Higher Asymmetric Dimethylarginine Research Articles

Changes in nitric oxide inhibitors and mortality in critically ill patients: a cohort study

BackgroundOptimal balance between macro- and microcirculation in critically ill patients is crucial for ensuring optimal organ perfusion. Nitric oxide (NO) is a regulator of vascular hemostasis and tone. The availability of NO is controlled by asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and the availability of the NO substrates arginine and homoarginine. We investigated the changes in plasma concentrations of ADMA, SDMA, arginine, and homoarginine days 1–5 of intensive care unit (ICU) admission and the association between the change in concentration days 1–3 and 30-day all-cause mortality.MethodsSingle-center cohort study of adult critically ill patients from the ICU at Copenhagen University Hospital – North Zealand. ADMA, SDMA, arginine, and homoarginine (NO-biomarkers) were measured on days 1–5. Initially, we determined the changes in NO-biomarkers days 1–5 with linear mixed models, and subsequently how the changes in NO-biomarkers days 1–3 were associated with 30-day all-cause mortality. Post-hoc we analyzed the association between plasma concentration at admission and 30-day all-cause mortality.ResultsIn total 567 out of 577 patients had plasma samples from days 1–5. Plasma concentrations of ADMA and arginine increased from days 1–5. SDMA concentrations increased from days 1–2, followed by a decrease from days 2–5. Concentrations of homoarginine did not change from days 1–3 but slightly increased from days 3–5. In total 512 patients were alive 3 days after ICU admission. Among these patients, a daily twofold increase in ADMA concentration from days 1–3 was associated with decreased mortality in multivariate analysis (HR 0.45; 95% CI 0.21–0.98; p = 0.046). An increase in SDMA, arginine, or homoarginine was not associated with mortality. Post-hoc we found that a twofold increase in ADMA or SDMA concentrations at admission was associated with mortality (HR 1.78; 95% CI 1.24–2.57; p = 0.0025, and HR 1.41; 95% CI 1.05–1.90; p = 0.024, respectively).ConclusionsIncreasing ADMA concentrations on days 1–3 are inversely associated with mortality, however not with the same strength as high ADMA or SDMA concentrations at admission. We suggest that admission concentrations are the focus of future research on ADMA and SDMA as predictors of mortality or potential therapeutical targets in ICU patients.

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

: 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). 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. 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.

A multicenter study of asymmetric and symmetric dimethylarginine as predictors of mortality risk in hospitalized COVID-19 patients

Mortality of patients hospitalized with COVID-19 has remained high during the consecutive SARS-CoV-2 pandemic waves. Early discrimination of patients at high mortality risk is crucial for optimal patient care. Symmetric (SDMA) and asymmetric dimethylarginine (ADMA) have been proposed as possible biomarkers to improve risk prediction of COVID-19 patients. We measured SDMA, ADMA, and other L-arginine-related metabolites in 180 patients admitted with COVID-19 in four German university hospitals as compared to 127 healthy controls. Patients were treated according to accepted clinical guidelines and followed-up until death or hospital discharge. Classical inflammatory markers (leukocytes, CRP, PCT), renal function (eGFR), and clinical scores (SOFA) were taken from hospital records. In a small subgroup of 23 COVID-19 patients, sequential blood samples were available and analyzed for biomarker trends over time until 14 days after admission. Patients had significantly elevated SDMA, ADMA, and L-ornithine and lower L-citrulline concentrations than controls. Within COVID-19 patients, SDMA and ADMA were significantly higher in non-survivors (n = 41, 22.8%) than in survivors. In ROC analysis, the optimal cut-off to discriminate non-survivors from survivors was 0.579 µmol/L for SDMA and 0.599 µmol/L for ADMA (both p < 0.001). High SDMA and ADMA were associated with odds ratios for death of 11.45 (3.37–38.87) and 5.95 (2.63–13.45), respectively. Analysis of SDMA and ADMA allowed discrimination of a high-risk (mortality, 43.7%), medium-risk (15.1%), and low-risk group (3.6%); risk prediction was significantly improved over classical laboratory markers. We conclude that analysis of ADMA and SDMA after hospital admission significantly improves risk prediction in COVID-19.

