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Background: Asymmetric dimethylarginine (ADMA) is associated with increased mortality in patients with chronic heart failure but it remains unclear if the etiology of heart failure influences the prognostic value of dimethylarginines.Methods and Results: L-Arginine, ADMA, and symmetric dimethylarginine (SDMA) were measured by liquid chromatography-tandem mass spectrometry in 341 patients with chronic heart failure due to dilated cardiomyopathy (DCM; n = 226) or ischemic cardiomyopathy (ICM; n = 115). Median (interquartile range [IQR]) ADMA and SDMA plasma levels were higher, L-arginine and the L-arginine-ADMA ratio were lower in patients with severe forms of heart failure (New York Heart Association (NYHA) functional class III or IV) compared with milder forms (NYHA functional class I or II) (ADMA 0.57 (0.14) μmol/L vs 0.54 (0.12) μmol/L [P < .001]; SDMA 0.47 (0.27) μmol/L vs 0.37 (0.13) μmol/L [P < .001]; L-arginine 81.8 (39.1) μmol/L vs 92.6 (39.3) μmol/L [P < .01]), but no significant differences were observed between the different etiologies. The L-arginine-ADMA ratio was associated with outcome only in patients with DCM. In multivariate analysis, the mortality risk of DCM patients was significantly lower for those in the highest quartile compared with the lowest quartile during a median observation time of 3.3 years (hazard ratio 0.31, 95% CI 0.11-0.88; P = .028, adjusted for other risk factors).Conclusions: DCM patients with unfavourable L-arginine-ADMA ratio are at increased risk for death. [ABSTRACT FROM AUTHOR]

Abstract 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.

Fetal undernutrition predisposes to hypertension development. Since nitric oxide (NO) is a key factor in blood pressure control, we aimed to investigate the role of NO alterations in hypertension induced by fetal undernutrition in rats. Male and female offspring from dams exposed to undernutrition during the second half of gestation (MUN) were studied at 21 days (normotensive) and 6 months of age (hypertension developed only in males). In aorta, we analyzed total and phosphorylated endothelial NO synthase (eNOS, p-eNOS), 3-nitrotyrosine (3-NT), and Nrf2 (Western blot). In plasma we assessed L-arginine, asymmetric and symmetric dimethylarginine (ADMA, SDMA; LC-MS/MS), nitrates (NOx, Griess reaction), carbonyl groups, and lipid peroxidation (spectrophotometry). In iliac arteries, we studied superoxide anion production (DHE staining, confocal microscopy) and vasodilatation to acetylcholine (isometric tension). Twenty-one-day-old MUN offspring did not show alterations in vascular e-NOS or 3NT expression, plasma L-Arg/ADMA ratio, or NOx. Compared to control group, 6-month-old MUN rats showed increased aortic expression of p-eNOS/eNOS and 3-NT, being Nrf2 expression lower, elevated plasma L-arginine/ADMA, NOx and carbonyl levels, increased iliac artery DHE staining and reduced acetylcholine-mediated relaxations. These alterations in MUN rats were sex-dependent, affecting males. However, females showed some signs of endothelial dysfunction. We conclude that increased NO production in the context of a pro-oxidative environment, leads to vascular nitrosative damage and dysfunction, which can participate in hypertension development in MUN males. Females show a better adaptation, but signs of endothelial dysfunction, which can explain hypertension in ageing., (© 2023. The Author(s).)

Male fetal sex associates with higher rates of materno-fetal complications. Inflammation and inadequate vasoactive responses are mechanisms implicated in obstetric complications, and alterations in maternal plasma cytokine profile and nitric oxide (NO) metabolites are potential predictive biomarkers. We aimed to assess if these parameters are influenced by fetal sex. A prospective, observational study was carried out in 85 healthy pregnant women with singleton pregnancies in the first trimester of gestation. A blood sample was extracted at the tenth week of gestation. In plasma, we assessed: 1) cytokines (micro-array): pro-inflammatory (IL1α, IL1 β, IL6, TNFα), anti-inflammatory (IL4, IL10, IL13), and chemoattractant (IL8, MCP1, IFNγ), and 2) NO metabolites (liquid chromatography-tandem mass spectrometry and Griess reaction): L-arginine, ADMA, SDMA, nitrates (NOx). Women with a male fetus (n = 50) exhibited, compared with those with a female (n = 35): higher IL1β (OR = 1.09 with 95% CI: 0.97-1.28), and lower IL13 (OR = 0.93 with 95% CI: 0.87-0.99), and higher plasma NOx (OR = 1.14 with 95% CI: 1.03-1.31). Our data suggest that fetal sex influences maternal plasma cytokine profile and NO in early pregnancy. Women with a male fetus may have a worse capacity to counteract an inflammatory response. They may have better vasodilator capacity, but in the presence of an oxidative environment, a higher nitrosative damage may occur. These data reinforce the need to include sex as variable in predictive models., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Objective: Chronic hypoxia causes pulmonary vasoconstriction leading to pulmonary hypertension and right ventricular hypertrophy. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthesis; its level increases in hypoxia (HX) concomitantly with reduced activity of dimethylarginine dimethylaminohydrolases (DDAH-1 and DDAH-2), enzymes metabolizing ADMA. Ddah1 knockout (KO) mice may therefore help to understand the pathophysiological roles of this enzyme and its substrate, ADMA, in the development of hypoxia-associated pulmonary hypertension. Methods: Ddah1 KO mice and their wild-type (WT) littermates were subjected to normoxia (NX) or for 21 days. We measured ADMA concentration in plasma and lungs, DDAH1 and DDAH2 mRNA and protein expression in the lungs, right ventricular systolic pressure (RVSP), right ventricular hypertrophy by the Fulton index, and cardiomyocyte hypertrophy by dystrophin staining of the heart. Results: Ddah1 KO mice had higher ADMA concentrations in plasma and in lung tissue than WT in NX ( p < 0.05). ADMA significantly increased in WT-HX in plasma and lungs, while there were no significant differences in WT-HX vs. KO-HX. This finding was paralleled by a 38 ± 13% reduction in Ddah1 but not Ddah2 mRNA expression, and reduced DDAH1 protein expression but stable DDAH2 protein levels in WT mice. Ddah1 KO mice showed significant elevation of DDAH2 protein but not mRNA levels, which further increased in HX. HX led to increased RVSP and right ventricular hypertrophy in both, WT and KO mice, with no significant differences between both genotypes. Conclusions: Chronic hypoxia causes an elevation of ADMA, which may impair NO production and lead to endothelial dysfunction and vasoconstriction. Downregulation of DDAH1 expression and activity may be involved in this; however, knockout of the Ddah1 gene does not modify the hypoxia-induced pathophysiological changes of pulmonary blood pressure and right ventricular hypertrophy, possibly due to compensatory upregulation of DDAH2 protein., (Copyright © 2020 Hannemann, Glatzel, Hillig, Zummack, Schumacher, Lüneburg, Harbaum and Böger.)

