Plasma Asymmetric Dimethylarginine Concentrations Research Articles

Associations between Aging and Vitamin D Status with Whole-Body Nitric Oxide Production and Markers of Endothelial Function

BackgroundAging and vitamin D deficiency have been associated with reduced nitric oxide (NO) synthesis and impaired endothelial function (EF) but the evidence in humans remains weak. ObjectivesTwo independent cross-sectional studies were designed to evaluate the association between age, sex, and plasma vitamin D concentrations with physiological and biochemical biomarkers of NO synthesis and EF in young and older healthy participants (Study 1) and in overweight and obese postmenopausal females (Study 2). MethodsIn Study 1, 40 young (20–49 y) and older (50–75 y) males and females (10 participants per age and sex group) were included. Resting blood pressure and ear-to-finger peripheral pulse wave velocity (PWV) were measured. A stable-isotopic method was used to determine whole-body NO production. Plasma 25-hydroxyvitamin D (25(OH)D), nitrate, nitrite, and asymmetric dimethylarginine (ADMA) concentrations were determined. In Study 2, 80 older overweight and obese females (age 61.2 ± 6.2 y, body mass index 29.5 ± 4.4 kg/m2) were recruited. Postocclusion reactive hyperemia (PORH) and peripheral PWV were measured. Plasma concentrations of 25(OH)D, nitrate, cyclic guanosine monophosphate, 3-nitrotyrosine (3-NT), endothelin-1, vascular endothelial growth factor, and ADMA were determined. ResultsIn Study 1, whole-body NO production was significantly greater in young compared with older participants (0.61 ± 0.30 μmol·h−1·kg−1 compared with 0.39 ± 0.10 μmol·h−1·kg−1, P = 0.01) but there was no evidence of a sex difference (P = 0.81). Plasma 25(OH)D concentration was not associated with PWV (r = 0.18, P = 0.28) or whole-body NO production (r = −0.20, P = 0.22). Plasma ADMA concentration was associated positively with age (r = 0.35, P = 0.03) and negatively with whole-body NO production (r = −0.33, P = 0.04). In Study 2, age was associated with lower PORH (r = −0.28, P = 0.02) and greater ADMA concentrations (r = 0.22, P = 0.04). Plasma 25(OH)D concentration was inversely associated with 3-NT concentrations (r = −0.31, P = 0.004). ConclusionsOlder age was associated with lower whole-body NO production. Plasma vitamin D concentrations were not associated with NO production or markers of EF but showed a weak, significant correlation with oxidative stress in postmenopausal overweight females.

Plasma concentrations of asymmetric dimethylarginine in Endothelial injury in HIV associated preeclampsia.

Plasma concentrations of asymmetric dimethylarginine in Endothelial injury in HIV associated preeclampsia.

Asymmetric Dimethylarginine (ADMA) in Cardiovascular Disease, Cardiac Ischemia/reperfusion Injury, and Ischemic Non-obstructive Coronary Artery Disease: Biochemical and Pharmacological Implications

Background: Several studies have shown that high plasma concentrations of asymmetric dimethylarginine (ADMA), a known endogenous competitive inhibitor of endothelial nitric oxide synthase (eNOS), correlate with the severity of coronary artery disease (CAD), with worsening of cardiac ischemia/reperfusion (I/R) injury and coronary atherosclerosis. It is believed that it may be an important risk factor for myocardial infarction. ADMA, when in high concentrations, can determine a significant decrease in the synthesis and bioavailability of NO (Nitric oxide) and therefore alter the mechanisms of regulation of coronary vasodilation and vasomotor function of epicardial coronary arteries. Higher serum ADMA concentration is associated with worsening of post-ischemic remodeling since coronary angiogenesis, vasculogenesis, and collateral coronary growth are seriously impaired. In addition, there are reasons to believe that elevated plasma ADMA levels are related to the development of diseases affecting coronary microcirculation, such as ischemic non-obstructive coronary artery disease (INOCA). Methods: Methods: With the aim of providing the pharmacologist engaged in the design and discovery of new ADMA-lowering drugs with a complete examination of the subject, in this review, we discuss the most important studies related to the correlations between serum ADMA levels and cardiovascular diseases mentioned above. In addition, we critically discuss the main aspects of enzymology, synthesis, and metabolism of ADMA as a prerequisite for understanding the molecular mechanisms through which high concentrations of ADMA could contribute to promoting cardiovascular diseases. Results and Conclusion: ADMA represents a new target for pharmacological modulation of cardiovascular endothelial function and therefore, there is a possibility of using selective pharmacological ADMA lowering drugs in cardiovascular disease with endothelial dysfunction and high plasma ADMA levels.

