Asymmetric dimethylarginine contributes to airway nitric oxide deficiency in patients with COPD

Arginine, Transsulfuration, and Folic Acid Pathway Metabolomics in Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

There is an increasing interest in biomarkers of nitric oxide dysregulation and oxidative stress to guide management and identify new therapeutic targets in patients with chronic obstructive pulmonary disease (COPD). We conducted a systematic review and meta-analysis of the association between circulating metabolites within the arginine (arginine, citrulline, ornithine, asymmetric, ADMA, and symmetric, SDMA dimethylarginine), transsulfuration (methionine, homocysteine, and cysteine) and folic acid (folic acid, vitamin B6, and vitamin B12) metabolic pathways and COPD. We searched electronic databases from inception to 30 June 2023 and assessed the risk of bias and the certainty of evidence. In 21 eligible studies, compared to healthy controls, patients with stable COPD had significantly lower methionine (standardized mean difference, SMD = -0.50, 95% CI -0.95 to -0.05, p = 0.029) and folic acid (SMD = -0.37, 95% CI -0.65 to -0.09, p = 0.009), and higher homocysteine (SMD = 0.78, 95% CI 0.48 to 1.07, p < 0.001) and cysteine concentrations (SMD = 0.34, 95% CI 0.02 to 0.66, p = 0.038). Additionally, COPD was associated with significantly higher ADMA (SMD = 1.27, 95% CI 0.08 to 2.46, p = 0.037), SDMA (SMD = 3.94, 95% CI 0.79 to 7.08, p = 0.014), and ornithine concentrations (SMD = 0.67, 95% CI 0.13 to 1.22, p = 0.015). In subgroup analysis, the SMD of homocysteine was significantly associated with the biological matrix assessed and the forced expiratory volume in the first second to forced vital capacity ratio, but not with age, study location, or analytical method used. Our study suggests that the presence of significant alterations in metabolites within the arginine, transsulfuration, and folic acid pathways can be useful for assessing nitric oxide dysregulation and oxidative stress and identifying novel treatment targets in COPD. (PROSPERO registration number: CRD42023448036.).

Diagnostic value of serum neuroactive substances in the acute exacerbation of chronic obstructive pulmonary disease complicated with depression

We aimed to investigate the potential diagnostic value of five serum neuroactive substances in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) complicated with depression. A total of 103 patients with AECOPD were enrolled between August 2020 and August 2021. All patients were assessed using a self-rating depression scale and divided into AECOPD with or without depression groups. Baseline data and serum neuroactive substance levels were compared between the two groups. Logistic regression was used to identify the risk factors. The diagnostic performance of neuroactive substances was evaluated using receiver operating characteristic (ROC) curves. Patients with AECOPD complicated with depression exhibited higher partial pressure of CO2 values and higher chronic obstructive pulmonary disease assessment test (CAT) scores. An elevated proportion of patients with more than two acute exacerbations (AEs) in the previous year was observed in this patient group (all P < 0.001). The CAT score and number of AEs during the previous year were identified as independent risk factors for AECOPD complicated with depression. No significant differences were observed in the levels of aspartic acid and glutamate between the two groups (P > 0.05). Serum γ-aminobutyric acid (GABA) and glycine (Gly) levels were decreased. In contrast, serum nitric oxide (NO) levels were increased in the AECOPD complicated with the depression group (P < 0.05). Serum GABA and Gly levels exhibited a negative correlation, and NO levels positively correlated with the number of AEs in the previous year and the CAT score. The area under the ROC curve values for GABA, Gly, and NO were 0.755, 0.695, and 0.724, respectively. Serum GABA exhibited a sensitivity of 85.1% and a specificity of 58.9%, below the cut-off value of 4855.98 nmol/L. Serum GABA, Gly, and NO may represent potential biomarkers for AECOPD complicated with depression.