High ADMA Is Associated with Worse Health Profile in Heart Failure Patients Hospitalized for Episodes of Acute Decompensation

Background and Objectives: episodes of acute decompensation in chronic heart failure (ADHF), a common health problem for the growing elderly population, pose a significant socio-economic burden on the public health systems. Limited knowledge is available on both the endothelial function in and the cardio-metabolic health profile of old adults hospitalized due to ADHF. This study aimed to investigate the connection between asymmetric dimethylarginine (ADMA)—a potent inhibitor of nitric oxide—and key health biomarkers in this category of high-risk patients. Materials and Methods: this pilot study included 83 individuals with a known ADHF history who were admitted to the ICU due to acute cardiac decompensation. Selected cardiovascular, metabolic, haemogram, renal, and liver parameters were measured at admission to the ICU. Key renal function indicators (serum creatinine, sodium, and potassium) were determined again at discharge. These parameters were compared between patients stratified by median ADMA (114 ng/mL). Results: high ADMA patients showed a significantly higher incidence of ischemic cardiomyopathy and longer length of hospital stay compared to those with low ADMA subjects. These individuals exhibited significantly higher urea at admission and creatinine at discharge, indicating poorer renal function. Moreover, their lipid profile was less favorable, with significantly elevated levels of total cholesterol and HDL. However, no significant inter-group differences were observed for the other parameters measured. Conclusions: the present findings disclose multidimensional, adverse ADMA-related changes in the health risk profile of patients with chronic heart failure hospitalized due to recurrent decompensation episodes.

ENDOTHELIAL FUNCTION, AS ASSESSED BY FLOW MEDIATED DILATION AND ASYMMETRIC DIMETHYLARGININE IS IMPAIRED IN NEWLY DIAGNOSED TYPE 2 DIABETES MELLITUS

Objective: Endothelial dysfunction precedes the onset of clinically detectable atherosclerosis diabetes mellitus in type 2 (T2DM) and contributes significantly to the development of vascular complications and mortality. The aim of the present study was to investigate the endothelial function in patients with a recent diagnosis of T2DM. Design and method: We studied patients with newly diagnosed T2DM (&lt;6 months from diagnosis) that did not receive antidiabetic treatment (except for metformin) and otherwise healthy individuals matched for age and blood pressure (BP). We recorded somatometric, BP (office and 24-hour) and hematological (lipids, renal function, fasting glucose, HBA1c) data. We also calculate the 10-year atherosclerotic cardiovascular risk (ASCVD risk score). We determined endothelial dysfunction with 2 methods: Asymmetric Dimethylarginine (ADMA) by ELISA (enzyme-linked immunosorbent assay) and the gold standard non-invasive method Flow Mediated Dilation (FMD). Results: Ninety subjects were studied, 33 patients with T2DM and 57 controls. Twenty T2DM patients were enrolled within 1 month from diagnosis, while the rest 13 had been diagnosed 3.69±2.14 months before. Similarly, 16 (48.48%) had received metformin for a median of 3 (interquartile range 18) weeks. T2DM showed significantly impaired FMD [4.68 (4.58)% versus 7.85 (7)%, (p = 0.012)] and higher ADMA [0.926±0.569 μmol/l versus 0.468 (0.27) μmol/l, (p = 0.032)], compared to controls. There was also an independent association of T2DM and FMD (Beta = -0.278, p = 0.012). Results were similar in the sub-group analysis of patients without hypertension. In this cohort, FMD lower than 7.5% was able to predict T2DM diagnosis with 87.5% sensitivity and 70.8% specificity. Conclusions: Patients with a very recent diagnosis of T2DM show impaired endothelial function as demonstrated by FMD and ADMA findings. This assessment highlights the early severe, damaging effect of hyperglycemia on the endothelium, emphasizing the need for early detection and management.

Asymmetric Dimethylarginine as a Biomarker in Coronary Artery Disease.