Our group previously demonstrated that dronedarone induces regression of left ventricular hypertrophy in spontaneously hypertensive rats (SHRs). We assessed changes in vascular remodeling and oxidative stress following short-term use of this agent. The coronary artery was isolated from 10-month-old male SHRs treated with 100 mg kg -1 dronedarone once daily for 14 days (SHR-D group), and age-matched untreated SHRs were used as hypertensive controls. We analyzed the geometry and composition of the artery and constructed dose-response curves for acetylcholine and serotonin (5-HT). We calculated a global score (OXY-SCORE) from plasma biomarkers of oxidative status: carbonyl levels, thiol levels, reduced glutathione levels, total antioxidant capacity, and superoxide anion scavenging activity. Finally, we analyzed asymmetric dimethylarginine (ADMA) concentrations in plasma. Dronedarone significantly decreased wall thickness (medial and adventitial layer thickness and cell count) and the cross-sectional area of the artery. Dronedarone significantly improved endothelium-dependent relaxation and reduced the contraction induced by 5-HT. The OXY-SCORE was negative in the SHR model group (suggesting an enhanced oxidative status) and was positive in the SHR-D group (suggesting enhanced antioxidant defense). Dronedarone significantly decreased the concentrations of ADMA. We conclude that dronedarone improves coronary artery remodeling in SHRs. The better global antioxidant status after treatment with dronedarone and decreased plasma ADMA levels could contribute to the cardiovascular protective effect of dronedarone.

Dysfunction of the pulmonary endothelium is associated with most lung diseases. Extracellular nucleotides modulate a plethora of endothelial functions in the lung such as vessel integrity, vasodilatation, inflammatory, and thrombotic responses as well as survival and DNA repair, mostly via Ca 2+ signaling pathways. However, a comprehensive analysis of the molecular components of the underlying P2 receptor-mediated Ca 2+ signaling pathways in the lung has not been conducted so far. Therefore, our aim was to identify the principal P2 receptor Ca 2+ signalosome in the human pulmonary endothelium and investigate potential dysregulation in pulmonary vascular disease. Comparative transcriptomics and quantitative immunohistochemistry were performed on publicly available RNA sequencing and protein datasets to identify the specific expression profile of the P2-receptor Ca 2+ signalosome in the healthy human pulmonary endothelium and endothelial cells (EC) dysfunctional due to loss of or defective bone morphogenetic protein receptor (BMPR2). Functional expression of signalosome components was tested by single cell Ca 2+ imaging. Comparative transcriptome analysis of 11 endothelial cell subtypes revealed a specific P2 receptor Ca 2+ signalosome signature for the pulmonary endothelium. Pulmonary endothelial expression of the most abundantly expressed Ca 2+ toolkit genes CALM1, CALM2, VDAC1, and GNAS was confirmed by immunohistochemistry (IHC). P2RX1, P2RX4, P2RY6, and P2YR11 showed strong lung endothelial staining by IHC, P2X5, and P2Y1 were found to a much lesser extent. Very weak or no signals were detected for all other P2 receptors. Stimulation of human pulmonary artery (HPA) EC by purine nucleotides ATP, ADP, and AMP led to robust intracellular Ca 2+ signals mediated through both P2X and P2Y receptors. Pyrimidine UTP and UDP-mediated Ca 2+ signals were generated almost exclusively by activation of P2Y receptors. HPAEC made dysfunctional by siRNA-mediated BMPR2 depletion showed downregulation of 18 and upregulation of 19 P2 receptor Ca 2+ signalosome genes including PLCD4, which was found to be upregulated in iPSC-EC from BMPR2-mutant patients with pulmonary arterial hypertension. In conclusion, the human pulmonary endothelium expresses a distinct functional subset of the P2 receptor Ca 2+ signalosome. Composition of the P2 receptor Ca 2+ toolkit in the pulmonary endothelium is susceptible to genetic disturbances likely contributing to an unfavorable pulmonary disease phenotype found in pulmonary arterial hypertension.

Background and Aims: Dronedarone is a new multichannel-blocking antiarrhythmic for the treatment of patients with atrial fibrillation. Our group has demonstrated that dronedarone produces regression of cardiac remodeling; however, its effect on the remodeling of the elastic arteries has not yet been reported. We aim to assess the effects of dronedarone on the regression of thoracic aortic remodeling in spontaneously hypertensive rats (SHRs)., Method: Ten-month-old male SHRs were randomly assigned to an intervention group (SHR-D), where the animals received dronedarone treatment (100 mg/kg), to a control group (SHR) where rats were given vehicle, or to a group (SHR-A) where they were given amiodarone. A fourth group of normotensive control rats (Wistar-Kyoto rats, WKY) was also added. After two weeks of treatment, we studied the structure, the elastic fiber content of the thoracic aorta using histological techniques and confocal microscopy, and the vascular mechanical properties using an organ bath and isometric tension analysis. A mass spectrometric determination of symmetric dimethylarginine (SDMA) concentrations was performed., Results: SHR group developed the classic remodeling expected from the experimental model: outward hypertrophic remodeling, increased elastic fiber content and wall stiffness. However, the SHR-D group showed statistically significantly lower values for aortic tunica media thickness, wall to lumen ratio, external diameter, cross-sectional area, volume density of the elastic fibers, wall stiffness, and aortic SDMA concentration when compared to the SHR group. These parameters were similar in the SHR and SHR-A groups. Interestingly, the values for tunica media thickness, volume density of the elastic fibers, wall stiffness, and SDMA concentration obtained from the SHR-D group were similar to those measured in the WKY group., Conclusion: These results suggest that dronedarone improves the structure and passive mechanical properties of the thoracic aorta in hypertensive rats, and that this protective effect could be associated with a reduction in the concentration of aortic SDMA., Competing Interests: The authors have declared that no competing interests exist.