A Metabolomic Severity Score for Airflow Obstruction and Emphysema

Chronic obstructive pulmonary disease (COPD) is a disease with marked metabolic disturbance. Previous studies have shown the association between single metabolites and lung function for COPD, but whether a combination of metabolites could predict phenotype is unknown. We developed metabolomic severity scores using plasma metabolomics from the Metabolon platform from two US cohorts of ever-smokers: the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) (n = 648; training/testing cohort; 72% non-Hispanic, white; average age 63 years) and the COPDGene Study (n = 1120; validation cohort; 92% non-Hispanic, white; average age 67 years). Separate adaptive LASSO (adaLASSO) models were used to model forced expiratory volume at one second (FEV1) and MESA-adjusted lung density using 762 metabolites common between studies. Metabolite coefficients selected by the adaLASSO procedure were used to create a metabolomic severity score (metSS) for each outcome. A total of 132 metabolites were selected to create a metSS for FEV1. The metSS-only models explained 64.8% and 31.7% of the variability in FEV1 in the training and validation cohorts, respectively. For MESA-adjusted lung density, 129 metabolites were selected, and metSS-only models explained 59.0% of the variability in the training cohort and 17.4% in the validation cohort. Regression models including both clinical covariates and the metSS explained more variability than either the clinical covariate or metSS-only models (53.4% vs. 46.4% and 31.6%) in the validation dataset. The metabolomic pathways for arginine biosynthesis; aminoacyl-tRNA biosynthesis; and glycine, serine, and threonine pathway were enriched by adaLASSO metabolites for FEV1. This is the first demonstration of a respiratory metabolomic severity score, which shows how a metSS can add explanation of variance to clinical predictors of FEV1 and MESA-adjusted lung density. The advantage of a comprehensive metSS is that it explains more disease than individual metabolites and can account for substantial collinearity among classes of metabolites. Future studies should be performed to determine whether metSSs are similar in younger, and more racially and ethnically diverse populations as well as whether a metabolomic severity score can predict disease development in individuals who do not yet have COPD.

Evaluation of Asymmetric Dimethylarginine Serum Level and Left Ventricular Function by 2D Speckle Tracking Echocardiography in Children on Regular Hemodialysis

Cardiovascular disease is the leading cause of morbidity and mortality in children with chronic kidney disease. Asymmetric dimethylarginine (ADMA) is thought to be related to chronic kidney disease patients' adverse cardiovascular effects. Our study is to assess ADMA concentrations in children on hemodialysis (HD) as a marker of cardiovascular risk and detect the relation to the left ventricular (LV) function by traditional and speckled tracking echo. Forty children with end-stage renal disease on regular HD were enrolled in the study and selected from the nephrology HD unit of Al-Zahraa Hospital, Al-Azhar University. Another group of 40 healthy children matches age and sex with the patient's group as a control. ADMA serum level, traditional echo, and tissue Doppler imaging spackled tracking were performed to assess: LV functions for both groups in the same line with the routine laboratory investigations. Moreover, bioimpedance was assessed after the HD session. Children on regular HD have a significantly higher (ADMA) serum level compared to their controls; the median is (72.5 ng/mL) and (25 ng/mL), respectively (P = 0.001) and a significant increase in high-sensitivity C-reactive protein and the median is (3.6 ng/mL) and (2.5 ng/mL), respectively (P = 0.001). Moreover, conventional echo detects 27 (67.5%) patients out of 40 had an impaired LV function; meanwhile, 33 (82.5%) had a global LV strain (LV GLS) detected by 2D (Speckle echo), a negative correlation between LV ejection fraction with serum (urea, cholesterol, and triglyceride) and a positive correlation between ADMA and LV systolic diameter. LV GLS (Speckle echo) is negatively correlated with LV end-diastolic diameter, LV end-systolic diameter and positively correlated with LV inter ventricular septum in diastole and reduced average systolic velocity (ml). The sensitivity and specificity of (ADMA), high-sensitivity C-reactive protein (hs-CRP), traditional, and Speckle echo for early left ventricular (LV) dysfunction were 92.50, 92, and 67.50, 97 and 67.50, 90.00, and 80.00, 92, respectively. An ADMA emerges as a sensitive and specific marker for early LV dysfunction in children on hemodialysis (HD); drugs targeting ADMA isessential in the future direction after clinical approval, to avoid early LV changes, furthermore (Speckle echo) is superior to the traditional echo for early detection of LV changes in chronic kidney disease (CKD) children.

When one says yes and the other says no; does calcineurin participate in physiologic cardiac hypertrophy?