Association of urine and plasma ADMA with atherosclerotic risk in DKD cardiovascular disease risk in diabetic kidney disease: findings from the Chronic Renal Insufficiency Cohort (CRIC) study.

Chronic kidney disease (CKD) is associated with atherosclerotic cardiovascular disease (ASCVD) risk, especially among those with diabetes. Altered metabolism of solutes that accumulate in CKD [asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and trimethylamine N-oxide (TMAO)] may reflect pathways linking CKD with ASCVD. This case-cohort study included Chronic Renal Insufficiency Cohort participants with baseline diabetes, estimated glomerular filtration rate <60mL/min/1.73 m2, and without prior history for each outcome. The primary outcome was incident ASCVD (time to first myocardial infarction, stroke or peripheral artery disease event) and secondary outcome was incident heart failure. The subcohort comprised randomly selected participants meeting entry criteria. Plasma and urine ADMA, SDMA and TMAO concentrations were determined by liquid chromatography-tandem mass spectrometry. Associations of uremic solute plasma concentrations and urinary fractional excretions with outcomes were evaluated by weighted multivariable Cox regression models, adjusted for confounding covariables. Higher plasma ADMA concentrations (per standard deviation) were associated with ASCVD risk [hazard ratio (HR) 1.30, 95% confidence interval (CI) 1.01-1.68]. Lower fractional excretion of ADMA (per standard deviation) was associated with ASCVD risk (HR 1.42, 95% CI 1.07-1.89). The lowest quartile of ADMA fractional excretion was associated with greater ASCVD risk (HR 2.25, 95% CI 1.08-4.69) compared with the highest quartile. Plasma SDMA and TMAO concentration and fractional excretion were not associated with ASCVD. Neither plasma nor fractional excretion of ADMA, SDMA and TMAO were associated with incident heart failure. These data suggest that decreased kidney excretion of ADMA leads to increased plasma concentrations and ASCVD risk.

Asymmetric dimethylarginine positively modulates calcium-sensing receptor signalling to promote lipid accumulation

Asymmetric dimethylarginine (ADMA) is generated through the irreversible methylation of arginine residues. It is an independent risk factor for cardiovascular disease, currently thought to be due to its ability to act as a competitive inhibitor of the nitric oxide (NO) synthase enzymes. Plasma ADMA concentrations increase with obesity and fall following weight loss; however, it is unknown whether they play an active role in adipose pathology. Here, we demonstrate that ADMA drives lipid accumulation through a newly identified NO-independent pathway via the amino-acid sensitive calcium-sensing receptor (CaSR). ADMA treatment of 3T3-L1 and HepG2 cells upregulates a suite of lipogenic genes with an associated increase in triglyceride content. Pharmacological activation of CaSR mimics ADMA while negative modulation of CaSR inhibits ADMA driven lipid accumulation. Further investigation using CaSR overexpressing HEK293 cells demonstrated that ADMA potentiates CaSR signalling via Gq intracellular Ca2+ mobilisation. This study identifies a signalling mechanism for ADMA as an endogenous ligand of the G protein-coupled receptor CaSR that potentially contributes to the impact of ADMA in cardiometabolic disease.

