Asymmetric dimethylarginine and the risk of cardiovascular events and death in patients with coronary artery disease: results from the AtheroGene Study

Genetics of NO Deficiency

The nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway plays a key role in regulating cardiovascular homeostasis, and genetic variants allocated to NO-cGMP pathway genes, leading to NO-cGMP deficiency, may influence the prevalence or course of cardiovascular disease. NO-cGMP deficiency can be caused by nitric oxide synthase substrate deficiency, substrate competition, defects, or uncoupling; endogenous inhibitors of nitric oxide synthase; decreased cGMP production; or increased cGMP degradation. This review presents evidence supporting the role of NO-cGMP deficiency in cardiovascular disease, including findings from genetic association studies for particular polymorphisms, haplotypes, and racial disparities. NO-cGMP pathway components including arginases, guanosine-5'-triphosphate cyclohydrolase 1, nitric oxide synthase, dimethylarginine dimethylaminohydrolases, soluble guanylyl cyclase, protein kinase G, phosphodiesterase 5, and natriuretic peptides will be discussed.

Asymmetric dimethylarginine downregulates sarco/endoplasmic reticulum calcium‑ATPase 3 and induces endoplasmic reticulum stress in human umbilical vein endothelial cells

Cardiovascular disease is the leading cause of mortality in patients with chronic kidney disease. Endothelial cell injury and apoptosis may promote atherosclerosis and cardiovascular disease. The present study investigated the potential mechanisms of asymmetric dimethylarginine (ADMA)‑induced apoptosis in human umbilical vein endothelial cells (HUVECs). It was demonstrated that ADMA decreased B‑cell lymphoma‑2 expression and increased cleaved‑caspase‑3 expression. Furthermore, terminal deoxynucleotidyl transferase (TdT)‑mediated‑digoxigenin‑11‑dUTP nick end labeling results indicated that ADMA induced apoptosis in HUVECs. These results suggest a potential mechanism of ADMA‑induced endothelial cell injury. It was also verified that ADMA induced the expression of phosphorylated protein kinase RNA‑like ER kinase, inositol requiring enzyme‑1, C/EBP homologous protein and glucose‑regulated protein, indicating activation of the endoplasmic reticulum (ER) stress response. Impaired function of sarco/endoplasmic reticulum calcium‑ATPase (SERCA) is considered a major contributor to ER stress. It was demonstrated that ADMA induced a significant downregulation of SERCA3, however not SERCA2b. Overall, the results indicated that ADMA induced apoptosis in HUVECs, and that this effect was closely associated with induction of ER stress and decreased SERCA3 expression.

Cardiomyocyte dimethylarginine dimethylaminohydrolase-1 (DDAH1) plays an important role in attenuating ventricular hypertrophy and dysfunction

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases that limits nitric oxide bioavailability. Dimethylarginine dimethylaminohydrolase-1 (DDAH1) exerts a critical role for ADMA degradation and plays an important role in NO signaling. In the heart, DDAH1 is observed in endothelial cells and in the sarcolemma of cardiomyocytes. While NO signaling is important for cardiac adaptation to stress, DDAH1 impact on cardiomyocyte homeostasis is not clear. Here we used the MerCreMer-LoxP model to specifically disrupt cardiomyocyte DDAH1 expression in adult mice to determine the physiological impact of cardiomyocyte DDAH1 under basal conditions and during hypertrophic stress imposed by transverse aortic constriction (TAC). Under control conditions, cardiomyocyte-specific DDAH1 knockout (cDDAH KO) had no detectable effect on plasma ADMA and left ventricular (LV) hypertrophy or function in adult or aging mice. In response to TAC, DDAH1 levels were elevated 2.5-fold in WT mice, which exhibited no change in LV or plasma ADMA content and moderate LV hypertrophy and LV dysfunction. In contrast, cDDAH1 KO mice exposed to TAC showed no increase in LV DDAH1 expression, slightly increased LV tissue ADMA levels, no increase in plasma ADMA, but significantly exacerbated LV hypertrophy, fibrosis, nitrotyrosine production, and LV dysfunction. These findings indicate cardiomyocyte DDAH1 activity is dispensable for cardiac function under basal conditions, but plays an important role in attenuating cardiac hypertrophy and ventricular remodeling under stress conditions, possibly through locally confined regulation of subcellular ADMA and NO signaling.

Marker of Endothelial Dysfunction Asymmetric Dimethylarginine Is Elevated in HIV Infection but Not Associated With Subclinical Atherosclerosis

BACKGROUND

Cardiovascular disease contributes to excess morbidity and mortality in HIV infection, and endothelial dysfunction may contribute to this pattern. We aimed to determine the endothelial function in treated and untreated HIV-infected individuals and investigate potential associations with viral replication, immune activation, coagulation, platelet function, and subclinical atherosclerosis.

METHODS

Asymmetric dimethylarginine (ADMA, marker of endothelial dysfunction) and soluble CD14 (sCD14, marker of monocyte activation) were measured in plasma from two previously established cross-sectional cohorts: cohort A including 50 untreated and 50 antiretroviral therapy (ART)-treated HIV-infected individuals with previously assessed coagulation and platelet function and cohort B including 105 HIV-infected individuals on ART and 105 uninfected controls with previously assessed coronary artery calcium score, myocardial perfusion defects, and carotid intima-media thickness.

RESULTS

Concentrations of ADMA were higher in HIV-infected individuals compared with uninfected controls, and higher ADMA was found in ART-treated compared with untreated HIV-infected individuals. ADMA was associated with viral load, sCD14, D-dimer, and low CD4 T-cell count in untreated HIV infection. Only viral load remained significant in multivariate analyses. In ART-treated HIV-infected individuals, ADMA was not associated with coronary artery calcium score, myocardial perfusion defects, or intima-media thickness.

CONCLUSIONS

Evidence of endothelial dysfunction was found in HIV infection and in untreated compared with treated HIV infection. In untreated HIV infection, the main driver of endothelial dysfunction was viral replication. Importantly, in treated HIV infection, ADMA was not associated with subclinical atherosclerosis. Thus, our data question the potential of ADMA as a useful biomarker of early atherosclerosis in treated HIV infection.

Arginine/Asymmetric Dimethylarginine Ratio in Colorectal Surgery

BACKGROUND

Asymmetric dimethylarginine (ADMA) is a naturally occurring amino acid that inhibits the effects of nitric oxide synthetases, producing considerable effects on the vascular system. Recent studies have suggested that increased ADMA is a major contributor to endothelial dysfunction, resulting in significant effects on cardiovascular and renal function.

METHODS

The study sample consisted of five male and 11 female patients scheduled for elective laparoscopic colorectal surgery; patients were between 41 and 77 years of age. Venous whole blood (8 - 10 mL) was collected from patients prior to colorectal surgery, as well as on postoperative day 1 and 2. Arginine, citrulline, ADMA, and symmetric dimethylarginine levels were measured in collected blood using liquid chromatography coupled to mass spectrometry.

RESULTS

Data from the amino-acid blood analysis demonstrated that the levels of L-citrulline and L-arginine decreased on postoperative days 1, coinciding with an increase of ADMA levels. The overall result of these changes was a decrease in the arginine to ADMA ratio by 21% from the preoperative period to postoperative day 2 (P = 0.02).

CONCLUSIONS

The data collected through this study demonstrate a significant increase in systemic ADMA levels following major laparoscopic colorectal surgery.

The issue of plasma asymmetric dimethylarginine reference range - A systematic review and meta-analysis

Background

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase, marker and mediator of endothelial dysfunction. Several studies have demonstrated its value in cardiovascular risk stratification and all-cause mortality prediction. The aim was to determine the reference range of plasma ADMA in healthy adults.