Introduction: Guanidino compounds, including l-homoarginine (l-hArg), symmetric dimethylarginine (SDMA), asymmetric dimethylarginine (ADMA) and l-arginine (l-Arg) are associated with mortality, fatal strokes, stroke incidence, and atherosclerosis., Objectives: We aimed to study the association of guanidino compounds (l-hArg/ADMA and l-hArg/SDMA) with stroke etiology, internal carotid artery (ICA) stenosis and CHA 2 DS 2 -VASc score in patients with cerebrovascular disease., Methods: We analyzed l-hArg, SDMA, ADMA, l-Arg, and compound molar ratios, i.e. l-hArg/ADMA and l-hArg/SDMA, in 272 patients with cerebrovascular disease in a cross-sectional discovery cohort and two cross-sectional validation cohorts of acute stroke patients from Germany (n = 137) and UK (n = 394). The guanidino compound levels were compared with clinical, imaging, and ultrasound parameters., Results: Low l-hArg/ADMA and l-hArg/SDMA molar ratios predicted territorial infarcts (OR 1.74; 95% CI 1.34-2.26 and OR 1.64; 95% CI 1.26-2.15, respectively) and were associated with stroke subtypes due to large vessel disease or cardio-embolism (OR 1.52; 95% CI 1.12-2.06 and OR 2.01; 95% CI 1.35-3.00, respectively) in meta-analysis of the discovery and validation cohort data. In line with these results, a low l-hArg/ADMA and l-hArg/SDMA molar ratio was found in patients with ICA stenosis (OR 0.73; 95% CI 0.55-0.97 and OR 0.69; 95% CI 0.50-0.94, respectively) in the discovery and validation cohort. Furthermore, guanidino compound ratios (i.e. l-hArg/ADMA and l-hArg/SDMA) were strongly correlated with CHA 2 DS 2 -VASC score (p < .001) in all three cohorts., Discussion: The results from these three cross-sectional studies reveal that guanidino compound ratios (i.e. l-hArg/ADMA and l-hArg/SDMA) can discriminate stroke etiologies, predict ICA stenosis and estimate risk prediction in patients with cerebrovascular disease., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The steady increase in the number of patients equipped with mechanical heart support implants, such as left ventricular assist devices (LVAD), along with virtually ubiquitous 24/7 internet connectivity coverage is motive to investigate and develop remote patient monitoring. In this study we explore machine learning approaches to infection severity recognition on driveline exit site images. We apply a U-net convolutional neural network (CNN) for driveline tube segmentation, resulting in a Dice score coefficient of 0.95. A classification CNN is trained to predict the membership of one out of three infection classes in photographs. The resulting accuracy of 67% in total is close to the measured expert level performance, which indicates that also for human experts there may not be enough information present in the photographs for accurate assessment. We suggest the inclusion of thermographic image data in order to better resolve mild and severe infections.

Background: Living at high altitude or with chronic hypoxia implies functional and morphological changes in the right ventricle and pulmonary vasculature with a 10% prevalence of high-altitude pulmonary hypertension (HAPH). The implications of working intermittently (day shifts) at high altitude (hypobaric hypoxia) over the long term are still not well-defined. The aim of this study was to evaluate the right cardiac circuit status along with potentially contributory metabolic variables and distinctive responses after long exposure to the latter condition. Methods: A cross-sectional study of 120 healthy miners working at an altitude of 4,400-4,800 m for over 5 years in 7-day commuting shifts was designed. Echocardiography was performed on day 2 at sea level. Additionally, biomedical and biochemical variables, Lake Louise scores (LLSs), sleep disturbances and physiological variables were measured at altitude and at sea level. Results: The population was 41.8 ± 0.7 years old, with an average of 14 ± 0.5 (range 5-29) years spent at altitude. Most subjects still suffered from mild to moderate symptoms of acute mountain sickness (mild was an LLS of 3-5 points, including cephalea; moderate was LLS of 6-10 points) (38.3%) at the end of day 1 of the shift. Echocardiography showed a 23% mean pulmonary artery pressure (mPAP) >25 mmHg, 9% HAPH (≥30 mmHg), 85% mild increase in right ventricle wall thickness (≥5 mm), 64% mild right ventricle dilation, low pulmonary vascular resistance (PVR) and fairly good ventricle performance. Asymmetric dimethylarginine (ADMA) (OR 8.84 (1.18-66.39); p < 0.05) and insulin (OR: 1.11 (1.02-1.20); p < 0.05) were associated with elevated mPAP and were defined as a cut-off. Interestingly, the correspondence analysis identified association patterns of several other variables (metabolic, labor, and biomedical) with higher mPAP. Conclusions: Working intermittently at high altitude involves a distinctive pattern. The most relevant and novel characteristics are a greater prevalence of elevated mPAP and HAPH than previously reported at chronic intermittent hypobaric hypoxia (CIHH), which is accompanied by subsequent morphological characteristics. These findings are associated with cardiometabolic factors (insulin and ADMA). However, the functional repercussions seem to be minor or negligible. This research contributes to our understanding and surveillance of this unique model of chronic intermittent high-altitude exposure.

Lüneburg, Nicole, Patricia Siques, Julio Brito, Juan José De La Cruz, Fabiola León-Velarde, Juliane Hannemann, Cristian Ibanez, and Rainer Böger. Long-term intermittent exposure to high altitude elevates asymmetric dimethylarginine in first exposed young adults. High Alt Med Biol. 18:226-233, 2017.-Hypoxia-induced dysregulation of pulmonary and cerebral circulation may be related to an impaired nitric oxide (NO) pathway. We investigated the effect of chronic intermittent hypobaric hypoxia (CIH) on metabolites of the NO pathway. We measured asymmetric and symmetric dimethylarginine (ADMA and SDMA) and monomethyl-L-arginine (L-NMMA) and assessed their associations with acclimatization in male draftees (n = 72) undergoing CIH shifts at altitude (3550 m) during 3 months. Sixteen Andean natives living at altitude (3675 m) (chronic hypobaric hypoxia [CH]) were included for comparison. In CIH, ADMA and L-NMMA plasma concentrations increased from 1.14 ± 0.04 to 1.95 ± 0.09 μmol/L (mean ± SE) and from 0.22 ± 0.07 to 0.39 ± 0.03 μmol/L, respectively, (p < 0.001 for both) after 3 months, whereas SDMA did not change. The concentrations of ADMA and L-NMMA were higher in CH (3.48 ± 0.07, 0.53 ± 0.08 μmol/L; p < 0.001) as compared with CIH. In both CIH and CH, ADMA correlated with hematocrit (r 2  = 0.07, p < 0.05; r 2  = 0.26; p < 0.01). In CIH, an association of ADMA levels with poor acclimatization status was observed. We conclude that the endogenous NO synthase inhibitors, ADMA and L-NMMA, are elevated in hypoxia. This may contribute to impaired NO production at altitude and may also be predictive of altitude-associated health impairment.