As atherosclerosis remains a leading cause of morbidity and mortality worldwide despite the advances in its medical and interventional management, the identification of markers associated with its incidence and prognosis constitutes an appealing prospect. In this regard, asymmetric dimethylarginine (ADMA), a well-studied endogenous endothelial nitric oxide synthase inhibitor, represents a core mediator of endothelial dysfunction in atherosclerotic diseases. Given the pathophysiologic background of this molecule, its importance in the most frequent atherosclerotic manifestation, coronary artery disease (CAD), has been extensively studied in the past decades. The available evidence suggests elevation of ADMA in the presence of common cardiovascular risk factors, namely diabetes mellitus, arterial hypertension, and hypertriglyceridemia, being related to endothelial dysfunction and incident major adverse cardiovascular events in these groups of patients. Moreover, ADMA is associated with CAD occurrence and severity, as well as its prognosis, especially in populations with renal impairment. Interestingly, even in the absence of obstructive CAD, increased ADMA may indicate coronary endothelial dysfunction and epicardial vasomotor dysfunction, which are prognostication markers for incident cardiovascular events. In the case of acute coronary syndromes, high ADMA levels signify an augmented risk of incomplete ST-segment elevation resolution and poorer prognosis. Abnormal ADMA elevations may indicate adverse outcomes following percutaneous or surgical coronary revascularization, such as in-stent restenosis, graft patency, and hard cardiovascular endpoints. Finally, since its association with inflammation is significant, chronic inflammatory conditions may present with coronary endothelial dysfunction and subclinical coronary atherosclerosis by means of increased coronary artery calcium, with augmented ADMA acting as a biomarker.

Assessment of asymmetric dimethylarginine and homocysteine in epileptic children receiving antiepileptic drugs

BackgroundEpilepsy is a neurological disease that requires long-term antiepileptic drugs (AEDs). The old generation of AEDs may affect serum homocysteine and asymmetric dimethylarginine (ADMA) and disturb lipid levels. The aim of the study was to evaluate serum ADMA, homocysteine, lipid profile, and carotid intima-media thickness (CIMT) in epileptic children.MethodsThis study was implemented on 159 epileptic children who were subdivided into 3 subgroups, with 53 receiving sodium valproate, 53 receiving levetiracetam, and 53 receiving polytherapy, for over 6 months and 53 healthy children.ResultsLow-density lipoprotein, triglycerides, and cholesterol levels were increased in epileptic children (p < 0.001), which were higher in those receiving multidrug followed by a valproate receiver. While high-density lipoprotein was lower in those receiving multidrug more than those receiving valproate. ADMA and homocysteine levels increased in epileptic patients than in controls (p < 0.001). Higher ADMA was also observed in the multidrug receiver (5.78 ± 0.62), followed by the levetiracetam group (5.56 ± 0.61). Homocysteine levels were significantly higher in multidrug and valproate-treated children than those treated with levetiracetam. CIMT was significantly higher in multidrug and valproate-treated patients (p < 0.001).ConclusionsLong-term use of AEDs, especially old-generation polytherapy, can elevate lipid profiles, homocysteine, ADMA levels, and carotid intima-media thickness compared to the minimal effect of new AEDs.ImpactThe long-term use of antiepileptic drugs, especially old-generation polytherapy, can increase lipid profiles, homocysteine levels, ADMA, and carotid intima thickness compared to the minimal effect of new antiepileptic generation.A routine follow-up of these markers and a lifestyle modification are recommended to avoid cerebrovascular events as much as possible.

Alcohol Drinks Induce Acute Lowering in Circulating l-Arginine in Obese and Type 2 Diabetic Subjects.

Since low serum l-arginine (Arg) and high asymmetric dimethylarginine (ADMA) can predict microvascular complications in type 2 diabetes mellitus (T2DM), we tested whether Arg and ADMA are affected by diet and physical activity in overweight/obese and T2DM subjects. We tested the effects on serum Arg and ADMA of single loads of dextrose, protein, fat, or alcohol (∼300 calories each); one episode of physical exercise; and 12 weeks of standard lifestyle modification (dietary and physical activity counseling). Alcohol drink was followed by ∼30% lowering in Arg. Arg and ADMA increased after a protein load but remained stable after glucose or fat load or 30 min of treadmill walk. Following 12 weeks of lifestyle modification, ADMA declined only in subjects achieving weight loss >5%. In conclusion, alcohol is a previously unrecognized acute suppressor of serum Arg. Lifestyle modification lowers ADMA in subjects who achieve weight loss >5%. Clinical Trial Registration Number: NCT04406402.