Methods and results

Taking into account the most widely used ADMA measurement methods, only studies using either high performance liquid chromatography (HPLC) -with fluorescence or mass spectrometric detection-, or enzyme-linked immunosorbent assay (ELISA) to quantify plasma ADMA concentrations were enrolled. 66 studies were included in the quantitative analysis (24 using ELISA and 42 using HPLC) reporting a total number of 5528 non-diabetic, non-hypertensive, non-obese adults without any medication (3178 men and 2350 women, 41.6 ± 16.9 years old). The reference range of ADMA (in μmol/l with 95% confidence interval in parenthesis) was 0.34 (0.29–0.38)– 1.10 (0.85–1.35) with a mean of 0.71 (0.57–0.85) (n = 4093) measured by HPLC and 0.25 (0.18–0.31)– 0.92 (0.76–1.09) with a mean of 0.57 (0.48–0.66) (n = 1435) by ELISA.

Conclusions

Numerous publications suggested that asymmetric dimethylarginine is not only an outstanding tool of disease outcome prediction but also a new potential therapeutic target substance; the reference range provided by this meta-analysis can become of great importance and aid to further investigations. However, developing a standard measurement method would be beneficial to facilitate the clinical usage of ADMA.

Functional and Biochemical Endothelial Profiling In Vivo in a Murine Model of Endothelial Dysfunction; Comparison of Effects of 1-Methylnicotinamide and Angiotensin-converting Enzyme Inhibitor

Although it is known that 1-methylnicotinamide (MNA) displays vasoprotective activity in mice, as yet the effect of MNA on endothelial function has not been demonstrated in vivo. Here, using magnetic resonance imaging (MRI) we profile the effects of MNA on endothelial phenotype in mice with atherosclerosis (ApoE/LDLR^-/-) in vivo, in comparison to angiotensin (Ang) -converting enzyme (ACE) inhibitor (perindopril), with known vasoprotective activity. On a biochemical level, we analyzed whether MNA- or perindopril-induced improvement in endothelial function results in changes in ACE/Ang II-ACE2/Ang-(1–7) balance, and L-arginine/asymmetric dimethylarginine (ADMA) ratio. Endothelial function and permeability were evaluated in the brachiocephalic artery (BCA) in 4-month-old ApoE/LDLR^-/- mice that were non-treated or treated for 1 month or 2 months with either MNA (100 mg/kg/day) or perindopril (10 mg/kg/day). The 3D IntraGate^®FLASH sequence was used for evaluation of BCA volume changes following acetylcholine (Ach) administration, and for relaxation time (T₁) mapping around BCA to assess endothelial permeability using an intravascular contrast agent. Activity of ACE/Ang II and ACE2/Ang-(1–7) pathways as well as metabolites of L-arginine/ADMA pathway were measured using liquid chromatography/mass spectrometry-based methods. In non-treated 6-month-old ApoE/LDLR^-/- mice, Ach induced a vasoconstriction in BCA that amounted to –7.2%. 2-month treatment with either MNA or perindopril resulted in the reversal of impaired Ach-induced response to vasodilatation (4.5 and 5.5%, respectively) and a decrease in endothelial permeability (by about 60% for MNA-, as well as perindopril-treated mice). Improvement of endothelial function by MNA and perindopril was in both cases associated with the activation of ACE2/Ang-(1–7) and the inhibition of ACE/Ang II axes as evidenced by an approximately twofold increase in Ang-(1–9) and Ang-(1–7) and a proportional decrease in Ang II and its active metabolites. Finally, MNA and perindopril treatment resulted in an increase in L-arginine/ADMA ratio by 107% (MNA) and 140% (perindopril), as compared to non-treated mice. Functional and biochemical endothelial profiling in ApoE/LDLR^-/- mice in vivo revealed that 2-month treatment with MNA (100 mg/kg/day) displayed a similar profile of vasoprotective effect as 2-month treatment with perindopril (10 mg/kg/day): i.e., the improvement in endothelial function that was associated with the beneficial changes in ACE/Ang II-ACE2/Ang (1–7) balance and in L-arginine/ADMA ratio in plasma.

The asymmetric dimethylarginine-mediated inhibition of nitric oxide in the rostral ventrolateral medulla contributes to regulation of blood pressure in hypertensive rats

Nitric oxide (NO) contributes to the central control of cardiovascular activity. The rostral ventrolateral medulla (RVLM) has been recognized as a pivotal region for maintaining basal blood pressure (BP) and sympathetic tone. It is reported that asymmetric dimethylarginine (ADMA), characterized as a cardiovascular risk marker, is an endogenous inhibitor of nitric oxide synthesis. The present was designed to determine the role of ADMA in the RVLM in the central control of BP in hypertensive rats. In Sprague Dawley (SD) rats, microinjection of ADMA into the RVLM dose-dependently increased BP, heart rate (HR), and renal sympathetic never activity (RSNA), but also reduced total NO production in the RVLM. In central angiotensin II (Ang II)-induced hypertensive rats and spontaneously hypertensive rat (SHR), the level of ADMA in the RVLM was increased and total NO production was decreased significantly, compared with SD rats treated vehicle infusion and WKY rats, respectively. These hypertensive rats also showed an increased protein level of protein arginine methyltransferases1 (PRMT1, which generates ADMA) and a decreased expression level of dimethylarginine dimethylaminohydrolases 1 (DDAH1, which degrades ADMA) in the RVLM. Furthermore, increased AMDA content and PRMT1 expression, and decreased levels of total NO production and DDAH1 expression in the RVLM in SHR were blunted by intracisternal infusion of the angiotensin II type 1 receptor (AT1R) blocker losartan. The current data indicate that the ADMA-mediated NO inhibition in the RVLM plays a critical role in involving in the central regulation of BP in hypertension, which may be associated with increased Ang II.

Myeloperoxidase, asymmetric dimethyl-arginine and the renin-angiotensin-aldosterone-system in cardiovascular risk patients: Cross-sectional findings from the Ludwigshafen Risk and Cardiovascular Health (LURIC) study

OBJECTIVES

The leukocyte-derived myeloperoxidase (MPO), the nitric oxidase synthase (NOS) inhibitor asymmetrical dimethyl-arginine (ADMA) and the renin-angiotensin-aldosterone-system (RAAS) are associated with cardiovascular diseases (CVD). This study aimed to investigate potential interactions between the RAAS, ADMA and MPO in cardiovascular risk patients.

DESIGN AND METHODS

All in all, 1446 patients, who were referred to coronary angiography, were included in this prospective study. MPO, ADMA and circulating serum markers of the RAAS system were measured. Additionally, all-cause and CVD mortality, cardiovascular risk factors, inflammatory and endothelial markers, and medication use were investigated.

RESULTS

MPO concentrations were significantly associated with ADMA (P=0.002), renin (P=0.001) and angiotensin II levels (P=0.015), whereas ADMA was in tendency associated with renin (P=0.059) and significantly with angiotensin II (P=0.001). Both, ADMA and MPO were inversely correlated with angiotensinogen, angiotensin I and the angiotensin I/angiotensin II ratio. ADMA and angiotensin II were found stronger independent risk factors for all-cause and CVD mortality compared to MPO.

CONCLUSIONS

MPO concentrations were significantly associated with higher ADMA levels and an up-regulated circulating RAAS in patients with CVD. Moreover, serum levels of ADMA and angiotensin II were shown to be more predictive for all-cause and CVD mortality compared to MPO.

Carotid Plaque Score and Risk of Cardiovascular Mortality in the Oldest Old: Results from the TOOTH Study

Aim: Accumulating evidence suggests that predictability of traditional cardiovascular risk factors declines with advancing age. We investigated whether carotid plaque scores (CPSs) were associated with cardiovascular disease (CVD) death in the oldest old, and whether asymmetrical dimethylarginine (ADMA), a marker of endothelial dysfunction, moderated the association between the CPS and CVD death.

Methods: We conducted a prospective cohort study of Japanese subjects aged ≥ 85 years without CVD at baseline. We followed this cohort for 6 years to investigate the association of CPS with CVD death via multivariable Cox proportional hazard analysis. We divided participants into three groups according to CPS (no, 0 points; low, 1.2–4.9 points; high, ≥5.0 points). The predictive value of CPS for estimating CVD death risk over CVD risk factors, including ADMA, was examined using C-statistics.