Developing engaging activities that build skills for understanding and appreciating research is important for undergraduate and postgraduate science students. Comparing and contrasting opposing research studies does this, and more: it also appropriately for these cohorts challenges higher level cognitive processing. Here, we present and discuss one such scenario, that of calcineurin in the heart and its response to exercise training. This scenario is further accentuated by the existence of only two studies. The background is that regular aerobic endurance exercise training stimulates the heart to physiologically adapt to chronically increase its ability to produce a greater cardiac output to meet the increased demand for oxygenated blood in working muscles, and this happens by two main mechanisms: 1) increased cardiac contractile function and 2) physiologic hypertrophy. The major underlying mechanisms have been delineated over the last decades, but one aspect has not been resolved: the potential role of calcineurin in modulating physiologic hypertrophy. This is partly because the existing research has provided opposing and contrasting findings, one line showing that exercise training does activate cardiac calcineurin in conjunction with myocardial hypertrophy, but another line showing that exercise training does not activate cardiac calcineurin even if myocardial hypertrophy is blatantly occurring. Here, we review and present the current evidence in the field and discuss reasons for this controversy. We present real-life examples from physiology research and discuss how this may enhance student engagement and participation, widen the scope of learning, and thereby also further facilitate higher level cognitive processing.

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.

Reactive Oxygen Species and Antioxidative Defense in Chronic Obstructive Pulmonary Disease

The respiratory system is continuously exposed to endogenous and exogenous oxidants. Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation of the airways, leading to the destruction of lung parenchyma (emphysema) and declining pulmonary function. It is increasingly obvious that reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the progression and amplification of the inflammatory responses related to this disease. First, we described the association between cigarette smoking, the most representative exogenous oxidant, and COPD and then presented the multiple pathophysiological aspects of ROS and antioxidative defense systems in the development and progression of COPD. Second, the relationship between nitric oxide system (endothelial) dysfunction and oxidative stress has been discussed. Third, we have provided data on the use of these biomarkers in the pathogenetic mechanisms involved in COPD and its progression and presented an overview of oxidative stress biomarkers having clinical applications in respiratory medicine, including those in exhaled breath, as per recent observations. Finally, we explained the findings of recent clinical and experimental studies evaluating the efficacy of antioxidative interventions for COPD. Future breakthroughs in antioxidative therapy may provide a promising therapeutic strategy for the prevention and treatment of COPD.

New horizons in arginine metabolism, ageing and chronic disease states

The elucidation of the metabolic pathways of the amino acid arginine and their role in health and disease have been an intensive focus of basic and clinical research for over a century. The recent advent of robust analytical techniques for biomarker assessment in large population cohorts has allowed the investigation of the pathophysiological role of specific arginine metabolites in key chronic disease states in old age, particularly those characterised by a reduced synthesis of endothelial nitric oxide, with consequent vascular disease and atherosclerosis. Two arginine metabolites have been increasingly studied in regard to their potential role in risk stratification and in the identification of novel therapeutic targets: the methylated arginine asymmetric dimethylarginine (ADMA) and the arginine analogue homoarginine. Higher circulating concentrations of ADMA, a potent inhibitor of nitric oxide synthesis, have been shown to predict adverse cardiovascular outcomes. By contrast, there is emerging evidence that homoarginine might exert cardioprotective effects. This review highlights recent advances in the biological and clinical role of ADMA and homoarginine in cardiovascular disease and other emerging fields, particularly chronic obstructive pulmonary disease, dementia, and depression. It also discusses opportunities for future research directions with the ultimate goal of translating knowledge of arginine metabolism, and its role in health and disease, into the clinical care of older adults.

Dietary nitrate improved exercise capacity in COPD but not blood pressure or pulmonary function: a 2 week, double-blind randomised, placebo-controlled crossover trial

Dietary nitrate may improve exercise tolerance in some healthy and clinical populations. Existing data regarding dietary nitrate in COPD is inconsistent. We conducted a 14d double-blind, randomised, placebo-controlled, crossover trial of daily nitrate-rich beetroot juice (BRJ; 12.9 mmol) versus nitrate-depleted BRJ (PL; 0.5 mmol). At baseline and after each condition, we assessed functional capacity (incremental shuttle walk test; ISWT), ambulatory blood pressure, pulmonary function, quality of life as well as exhaled nitric oxide (eNO), and plasma nitrate/nitrite (NOx). Eight subjects with COPD completed the trial. BRJ supplementation was associated with significantly increased NOx (p < .05) and a 14.6% increase in ISWT distance (+56 m, p = .00004) as well as a trend towards increased eNO compared to PL. There was no other differences. Dietary nitrate appears to have ergogenic effect in subjects with mild-moderate COPD. This effect does not appear to be related to altering blood pressure or pulmonary function.