A Therapeutic Extracorporeal Device for Specific Removal of Pathologic Asymmetric Dimethylarginine from the Blood

Introduction: Blood levels of uremic toxin, asymmetric dimethylarginine (ADMA), are strongly associated with mortality in sepsis, renal failure, and cardiovascular and renal disease patients. Methods: An extracorporeal approach to reduce pathological ADMA was developed. The dimethylarginine dimethylaminohydrolase (DDAH) was immobilized on agarose beads to prepare a cartridge. The efficacy of cartridge for ADMA lowering in blood was investigated. Results: The DDAH beads and cartridge reduced ADMA from solution or plasma. The magnitude of ADMA removal was dependent on the quantity of DDAH linked to the beads and the flow rate. When tested in association with plasmapheresis, the DDAH-cartridge was highly effective in ADMA removal from the blood and improved the arginine/ADMA ratio in a pig model. Conclusion: A new, safe, and effective extracorporeal approach to lower ADMA was developed which may have application in improving outcomes in patients with vascular complications and risk of mortality associated with high ADMA.

Diabetes acts on mortality in hemodialysis patients predicted by asymmetric dimethylarginine and inflammation

BackgroundThe mortality rate of diabetic patients on dialysis is higher than that of non-diabetic patients. Asymmetric dimethylarginine and inflammation are strong predictors of death in hemodialysis. This study aimed to evaluate asymmetric dimethylarginine and C-reactive protein interaction in predicting mortality in hemodialysis according to the presence or absence of diabetes. MethodsAsymmetric dimethylarginine and C-reactive protein were measured in 202 patients in maintenance hemodialysis assembled from 2011 to 2012 and followed for four years. Effect modification of C-reactive protein on the relationship between asymmetric dimethylarginine and all-cause mortality was investigated dividing the population into four categories according to the median of asymmetric dimethylarginine and C-reactive protein. ResultsAsymmetric dimethylarginine and C-reactive protein levels were similar between diabetics and non-diabetics. Asymmetric dimethylarginine – median IQR μM – (1.95 1.75–2.54 versus 1.03 0.81–1.55 P=0.000) differed in non-diabetics with or without evolution to death (HR 2379 CI 1.36–3.68 P=0.000) and was similar in diabetics without or with evolution to death. Among non-diabetics, the category with higher asymmetric dimethylarginine and C-reactive protein levels exhibited the highest mortality (69.0% P=0.000). No differences in mortality were seen in diabetics. A joint effect was found between asymmetric dimethylarginine and C-reactive protein, explaining all-cause mortality (HR 15.21 CI 3.50–66.12 P=0.000). ConclusionsAsymmetric dimethylarginine is an independent predictor of all-cause mortality in non-diabetic patients in hemodialysis. Other risk factors may overlap asymmetric dimethylarginine in people with diabetes. Inflammation dramatically increases the risk of death associated with high plasma asymmetric dimethylarginine in hemodialysis.

Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance

The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.

A Recombinant Dimethylarginine Dimethylaminohydrolase-1-Based Biotherapeutics to Pharmacologically Lower Asymmetric Dimethyl Arginine, thus Improving Postischemic Cardiac Function and Cardiomyocyte Mitochondrial Activity.