Background: Chronic inflammation emerges as a feature of the pathogenesis of pulmonary arterial hypertension (PAH) in experimental models. Alterations of circulating cell subsets have been observed in patients with PAH. We aimed to assess associations of the white blood cell count with disease severity and outcome in patients with PAH., Methods: The total and differential white blood cell count was related to functional parameters, pulmonary hemodynamics and transplantation-free survival in 77 patients with PAH in an observational single center study., Results: An increased neutrophil/lymphocyte ratio was associated with poor World Health Organization functional class and shorter 6-minute walking distance, as well as with elevated right atrial pressure and high level of N-terminal prohormone of brain natriuretic peptide. During a median follow-up period of 31 months (range 16-56) 23 patients died and 2 patients were referred to lung transplantation. Using uni- and subsequent bivariate Cox proportional hazards analyses an increased neutrophil/lymphocyte ratio was associated with unfavorable transplantation-free survival independent of hemodynamic parameters and C-reactive protein. The prognostic implication sustained in subsets of patients with incident PAH and in the absence of cardiovascular risk factors., Conclusions: The results of this analysis indicate that a neutrophilic inflammation may be associated with clinical deterioration and poor outcome in patients with PAH. Assessing the composition of the differential white blood cell count may render prognostic information and could represent a step towards incorporating an inflammatory marker into the clinical management of patients with PAH.

Esmolol produces early regression of left ventricular hypertrophy and improves coronary artery remodeling, although the impact of short-term treatment with this beta-blocker on remodeling in large arteries has not yet been studied. We hypothesized that even a short (48h) course of esmolol might alter remodeling of the aorta in the spontaneously hypertensive rat (SHR). Fourteen-month-old male SHRs were treated intravenously with vehicle (SHR, n=8) or esmolol (SHR-E, n=8) (300μg/kg/min). Age-matched, vehicle-treated male Wistar-Kyoto rats (WKY, n=8) served as controls. After 48h, we studied the structure, volume density of elastic fibers, and passive mechanical properties of the aorta. Determination of asymmetrical dimethylarginine concentrations and total protein carbonyls in the aorta were analyzed. Esmolol significantly attenuated abnormal aortic wall thickness, cross-sectional area, wall-to-lumen ratio, volume density of elastic fibers, and wall stiffness. The protective effect of esmolol could be related to a decrease in asymmetrical dimethylarginine levels after down-regulation by oxidative stress. These findings could play a key role in the selection of antihypertensive therapy in patients with hypertension and aortic remodeling., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: Exercise training positively influences exercise tolerance and functional capacity of patients with idiopathic pulmonary arterial hypertension (IPAH). However, the underlying mechanisms are unclear. We hypothesized that exercise modulates the activated inflammatory state found in IPAH patients., Methods: Single cardiopulmonary exercise testing was performed in 16 IPAH patients and 10 healthy subjects. Phenotypic characterization of peripheral blood mononuclear cells and circulating cytokines were assessed before, directly after and 1 h after exercise., Results: Before exercise testing, IPAH patients showed elevated Th2 lymphocytes, regulatory T lymphocytes, IL-6, and TNF-alpha, whilst Th1/Th17 lymphocytes and IL-4 were reduced. In IPAH patients but not in healthy subject, exercise caused an immediate relative decrease of Th17 lymphocytes and a sustained reduction of IL-1-beta and IL-6. The higher the decrease of IL-6 the higher was the peak oxygen consumption of IPAH patients., Conclusions: Exercise seems to be safe from an immune and inflammatory point of view in IPAH patients. Our results demonstrate that exercise does not aggravate the inflammatory state and seems to elicit an immune-modulating effect in IPAH patients.

Our preclinical study demonstrated that esmolol produces early regression of left ventricular hypertrophy in arterial hypertension. The aim of this study was to assess the effects of short-term esmolol therapy on the regression of left anterior descending artery remodeling in spontaneously hypertensive rats (SHRs), and to determine whether the asymmetric dimethylarginine (ADMA)/dimethylarginine dimethylaminohydrolase (DDAH) pathway, a regulator of nitric oxide (NO) bioavailability, accounted for this regression. Fourteen-month-old male SHRs were treated intravenously with vehicle (SHR, n=15) or esmolol (SHR-E, n=20) (300 μg kg -1  min -1 ). Age-matched, vehicle-treated male Wistar-Kyoto rats (WKY, n=15) served as controls. SHRs were also treated with nitroglycerin (SHR-N, n=5). After 48 h, the left anterior descending artery structure and morphology were assessed, and dose-response curves for 5-hydroxytryptamine (5-HT, 10 -9 -3 × 10 -5 mol l -1 ) were constructed. ADMA concentrations in plasma and left ventricle and DDAH activity in tissue were analyzed. Wall thickness and cross-sectional area were significantly lower after treatment with esmolol in SHR-E than in SHR. Media thickness and smooth muscle cell count were lower in SHR-E than in SHR. Esmolol induced a significant reduction in adventitial cell count in SHR-E. The area under the concentration-response curves was significantly higher in SHR than in SHR-E, as were the esmolol normalized coronary artery contracting responses to 5-HT. We found significantly lower ADMA levels and significantly higher DDAH activity in the ventricle in SHR-E than in SHR. The protective effect of esmolol on the regression of left anterior descending artery remodeling may be related to the reduction in ADMA levels.

Chronic intermittent hypoxia (CIH) and chronic hypoxia (CH) are associated with high-altitude pulmonary hypertension (HAPH). Asymmetric dimethylarginine (ADMA), a NO synthase (NOS) inhibitor, may contribute to HAPH. This study assessed changes in the ADMA/NO pathway and the underlying mechanisms in rat lungs following exposure to CIH or CH simulated in a hypobaric chamber at 428 Torr. Twenty-four adult Wistar rats were randomly assigned to three groups: CIH2x2 (2 days of hypoxia/2 days of normoxia), CH, and NX (permanent normoxia), for 30 days. All analyses were performed in whole lung tissue. L-Arginine and ADMA were analyzed using LC-MS/MS. Under both hypoxic conditions right ventricular hypertrophy was observed (p < 0.01) and endothelial NOS mRNA increased (p < 0.001), but the phosphorylated/nonphosphorylated vasodilator-stimulated phosphoprotein (VASP) ratio was unchanged. ADMA increased (p < 0.001), whereas dimethylarginine dimethylaminohydrolase (DDAH) activity decreased only under CH (p < 0.05). Although arginase activity increased (p < 0.001) and L-arginine exhibited no changes, the L-arginine/ADMA ratio decreased significantly (p < 0.001). Moreover, NOX4 expression increased only under CH (p < 0.01), but malondialdehyde (MDA) increased (up to 2-fold) equally in CIH2x2 and CH (p < 0.001). Our results suggest that ADMA and oxidative stress likely reduce NO bioavailability under altitude hypoxia, which implies greater pulmonary vascular reactivity and tone, despite the more subdued effects observed under CIH.