Results: We analyzed 347 participants (151 men, 196 women; mean age, 87.6 years), of which 135 (38.9%) had no carotid plaque at baseline, and 48 (13.8%) had high CPS. Of the total, 29 (8.4%) participants experienced CVD-related death during the study period. Multivariable analysis revealed a significant association of high CPS with CVD-related mortality relative to no CPS (hazard ratio, 3.90; 95% confidence interval: 1.47–10.39). ADMA was not associated with CVD death, but the significant association between CPS and CVD death was observed only in lower ADMA level. The addition of CPS to other risk factors improved the predictability of CVD death (p = 0.032).

Conclusions: High CPS correlated significantly with a higher CVD death risk in the oldest old with low cardiovascular risk. Ultrasound carotid plaque evaluation might facilitate risk evaluations of CVD death in the very old.

Repetitive ischemia increases myocardial dimethylarginine dimethylaminohydrolase 1 expression

Pharmacologic inhibition of nitric oxide production inhibits growth of coronary collateral vessels. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) is the major enzyme that degrades asymmetric dimethylarginine (ADMA), a potent inhibitor of nitric oxide synthase. Here we examined regulation of the ADMA-DDAH1 pathway in a canine model of recurrent myocardial ischemia during the time when coronary collateral growth is known to occur. Under basal conditions, DDAH1 expression was non-uniform across the left ventricular (LV) wall, with expression strongest in the subepicardium. In response to ischemia, DDAH1 expression was up-regulated in the midmyocardium of the ischemic zone, and this was associated with a significant reduction in myocardial interstitial fluid (MIF) ADMA. The decrease in MIF ADMA during ischemia was likely due to increased DDAH1 because myocardial protein arginine N-methyl transferase 1 (PRMT1) and the methylated arginine protein content (the source of ADMA) were unchanged or increased, respectively, at this time. The inflammatory mediators interleukin (IL-1β) and tumor necrosis factor (TNF-α) were also elevated in the midmyocardium where DDAH1 expression was increased. Both of these factors significantly up-regulated DDAH1 expression in cultured human coronary artery endothelial cells. Taken together, these results suggest that inflammatory factors expressed in response to myocardial ischemia contributed to up-regulation of DDAH1, which was responsible for the decrease in MIF ADMA.

Arginine methylation dysfunction increased risk of acute coronary syndrome in coronary artery disease population: A case-control study

The plasma levels of asymmetric dimethylarginine (ADMA) had been proved to be an independent cardiovascular risk factor. Few studies involved the entire arginine methylation dysfunction. This study was designed to investigate whether arginine methylation dysfunction is associated with acute coronary syndrome risk in coronary artery disease population.In total 298 patients undergoing coronary angiography because of chest pain with the diagnosis of stable angina pectoris or acute coronary syndrome from February 2013 to June 2014 were included. Plasma levels of free arginine, citrulline, ornithine, and the methylated form of arginine, ADMA, and symmetric dimethylarginine (SDMA) were measured with high-performance liquid chromatography coupled with tandem mass spectrometry. We examined the relationship between arginine metabolism-related amino acids or arginine methylation index (AMI, defined as ratio of [arginine + citrulline + ornithine]/[ADMA + SDMA]) and acute coronary events.We found that plasma ADMA levels were similar in the stable angina pectoris group and the acute coronary syndrome group (P = 0.88); the AMI differed significantly between 2 groups (P < 0.001). Multivariate logistic regression demonstrated that AMI was an independent risk factor of acute coronary events in patients with coronary artery disease (OR = 0.975, 95% confidence interval 0.956-0.993; P = 0.008).Our study suggested that ADMA levels were very similar in the stable angina and acute coronary syndrome patients; AMI might be an independent risk factor of acute coronary events in coronary artery disease population.

The Burden of Major Adverse Cardiac Events and Antiplatelet Prevention in Patients with Coronary or Peripheral Arterial Disease

BACKGROUND

Patients with a history of a cardiovascular (CV) disease are at high risk of suffering secondary major adverse cardiac events (MACE), namely death, nonfatal myocardial infarction (MI), stroke, symptomatic pulmonary embolism, CV and all-cause hospitalization, and bleeding.

METHODS

A comprehensive review of the literature was conducted to review the epidemiology and burden of MACE in patients with coronary or peripheral arterial disease (CAD or PAD) in Europe and other ex-US regions. Relevant articles published between 2003 and 2013 were retrieved from PubMed and other sites.

RESULTS

MACE incidence and prevalence in patients with CAD or PAD were increased by at least 1.4-fold compared with matched controls with no CV disease. In patients with CAD, MACE mostly occurred within 30 days of primary percutaneous coronary intervention; incidence decreased with time. Increased oxidative stress in coronary and peripheral arteries, diabetes, and chronic kidney disease were identified as the main risk factors for MACE in patients with CAD and PAD. Registry data showed that, although preventive antiplatelet therapy was prescribed at high rates, a large proportion (9-56%) of patients did not receive treatment. Furthermore, adherence to treatment declined over time, potentially leading to disease worsening.

CONCLUSION

Despite gaps in the literature, this assessment showed that MACE's risk is substantial among patients with CAD or PAD and that the use of preventive therapies is suboptimal. Development of additional preventive therapies for these patients is warranted.

Increased brachial intima-media thickness is associated with circulating levels of asymmetric dimethylarginine in patients with COPD

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with an increased cardiovascular risk. However, the mechanisms for this association are yet unclear. The aim of this study was to investigate the relationship between brachial intima-media thickness (B-IMT), an independent predictor of cardiovascular risk, systemic inflammation, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, in patients with COPD and respective controls.

METHODS

The study sample consisted of 60 patients with stable COPD, free from overt cardiovascular disorders, as well as 20 smoking and 20 nonsmoking controls. Ultrasound assessment of B-IMT, spirometry, venous blood sampling for quantification of inflammatory markers and ADMA levels were carried out, and individual cardiovascular risk was calculated via the Framingham risk score.

RESULTS

Patients with COPD showed significantly higher B-IMT compared to smoking (P=0.007) and nonsmoking controls (P=0.033). COPD patients with elevated B-IMT had a twofold increased calculated 10-year risk for cardiovascular events compared to those below the recommended cutoff (P=0.002). B-IMT was significantly associated with systemic inflammation (interleukin-6 [IL-6]; r=0.365, P=0.006) and ADMA (r=0.331, P=0.013) in COPD. Multivariate linear regression revealed male sex and ADMA as independent predictors of B-IMT in this study sample.

CONCLUSION

B-IMT is significantly increased in patients with COPD and is associated with systemic inflammation and ADMA levels.

Application of Biomarkers for Risk Stratification in Patients with Atrial Fibrillation

BACKGROUND

Atrial fibrillation is the most common sustained arrhythmia and an important contributor to cardiovascular morbidity and mortality. Several strategies have been proposed for prediction of outcomes and individualization of treatments to better balance the benefits of stroke prevention and risks of bleeding during anticoagulation.

CONTENT

The availability of analytically more specific and sensitive methods to measure circulating biomarkers of cellular and organ stress and dysfunction has led to testing of their utility in several cardiovascular conditions. In patients with atrial fibrillation, biomarkers of myocardial injury (troponin) and cardiovascular stress and dysfunction (natriuretic peptides, growth differentiation factor 15), myocardial fibrosis (galectin-3), renal dysfunction (creatinine, cystatin C), inflammation (C-reactive protein, cytokines) and coagulation activity (d-dimer) have been found associated with underlying pathophysiology, clinical outcomes and effects of treatment. Measurements of these markers might therefore expand the understanding of the pathophysiology, improve risk assessment and optimize treatment in individual patients with atrial fibrillation.

SUMMARY

Biomarkers for risk stratification have potential roles as tools for evaluation of patients with atrial fibrillation and for selection of the best treatment strategies to prevent stroke, major bleeding, and mortality.