Urinary excretion of asymmetric (ADMA) and symmetric (SDMA) dimethylarginine is positively related to nitric oxide level in tissues of normotensive and hypertensive rats

Nitric oxide (NO) is one of the gaseous transmitters which play a very important role in the regulation of the circulatory system. Decreased NO availability is associated with hypertension, cardiovascular and kidney diseases. Endogenous NO is generated enzymatically by nitric oxide synthase (NOS) depending on the availability of the substrate, cofactors, or presence/absence of inhibitors, such as asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). The objective of this study was to evaluate the potential relationship between NO level in rat tissues (heart and kidneys) and the concentrations of endogenous metabolites related to NO in plasma and urine. The experiment was carried out with 16- and 60-week-old male Wistar Kyoto (WKY) and age-matched male Spontaneously Hypertensive Rats (SHR). NO level in tissue homogenates was determined by the colorimetric method. RT-qPCR was used to verify the expression of the eNOS (endothelial NOS) gene. Plasma and urine concentrations of arginine, ornithine, citrulline, and dimethylarginines were examined by the UPLC-MS/MS method. 16-week-old WKY rats had the highest tissue NO and plasma citrulline levels. Furthermore, 16-week-old WKY rats showed higher urinary excretion of ADMA/SDMA compared to other experimental groups, however, plasma concentrations of arginine, ADMA, and SDMA were comparable between the groups. In conclusion, our research shows that hypertension and aging decrease tissue NO levels and are associated with reduced urinary excretion of NOS inhibitors, i.e., ADMA and SDMA.

Asymmetric Dimethylarginine in an NMU-induced Rat Mammary Tumor Model.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) production and a newly discovered risk factor involved in endothelial dysfunction and adverse cardiovascular events. Recently, both NO and ADMA have also emerged as molecules of interest in carcinogenesis and tumor growth progression. Our earlier studies have confirmed elevated plasma ADMA levels in patients with hematological malignancies. However, the cause of elevated ADMA was unclear. The aim of this study was to assess the concentrations of ADMA, symmetric dimethylarginine (SDMA) and L-arginine in rats exposed to N-nitroso-N-methylurea (NMU) for the induction of mammary tumors. A total of 95 female rats of the Sprague-Dawley strain were used in the study. Plasma concentrations of ADMA, SDMA and L-arginine were quantified and statistically analyzed. Mean ADMA levels were higher in the tumor-bearing group compared to the control group. Mean plasma levels of SDMA and L-Arginine were not significantly different between the groups. The L-ARG/ADMA ratio was lower in rats with tumors compared to controls. Histological assessment confirmed expression of ADMA within the tumor cells, which strongly suggests that these tumor cells were the source of ADMA. Other studies are warranted to further explain the role of ADMA in neoplastic diseases.

Asymmetric dimethylarginine and gestational diabetes mellitus: a systematic review and meta-analysis.

Emerging evidence demonstrates that asymmetric dimethylarginine (ADMA) levels are elevated in patients with or at risk of cardiovascular disease (CVD). Since women with gestational diabetes mellitus (GDM) are at high risk of future CVD, we conducted a systematic review and meta-analysis to compare ADMA concentrations between women with and without GDM during pregnancy and postpartum. PubMed, Google Scholar, EMBASE, and CINAHL databases were searched. The review protocol is registered in PROSPERO (CRD42021276796). Study selection, data extraction, and data analyses were performed in accordance with PRISMA guidelines. Random-effects model was used to quantify ADMA levels in the study groups. Eleven studies provided data on 1148 women. Mean plasma ADMA concentration was 0.04 μmol/L (95% confidence interval (CI) -0.06-0.15) higher in pregnant women with GDM than those without GDM, but no significant difference was observed. In contrast, our meta-analysis demonstrated a significant increase in postpartum mean ADMA concentration (Mean Difference (MD) 0.11 μmol/L; 95% CI 0.05-0.16) among women with previous GDM compared to women without previous GDM. Elevated ADMA levels in GDM may be a CVD risk factor, suggesting that ADMA may be a potential biomarker for early CVD risk prediction in women with GDM.