Systemic concentrations of asymmetric dimethylarginine (ADMA) in chronic obstructive pulmonary disease (COPD): state of the art

Experimental evidence suggests that oxidative stress (OS) may increase the activity of arginine methylating enzymes that produce the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA). In addition, it is well documented that OS can significantly decrease the synthesis and/or activity of ADMA degrading enzymes, thus causing ADMA accumulation in biological fluids. Recent reports have focused on circulating methylated arginine concentrations in chronic obstructive pulmonary disease, a disease characterized by a significant increase in OS. This review discusses the results of these studies and the opportunities for further research in this area.

Cigarette Smoke-Induced Acquired Dysfunction of Cystic Fibrosis Transmembrane Conductance Regulator in the Pathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a disease state characterized by airflow limitation that is not fully reversible. Cigarette smoke and oxidative stress are main etiological risks in COPD. Interestingly, recent studies suggest a considerable overlap between chronic bronchitis (CB) phenotypic COPD and cystic fibrosis (CF), a common fatal hereditary lung disease caused by genetic mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Phenotypically, CF and COPD are associated with an impaired mucociliary clearance and mucus hypersecretion, although they are two distinct entities of unrelated origin. Mechanistically, the cigarette smoke-increased oxidative stress-induced CFTR dysfunction is implicated in COPD. This underscores CFTR in understanding and improving therapies for COPD by altering CFTR function with antioxidant agents and CFTR modulators as a great promising strategy for COPD treatments. Indeed, treatments that restore CFTR function, including mucolytic therapy, antioxidant ROS scavenger, CFTR stimulator (roflumilast), and CFTR potentiator (ivacaftor), have been tested in COPD. This review article is aimed at summarizing the molecular, cellular, and clinical evidence of oxidative stress, particularly the cigarette smoke-increased oxidative stress-impaired CFTR function, as well as signaling pathways of CFTR involved in the pathogenesis of COPD, with a highlight on the therapeutic potential of targeting CFTR for COPD treatment.

Augmentation of S-Nitrosoglutathione Controls Cigarette Smoke-Induced Inflammatory-Oxidative Stress and Chronic Obstructive Pulmonary Disease-Emphysema Pathogenesis by Restoring Cystic Fibrosis Transmembrane Conductance Regulator Function

AIMS

Cigarette smoke (CS)-mediated acquired cystic fibrosis transmembrane conductance regulator (CFTR)-dysfunction, autophagy-impairment, and resulting inflammatory-oxidative/nitrosative stress leads to chronic obstructive pulmonary disease (COPD)-emphysema pathogenesis. Moreover, nitric oxide (NO) signaling regulates lung function decline, and low serum NO levels that correlates with COPD severity. Hence, we aim to evaluate here the effects and mechanism(s) of S-nitrosoglutathione (GSNO) augmentation in regulating inflammatory-oxidative stress and COPD-emphysema pathogenesis.

RESULTS

Our data shows that cystic fibrosis transmembrane conductance regulator (CFTR) colocalizes with aggresome bodies in the lungs of COPD subjects with increasing emphysema severity (Global Initiative for Chronic Obstructive Lung Disease [GOLD] I - IV) compared to nonemphysema controls (GOLD 0). We further demonstrate that treatment with GSNO or S-nitrosoglutathione reductase (GSNOR)-inhibitor (N6022) significantly inhibits cigarette smoke extract (CSE; 5%)-induced decrease in membrane CFTR expression by rescuing it from ubiquitin (Ub)-positive aggresome bodies (p < 0.05). Moreover, GSNO restoration significantly (p < 0.05) decreases CSE-induced reactive oxygen species (ROS) activation and autophagy impairment (decreased accumulation of ubiquitinated proteins in the insoluble protein fractions and restoration of autophagy flux). In addition, GSNO augmentation inhibits protein misfolding as CSE-induced colocalization of ubiquitinated proteins and LC3B (in autophagy bodies) is significantly reduced by GSNO/N6022 treatment. We verified using the preclinical COPD-emphysema murine model that chronic CS (Ch-CS)-induced inflammation (interleukin [IL]-6/IL-1β levels), aggresome formation (perinuclear coexpression/colocalization of ubiquitinated proteins [Ub] and p62 [impaired autophagy marker], and CFTR), oxidative/nitrosative stress (p-Nrf2, inducible nitric oxide synthase [iNOS], and 3-nitrotyrosine expression), apoptosis (caspase-3/7 activity), and alveolar airspace enlargement (Lm) are significantly (p < 0.05) alleviated by augmenting airway GSNO levels. As a proof of concept, we demonstrate that GSNO augmentation suppresses Ch-CS-induced perinuclear CFTR protein accumulation (p < 0.05), which restores both acquired CFTR dysfunction and autophagy impairment, seen in COPD-emphysema subjects.