Plasma asymmetric dimethylarginine (ADMA) levels in Mexican women exposed to polycyclic aromatic hydrocarbons (PAHs): A preliminary study

Recent studies indicate that exposure to environmental pollutants (as polycyclic aromatic hydrocarbons) is a very important risk factor for development of cardiovascular diseases (CVDs). Correspondingly, in recent times asymmetric dimethylarginine (ADMA) has been proposed as a new and meaningful biomarker predictor for the risk of CVDs. Therefore, the objective of this study was to evaluate plasma ADMA concentrations in Mexican women (n=155) exposed to polycyclic aromatic hydrocarbons (PAHs). Urinary 1-hydroxypyrene [(1-OHP), exposure biomarker for PAHs] levels were quantified using a high performance liquid chromatography (HPLC) technique and plasma ADMA concentrations were analyzed using a commercially available ELISA kit. Urinary 1-OHP levels in all women assessed ranged from <LOD to 8.80μmol/mol creatinine. Regarding plasma ADMA concentrations, the mean levels ranged from 0.66 to 1.00μmol/L. Moreover, a significantly relationship was found between plasma ADMA concentrations and urinary 1-OHP levels (p=0.005; r=0.390). In conclusion, the results showed in this study demonstrated that the urinary 1-OHP levels were significant predictors of plasma ADMA concentrations in Mexican women exposed to PAHs. Although with due caution regarding the low representativeness of the present screening, it can be considered as a preliminary work to perform prospective studies including greater number of individuals and focusing in a more complete characterization of the effects produced by PAHs exposure on cardiovascular health.

Asymmetric and Symmetric Dimethylarginine as Risk Markers for Total Mortality and Cardiovascular Outcomes: A Systematic Review and Meta-Analysis of Prospective Studies

Background

A growing number of studies linked elevated concentrations of circulating asymmetric (ADMA) and symmetric (SDMA) dimethylarginine to mortality and cardiovascular disease (CVD) events. To summarize the evidence, we conducted a systematic review and quantified associations of ADMA and SDMA with the risks of all-cause mortality and incident CVD in meta-analyses accounting for different populations and methodological approaches of the studies.

Methods

Relevant studies were identified in PubMed until February 2015. We used random effect models to obtain summary relative risks (RR) and 95% confidence intervals (95%CIs), comparing top versus bottom tertiles. Dose-response relations were assessed by restricted cubic spline regression models and potential non-linearity was evaluated using a likelihood ratio test. Heterogeneity between subgroups was assessed by meta-regression analysis.

Results

For ADMA, 34 studies (total n = 32,428) investigating associations with all-cause mortality (events = 5,035) and 30 studies (total n = 30,624) investigating the association with incident CVD (events = 3,396) were included. The summary RRs (95%CI) for all-cause mortality were 1.52 (1.37–1.68) and for CVD 1.33 (1.22–1.45), comparing high versus low ADMA concentrations. Slight differences were observed across study populations and methodological approaches, with the strongest association of ADMA being reported with all-cause mortality in critically ill patients. For SDMA, 17 studies (total n = 18,163) were included for all-cause mortality (events = 2,903), and 13 studies (total n = 16,807) for CVD (events = 1,534). High vs. low levels of SDMA, were associated with increased risk of all-cause mortality [summary RR (95%CI): 1.31 (1.18–1.46)] and CVD [summary RR (95%CI): 1.36 (1.10–1.68) Strongest associations were observed in general population samples.

Conclusions

The dimethylarginines ADMA and SDMA are independent risk markers for all-cause mortality and CVD across different populations and methodological approaches.

Asymmetric Dimethylarginine (ADMA) Levels Are Lower in Hemodialysis Patients Treated With Paricalcitol

Introduction

Chronic kidney disease is a major public health problem. In the last decade, it has been shown that the early stages of chronic kidney disease are associated with an inflammatory condition involving an increased risk of cardiovascular morbidity and long-term mortality. In patients with chronic kidney disease and more specifically those on hemodialysis, cardiovascular events are the most common cause of death. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and may be an independent risk factor for endothelial dysfunction and cardiovascular disease.

Methods

We performed a cross-sectional analysis to identify factors that were associated with ADMA such as certain medications related to cardiovascular disease in dialysis patients.

Results

Patients who were treated with paricalcitol had significantly lower levels of ADMA (0.21 ± 0.19 μmol/l) compared with those not treated with paricalcitol (0.42 ± 0.35 μmol/l) (P = 0.00027). Dividing ADMA levels by quartiles, patients treated with paricalcitol were less likely to have very high level ADMA (P = 0.014), whereas there were no significant differences with other medications. Higher dose of paricalcitol was also related to lower levels of ADMA noting an inverse correlation (r = –0.36, P = 0.013).

Discussion

Hemodialysis patients treated with paricalcitol presented significantly decreased ADMA levels compared with those who did not receive this treatment. Possible beneficial effects in terms of cardiovascular morbidity and mortality by paricalcitol and its association with ADMA and nitric oxide synthesis are unknown. Studies to confirm this effect and determine the underlying pathophysiological mechanism are necessary.

Asymmetric dimethyl-arginine and coronary artery calcification in young adults entering middle age: the CARDIA Study

BACKGROUND

Normal endothelial function depends on nitric oxide (NO) release by endothelial cells. Asymmetric dimethylarginine (ADMA), by competing with L-arginine, inhibits NO production and may lead to endothelial dysfunction and atherosclerotic development. Our aim was to ascertain the association between ADMA and coronary artery calcification (CAC), a marker of atherosclerotic coronary disease burden.

DESIGN

A nested case-control study within the Coronary Artery Risk Development in Young Adults (CARDIA) cohort, an observational study among young adults residing in four US cities.

METHODS

Participants were 263 white and black male and female cases with the presence of CAC and 263 sex and race-matched controls without evidence of CAC by computed tomography, 33-47 years old in 2000-2001.

RESULTS

The median level (range) of ADMA was significantly higher in cases (0.55; 0.20-2.22 micromol/l) than in controls (0.53; 0.32-1.30 micromol/l; P=0.03). In conditional logistic regression adjusting for age, field center, educational attainment, smoking status, alcohol consumption, body mass index, waist circumference, hypertension, diabetes, low-density lipoprotein and high-density lipoprotein-cholesterol, triglycerides, renal function and C-reactive protein, the highest tertile of ADMA, compared with the lowest tertile, was associated with 1.80 (95% confidence interval 1.03-3.15) increased odds of the presence of any CAC. By linear regression, a significant independent relationship was also found between ADMA and the degree of CAC.

CONCLUSION

These results support a role for ADMA as a biochemical marker of CAC.

Asymmetric Dimethylarginine Is a Well Established Mediating Risk Factor for Cardiovascular Morbidity and Mortality-Should Patients with Elevated Levels Be Supplemented with Citrulline?

The arginine metabolite asymmetric dimethylarginine (ADMA) is a competitive inhibitor and uncoupler of endothelial nitric oxide synthase (eNOS), an enzyme that acts in multifarious ways to promote cardiovascular health. This phenomenon likely explains, at least in part, why elevated ADMA has been established as an independent risk factor for cardiovascular events, ventricular hypertrophy, and cardiovascular mortality. Fortunately, the suppressive impact of ADMA on eNOS activity can be offset by increasing intracellular arginine levels with supplemental citrulline. Although the long-term impact of supplemental citrulline on cardiovascular health in patients with elevated ADMA has not yet been studied, shorter-term clinical studies of citrulline administration demonstrate effects suggestive of increased NO synthesis, such as reductions in blood pressure and arterial stiffness, improved endothelium-dependent vasodilation, increased erection hardness, and increased ejection fractions in patients with heart failure. Supplemental citrulline could be a practical option for primary or secondary prevention of cardiovascular events and mortality, as it is inexpensive, has a mild flavor, and is well tolerated in doses (3-6 g daily) that can influence eNOS activity. Large and long-term clinical trials, targeting patients at high risk for cardiovascular events in whom ADMA is elevated, are needed to evaluate citrulline's potential for aiding cardiovascular health.