Gremlin-1, an intrinsic antagonist of bone morphogenetic protein (BMP) signaling, has been implicated in the pathophysiology of pulmonary arterial hypertension (PAH). However, it is unknown whether gremlin-1 can be detected in the circulation of PAH patients and whether it is associated with patients' functional status and outcome. With a mean level of 242 ± 24 ng/ml, gremlin-1 levels of 31 PAH patients were significantly elevated compared to 151 ± 18 ng/ml in 15 age- and gender-matched healthy subject (p = 0.016). In PAH patients, increasing gremlin-1 levels correlated with N-terminal prohormone of brain natriuretic peptide levels (r = 0.608, p < 0.001) and inversely with the 6-minute walking distance (r = -0.412, p = 0.029). Furthermore, gremlin-1 significantly stratified survival in PAH patients (p = 0.015). Gremlin-1 may represent a new biomarker for PAH which can be linked directly to the underlying pathomechanism. Elevated levels of gremlin-1 are associated with patients' functional status and survival, thus gremlin-1 neutralization could represent a potential therapeutic strategy to increase BMPR2 signaling.

Background: Dimethylarginines (DMA) interfere with nitric oxide formation by inhibiting nitric oxide synthase (asymmetrical DMA [ADMA]) and l-arginine uptake into the cell (ADMA and symmetrical DMA [SDMA]). In prospective clinical studies, ADMA has been characterized as a cardiovascular risk marker, whereas SDMA is a novel marker for renal function and associated with all-cause mortality after ischemic stroke. The aim of the current study was to characterize the environmental and genetic contributions to interindividual variability of these biomarkers., Methods and Results: This study comprised a genome-wide association analysis of 3 well-characterized population-based cohorts (Framingham Heart Study [FHS; n=2992], Gutenberg Health Study [GHS; n=4354], and Multinational Monitoring of Trends and Determinants in Cardiovascular Disease Study [MONICA]/Cooperative Health Research in the Augsburg Area, Augsburg, Bavaria, Germany [KORA] F3 [n=581]) and identified replicated loci (DDAH1, MED23, Arg1, and AGXT2) associated with the interindividual variability in ADMA, l-arginine, and SDMA. Experimental in silico and in vitro studies confirmed functional significance of the identified AGXT2 variants. Clinical outcome analysis in 384 patients of the Leeds stroke study demonstrated an association between increased plasma levels of SDMA, AGXT2 variants, and various cardiometabolic risk factors. AGXT2 variants were not associated with poststroke survival in the Leeds study or were they associated with incident stroke in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium., Conclusions: These genome-wide association study support the importance of DDAH1 and MED23/Arg1 in regulating ADMA and l-arginine metabolism, respectively, and identify a novel regulatory renal pathway for SDMA by AGXT2. AGXT2 variants might explain part of the pathogenic link between SDMA, renal function, and outcome. An association between AGXT2 variants and stroke is unclear and warrants further investigation., (© 2014 American Heart Association, Inc.)

Fibrinogen has a crucial role in both inflammation and coagulation, two processes pivotal for the pathogenesis of pulmonary hypertension. We therefore aimed to investigate whether fibrinogen plasma concentrations a) are elevated in pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) and b) may serve as a novel biomarker for haemodynamic impairment. In a dual-centre, retrospective analysis including 112 patients with PAH (n = 52), CTEPH (n = 49) and a control cohort of patients with suspected PAH ruled out by right heart catheterisation (n = 11), we found fibrinogen plasma concentrations to be increased in patients with PAH (4.1 ± 1.4 g/l) and CTEPH (4.3 ± 1.2 g/l) compared to control patients (3.4 ± 0.5 g/l, p = 0.0035 and p = 0.0004, respectively). In CTEPH patients but not in PAH patients fibrinogen was associated with haemodynamics (p < 0.036) and functional parameters (p < 0.041). Furthermore, fibrinogen was linked to disease severity (WHO functional class, p = 0.017) and independently predicted haemodynamic impairment specifically in CTEPH (p < 0.016). Therefore, fibrinogen seems to represent an important factor in CTEPH pathophysiology and may have the potential to guide clinical diagnosis and therapy.

N-terminal pro-brain natriuretic peptide (NT-proBNP) is a routinely used prognostic parameter in patients with pre-capillary pulmonary hypertension (PH). As it accumulates in the presence of impaired renal function, the clinical utility of NT-proBNP in PH patients with concomitant renal insufficiency remains unclear. In a retrospective approach, patients with pre-capillary PH (group I or IV) and concomitant renal insufficiency at time of right heart catheterization (glomerular filtration rate (GFR) ≤60 ml/min/1.73 m2) were identified out of all prevalent pre-capillary PH patients treated at a single center. Forty patients with renal insufficiency (25.8%) were identified and matched regarding hemodynamic parameters with a control group of 56 PH patients with normal renal function (GFR >60 ml/min/1.73 m2). Correlations of NT-proBNP levels with hemodynamic and prognostic parameters (time to clinical worsening and overall survival) were assessed. Overall, GFR correlated inversely with NT-proBNP and had the strongest influence on NT-proBNP levels in a stepwise multiple linear regression model including hemodynamic parameters and age (r2 = 0.167). PH patients with renal insufficiency had significant higher levels of NT-proBNP (median: 1935 ng/l vs. 573 ng/l, p = 0.001). Nevertheless, NT-proBNP correlated with invasive hemodynamic parameters in these patients. Using higher cut-off values than in patients with preserved renal function, NT-proBNP levels were significantly associated with time to clinical worsening (>1660 ng/l, p = 0.001) and survival (>2212 ng/l, p = 0.047) in patients with renal insufficiency. Multivariate Cox's proportional hazards analysis including established prognostic parameters, age and GFR confirmed NT-proBNP as an independent risk factor for clinical worsening in PH patients with renal insufficiency (hazard ratio 4.8, p = 0.007). Thus, in a retrospective analysis we showed that NT-proBNP levels correlated with hemodynamic parameters and outcome regardless of renal function. By using higher cut-off values, NT-proBNP seems to represent a valid clinical marker even in PH patients with renal insufficiency.