High serum levels of asymmetric dimethyl arginine (ADMA) are associated with cardiovascular disease and mortality. Pharmacological agents to specifically lower ADMA and their potential impact on cardiovascular complications are not known. In this study, we aimed to investigate the effect of specific lowering of ADMA on myocardial response to ischemia-reperfusion injury (I/R) and direct effects on cardiomyocyte function. Effects of recombinant dimethylarginine dimethylaminohydrolase (rDDAH)-1 on I/R injury were determined using isolated mouse heart preparation. Respiration capacity and mitochondrial reactive oxygen species (ROS) generation were determined on mouse cardiomyocytes. Our results show that lowering ADMA by rDDAH-1 treatment resulted in improved recovery of cardiac function and reduction in myocardial infarct size in mouse heart response to I/R injury (control 22.24 ±4.60% versus rDDAH-1 15.90 ±4.23%, P < 0.01). In mouse cardiomyocytes, rDDAH-1 treatment improved ADMA-induced dysregulation of respiration capacity and decreased mitochondrial ROS. Furthermore, in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes with impaired contractility under hypoxia and high ADMA, rDDAH-1 treatment improved recovery and beating frequency (P < 0.05). rDDAH-1 treatment selectively modified I/R-induced myocardial cytokine expression, resulting in reduction in proinflammatory cytokine IL-17A (P < 0.001) and increased expression of anti-inflammatory cytokines IL-10 and IL-13 (P < 0.01). Further in vitro studies showed that IL-17A was the predominant and common cytokine modulated by ADMA-DDAH pathway in heart, cardiomyocytes, and endothelial cells. These studies show that lowering ADMA by pharmacological treatment with rDDAH-1 reduced I/R injury, improved cardiac function, and ameliorated cardiomyocyte bioenergetics and beating activity. These effects may be attributable to ADMA lowering in cardiomyocytes and preservation of cardiomyocyte mitochondrial function. SIGNIFICANCE STATEMENT: The pathological role of asymmetric dimethyl arginine (ADMA) has been demonstrated by its association with cardiovascular disease and mortality. Currently, pharmacological drugs to specifically lower ADMA are not available. The present study provides the first evidence that lowering of ADMA by recombinant recombinant dimethylarginine dimethylaminohydrolase (rDDAH)-1 improved postischemic cardiac function and cardiomyocyte bioenergetics and beating activity. Our studies suggest that lowering of ADMA by pharmacologic treatment offers opportunity to develop new therapies for the treatment of cardiovascular and renal disease.

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.

α-Klotho, Plasma Asymmetric Dimethylarginine, and Kidney Disease Progression

Rationale & ObjectiveWe aimed to explore the associated factors of endothelial injury in chronic kidney disease (CKD) and the relationship between endothelial dysfunction and CKD prognosis.Study DesignA prospective observational cohort study.Setting & Participants77 adults with CKD stages 1-5 were enrolled January 2010 to December 2010 and followed up until December 2015.ExposureSerum asymmetric dimethylarginine (ADMA) level at baseline, α-klotho, sodium-phosphorus synergistic transporter, and dimethylarginine-dimethylamine hydrolase expression in kidney biopsy samples.OutcomeInitiation of kidney replacement therapy (KRT).Analytical ApproachKaplan-Meier analysis was used for evaluation of the incidence rate of KRT. All tests were 2 tailed, and statistical significance was defined as P < 0.05.ResultsMean serum ADMA level of 77 patients was 64.3 ± 34.6 ng/mL. ADMA level increased with CKD stages (P = 0.06) and declining kidney function (r = −0.267; P = 0.02). The expression of α-klotho in kidney biopsy specimens also decreased. Median follow-up time was 56 (interquartile range, 50.5-62) months. Kaplan-Meier analyses showed that during a total follow-up of 6 years, the incidence of KRT initiation in the high-ADMA group was significantly higher than that in the low group (35.9% vs 13.2%; P = 0.03). ADMA level was negatively correlated with α-klotho (r = −0.233; P = 0.04) and positively correlated with phosphorus level (r = 0.243; P = 0.04). The expression of sodium-phosphorus synergistic transporter in kidney tubules, which promoted phosphorus reabsorption, and the expression of dimethylarginine-dimethylamine hydrolase isoform 1, which regulated ADMA, were decreased. Correlation analysis also showed that ADMA level decreased while age increased at baseline (r = −0.292; P = 0.01).LimitationsSmall sample size with limited longer-term follow-up.ConclusionsSerum ADMA levels increased as kidney function declined, and high serum ADMA level was associated with incident kidney failure. Low tissue α-klotho and high levels of plasma phosphorus or tissue expression of type II sodium/phosphate cotransporter in the kidney are associated with higher circulating ADMA levels, suggesting that they may be involved in the pathogenesis of endothelial dysfunction in patients with CKD.