Relationship of asymmetric dimethylarginine (ADMA) with extent and functional severity of coronary atherosclerosis

BACKGROUND

Elevated serum levels of asymmetric dimethylarginine (ADMA) are associated with endothelial dysfunction and atherogenesis. In patients with suspected coronary artery disease (CAD), we assessed the correlation of serum ADMA levels with extent and functional significance of coronary atherosclerosis.

METHODS

We enrolled 281 patients with suspected CAD undergoing coronary angiogram. Angiographic CAD severity was evaluated by Bogaty score. In patients with angiographic evidence of at least one intermediate coronary stenosis (≥50% diameter stenosis), functional significance was assessed by fractional flow reserve (FFR). Blood samples were collected in all patients prior to coronary angiography for measurement of serum ADMA levels.

RESULTS

We observed across tertiles of ADMA levels increasingly higher values of both Stenosis Score (2.25±1.70 vs. 2.89±1.99 vs. 2.95±1.82, p=0.016) and Extent Index (0.52±0.32 vs. 0.61±0.39 vs. 0.72±0.47, p=0.003). The association between ADMA levels and Extent Index remained significant after multivariate adjustment (p=0.005). Patients with FFR ≤0.80 in at least one vessel (n=113) had significantly higher ADMA levels compared with patients without functionally significant CAD (0.51 [0.43-0.64] vs. 0.46 [0.39-0.58]μmol/L, p=0.005). Serum ADMA levels were independent predictors of abnormal FFR after adjustment for extent score (odds ratio 7.35, 95% confidence interval 1.05-56.76, p=0.046).

CONCLUSIONS

Serum ADMA levels are independent predictors of coronary atherosclerosis extent and functional significance of CAD.

Asymmetric dimethylarginine, related arginine derivatives, and incident atrial fibrillation

BACKGROUND

Oxidative stress plays an important role in the development of atrial fibrillation (AF). Arginine derivatives including asymmetric dimethylarginine (ADMA) are central to nitric oxide metabolism and nitrosative stress. Whether blood concentrations of arginine derivatives are related to incidence of AF is uncertain.

METHODS AND RESULTS

In 3,310 individuals (mean age 58 ± 10 years, 54% women) from the community-based Framingham Study, we prospectively examined the relations of circulating levels of ADMA, l-arginine, symmetric dimethylarginine (SDMA), and the ratio of l-arginine/ADMA to incidence of AF using proportional hazards regression models. Over a median follow-up time of 10 years, 247 AF cases occurred. Using age- and sex-adjusted regression models, ADMA was associated with a hazard ratio of 1.15 per 1-SD increase in loge-biomarker concentration (95% CI 1.02-1.29, P = .02) for AF, which was no longer significant after further risk factor adjustment (hazard ratio 1.09, 95% CI 0.97-1.23, P = .15). Neither l-arginine nor SDMA was related to new-onset AF. A clinical model comprising clinical risk factors for AF (for age, sex, height, weight, systolic blood pressure, diastolic blood pressure, current smoking, diabetes, hypertension treatment, myocardial infarction, and heart failure; c statistic = 0.781; 95% CI 0.753-0.808) was not improved by the addition of ADMA (0.782; 95% CI 0.755-0.809).

CONCLUSIONS

Asymmetric dimethylarginine and related arginine derivatives were not associated with incident AF in the community after accounting for other clinical risk factors and confounders. Its role in the pathogenesis of AF needs further refinement.

Determination of Asymmetric and Symmetric Dimethylarginine in Serum from Patients with Chronic Kidney Disease: UPLC-MS/MS versus ELISA

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis, and its structural isomer symmetric dimethylarginine (SDMA) are uremic toxins accumulating in chronic kidney disease (CKD) patients. The objective of this study was to develop and validate a robust UPLC-MS/MS method for the simultaneous determination of ADMA and SDMA in human serum. Chromatographic separation after butyl ester derivatization was achieved on an Acquity UPLC BEH C18 column, followed by tandem mass spectrometric detection. After validation, the applicability of the method was evaluated by the analysis of serum samples from 10 healthy controls and 77 CKD patients on hemodialysis (CKD5HD). Both ADMA (0.84 ± 0.19 µM vs. 0.52 ± 0.07 µM) and SDMA concentrations (2.06 ± 0.82 µM vs. 0.59 ± 0.13 µM) were significantly (p < 0.001) elevated in CKD5HD patients compared to healthy controls. In general, low degrees of protein binding were found for both ADMA and SDMA. In addition, an established commercially available ELISA kit was utilized on the same samples (n = 87) to compare values obtained both with ELISA and UPLC-MS/MS. Regression analysis between these two methods was significant (p < 0.0001) but moderate for both ADMA (R = 0.78) and SDMA (R = 0.72).

Asymmetric Dimethylarginine versus Proton Pump Inhibitors Usage in Patients with Stable Coronary Artery Disease: A Cross-Sectional Study

A recent experimental study suggested that proton pump inhibitors (PPI), widely used to prevent gastroduodenal complications of dual antiplatelet therapy, may increase the accumulation of the endogenous nitric oxide synthesis antagonist asymmetric dimethylarginine (ADMA), an adverse outcome predictor. Our aim was to assess the effect of PPI usage on circulating ADMA in coronary artery disease (CAD). Plasma ADMA levels were compared according to PPI use for ≥1 month prior to admission in 128 previously described non-diabetic men with stable CAD who were free of heart failure or other coexistent diseases. Patients on PPI tended to be older and with insignificantly lower estimated glomerular filtration rate (GFR). PPI use was not associated with any effect on plasma ADMA (0.51 ± 0.11 (SD) vs. 0.50 ± 0.10 µmol/L for those with PPI (n = 53) and without PPI (n = 75), respectively; p = 0.7). Additionally, plasma ADMA did not differ between PPI users and non-users stratified by a history of current smoking, CAD severity or extent. The adjustment for patients’ age and GFR did not substantially change the results. Thus, PPI usage does not appear to affect circulating ADMA in non-diabetic men with stable CAD. Whether novel mechanisms of adverse PPI effects on the vasculature can be translated into clinical conditions, requires further studies.

Association between Body Mass Index, Asymmetric Dimethylarginine and Risk of Cardiovascular Events and Mortality in Norwegian Patients with Suspected Stable Angina Pectoris

Background

Asymmetric dimethylarginine (ADMA) is associated with increased risk of atherosclerotic cardiovascular disease and mortality through inhibition of nitrogen oxide (NO) synthesis. As positive correlations between serum concentrations of NO and body mass index (BMI) have been observed, we aimed to explore whether the potential associations between plasma ADMA levels and the risk of acute myocardial infarction (AMI) and mortality were modified by BMI.

Methods

Multivariable Cox proportional hazard models were used to estimate the hazard ratios (HR) for AMI, cardiovascular death and all-cause mortality according to baseline plasma ADMA levels in 4122 patients with suspected stable angina pectoris. Analyses were subsequently repeated in patients with BMI below (low BMI) or above (high BMI) median.

Results

A total of 2982 patients (72%) were men. Median (range) age, plasma ADMA level and BMI were 62 (21–88) years, 0.54 (0.10–1.25) μmol/L and 26.3 (18.5–54.3) kg/m², respectively. During a mean (standard deviation) follow-up time of 4.7 (1.4) years, 337 (8%) patients suffered from an AMI, 300 (7%) died, whereof 165 (55%) due to cardiovascular disease. Each 0.1 μmol/L increment in plasma ADMA level was associated with an increased risk of AMI (HR (95% CI) 1.21 (1.08, 1.35) and cardiovascular death 1.30 (1.13, 1.49) in participants with low BMI only. Interactions were significant for AMI (p = 0.04) and CV death (p = 0.03). BMI did not modify the association between plasma ADMA levels and all-cause mortality.

Conclusion

Plasma ADMA levels were associated with risk of AMI and cardiovascular death among patients with low BMI only.

