may play a role in airway diseases, including asthma and pulmonary fibrosis, through NOS inhibition and enhancement of arginase activity.

Endothelial dysfunction in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease, even in the presence of intensive glycemic control. Substantial clinical and experimental evidence suggest that both diabetes and insulin resistance cause a combination of endothelial dysfunctions, which may diminish the anti-atherogenic role of the vascular endothelium. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Microalbuminuria is now considered to be an atherosclerotic risk factor and predicts future cardiovascular disease risk in diabetic patients, in elderly patients, as well as in the general population. It has been implicated as an independent risk factor for cardiovascular disease and premature cardiovascular mortality for patients with type 1 and type 2 diabetes mellitus, as well as for patients with essential hypertension. A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. The role of chronic hyperglycemia in the development of diabetic microvascular complications and in neuropathy has been clearly established. However, the biochemical or cellular links between elevated blood glucose levels, and the vascular lesions remain incompletely understood. A number of trials have demonstrated that statins therapy as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes. In the present review we provide the up to date details on this subject.

Metformin and oral contraceptive treatments reduced circulating asymmetric dimethylarginine (ADMA) levels in patients with polycystic ovary syndrome (PCOS)

There is a little information in literature about circulating asymmetric dimethylarginine (ADMA) concentrations in polycystic ovary syndrome (PCOS) and the results reported are discrepant. In this study, therefore, we aimed (1) to determine the circulating ADMA concentrations in 44 women with PCOS and 22 age- and BMI-matched healthy controls, (2) to evaluate its correlations with insulin resistance, gonadotrophins, and androgen secretion, and (3) to compare effects of metformin and ethinyl estradiol-cyproterone acetate (EE/CPA) treatments on circulating ADMA concentrations. In conclusion, our data indicate that circulating ADMA concentrations in non-obese, non-hypertensive and young women with PCOS are significantly higher than healthy controls and they improved by a 3-month course of metformin and oral contraceptive treatments.

Effects of combined supplementation with B vitamins and antioxidants on plasma levels of asymmetric dimethylarginine (ADMA) in subjects with elevated risk for cardiovascular disease

Elevated plasma asymmetric dimethylarginine (ADMA) concentrations have been suggested as a potential risk factor for cardiovascular disease (CVD). Studies indicate a linkage between hyperhomocysteinemia, oxidative stress and ADMA metabolism. We tested the hypothesis that combined supplementation of B vitamins and antioxidants reduces ADMA concentrations in subjects with at least two CVD risk factors. A total of 123 men and women (58+/-8.1 years) were randomly assigned to take either a preparation including B vitamins and antioxidants (verum) or placebo for 6 months in a double-blind design. Blood concentrations of ADMA, symmetric dimethylarginine (SDMA), L-arginine, B vitamins, total homocysteine (tHcy), alpha-tocopherol, antioxidant capacity (TEAC), and oxLDL were measured pre- and post-intervention. Treatment with verum significantly decreased tHcy (-2.14 micromol/L; P<0.001) and significantly increased TEAC values (+39.3 microM; P<0.022), but no effect on ADMA was observed. OxLDL was significantly reduced in verum (-7.3 U/L; P=0.001) and placebo (-9.2U/L; P<0.001). At baseline, significant correlations were found only between ADMA and SDMA (r=0.281; P=0.002), L-arginine/ADMA and SDMA (r=-0.294; P<0.001), L-arginine/ADMA and oxLDL (r=-0.281; P=0.016), and L-arginine/ADMA and age (r=-0.231; P=0.010). Our results indicate that combined supplementation of B vitamins and antioxidants is not an adequate strategy to reduce ADMA plasma levels in subjects with elevated CVD risk.

Role of asymmetric dimethylarginine in homocysteine-induced apoptosis of vascular smooth muscle cells

Homocysteine (Hcy) could induce apoptosis of vascular smooth muscle cells (VSMC). Asymmetric dimethylarginine (ADMA) has been thought as a novel risk factor for cardiovascular diseases. We hypothesized that ADMA mediates homocysteine-induced apoptosis of VSMC. In this experiment the level of ADMA in the medium measured by high-performance liquid chromatography (HPLC) was elevated when the apoptosis of T/G HA-VSMC was induced by Hcy which was detected by Hoechst33342 staining or flow cytometry (FCM) with Annecin V+Propidium Iodide (PI). Exogenous ADMA induced the apoptosis of VSMC. At the same time, ADMA elevated the level of intracellular reactive oxidative species (ROS) determined by fluorescent ROS detection kit. The activation of JNK and p38MAPK contributed to ADMA-induced apoptosis of VSMC. The present results suggest that endogenous ADMA is involved in apoptosis of VSMC induced by Hcy, and the effects of ADMA is related to elevation of intracellular ROS and activation of JNK/p38MAPK signaling pathways.

l-Arginine, the substrate for NO synthesis: An alternative treatment for premature atherosclerosis?