Far-Infrared Therapy Improves Arteriovenous Fistula Patency and Decreases Plasma Asymmetric Dimethylarginine in Patients with Advanced Diabetic Kidney Disease: A Prospective Randomized Controlled Trial.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and plays a significant role in the pathogenesis of arteriovenous fistula (AVF) dysfunction. The aim of this study is to evaluate the effect of far-infrared (FIR) therapy on the maturation and patency of newly-created AVFs in patients with advanced diabetic kidney disease (DKD) as well as the concurrent change in plasma ADMA. The study enrolled 144 participants with advanced DKD where 101 patients were randomly allocated to the FIR therapy group (N = 50) and control group (N = 51). Patients receiving FIR therapy had a decreased AVF failure rate within 12 months (16% versus 35.3%; p = 0.027); decreased incremental change of ADMA concentration at the 3rd and 12th month; increased AVF blood flow at the 1st, 3rd, and 12th month; increased 3-month physiologic maturation rate (88% versus 68.6%; p = 0.034); increased 1-year unassisted AVF patency rate (84% versus 64.7%; p = 0.017); and increased clinical AVF maturation rate within 12 months (84% versus 62.7%; p = 0.029) compared to the control group. The study demonstrates that FIR therapy can reduce the incremental changes in plasma ADMA concentration, which may be associated with the improvement of AVF prognosis in patients with advanced DKD.

The Impact of Periodontal Inflammation on Endothelial Function Assessed by Circulating Levels of Asymmetric Dimethylarginine: A Single-Blinded Randomized Clinical Trial.

Background: Endothelial dysfunction is one of the early pathogenic events of the atherosclerotic process. Severe periodontitis is considered to be an independent contributing risk factor for the pathophysiology of endothelial dysfunction. High blood concentration of asymmetric dimethylarginine (ADMA), an L-arginine analogue that inhibits nitric oxide (NO) formation, has emerged as one of the most powerful independent risk predictors of cardiovascular disease. Abrogation of periodontal inflammation might have clinical relevance, affecting the ADMA. Insufficient clinical evidence exists for drawing clear conclusions regarding the long-term effects of periodontal disease on endothelial function, and even less evidence is available specifically on ADMA concentrations and their relationship with periodontitis. The objective of this study was to evaluate the effects of intensive periodontal treatment in modulating the endothelial function via the assessment of plasma ADMA concentration in patients diagnosed severe periodontitis. Methods: This was a 6-month randomized controlled trial, including 140 patients between 41 and 63 years old who were diagnosed with severe periodontitis, free from cardiovascular disease (CVD), and had traditional cardiovascular risk factors. All patients underwent a complete medical and clinical periodontal examination, a laboratory analysis of ADMA, and an ultrasound assessment of FMD of the right brachial artery. After the screening, they were randomly assigned to receive either intensive periodontal treatment (test group, n = 70) or community-based periodontal care (control group, n = 70). A full examination was carried out at baseline, 3 and 6 months after the periodontal treatment. Results: A total of 236 individuals diagnosed with periodontitis were screened. One hundred forty participants were enrolled. No statistically significant difference was observed over the time in ADMA concentration after the intensive periodontal treatment within the test group. No differences were revealed between the groups in the ADMA concentration at baseline and during follow-up. Conclusions: Intensive periodontal treatment does not affect the plasma levels of ADMA in patients without any risk for cardiovascular disease.

Overexpression of alanine-glyoxylate aminotransferase 2 protects from asymmetric dimethylarginine-induced endothelial dysfunction and aortic remodeling

Elevated plasma concentrations of asymmetric dimethylarginine (ADMA) are associated with an increased risk of mortality and adverse cardiovascular outcomes. ADMA can be metabolized by dimethylarginine dimethylaminohydrolases (DDAHs) and by alanine-glyoxylate aminotransferase 2 (AGXT2). Deletion of DDAH1 in mice leads to elevation of ADMA in plasma and increase in blood pressure, while overexpression of human DDAH1 is associated with a lower plasma ADMA concentration and protective cardiovascular effects. The possible role of alternative metabolism of ADMA by AGXT2 remains to be elucidated. The goal of the current study was to test the hypothesis that transgenic overexpression of AGXT2 leads to lowering of plasma levels of ADMA and protection from vascular damage in the setting of DDAH1 deficiency. We generated transgenic mice (TG) with ubiquitous overexpression of AGXT2. qPCR and Western Blot confirmed the expression of the transgene. Systemic ADMA levels were decreased by 15% in TG mice. In comparison with wild type animals plasma levels of asymmetric dimethylguanidino valeric acid (ADGV), the AGXT2 associated metabolite of ADMA, were six times higher. We crossed AGXT2 TG mice with DDAH1 knockout mice and observed that upregulation of AGXT2 lowers plasma ADMA and pulse pressure and protects the mice from endothelial dysfunction and adverse aortic remodeling. Upregulation of AGXT2 led to lowering of ADMA levels and protection from ADMA-induced vascular damage in the setting of DDAH1 deficiency. This is especially important, because all the efforts to develop pharmacological ADMA-lowering interventions by means of upregulation of DDAHs have been unsuccessful.