Effect of asymmetric dimethylarginine (ADMA) on heart failure development

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases that limits nitric oxide bioavailability and can increase production of NOS derived reactive oxidative species. Increased plasma ADMA is a one of the strongest predictors of mortality in patients who have had a myocardial infarction or suffer from chronic left heart failure, and is also an independent risk factor for several other conditions that contribute to heart failure development, including hypertension, coronary artery disease/atherosclerosis, diabetes, and renal dysfunction. The enzyme responsible for ADMA degradation is dimethylarginine dimethylaminohydrolase-1 (DDAH1). DDAH1 plays an important role in maintaining nitric oxide bioavailability and preserving cardiovascular function in the failing heart. Here, we examine mechanisms of abnormal NO production in heart failure, with particular focus on the role of ADMA and DDAH1.

Novel Pathophysiological Mechanisms in Hypertension

Hypertension is the most common disease affecting humans and imparts a significant cardiovascular and renal risk to patients. Extensive research over the past few decades has enhanced our understanding of the underlying mechanisms in hypertension. However, in most instances, the cause of hypertension in a given patient continues to remain elusive. Nevertheless, achieving aggressive blood pressure goals significantly reduces cardiovascular morbidity and mortality, as demonstrated in the recently concluded SPRINT trial. Since a large proportion of patients still fail to achieve blood pressure goals, knowledge of novel pathophysiologic mechanisms and mechanism based treatment strategies is crucial. The following chapter will review the novel pathophysiological mechanisms in hypertension, with a focus on role of immunity, inflammation and vascular endothelial homeostasis. The therapeutic implications of these mechanisms will be discussed where applicable.

Asymmetric dimethylarginine as a mediator of vascular dysfunction in cirrhosis

Cirrhosis is associated with marked abnormalities in the circulatory function that involve a reduction in systemic vascular resistance. An important cause of this vasodilatation is the increased production or activity of nitric oxide (NO) in the splanchnic circulation. During portal hypertension and cirrhosis an increased endothelial NO synthase (eNOS) activity is demonstrated in splanchnic vessels. In contrast, the activity of eNOS in the cirrhotic liver is decreased, which suggests a different regulation of eNOS in the liver and in the splanchnic vessels. Asymmetric dimethylarginine (ADMA) is an endogenous NO inhibitor and higher plasma levels of ADMA are related to increased cardiovascular risk in both the general population and among patients with cirrhosis. It has been demonstrated that the liver is a key player in the metabolism of ADMA. This observation was further supported by investigations in human patients, showing a close correlation between ADMA plasma levels and the degree of hepatic dysfunction. ADMA is degraded to citrulline and dimethylamine by dimethylarginine dimethylaminohydrolases (DDAHs). DDAHs are expressed as type 1 and 2 isoforms and are widely distributed in various organs and tissues, including the liver. In this review, we discuss experimental and clinical data that document the effects of dimethylarginines on vascular function in cirrhosis. Our increasing understanding of the routes of synthesis and metabolism of methylarginines is beginning to provide insights into novel mechanisms of liver disease and allowing us to identify potential therapeutic opportunities.

Resolution and quantification of arginine, monomethylarginine, asymmetric dimethylarginine, and symmetric dimethylarginine in plasma using HPLC with internal calibration

N(G) ,N(G) -dimethyl-l-arginine (asymmetric dimethylarginine, ADMA),N(G) -monomethyl-l-arginine (l-NMMA) and N(G) ,N(G') -dimethyl-l-arginine (symmetric dimethylarginine, SDMA) are released during hydrolysis of proteins containing methylated arginine residues. ADMA and l-NMMA inhibit nitric oxide synthase by competing with l-arginine substrate. All three methylarginine derivatives also inhibit arginine transport. To enable investigation of methylarginines in diseases involving impaired nitric oxide synthesis, we developed a high-performance liquid chromatography (HPLC) assay to simultaneously quantify arginine, ADMA, l-NMMA and SDMA. Our assay requires 12 μL of plasma and is ideal for applications where sample availability is limited. We extracted arginine and methylarginines with mixed-mode cation-exchange columns, using synthetic monoethyl-l-arginine as an internal standard. Metabolites were derivatized with ortho-phthaldialdeyhde and 3-mercaptopropionic acid, separated by reverse-phase HPLC and quantified with fluorescence detection. Standard curve linearity was ≥0.9995 for all metabolites. Inter-day coefficient of variation (CV) values were ≤5% for arginine, ADMA and SDMA in human plasma and for arginine and ADMA in mouse plasma. The CV value for l-NMMA was higher in human (10.4%) and mouse (15.8%) plasma because concentrations were substantially lower than ADMA and SDMA. This assay provides unique advantages of small sample volume requirements, excellent separation of target metabolites from contaminants and validation for both human and mouse plasma samples.

Association of circulating angiogenesis inhibitors and asymmetric dimethyl arginine with coronary plaque burden

BACKGROUND

Chronic kidney disease (CKD) is an independent risk factor for the development and severity of coronary artery disease (CHD) and endothelial dysfunction. There is an increase in the circulating angiogenesis inhibitors endostatin (END), thrombospondin-2 (TSP), angiopoietin-2 (ANG) and the nitric oxide (NO) inhibitor asymmetric dimethyl arginine (ADMA) in CKD patients. The aim of this study was to evaluate associations of the serum level of these factors and of the related angiogenesis inhibitor, endoglin (ENG), with burden of coronary atherosclerosis.

METHODS

One hundred twenty-two patients undergoing coronary angiography were recruited from the cardiac catheterization lab at a single center. The total burden of coronary plaque (mm(2)) and the presence of coronary collaterals were quantified using quantitative coronary angiography (QCA). Serum levels of angiogenesis inhibitors were measured by ELISA (ENG, END, and ANG), Luminex assay (TSP), or HLPC (ADMA), respectively. Associations with plaque burden and coronary collateral supply were analyzed in multi-variable linear and logistic regression models.

RESULTS

There was no significant association found between levels of circulating ADMA, ENG, END, ANG, or TSP and coronary plaque burden or collateral formation.

CONCLUSIONS

Our findings suggest that associations of circulating END, ENG, TSP, and ANG with cardiovascular mortality are unlikely to be mediated via direct effects on coronary plaque formation or by inhibition of collateral formation. Whether associations of these factors with mortality are mediated via local concentrations, myocardial tissue, or intra-plaque expression of these factors or by an effect on plaque vulnerability merits additional investigation.

Atrial Fibrillation Is Associated with a Marker of Endothelial Function and Oxidative Stress in Patients with Acute Myocardial Infarction

Background

Atrial fibrillation (AF), whether silent or symptomatic, is a frequent and severe complication of acute myocardial infarction (AMI). Asymmetric dimethylarginine (ADMA), an endogenous eNOS inhibitor, is a risk factor for endothelial dysfunction. We addressed the relationship between ADMA plasma levels and AF occurrence in AMI.

Methods

273 patients hospitalized for AMI were included. Continuous electrocardiographic monitoring (CEM) ≥48 hours was recorded and ADMA was measured by High Performance Liquid Chromatography on admission blood sample.

Results

The incidence of silent and symptomatic AF was 39(14%) and 29 (11%), respectively. AF patients were markedly older than patients without AF (≈ 20 y). There was a trend towards higher ADMA levels in patients with symptomatic AF than in patients with silent AF or no AF (0.53 vs 0.49 and 0.49 μmol/L, respectively, p = 0.18,). After matching on age, we found that patients with symptomatic AF had a higher heart rate on admission and a higher rate of patients with LV dysfunction (28% vs. 3%, p = 0.025). Patients who developed symptomatic AF had a higher ADMA level than patients without AF (0.53 vs. 0.43 μmol/L; p = 0.001). Multivariate logistic regression analysis to estimate symptomatic AF occurrence showed that ADMA was independently associated with symptomatic AF (OR: 2.46 [1.21–5.00], p = 0.013) beyond history of AF, LVEF<40% and elevated HR.

Conclusion

We show that high ADMA level is associated with the occurrence of AF. Although no causative role can be concluded from our observational study, our work further supports the hypothesis that endothelial dysfunction is involved in the pathogenesis of AF in AMI.