INNOVATION

GSNO augmentation alleviates CS-induced acquired CFTR dysfunction and resulting autophagy impairment.

CONCLUSION

Overall, we found that augmenting GSNO levels controls COPD-emphysema pathogenesis by reducing CS-induced acquired CFTR dysfunction and resulting autophagy impairment and chronic inflammatory-oxidative stress. Antioxid. Redox Signal. 27, 433-451.

Immunobiology of Nitric Oxide and Regulation of Inducible Nitric Oxide Synthase

Nitric oxide (NO) is a bioactive gas that has multiple roles in innate and adaptive immune responses. In macrophages, nitric oxide is produced by inducible nitric oxide synthase upon microbial and cytokine stimulation. It is needed for host defense against pathogens and for immune regulation. This review will summarize the role of NO and iNOS in inflammatory and immune responses and will discuss the regulatory mechanisms that control inducible nitric oxide synthase expression and activity.

Metabolomics analysis identifies sex-associated metabotypes of oxidative stress and the autotaxin-lysoPA axis in COPD

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease and a leading cause of mortality and morbidity worldwide. The aim of this study was to investigate the sex dependency of circulating metabolic profiles in COPD.

Serum from healthy never-smokers (healthy), smokers with normal lung function (smokers), and smokers with COPD (COPD; Global Initiative for Chronic Obstructive Lung Disease stages I–II/A–B) from the Karolinska COSMIC cohort (n=116) was analysed using our nontargeted liquid chromatography–high resolution mass spectrometry metabolomics platform.

Pathway analyses revealed that several altered metabolites are involved in oxidative stress. Supervised multivariate modelling showed significant classification of smokers from COPD (p=2.8×10⁻⁷). Sex stratification indicated that the separation was driven by females (p=2.4×10⁻⁷) relative to males (p=4.0×10⁻⁴). Significantly altered metabolites were confirmed quantitatively using targeted metabolomics. Multivariate modelling of targeted metabolomics data confirmed enhanced metabolic dysregulation in females with COPD (p=3.0×10⁻³) relative to males (p=0.10). The autotaxin products lysoPA (16:0) and lysoPA (18:2) correlated with lung function (forced expiratory volume in 1 s) in males with COPD (r=0.86; p<0.0001), but not females (r=0.44; p=0.15), potentially related to observed dysregulation of the miR-29 family in the lung.

These findings highlight the role of oxidative stress in COPD, and suggest that sex-enhanced dysregulation in oxidative stress, and potentially the autotaxin–lysoPA axis, are associated with disease mechanisms and/or prevalence.

Oxidative stress and the autotaxin–lysoPA axis evidence sex-associated metabotypes in the serum of COPD patientshttp://ow.ly/kAeE309MpdI

Positive correlation of airway resistance and serum asymmetric dimethylarginine level in COPD patients with systemic markers of low-grade inflammation