MO079: Treatment with Nebivolol Ameliorates Renovascular Alterations and Oxidative Stress in Tenofovir-Induced Nephrotoxicity in Rats

Abstract BACKGROUND AND AIMS Human immunodeficiency virus (HIV) continues to be a major global public health issue, having claimed millions of lives so far. Tenofovir disoproxil fumarate (TDF), a widely prescribed component in antiretroviral regimens for HIV treatment, has been associated with nephrotoxicity. Nebivolol (NBV) is a third generation selective β-1 adrenergic receptor blocker currently used in the treatment of hypertension and cardiovascular diseases. The potential mechanisms by which NBV may protect renal structure and function include suppression of oxidative stress and enhancement of nitric oxide synthesis. The aim of this study was to investigate whether NBV could be an effective therapeutic option to mitigate TDF-induced nephrotoxicity. METHOD We divided Wistar rats into four groups: control (C, n = 8), received a standard diet for 30 days; TDF (n = 9), received a standard diet with the addition of TDF (300 mg/kg food) for 30 days; NBV (n = 8), received a standard diet for 30 days with the addition of NBV (100 mg/kg food) in the last 15 days; and TDF + NBV (n = 9), received a standard diet with the addition of TDF for 30 days and NBV in the last 15 days. We evaluated inulin clearance (GFR); tubular injury; mean arterial pressure (MAP); renal blood flow (RBF) and calculated renal vascular resistance (RVR); plasma and tissue angiotensin II (AIIp and AIIt, respectively); plasma aldosterone; plasma asymmetric dimethylarginine (ADMA); plasma and urinary thiobarbituric acid reactive substances (TBARSp and TBARSu, respectively); and whole blood glutathione (GSH). In renal tissue, we immunoblotted for endothelial nitric oxide synthase (eNOS), p47phox and p67phox. Data are expressed as mean ± SEM. RESULTS TDF + NBV rats showed an improvement in renal function, a normalization of MAP and attenuation in renal vasoconstriction, evidenced by increased RBF and diminished RVR. Administration of NBV also reduced AII and aldosterone levels in TDF-treated animals. Furthermore, the TDF + NBV group showed a lower plasma ADMA concentration and a higher protein expression of eNOS. Treatment with NBV was responsible for the maintenance of an adequate balance of TBARS and GSH levels, and it was associated with reductions in renal p47phox and p67phox. All results are described in Table 1. CONCLUSION Our data demonstrated the protective role of NBV in TDF-induced nephrotoxicity. The beneficial effects of NBV include a reduction in oxidative stress and RAAS activation, as well as a decrease in endothelial dysfunction, observed by an upregulation on the NO cascade. Therefore, NBV may be an effective therapeutic strategy in the treatment of patients with TDF-induced nephrotoxicity. Financial support: CAPES and FAPESP (2019/20840–0, 2018/12297–1, 2018/04930–6).

Association of Genes of the NO Pathway with Altitude Disease and Hypoxic Pulmonary Hypertension.

Chronic intermittent hypoxia leads to high-altitude pulmonary hypertension, which is associated with high asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthesis. Therefore, we aimed to understand the relation of single nucleotide polymorphisms in this pathway to high-altitude pulmonary hypertension (HAPH). We genotyped 69 healthy male Chileans subjected to chronic intermittent hypoxia. Acclimatization to altitude was determined using the Lake Louise Score and the presence of acute mountain sickness. Echocardiography was performed after six months in 24 individuals to estimate pulmonary arterial pressure. The minor allele of dimethylarginine dimethylaminohydrolase (DDAH)1 rs233112 was associated with high-baseline plasma ADMA concentration, while individuals homozygous for the major allele of DDAH2 rs805304 had a significantly greater increase in ADMA during chronic intermittent hypoxia. The major allele of alanine glyoxylate aminotransferase-2 (AGXT2) rs37369 was associated with a greater reduction of plasma symmetric dimethylarginine (SDMA). Several genes were associated with high-altitude pulmonary hypertension, and the nitric oxide synthase (NOS)3 and DDAH2 genes were related to acute mountain sickness. In conclusion, DDAH1 determines baseline plasma ADMA, while DDAH2 modulates ADMA increase in hypoxia. AGXT2 may be up-regulated in hypoxia. Genomic variation in the dimethylarginine pathway affects the development of HAPH and altitude acclimatization.