Asymmetric dimethylarginine, a biomarker of cardiovascular complications in diabetes mellitus

Cardiovascular (CV) complications are an essential causal element of prospect in diabetes mellitus (DM), with carotid atherosclerosis being a common risk factor for prospective crisis of coronary artery diseases and/or cerebral infarction in DM subjects. From another point of view, asymmetric dimethylarginine (ADMA) has been established as an inhibitor of endogenous nitric oxide synthesis and the relationship between ADMA and arteriosclerosis has been reported. In our study with 87 type 2 DM (T2DM) patients, we have examined whether ADMA and other CV risk factors are the useful predictors of DMCV complications. After the measurement of the respective CV risk factors, we have followed the enrolled T2DM patients for 5 years. We have finally analyzed 77 patients. DMCV complications developed in 15 cases newly within 5 years, and 4 cases recurred. The concentrations of ADMA in plasma were markedly more elevated in 19 DM patients with CV complications than in 58 DM patients without CV complications. Urinary albumin (U-Alb), mean intimal-medial thickness (IMT) and ankle brachial index (ABI) were also higher in patients with CV complications. Multiple regression analyses showed that U-Alb had an influence on the high level of ADMA (standardized β = 6.59, P = 0.00014) independently of age, systolic BP, fibrinogen, mean IMT, plaque score, and ABI. The review indicates what is presently known regarding plasma ADMA that might be a new and meaningful biomarker of CV complications in DM subjects.

Dimethylarginine dimethylaminohydrolase 2 regulates nitric oxide synthesis and hemodynamics and determines outcome in polymicrobial sepsis

OBJECTIVE

Nitric oxide is a key to numerous physiological and pathophysiological processes. Nitric oxide production is regulated endogenously by 2 methylarginines, asymmetric dimethylarginine (ADMA) and monomethyl-L-arginine. The enzyme that specifically metabolizes asymmetric dimethylarginine and monomethyl-L-arginine is dimethylarginine dimethylaminohydrolase (DDAH). The first isoform dimethylarginine dimethylaminohydrolase 1 has previously been shown to be an important regulator of methylarginines in both health and disease. This study explores for the first time the role of endogenous dimethylarginine dimethylaminohydrolase 2 in regulating cardiovascular physiology and also determines the functional impact of dimethylarginine dimethylaminohydrolase 2 deletion on outcome and immune function in sepsis.

APPROACH AND RESULTS

Mice, globally deficient in Ddah2, were compared with their wild-type littermates to determine the physiological role of Ddah2 using in vivo and ex vivo assessments of vascular function. We show that global knockout of Ddah2 results in elevated blood pressure during periods of activity (mean [SEM], 118.5 [1.3] versus 112.7 [1.1] mm Hg; P=0.025) and changes in vascular responsiveness mediated by changes in methylarginine concentration, mean myocardial tissue asymmetric dimethylarginine (SEM) was 0.89 (0.06) versus 0.67 (0.05) μmol/L (P=0.02) and systemic nitric oxide concentrations. In a model of severe polymicrobial sepsis, Ddah2 knockout affects outcome (120-hour survival was 12% in Ddah2 knockouts versus 53% in wild-type animals; P<0.001). Monocyte-specific deletion of Ddah2 results in a similar pattern of increased severity to that seen in globally deficient animals.

CONCLUSIONS

Ddah2 has a regulatory role both in normal physiology and in determining outcome of severe polymicrobial sepsis. Elucidation of this role identifies a mechanism for the observed relationship between Ddah2 polymorphisms, cardiovascular disease, and outcome in sepsis.

Proton pump inhibitors and vascular function: A prospective cross-over pilot study

Proton pump inhibitors (PPIs) are commonly used drugs for the treatment of gastric reflux. Recent retrospective cohorts and large database studies have raised concern that the use of PPIs is associated with increased cardiovascular (CV) risk. However, there is no prospective clinical study evaluating whether the use of PPIs directly causes CV harm. We conducted a controlled, open-label, cross-over pilot study among 21 adults aged 18 and older who are healthy (n=11) or have established clinical cardiovascular disease (n=10). Study subjects were assigned to receive a PPI (Prevacid; 30 mg) or a placebo pill once daily for 4 weeks. After a 2-week washout period, participants were crossed over to receive the alternate treatment for the ensuing 4 weeks. Subjects underwent evaluation of vascular function (by the EndoPAT technique) and had plasma levels of asymmetric dimethylarginine (ADMA, an endogenous inhibitor of endothelial function previously implicated in PPI-mediated risk) measured prior to and after each treatment interval. We observed a marginal inverse correlation between the EndoPAT score and plasma levels of ADMA (r = -0.364). Subjects experienced a greater worsening in plasma ADMA levels while on PPI than on placebo, and this trend was more pronounced amongst those subjects with a history of vascular disease. However, these trends did not reach statistical significance, and PPI use was also not associated with an impairment in flow-mediated vasodilation during the course of this study. In conclusion, in this open-label, cross-over pilot study conducted among healthy subjects and coronary disease patients, PPI use did not significantly influence vascular endothelial function. Larger, long-term and blinded trials are needed to mechanistically explain the correlation between PPI use and adverse clinical outcomes, which has recently been reported in retrospective cohort studies.

Immunomodulatory and antioxidant function of albumin stabilises the endothelium and improves survival in a rodent model of chronic liver failure

BACKGROUND & AIMS

Liver failure is characterized by endothelial dysfunction, which results in hemodynamic disturbances leading to renal failure. Albumin infusion improves hemodynamics and prevents renal dysfunction in advance liver failure. These effects are only partly explained by the oncotic properties of albumin. This study was designed to test the hypothesis that albumin exerts its beneficial effects by stabilising endothelial function.

METHODS

In vivo: systemic hemodynamics, renal function, markers of endothelial dysfunction (ADMA) and inflammation were studied in analbuminaemic and Sprague-Dawley rats, 6-weeks after sham/bile duct ligation surgery. In vitro: human umbilical vein endothelial cells were stimulated with LPS with or without albumin. We studied protein expression and gene expression of adhesion molecules, intracellular reactive oxygen species, and cell stress markers.

RESULTS

Compared to controls, analbuminaemic rats had significantly greater hemodynamic deterioration after bile duct ligation, resulting in worse renal function and shorter survival. This was associated with significantly greater plasma renin activity, worse endothelial function, and disturbed inflammatory response. In vitro studies showed that albumin was actively taken up by endothelial cells. Incubation of albumin pre-treated endothelial cells with LPS was associated with significantly less activation compared with untreated cells, decreased intracellular reactive oxygen species, and markers of cell stress.

CONCLUSIONS

These results show, for the first time, that absence of albumin is characterised by worse systemic hemodynamics, renal function and higher mortality in a rodent model of chronic liver failure and illustrates the important non-oncotic properties of albumin in protecting against endothelial dysfunction.

Influence of immune activation and inflammatory response on cardiovascular risk associated with the human immunodeficiency virus

Patients infected with the human immunodeficiency virus (HIV) have an increased cardiovascular risk. Although initially this increased risk was attributed to metabolic alterations associated with antiretroviral treatment, in recent years, the attention has been focused on the HIV disease itself. Inflammation, immune system activation, and endothelial dysfunction facilitated by HIV infection have been identified as key factors in the development and progression of atherosclerosis. In this review, we describe the epidemiology and pathogenesis of cardiovascular disease in patients with HIV infection and summarize the latest knowledge on the relationship between traditional and novel inflammatory, immune activation, and endothelial dysfunction biomarkers on the cardiovascular risk associated with HIV infection.

Cumulative inflammation associates with asymmetric dimethylarginine in rheumatoid arthritis: a 6 year follow-up study

OBJECTIVE

The aim of the present study was to investigate the associations of cumulative inflammatory burden (assessed by serial measurements of inflammatory markers) and classical cardiovascular disease (CVD) risk factors with asymmetric dimethylarginine (ADMA) in a large prospective cohort of patients with established RA.