Objective: To investigate determinants of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), including single nucleotide polymorphisms (SNPs), in the DDAH1, DDAH2, and AGXT2 genes and their associations with prevalent and incident cardiovascular disease (CVD) in older adults with type 2 diabetes mellitus., Research Design and Methods: Prevalent CVD was assessed in men and women aged 60-75 years with type 2 diabetes as part of the Edinburgh Type 2 Diabetes Study (ET2DS), and the participants were prospectively followed up for 4 years for incident CVD. Dimethylarginines were measured in 783 of these subjects, and genotyping for tag SNPs in the DDAH1, DDAH2, and AGXT2 genes was performed in 935 subjects., Results: Plasma ADMA levels were significantly associated with SNPs in DDAH1 (top SNP rs1554597; P = 9.0E-09), while SDMA levels were associated with SNPs in AGXT2 (top SNP rs28305; P = 1.3E-04). Significant, independent determinants of plasma ADMA were sex, L-arginine, creatinine, fasting glucose, and rs1554597 (all P < 0.05; combined R(2) = 0.213). Determinants of SDMA were age, sex, creatinine, L-arginine, diabetes duration, prevalent CVD, and rs28305 (all P < 0.05; combined R(2) = 0.425). Neither dimethylarginine was associated with incident CVD. None of the investigated SNPs were associated with overall CVD, although subgroup analysis revealed a significant association of AGXT2 rs28305 with intermittent claudication., Conclusions: Our study in a well-characterized population with type 2 diabetes does not support reported associations or causal relationship between ADMA and features of diabetes or CVD.

Since its discovery, many adhere to the view that asymmetric dimethylarginine (ADMA), as an inhibitor of the synthesis of nitric oxide (NO), contributes to the pathogenesis of various diseases. Particularly, this is evident in disease of the cardiovascular system, in which endothelial dysfunction results in an imbalance between vasoconstriction and vasodilatation. Even if increased ADMA concentrations are closely related to an endothelial dysfunction, several studies pointed to a potential beneficial effect of ADMA, mainly in the context of angioproliferative disease such as cancer and fibrosis. Antiproliferative properties of ADMA independent of NO have been identified in this context. In particular, the regulation of ADMA by its degrading enzyme dimethylarginine dimethylaminohydrolase (DDAH) is the object of many studies. DDAH is discussed as a promising therapeutic target for the indirect regulation of NO. In hypoxia-related chronic respiratory diseases, this controversy discussion of ADMA and DDAH is particularly evident and is therefore subject of this review.

Objective: Increased asymmetrical dimethylarginine (ADMA), a NO synthase inhibitor, and its congener symmetrical dimethylarginine (SDMA), predict cardiovascular and all-cause mortality in at-risk populations. Their prognostic value in the general population remains uncertain. We investigated the correlations of SDMA and ADMA with atherosclerosis and cardiovascular/all-cause mortality in the Dallas Heart Study, a multiethnic probability-based cohort aged 30 to 65 years., Approach and Results: SDMA and ADMA were measured by liquid chromatography-tandem mass-spectrometry (n=3523), coronary artery calcium by electron-beam computed tomography, and abdominal aortic wall thickness by MRI. In unadjusted analyses, categories of increasing SDMA and ADMA were associated with higher prevalence of cardiovascular risk factors, increased risk markers, and all-cause and cardiovascular mortality (median follow-up, 7.4 years). After adjustment for age, sex, and race, traditional cardiovascular risk factors, and renal function, SDMA and ADMA analyzed as continuous variables were associated with coronary artery calcium >10, but only SDMA was associated with abdominal aortic wall thickness. SDMA, but not ADMA, was associated with cardiovascular mortality (hazard ratio per log unit change, 3.36 [95% confidence interval, 1.49-7.59]; P=0.004). SDMA and ADMA were both associated with all-cause mortality, but after further adjustment for N-terminal pro-brain-type natriuretic peptide, high-sensitivity C-reactive protein, and high-sensitivity cardiac troponin T, only SDMA was associated with all-cause mortality (hazard ratio per log unit change, 1.86 [95% confidence interval, 1.04-3.30]; P=0.01)., Conclusions: SDMA, but not ADMA, was an independent predictor of all-cause and cardiovascular mortality in a large multiethnic population-based cohort.

Background: Endogenous arginine homologues, including homoarginine, have been identified as novel biomarkers for cardiovascular disease and outcomes. Our studies of human cohorts and a confirmatory murine model associated the arginine homologue homoarginine and its metabolism with stroke pathology and outcome., Methods and Results: Increasing homoarginine levels were independently associated with a reduction in all-cause mortality in patients with ischemic stroke (7.4 years of follow-up; hazard ratio for 1-SD homoarginine, 0.79 [95% confidence interval, 0.64-0.96]; P=0.019; n=389). Homoarginine was also independently associated with the National Institutes of Health Stroke Scale+age score and 30-day mortality after ischemic stroke (P<0.05; n=137). A genome-wide association study revealed that plasma homoarginine was strongly associated with single nucleotide polymorphisms in the L-arginine:glycine amidinotransferase (AGAT) gene (P<2.1 × 10(-8); n=2806), and increased AGAT expression in a cell model was associated with increased homoarginine. Next, we used 2 genetic murine models to investigate the link between plasma homoarginine and outcome after experimental ischemic stroke: (1) an AGAT deletion (AGAT(-/-)) and (2) a guanidinoacetate N-methyltransferase deletion (GAMT(-/-)) causing AGAT upregulation. As suggested by the genome-wide association study, homoarginine was absent in AGAT(-/-) mice and increased in GAMT(-/-) mice. Cerebral damage and neurological deficits in experimental stroke were increased in AGAT(-/-) mice and attenuated by homoarginine supplementation, whereas infarct size in GAMT(-/-) mice was decreased compared with controls., Conclusions: Low homoarginine appears to be related to poor outcome after ischemic stroke. Further validation in future trials may lead to therapeutic adjustments of homoarginine metabolism that alleviate stroke and other vascular disorders.