Effect of a Low Dose of Carvedilol on Cyclophosphamide-Induced Urinary Toxicity in Rats-A Comparison with Mesna.

One of the major side effects of cyclophosphamide (CPX)—an alkylating anticancer drug that is still clinically used—is urotoxicity with hemorrhagic cystitis. The present study was designed to evaluate the ability of carvedilol to protect rats from cyclophosphamide-induced urotoxicity. Rats were injected intraperitoneally (i.p.) with CPX (200 mg/kg) and administered carvedilol (2 mg/kg) intragastrically a day before, at the day and a day after a single i.p. injection of CPX, with or without mesna (40, 80, and 80 mg/kg i.p. 20 min before, 4 h and 8 h after CPX administration, respectively). Pretreatment with carvedilol partly prevented the CPX-induced increase in urinary bladder and kidney index, and completely protects from CPX-evoked alterations in serum potassium and creatinine level, but did not prevent histological alterations in the urinary bladder and hematuria. However, carvedilol administration resulted in significant restoration of kidney glutathione (GSH) level and a decrease in kidney interleukin 1β (IL-1β) and plasma asymmetric dimethylarginine (ADMA) concentrations. Not only did mesna improve kidney function, but it also completely reversed histological abnormalities in bladders and prevented hematuria. In most cases, no significant interaction of carvedilol with mesna was observed, although the effect of both drugs together was better than mesna given alone regarding plasma ADMA level and kidney IL-1β concentration. In conclusion, carvedilol did not counteract the injury caused in the urinary bladders but restored kidney function, presumably via its antioxidant and anti-inflammatory properties.

Abstract 13928: Asymmetric Dimethylarginine (ADMA) Mediates the Effect of miRNA-762 on All-Cause Mortality in Patients With Coronary Artery Disease

Introduction: Plasma concentrations of the endogenous L-arginine homologue asymmetric dimethylarginine (ADMA) independently predict cardiovascular and all-cause mortality. We sought to identify miRNAs that mediate the effects of ADMA on mortality or influence mortality through regulation of ADMA concentrations. Methods: In 993 participants of the Ludwigshafen Risk and Cardiovascular Health study (age 63.0±10.5 years, 31.4% females and 74.7% with coronary artery disease (CAD)) we measured ADMA and miRNAs concentrations in citrate plasma and investigated associations between them and with all-cause mortality. Results: miRNA-762 was positively and significantly correlated with ADMA concentrations (p=0.0013) and with all-cause mortality after adjusting for age and sex (HR (95%CI: 1.51(1.26-1.81); p=7.37E-06). The association remained significant after additionally adjusting for body mass index, CAD, arterial hypertension, diabetes, smoking, lipids, C-reactive protein, fibrinogen, renal function, homocysteine and medication (p=0.04). Mediation analyses showed that ADMA mediated 67% of the effect of miRNA-762 on mortality while miRNA-762 only mediated 8% of the effect of ADMA. Conclusions: miRNA-762 is an independent predictor of all-cause mortality in patients with CAD. The effects of miRNA-762 on mortality might be at least partially mediated by ADMA. miRNA-762 has been recently shown to regulate apoptosis in cardiomyocytes in myocardial infarction. We are currently investigating the effects of miRNA-762 on ADMA metabolism and stress responses in cultured cardiomyocytes and endothelial cells.