METHODS

Two hundred and one RA patients [155 females, median age 67 years (range 59-73)] were assessed at baseline (2006) for the presence of classical CVD risk factors and determination of systemic inflammation by CRP and ESR. Global CVD risk was identified by the Framingham Risk Score and the Reynolds Risk Score. At follow-up (2012), ADMA levels were measured by ELISA. A quarterly measurement of CRP and ESR for each year the patient was in the study was used to produce an average area under the curve (AAUC) for ESR and CRP.

RESULTS

Regression analysis revealed that baseline ESR in 2006 and the AAUC of ESR and CRP all had significant positive relationships with current ADMA (P = 0.004, P < 0.001 and P = 0.002, respectively). Baseline CRP in 2006 was not a significant predictor of ADMA (P = 0.093), although this relationship was in the same direction as the other factors. These results remained consistent after adjustment for classical CVD risk factors.

CONCLUSION

Cumulative inflammatory burden is positively associated with ADMA levels, suggesting a potential pathogenic mechanism through which chronic systemic inflammation exerts deleterious effects on nitric oxide metabolism and endothelial homeostasis. This association is independent of classical CVD risk factors.

Changes in ADMA/DDAH pathway after hepatic ischemia/reperfusion injury in rats: the role of bile

We investigated the effects of hepatic ischemia/reperfusion (I/R) injury on asymmetric dimethylarginine (ADMA, a nitric oxide synthase inhibitor), protein methyltransferase (PRMT) and dimethylarginine dimethylaminohydrolase (DDAH) (involved, resp., in ADMA synthesis and degradation), and the cationic transporter (CAT). Male Wistar rats were subjected to 30 or 60 min hepatic ischemia followed by 60 min reperfusion. ADMA levels in serum and bile were determined. Tissue ADMA, DDAH activity, DDAH-1 and CAT-2 protein, DDAH-1 and PRMT-1 mRNA expression, GSH/GSSG, ROS production, and lipid peroxidation were detected. ADMA was found in bile. I/R increased serum and bile ADMA levels while an intracellular decrease was detected after 60 min ischemia. Decreased DDAH activity, mRNA, and protein expression were observed at the end of reperfusion. No significant difference was observed in GSH/GSSG, ROS, lipid peroxidation, and CAT-2; a decrease in PRMT-1 mRNA expression was found after I/R. Liver is responsible for the biliary excretion of ADMA, as documented here for the first time, and I/R injury is associated with an oxidative stress-independent alteration in DDAH activity. These data are a step forward in the understanding of the pathways that regulate serum, tissue, and biliary levels of ADMA in which DDAH enzyme plays a crucial role.

Ratio Of Serum Asymmetric Dimethyl Arginine (ADMA)/ Nitric Oxide in Coronary Artery Disease patients

BACKGROUND

Coronary artery disease (CAD) is the leading cause of mortality and morbidity in the world. Current predictions estimate that by the year 2020 cardiovascular diseases, notably atherosclerosis will become the leading global cause of the total disease burden. Atherosclerosis of the Coronary artery causes myocardial infarction and angina pectoris. Endothelial Nitric oxide (NO), released by the intact and healthy endothelium plays a very important role in the maintenance of vascular tone and structure. Decreased NO level leads to endothelial dysfunction is an initial event in the atherosclerosis. Endogenous Asymmetric dimethylarginine (ADMA) is a structural analog of L-arginine, competitively inhibits the enzyme NO synthase and thus decreases the NO level.

AIM

To study the ratio of serum ADMA / NO as a marker of severity of CAD.

MATERIALS AND METHODS

The study comprises of 60 patients of CAD diagnosed by coronary angiography. We divided them into two Groups according to percentage of atherosclerotic block, Group A (71% and more block, n=30) and Group B (40% - 70% block, n=30). We measured serum ADMA, serum NO and calculated ADMA/ NO ratio. RESULTS were compared with 30 healthy age and sex matched controls. Serum ADMA was determined by reverse phase high performance liquid chromatography. Serum NO was measured by cadmium reduction method. Statistical analysis of data analysis was done using the SPSS (Statistical Package for the Social Science) Version 11 for window.

RESULTS

Serum ADMA was correlated positively with the presence and severity of CAD and inversely related with the serum NO levels. Serum ADMA / NO ratio was statistically significant in CAD patients with atherosclerotic block 71% and above (Group A) but ratio was not significant in Group B (block 40% - 70%).

CONCLUSION

Serum ADMA/ NO ratio can be the better predictive marker for the severity of the CAD where patient is at the risk of angina pectoris or myocardial infarction due to the extent of coronary atherosclerotic block than individual serum ADMA levels .

Role of alanine:glyoxylate aminotransferase 2 in metabolism of asymmetric dimethylarginine in the settings of asymmetric dimethylarginine overload and bilateral nephrectomy

BACKGROUND

Asymmetric and symmetric dimethylarginines (ADMA and SDMA) predict complications and mortality in cardiovascular and renal diseases. Alanine:glyoxylate aminotransferase 2 (AGXT2) can metabolize both ADMA and SDMA; however, this metabolic pathway is still poorly understood. The goal of our study was to test the hypothesis that AGXT2 is compensatory upregulated in the settings of ADMA overload and bilateral nephrectomy.

METHODS

ADMA was infused for 3 days using osmotic minipumps in mice. Half of the mice underwent bilateral nephrectomy 24 h before the end of the infusion.

RESULTS

Infusion of ADMA caused a 3- to 4-fold increase in plasma and urine ADMA levels and a 2- to 3-fold increase in plasma and urine levels of the ADMA-specific metabolite of AGXT2 α-keto-δ-(N,N-dimethylguanidino)valeric acid (DMGV). Bilateral nephrectomy led to an ∼4-fold increase of plasma SDMA levels, but did not change plasma ADMA levels. Interestingly, plasma levels of DMGV were elevated 32-fold in the mice, which underwent bilateral nephrectomy. Neither bilateral nephrectomy nor ADMA infusion caused upregulation of AGXT2 expression or activity.

CONCLUSIONS

Our data demonstrate that short-term elevation of systemic levels of ADMA leads to a dramatic increase of DMGV formation without upregulation of AGXT2 expression or activity, which suggests that AGXT2-mediated pathway of ADMA metabolism is not saturated under normal conditions and may play a major role in the maintenance of ADMA homeostasis in the setting of local or systemic elevation of ADMA levels.

Disparate effects of anti-TNF-α therapies on measures of disease activity and mediators of endothelial damage in ankylosing spondylitis

BACKGROUND

Asymmetric dimethylarginine (ADMA) is associated with endothelial injury. Increased ADMA levels are found in rheumatoid arthritis (RA) and ankylosing spondylitis (AS). We set out to assess the ADMA and symmetric dimethylarginine (SDMA) levels in AS, RA, and healthy controls, and in the anti-TNF treated patients with active AS.

METHODS

In 78AS patients and 29 RA patients who were anti-TNF treatment naive at baseline, along with 23 healthy control subjects, we assessed erythrocyte sedimentation rate (ESR), high-sensitivity C-reactive protein (hsCRP), ADMA, and SDMA. For AS patients, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), back pain VAS and patient's global activity of disease were calculated. After 6 months, we repeated the assessment in 30 out of the 78 AS patients in whom the anti-TNF treatment was initiated.

RESULTS

The baseline mean (SD) plasma ADMA concentration of AS patients was 0.64 (0.19) μmol/l and did not differ from controls (0.65 [0.19] μmol/l, p > 0.05). In the RA group, ADMA concentration was higher than in controls (0.77 vs. 0.65 μmol/l, p < 0.05). Both at baseline and at follow-up, ADMA levels correlated positively with BASDAI (R = 0.52, p = 0.02, and R = 0.47, p = 0.04, baseline and follow-up, respectively). Six months of anti-TNF treatment did not influence ADMA concentration (0.51 [0.12] vs. 0.51 [0.11] μmol/l, p = 0.70).

CONCLUSION

An absence of changes in plasma ADMA levels in the anti-TNF treated AS group despite the improvement in disease activity (BASDAI) and inflammation (ESR, CRP) may suggest either a lack of effect, or, even if such an effect were to take place, it needs not imply measurable changes in blood ADMA.