The major feature of COPD is a progressive airflow limitation caused by chronic airway inflammation and consequent airway remodeling. Modified arginase and nitric oxide synthase (NOS) pathways are presumed to contribute to the inflammation and fibrosis. Asymmetric dimethylarginine (ADMA) may shunt L-arginine from the NOS pathway to the arginase one by uncoupling and competitive inhibition of NOS and by enhancing arginase activity. To attest the interplay of these pathways, the relationship between ADMA and airflow limitation, described by airway resistance (R_aw), was investigated in a cohort of COPD patients. Every COPD patient willing to give consent to participate (n=74) was included. Case history, laboratory parameters, serum arginine and ADMA, pulmonary function (whole-body plethysmography), and disease-specific quality of life (St George’s Respiratory Questionnaire) were determined. Multiple linear regression was used to identify independent determinants of R_aw. The final multiple model was stratified based on symptom control. The log R_aw showed significant positive correlation with log ADMA in the whole sample (Pearson’s correlation coefficient: 0.25, P=0.03). This association remained significant after adjusting for confounders in the whole data set (β: 0.42; confidence interval [CI]: 0.06, 0.77; P=0.022) and in the worse-controlled stratum (β: 0.84; CI: 0.25, 1.43; P=0.007). Percent predicted value of forced expiratory flow between 25% and 75% of forced vital capacity showed that significant negative, elevated C-reactive protein exhibited significant positive relationship with R_aw in the final model. Positive correlation of R_aw with ADMA in COPD patients showing evidence of a systemic low-grade inflammation implies that ADMA contributes to the progression of COPD, probably by shunting L-arginine from the NOS pathway to the arginase one.

Toxic Dimethylarginines: Asymmetric Dimethylarginine (ADMA) and Symmetric Dimethylarginine (SDMA)

Asymmetric and symmetric dimethylarginine (ADMA and SDMA, respectively) are toxic, non-proteinogenic amino acids formed by post-translational modification and are uremic toxins that inhibit nitric oxide (NO) production and play multifunctional roles in many human diseases. Both ADMA and SDMA have emerged as strong predictors of cardiovascular events and death in a range of illnesses. Major progress has been made in research on ADMA-lowering therapies in animal studies; however, further studies are required to fill the translational gap between animal models and clinical trials in order to treat human diseases related to elevated ADMA/SDMA levels. Here, we review the reported impacts of ADMA and SDMA on human health and disease, focusing on the synthesis and metabolism of ADMA and SDMA; the pathophysiological roles of these dimethylarginines; clinical conditions and animal models associated with elevated ADMA and SDMA levels; and potential therapies against ADMA and SDMA. There is currently no specific pharmacological therapy for lowering the levels and counteracting the deleterious effects of ADMA and SDMA. A better understanding of the mechanisms underlying the impact of ADMA and SDMA on a wide range of human diseases is essential to the development of specific therapies against diseases related to ADMA and SDMA.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Arginines Plasma Concentration and Oxidative Stress in Mild to Moderate COPD

Background

Elevated plasma concentrations of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) have been observed in respiratory conditions such as asthma and cystic fibrosis. Since oxidative stress has been shown to increase the activity of arginine methylating enzymes, hence increased ADMA synthesis, and to reduce ADMA degrading enzymes, hence increased ADMA concentrations, we assessed methylated arginines concentrations in chronic obstructive pulmonary disease (COPD), a disease characterized by increased oxidative stress.

Methods

Plasma arginine, ADMA and symmetric dimethylarginine (SDMA), oxidative stress markers (thiobarbituric acid reactive substances, TBARS, and plasma proteins SH, PSH) and antioxidants (taurine and paraoxonase 1, PON1, activity) were measured in 43 COPD patients with mild (n = 29) or moderate (n = 14) disease and 43 age- and sex-matched controls.

Results

TBARS significantly increased with COPD presence and severity (median 2.93 vs 3.18 vs 3.64 μmol/L, respectively in controls, mild and moderate group, p<0.0001 by ANOVA) whereas PSH decreased (6.69±1.15 vs 6.04±0.85 vs 5.33±0.96 μmol/gr prot, p<0.0001 by ANOVA). Increased ADMA/arginine ratio, primarily due to reduced arginine concentrations, was also observed with COPD presence and severity (median 0.0067 vs 0.0075 vs 0.0100, p<0.0001 by ANOVA). In multiple logistic regression analysis, only TBARS (OR 0.44, 95% CI 0.25–0.77; p = 0.0045) and ADMA/Arginine ratio (OR 1.72, 95% CI 2.27–13.05; p = 0.02) were independently associated with COPD severity.

Conclusion

COPD presence and severity are associated with increased oxidative stress and alterations in arginine metabolism. The reduced arginine concentrations in COPD may offer a new target for therapeutic interventions increasing arginine availability.