Diabetes acts on mortality in hemodialysis patients predicted by asymmetric dimethylarginine and inflammation

BackgroundThe mortality rate of diabetic patients on dialysis is higher than that of non-diabetic patients. Asymmetric dimethylarginine and inflammation are strong predictors of death in hemodialysis. This study aimed to evaluate asymmetric dimethylarginine and C-reactive protein interaction in predicting mortality in hemodialysis according to the presence or absence of diabetes. MethodsAsymmetric dimethylarginine and C-reactive protein were measured in 202 patients in maintenance hemodialysis assembled from 2011 to 2012 and followed for four years. Effect modification of C-reactive protein on the relationship between asymmetric dimethylarginine and all-cause mortality was investigated dividing the population into four categories according to the median of asymmetric dimethylarginine and C-reactive protein. ResultsAsymmetric dimethylarginine and C-reactive protein levels were similar between diabetics and non-diabetics. Asymmetric dimethylarginine – median IQR μM – (1.95 1.75–2.54 versus 1.03 0.81–1.55 P=0.000) differed in non-diabetics with or without evolution to death (HR 2379 CI 1.36–3.68 P=0.000) and was similar in diabetics without or with evolution to death. Among non-diabetics, the category with higher asymmetric dimethylarginine and C-reactive protein levels exhibited the highest mortality (69.0% P=0.000). No differences in mortality were seen in diabetics. A joint effect was found between asymmetric dimethylarginine and C-reactive protein, explaining all-cause mortality (HR 15.21 CI 3.50–66.12 P=0.000). ConclusionsAsymmetric dimethylarginine is an independent predictor of all-cause mortality in non-diabetic patients in hemodialysis. Other risk factors may overlap asymmetric dimethylarginine in people with diabetes. Inflammation dramatically increases the risk of death associated with high plasma asymmetric dimethylarginine in hemodialysis.

Levels of Biological Markers of Nitric Oxide in Serum of Patients with Mandible Fractures.

Background: Nitric oxide is a small gaseous molecule with significant bioactivity. It has been observed that NO may have a dual role dependent on its production and concentrations in the bone microenvironment. The objective of the study was to assess the concentration of total nitric oxide malonyldialdehyde, nitrotyrosine, and asymmetric dimethylarginine in the serum of patients with mandibular fractures and to understand the relationship between these compounds, in order to expand the knowledge base of the role of nitric oxide and its activity indicators in the process of bone fracture healing. Material and Methods: The study included 20 patients with mandibular fractures who were undergoing inpatient and outpatient treatments and a control group of 15 healthy people. Results were analyzed with respect to the measurement time. Total nitric oxide concentration in the blood serum was determined according to the Griess reaction, while the concentration of malonyldialdehyde, nitrotyrosine, and asymmetric dimethylarginine was estimated using the immunoenzymatic method (i.e., enzyme-linked immunosorbent assay). Results: Before the procedure, as well as on the first day and 2 and 6 weeks after the procedure, higher concentrations of total nitric oxide and lower concentrations of malonyldialdehyde were observed in the blood serum of patients with mandibular fractures compared to the control group. No statistically significant differences were found in nitrotyrosine concentrations in the blood serum of patients throughout the measurement period. However, a significantly higher asymmetric dimethylarginine concentration was observed in the patient serum before the procedure and on the first day of operation as compared with the control group. Analysis of the results observed in patient serum with respect to the number of fractures within the mandible demonstrated the same trend of concentrations for the tested compounds for the entire study group. Conclusions: In summary, our results revealed that the intensity of local processes resulting from mandibular fractures is associated with the concentration of nitric oxide, confirming its significant role, as well as that of its indicators, in the process of bone fracture healing in this patient population.