Objectives: Asymmetric dimethylarginine (ADMA) is a key regulator of nitric oxide production. Elevations of ADMA have previously been associated with endothelial dysfunction in pre-eclamptic women. ADMA is degraded mainly by dimethylarginine dimethylaminohydrolase (DDAH), which is also expressed in placental tissue. Therefore, we measured placental DDAH expression and activity in pre-eclampsia and normal pregnancies in order to determine whether impairment of this enzyme in the pre-eclamptic placenta could contribute to elevations of ADMA levels in these women., Study Design: ADMA plasma levels were measured by LC-MS/MS in 18 pre-eclamptic patients and 28 controls. Placental DDAH activity was determined by measuring the degradation of [(2)H(6)]-labeled ADMA in tissue homogenates from placental biopsies in 15 women with pre-eclampsia and 16 controls. Placental mRNA expression of DDAH 1, DDAH 2, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and protein-arginine methyltransferase 1 (PRMT1) was determined in tissue biopsies by RT-PCR., Results: Placental DDAH activity was almost undetectable in pre-eclampsia, and it was significantly higher in controls. ADMA plasma levels were higher in pre-eclampsia as compared to normal pregnancies (0.51±0.15μmol/l vs. 0.42±0.07μmol/l; p=0.005), and the difference between maternal and fetal ADMA levels (feto-maternal ADMA gradient) was lower in pre-eclampsia (0.63±0.20μmol/l vs. 0.80±0.18μmol/l; p=0.02). Furthermore, mRNA expression levels of DDAH 2 were significantly lower in pre-eclamptic women (p=0.04), while PRMT1 expression levels were the same. In pre-eclampsia, we found only weak correlations between maternal ADMA levels and DDAH 1 (r=-0.41; p=0.22) and DDAH 2 expressions (r=-0.45; p=0.17) but a slightly stronger correlation between DDAH 2 expression and feto-maternal ADMA gradient (r=0.60; p=0.07)., Conclusion: Decreased DDAH activity in the pre-eclamptic placenta might contribute to elevated ADMA levels in these patients., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Methylarginines have been shown to interfere with NO (nitric oxide) formation by inhibiting NOS (NO synthase)-ADMA (asymmetric dimethylarginine) and cellular L-arginine uptake into the cell [ADMA and SDMA (symmetric dimethylarginine)]. In a recent study, elevation of SDMA was related to long-term mortality in patients recruited 30 days after a stroke event. In the present study, we aimed at investigating the association of SDMA and adverse clinical outcome in the early phase (first 30 days) after acute ischaemic stroke. A total of 137 patients were recruited immediately upon admission to the emergency unit with an acute ischaemic stroke. Plasma levels of methylarginines were determined by a validated LC-MS/MS (liquid chromatography-tandem MS) method. Patients were prospectively followed for 30 days. A total of 25 patients (18.2%) experienced the primary composite endpoint [death, recurrent stroke, MI (myocardial infarction) and rehospitalization]. SDMA plasma levels were significantly higher in stroke patients compared with patients without event (0.89 ± 0.80 compared with 0.51 ± 0.24 μmol/l; P<0.001). SDMA levels were significantly correlated with markers of renal function. Kaplan-Meier survival analysis demonstrated that cumulative survival decreased significantly with ascending tertiles of SDMA (P<0.001). Our study provides the first data indicating that SDMA is strongly associated with adverse clinical outcome during the first 30 days after ischaemic stroke. Our results strengthen the prognostic value of renal function in patients with stroke and confirm the hypothesis that SDMA is a promising marker for renal function.

L-arginine, as a precursor of NO synthesis, has attracted much scientific attention in recent years. Experimental mouse models suggest that L-arginine supplementation can retard, halt, or even reverse atherogenesis. In human studies, supplementation with L-arginine improved endothelium-dependent vasodilation. However, L-arginine levels are best interpreted in the context of levels of asymmetric dimethylarginine (ADMA), a competitive inhibitor of NO synthase. Thus, reference limits for circulating L-arginine and the L-arginine:ADMA ratio may help to determine the nutritional state of individuals at high cardiovascular risk in light of increased ADMA levels. We defined reference limits for plasma L-arginine in 1141 people and for the L-arginine:ADMA ratio in 1138 relatively healthy individuals from the Framingham Offspring Cohort. Plasma L-arginine and ADMA concentrations were determined by using a stable isotope-based LC-MS/MS method. The reference limits (2.5th and 97.5th percentiles) for plasma L-arginine were 41.0 μmol/L (95% CI = 39.5-42.5 μmol/L) and 114 μmol/L (95% CI = 112-115 μmol/L), whereas corresponding reference limits (2.5th and 97.5th percentiles) for the L-arginine:ADMA ratio were 74.3 μmol/L (95% CI = 71.1-77.3 μmol/L) and 225 μmol/L (95% CI = 222-228 μmol/L). Plasma L-arginine was positively associated with the estimated glomerular filtration rate (eGFR) and blood glucose levels, whereas the L-arginine:ADMA ratio was positively associated with eGFR and diastolic blood pressure but inversely associated with homocysteine and (log)C-reactive protein. We report reference levels for plasma L-arginine and for the L-arginine:ADMA ratio that may be helpful for evaluation of the effects of L-arginine supplementation in participants with an impaired L-arginine/NO pathway.

Background: Symmetric dimethylarginine (SDMA) is a by-product of protein methylation. Once released from proteins, SDMA is eliminated by the kidneys; consequently, plasma concentration has been suggested as a sensitive marker of renal function. Furthermore, recent work implicates SDMA in the pathogenesis of cardiovascular disease. To date, reference limits for SDMA plasma concentrations in healthy individuals are lacking., Methods: This study defined reference limits for plasma SDMA concentrations in 840 relatively healthy individuals of the Offspring Cohort from Framingham Heart Study (mean age 56 years, 61% women). Plasma SDMA concentrations were determined by LC-MS/MS using a stable isotope dilution assay., Results: The median SDMA concentration in the reference sample was 0.37 μmol/L (Q1, Q3:0.32, 0.43 μmol/L) and the reference limits were 0.225 and 0.533 (2.5th and 97.5th percentile). In a multivariable regression model, serum creatinine, age and total homocysteine were positively associated with SDMA (p<0.001 for all), whereas the body mass index and diastolic blood pressure were inversely related to SDMA (p-values<0.01 and 0.03, respectively)., Conclusions: This study reports plasma SDMA reference limits from the community-based Framingham Heart Study. Plasma SDMA concentration was related positively to advancing age, but inversely to renal function. These reference limits may allow the identification of individuals with raised plasma SDMA concentrations.