L-Arginine is the substrate of endothelial nitric oxide synthase (eNOS) and the main precursor of nitric oxide (NO) in the vascular endothelium. L-Arginine improves endothelial function in patients with hypercholesterolemia, hypertension and smokers, while its role in diabetes remains unclear. Oral supplementation of L-arginine leads to a significant improvement of endothelium-dependent forearm vasodilation in hypercholesterolemic patients, while intravenous infusion of L-arginine improves endothelial function in healthy smokers. L-Arginine has anti-hypertensive properties, although its effects on endothelial function in hypertensive patients needs further evaluation. In conclusion, L-arginine administration may be useful in patients with premature atherosclerosis.

Asymmetric dimethylarginine (ADMA) and cardiovascular disease: insights from prospective clinical trials

Evidence has accumulated that asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase. ADMA inhibits vascular NO production at concentrations found in pathophysiological conditions; it also causes local vasoconstriction when infused intra-arterially. ADMA is increased in the plasma of humans with hypercholesterolemia, atherosclerosis, hypertension, chronic renal failure, chronic heart failure, and other clinical conditions. Increased ADMA levels are associated with reduced NO synthesis as assessed by impaired endothelium-dependent vasodilation or reduced NO metabolite levels. In several prospective and cross-sectional studies, ADMA has evolved as a marker of cardiovascular risk. Moreover, prospective clinical studies have suggested that it may play a role as a novel cardiovascular risk factor. Zoccali and coworkers were the first to show that elevated ADMA is associated with a three-fold increased risk of future severe cardiovascular events and mortality in patients undergoing hemodialysis. Valkonen and coworkers demonstrated in a nested case-control study that elevated ADMA was associated with a four-fold increased risk for acute coronary events in clinically healthy, nonsmoking men. In patients with stable angina pectoris, preinterventional ADMA indicates the risk of developing restenosis or severe clinical events after coronary intervention. Furthermore, in humans with no underlying cardiovascular disease who are undergoing intensive care unit treatment, ADMA is a marker of the mortality risk. A number of additional prospective clinical trials are currently under way in diverse patient populations, among them individuals with congestive heart failure, cardiac transplantation patients, and patients with pulmonary hypertension. In summary, an increasing number of prospective clinical trials have shown that the association between elevated ADMA levels and major cardiovascular events and total mortality is robust and extends to diverse patient populations. However, we need to define more clearly in the future who will profit from ADMA determination, in order to use this novel risk marker as a more specific diagnostic tool.

Probucol Decreases Asymmetrical Dimethylarginine Level by Alternation of Protein Arginine Methyltransferase I and Dimethylarginine Dimethylaminohydrolase Activity

HYPOTHESIS

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor (NOS), may play an important role in endothelium dysfunction. Probucol, a potent antioxidant drug, may improve endothelium function via reduction of NOS inhibitor level. The present study examined whether the decreased level of ADMA by probucol is related to enhancement of protein arginine methyltransferase I (PRMT I) expression and reduction of dimethylarginine dimethylaminohydrolase (DDAH) activity.

METHODS

Endothelial cells were cultured and used for all these studies. ADMA concentration and DDAH activity were determined by HPLC. Expression of PRMT I and eNOS were characterized by western blot.

RESULTS

Pretreatment with oxidized-low density lipoprotein (ox-LDL) (10, 30 or 100 microg/ml) or lysophosphatidylcholine (LPC) (1.0, 2.5 or 5.0 microg/ml) for 12, 24 or 48 h markedly increased the activity of lactate dehydrogenase (LDH) in cultured endothelial cell. Incubation ofendothelial cells with ox-LDL (100 microg/ml) or LPC (5.0 microg/ml) for 48 h significantly increased the expression of PRMT I, and levels of MDA and ADMA, and decreased the concentration of nitrite/nitrate, the expression of eNOS and the activity of DDAH. Probucol significantly decreased the level of ADMA, concomitantly with reduction of PRMT I expression and elevation of DDAH activity and up-regulation of eNOS expression.

CONCLUSION

In summary, the present results suggest that the protective effect of probucol on endothelium is related to reduction of ADMA concentration by inhibition of PRMT I expression and enhancement of DDAH activity.