895-P: Children with Type 2 Diabetes (T2D) Have Lower Fasting Arginine and Citrulline but Higher Asymmetric Dimethylarginine (ADMA) Levels Compared with Healthy Controls

We studied fasting amino acid levels in 12 children (6 T2D and 6 controls). The mean age was 16.2 ± 0.7 years. The study cohort comprised 42% females, 67% Hispanic, 25% black, and 8% non-Hispanic white. Mean BMI percentile was higher in the T2D group vs. controls (99.1 vs. 50.9 percentiles, p<0.001). In children with T2D, mean HbA1c was 6.4% ± 1% with mean diabetes duration of 1.3 ± 0.3 years. Age, sex, race/ethnicity, the amount of protein intake in the preceding day (61 ± 29 gram), and the duration of fasting (13.5 ± 1 h) were similar between the groups. Fasting citrulline concentration was lower (17.8 vs. 27.8 µmol/L, p=0.01) and fasting ADMA concentration higher (0.523 vs. 0.455 µmol/L, p=0.05) in the children with T2D vs. controls. Fasting arginine level was also lower in the T2D group compared to controls (79.6 vs. 97 µmol/L), but the difference did not attain statistical significance (p=0.22). After Grubb’s test uncovered an outlier in the T2D group, fasting arginine level was also statistically different (69.5 µmol/L in the T2D group vs. 97 µmol/L in controls, p=0.02) (Figure 1). We found a unique metabolomic signature in children with T2D indicating disturbed arginine-citrulline metabolism. Defective arginine-citrulline metabolism may play a role in the pathogenesis of T2D in children, with implications for targeted nutritional therapy.View largeDownload slideView largeDownload slide DisclosureM. Tosur: Advisory Panel; Self; Provention Bio, Inc. J. W. Hsu: None. S. Deen: None. S. Uysal: None. M. Astudillo: None. M. J. Redondo: Advisory Panel; Self; Provention Bio, Inc. F. Jahoor: None. A. Balasubramanyam: None.FundingTexas Children’s Hospital

Specific Lowering of Asymmetric Dimethylarginine by Pharmacological Dimethylarginine Dimethylaminohydrolase Improves Endothelial Function, Reduces Blood Pressure and Ischemia-Reperfusion Injury.

Multiple clinical and preclinical studies have demonstrated that plasma levels of asymmetric dimethylarginine (ADMA) are strongly associated with hypertension, diabetes, and cardiovascular and renal disease. Genetic studies in rodents have provided evidence that ADMA metabolizing dimethylarginine dimethylaminohydrolase (DDAH)-1 plays a role in hypertension and cardiovascular disease. However, it remains to be established whether ADMA is a bystander, biomarker, or sufficient contributor to the pathogenesis of hypertension and cardiovascular and renal disease. The goal of the present investigation was to develop a pharmacological molecule to specifically lower ADMA and determine the physiologic consequences of ADMA lowering in animal models. Further, we sought to determine whether ADMA lowering will produce therapeutic benefits in vascular disease in which high ADMA levels are produced. A novel long-acting recombinant DDAH (M-DDAH) was produced by post-translational modification, which effectively lowered ADMA in vitro and in vivo. Treatment with M-DDAH improved endothelial function as measured by increase in cGMP and in vitro angiogenesis. In a rat model of hypertension, M-DDAH significantly reduced blood pressure (vehicle: 187 ± 19 mm Hg vs. M-DDAH: 157 ± 23 mm Hg; P < 0.05). Similarly, in a rat model of ischemia-reperfusion injury, M-DDAH significantly improved renal function as measured by reduction in serum creatinine (vehicle: 3.14 ± 0.74 mg/dl vs. M-DDAH: 1.1 ± 0.75 mg/dl; P < 0.01), inflammation, and injured tubules (vehicle: 73.1 ± 11.1% vs. M-DDAH: 22.1 ± 18.4%; P < 0.001). These pharmacological studies have provided direct evidence for a pathologic role of ADMA and the therapeutic benefits of ADMA lowering in preclinical models of endothelial dysfunction, hypertension, and ischemia-reperfusion injury. SIGNIFICANCE STATEMENT: High levels of ADMA occur in patients with cardiovascular and renal disease. A novel modified dimethylarginine dimethylaminohydrolase by PEGylation effectively lowers ADMA, improves endothelial function, reduces blood pressure and protects from ischemia-reperfusion renal injury.