Asymmetric dimethylarginine (ADMA) has evolved as an important regulator of nitric oxide (NO) synthesis in recent years. Elevated levels of ADMA have been reported in many conditions associated with a high cardiovascular risk. Moreover, ADMA is a biomarker for major cardiovascular events and mortality in cohorts with high, intermediate and low overall cardiovascular risk. Discrepant data have been reported on cardiovascular risk in people with and without diabetes mellitus, and the association of ADMA with diabetes mellitus per se has also remained controversial, possibly relating to type and stage of diabetes. Clinical and experimental data suggest that there is a multifaceted link between ADMA and insulin metabolism and action on one hand, and ADMA and glucose utilisation on the other. This interplay may be regulated by the enzyme involved in the metabolic degradation of ADMA, dimethylarginine dimethylaminohydrolase (DDAH). Recent data from prospective clinical studies suggest that whilst ADMA may be a marker for total mortality in patients without diabetes, elevated ADMA may exert beneficial effects in patients with diabetes. In this respect, ADMA could serve as a re-coupling agent overcoming endothelial nitric oxide synthase (eNOS) uncoupling in patients with diabetes. Anticipated advances in clinical and experimental investigation will help us to better understand this complex interrelationship between diabetes, eNOS, DDAH and ADMA.

Preeclampsia is a major cause of maternal and neonatal morbidity and mortality worldwide. Despite recent advances in screening, sensitive and specific biomarkers that help to identify pregnant women at risk of developing preeclampsia are lacking. One of the major mediators from healthy endothelium is nitric oxide; its production is regulated by asymmetric dimethylarginine (ADMA). ADMA has been shown to be elevated in cardiovascular and metabolic diseases; elevated ADMA levels are a prognostic marker for major cardiovascular events and mortality in patients with established cardiovascular disease and in the general population. Several studies have reported elevated ADMA levels in preeclampsia; some studies also suggested that ADMA is elevated in early stages of pregnancy in women who later develop preeclampsia. Moreover, ADMA has been associated with uterine artery flow disturbances. Its plasma concentration is regulated by dimethylarginine dimethylaminohydrolase (DDAH). Single nucleotide polymorphisms in the gene encoding for DDAH have been associated with the incidence of preeclampsia. Recently, diagnostic assays for ADMA, e.g. by ELISA, have become available, which render ADMA a possible biomarker to identify pregnant women at risk of developing preeclampsia., (Copyright 2009 S. Karger AG, Basel.)

In large population-based cohorts, elevated plasma levels of asymmetric dimethylarginine (ADMA) were found to be associated with cardiovascular events and mortality. Impairment of nitric oxide (NO) synthesis from l-arginine has been postulated as underlying mechanism. In the present review, we compare different experimental models of NOS deficiency or overexpression with corresponding models of altered metabolism of ADMA by dimethylarginine dimethylaminohydrolase (DDAH). The latter models show a considerable overlap with the pathophysiological features of impaired NO synthesis, such as impaired endothelial function, elevation of blood pressure, and microvascular fibrosis. In line with these findings, first data regarding genetic variation of DDAH-metabolism in humans are reminiscent of the (rather modest) effects previously observed with polymorphisms of the eNOS gene. However, several peculiar observations suggest that ADMA- or DDAH-related pathology may extend beyond impairment of NO-mediated signalling. Notably, the complete knock out of DDAH1 appears to be lethal while triple NOS(-/-) mice are viable. Moreover, some ADMA-mediated pathology appears to respond rather to ACE-inhibition than to l-arginine. Here, a further investigation of alternative target enzymes for ADMA and other endogenous DDAH substrates is warranted.Taken together, the current data suggest that ADMA-related pathology can largely but not completely be explained by impaired NO metabolism.

Unlabelled: Infusion of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) causes an elevation of blood pressure and depression of cardiac output. Polymorphisms in the promoter region of the ADMA-degrading enzyme dimethylarginine dimethylaminohydrolase 2 (DDAH2) gene have been associated with elevated ADMA concentrations and adverse outcomes in critically ill patients. We hypothesized that two DDAH2 promoter -1151 A/C and -449 G/C polymorphisms (rs805304 and rs805305) will be associated with blood pressure levels, hypertension prevalence and measures of cardiac structure and function in the general population., Methods and Results: We genotyped rs805304 and rs805305 in 783 participants of the population-based Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) Augsburg S3 study. Plasma ADMA concentrations did not differ by rs805304 and rs805305 genotypes. Both polymorphisms were associated with a higher prevalence of hypertension. The odds ratio (adjusted for age, gender and body mass index) for hypertension was 1.70 (95%CI: 1.22-2.36: p=0.002) for those homozygous (n=348) for the -1151A allele and 1.80 (95%CI: 1.29-2.49, p<0.001) for individuals homozygous for the -449G allele (n=350). However, both polymorphisms were not related to measures of cardiac structure and function (left ventricular [LV] mass, LV wall thickness, LV end-diastolic diameter, ejection fraction, E/A ratio, isovolumetric relaxation time) in multivariable-adjusted models., Conclusion: The present study indicates that the -1151 A/C and -449 G/C polymorphisms in the DDAH2 promoter region are not related to plasma ADMA levels or measures of cardiac structure and function but are associated with an increased prevalence of hypertension. The mechanisms of this association need further investigation.

Background: Endothelial function is impaired in hypercholesterolemia and atherosclerosis. Based on mostly indirect evidence, this impairment is attributed to reduced synthesis or impaired biological activity of endothelium-derived nitric oxide (NO). It was the aim of this study to directly estimate and compare whole-body NO production in normo- and hypercholesterolemia by applying a nonradioactive stable isotope dilution technique in vivo., Methods: We enrolled 12 normocholesterolemic and 24 hypercholesterolemic volunteers who were all clinically healthy. To assess whole-body NO synthesis, we intravenously administered l-[guanidino-((15)N(2))]-arginine and determined the urinary excretion of (15)N-labeled nitrate, the specific end product of NO oxidation in humans, by use of gas chromatography-mass spectrometry. In addition, we measured flow-mediated vasodilation (FMD) of the brachial artery, expression of endothelial NOS (eNOS) in platelets, plasma concentration of the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA), and urinary excretion of 8-isoprostaglandin F(2alpha) (8-iso-PGF(2alpha))., Results: After infusion of l-[guanidino-((15)N(2))]-arginine, cumulative excretion of (15)N-labeled-nitrate during 48 h was 40% [95% CI 15%-66%] lower in hypercholesterolemic than normocholesterolemic volunteers [mean 9.2 (SE 0.8) micromol vs 15.4 (2.3) micromol/l, P = 0.003]. FMD was on average 36% [4%-67%] lower in hypercholesterolemic than normocholesterolemic volunteers [6.3 (4.0)% vs 9.4 (4.6)%, P = 0.027]. Normalized expression of NOS protein in platelets was also significantly lower in hypercholesterolemic volunteers, whereas there were no significant differences in plasma ADMA concentration or urinary excretion of 8-iso-PGF(2alpha) between the 2 groups., Conclusions: This study provides direct evidence for a decreased whole body NO synthesis rate in healthy people with hypercholesterolemia.