Whole-body arginine dimethylation is associated with all-cause mortality in adult renal transplant recipients

Arginine residues in proteins can be singly or doubly methylated post-translationally. Proteolysis of arginine-methylated proteins provides monomethyl arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). ADMA and SDMA are considered cardiovascular risk factors, with the underlying mechanisms being not yet fully understood. SDMA lacks appreciable metabolism and is almost completely eliminated by the kidney, whereas ADMA is extensively metabolized to dimethylamine (DMA), with a minor ADMA fraction of about 10% being excreted unchanged in the urine. Urinary DMA and ADMA are useful measures of whole-body asymmetric arginine-dimethylation, while urinary SDMA serves as a whole-body measure of symmetric arginine-dimethylation. In renal transplant recipients (RTR), we previously found that higher plasma ADMA concentrations and lower urinary ADMA and SDMA concentrations were associated with a higher risk of all-cause mortality. Yet, in this RTR collective, no data were available for urinary DMA. For the present study, we additionally measured the excretion rate of DMA in 24-h collected urine samples of the RTR and of healthy kidney donors in the cohort, with the aim to quantitate whole-body asymmetric (ADMA, DMA) and symmetric (SDMA) arginine-dimethylation. We found that lower DMA excretion rates were associated with higher all-cause mortality, yet not with cardiovascular mortality. In the healthy donors, kidney donation was associated with considerable decreases in ADMA (by − 39%, P < 0.0001) and SDMA (by − 21%, P < 0.0001) excretion rates, yet there was no significant change in DMA (by − 9%, P = 0.226) excretion rate. Our results suggest that protein-arginine dimethylation is altered in RTR compared to healthy kidney donors and that it is pronouncedly shifted from symmetric to asymmetric arginine-dimethylation, with whole-body protein-arginine dimethylation being almost unaffected.

Association of proton pump inhibitor use with endothelial function and metabolites of the nitric oxide pathway: A cross-sectional study.

Long-term intake of proton pump inhibitors (PPIs) might increase the risk of cardiovascular events. One suggested mechanism is that PPIs inhibit the enzyme dimethylarginine dimethylaminohydrolase (DDAH) and thereby block the degradation of endothelial asymmetrical dimethylarginine (ADMA). Excess ADMA in turn leads to impaired endothelial nitric oxide (NO) generation. So far, this mechanism has only been established in human cell cultures. Previous studies that examined this pathway in human populations measured circulating ADMA and found no association with PPI use and excess plasma ADMA. But in a recent study, plasma ADMA was not correlated with intracellular ADMA. We therefore focused on changes in plasma citrulline as an indicator for potential DDAH inhibition. We analyzed the association between regular daily PPI intake and flow-mediated dilation (FMD) of the brachial artery as well as plasma concentrations of citrulline, arginine, ADMA, and symmetric dimethylarginine using inverse probability weighting to adjust for confounding and censoring. Data of 1298 participants from two independent cohorts of the population-based Study of Health in Pomerania were used. Participants of the population-based Study of Health in Pomerania are a stratified random sample of the study region. Regular daily intake of PPIs. FMD of the brachial artery and plasma concentrations of citrulline, arginine, ADMA, and symmetric dimethylarginine. Eighty-seven participants (57.5% female) were regular daily users of PPIs. In the fully adjusted models, associations were identified for FMD and plasma citrulline concentrations. PPI users revealed a 0.99% (95% CI: -1.96 to -0.02) lower FMD and 3.03µmol/L (95% CI: -4.96 to -1.10) lower plasma citrulline levels as compared to non-users. Our data provide evidence that long-term intake of PPIs might inhibit human DDAH activity, resulting in impaired endothelial NO production and reduced vascular function. In the long run, this might explain an increased risk for cardiovascular diseases associated with long-term PPI use.

Upregulation of DDAH2 Limits Pulmonary Hypertension and Right Ventricular Hypertrophy During Chronic Hypoxia in Ddah1 Knockout Mice.

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.

Features of the Functional State of the L-arginine / NO-synthase / Arginase System and Oxidative Processes in Patients with end-stage Renal Disease due to Chronic Glomerulonephritis Before and After a Hemodialysis Session

Features of the Functional State of the L-arginine / NO-synthase / Arginase System and Oxidative Processes in Patients with end-stage Renal Disease due to Chronic Glomerulonephritis Before and After a Hemodialysis Session

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

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