Abstract 15303: Dimethylarginine Dimethylaminohydrolase-1 is Not Involved in Chronic Hypoxic Pulmonary Hypertension and Right Ventricular Hypertrophy in Mice

Introduction: Chronic hypoxia causes persistent pulmonary vasoconstriction and leads to pulmonary hypertension and right ventricular hypertrophy. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis; its level increases in hypoxia concomitantly with reduced activity of dimethylarginine dimethylaminohydrolases (DDAH-1 and DDAH-2), the enzymes metabolizing ADMA. DDAH knockout models may therefore help to understand the pathophysiological roles of this enzyme and its substrate, ADMA, in the development of hypoxia-associated pulmonary hypertension. Hypothesis: We hypothesized that DDAH1 knock-out mice have an attenuated hypoxia-induced elevation of ADMA and reduced right ventricular hypertrophy. Methods: DDAH1 knock-out mice (KO) and their wild-type littermates (WT) were subjected to normoxia (NX) or hypoxia (HX) during 21 days. We measured ADMA concentration in plasma, DDAH1 and DDAH2 expression in the lung, right ventricular hypertrophy by the Fulton index, cardiomyocyte hypertrophy by dystrophin staining of heart tissues, and muscularization of pulmonary arterioles by CD31 and α-actin staining of lung sections. Results: DDAH1 KO mice had higher ADMA concentration than WT under NX (2.31±0.33 μmol/l vs. 1.20±0.17 μmol/l; p &lt; 0.05). ADMA significantly increased in WT-HX (to 1.74±0.86 μmol/l; p &lt; 0.05 vs. normoxia), whilst it did not further increase in KO-HX (2.58±0.58 μmol/l; p = n.s.). This was paralleled by a 38±13% reduction in DDAH1 mRNA but not DDAH2 mRNA expression, and reduced DDAH protein expression. We observed right ventricular hypertrophy under hypoxia in both, WT and KO mice, with no significant differences between both genotypes. Further, cardiomyocyte hypertrophy and pulmonary arteriolar muscularization were significantly increased by hypoxia, but not significantly different between WT and KO mice. Conclusions: We conclude that chronic hypoxia causes an elevation of ADMA, which impairs NO production and leads to endothelial dysfunction and vasoconstriction. Downregulation of DDAH expression and activity may be involved in this; however, knockout of DDAH1 does not modify the pathophysiological changes in remodeling of the pulmonary vasculature and the right ventricle.

Activation of arginase II by asymmetric dimethylarginine and homocysteine in hypertensive rats induced by hypoxia: a new model of nitric oxide synthesis regulation in hypertensive processes?

In recent years, the increase in blood pressure at high altitudes has become an interesting topic among high-altitude researchers. In our animal studies using Wistar rats, we observed the existence of two rat populations that exhibit differential physiological responses during hypoxic exposure. These rats were classified as hypoxia-induced hypertensive rats and nonhypertensive rats. A decrease in nitric oxide levels was reported in different hypertension models associated with increased concentrations of asymmetric dimethylarginine (ADMA) and homocysteine, and we recently described an increase in arginase type II expression under hypoxia. ADMA and homocysteine decrease nitric oxide (NO) bioavailability; however, whether ADMA and homocysteine have a regulatory effect on arginase activity and therefore regulate another NO synthesis pathway is unknown. Therefore, the aim of this study was to measure basal ADMA and homocysteine levels in hypoxia-induced hypertensive rats and evaluate their effect on arginase II activity. Our results indicate that hypoxia-induced hypertensive rats presented lower nitric oxide concentrations than nonhypertensive rats, associated with higher concentrations of homocysteine and ADMA. Hypoxia-induced hypertensive rats also presented lower dimethylarginine dimethylaminohydrolase-2 and cystathionine β-synthase levels, which could explain the high ADMA and homocysteine levels. In addition, we observed that both homocysteine and ADMA had a significant effect on arginase II activation in the hypertensive rats. Therefore, we suggest that ADMA and homocysteine have dual regulatory effects on NO synthesis. The former has an inhibitory effect on eNOS, and the latter has a secondary activating effect on arginase II. We propose that arginase II is activated by AMDA and homocysteine in hypoxia-induced hypertensive rats.