Plasma arginine/ADMA ratio as a sensitive risk marker for atherosclerosis: Shimane CoHRE study

Asymmetric and symmetric dimethylarginine as markers of endothelial dysfunction in cerebrovascular disease: A prospective study

BACKGROUND AND AIM

Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) have been proposed as mediators of endothelial dysfunction. In this study, we aimed to investigate the diagnostic and prognostic role of ADMA and SDMA in acute cerebrovascular disease.

METHODS AND RESULTS

A prospective case-control study was performed, enrolling 48 patients affected by ischemic stroke with no cardioembolic origin, 20 patients affected by TIA, 40 subjects at high cardiovascular risk and 68 healthy subjects. ADMA levels were significantly lower in high-risk subjects (18.85 [11.78-22.83] μmol/L) than in patients with brain ischemic event, both transient (25.70 [13.15-40.20] μmol/L; p = 0.032) and permanent (24.50 [18.0-41.33] μmol/L; p = 0.001). SDMA levels were different not only between high-risk subjects and ischemic patients, but also between TIA and stroke patients, reaching higher levels in TIA group and lower levels in stroke group (1.15 [0.90-2.0] vs 0.68 [0.30-1.07] μmol/L; p < 0.001). SDMA was also correlated with short-term prognosis, with lower levels in case of adverse clinical course, evaluated by type of discharge (p = 0.009) and need of prolonged rehabilitation (p = 0.042).

CONCLUSIONS

The present study highlights the relationship between l-arginine, ADMA, SDMA and acute cerebrovascular events. Therefore, our results suggested a potential role of SDMA as a specific marker of transient ischemic damage and as a short-term positive prognostic marker.

Plasma arginine metabolites in health and chronic kidney disease

BACKGROUND

Elevated plasma asymmetric and symmetric dimethylarginine (ADMA and SDMA) are risk factors for chronic kidney disease (CKD) and cardiovascular disease. Using plasma cystatin C (pCYSC)-based estimated glomerular filtration rate (eGFR) trajectories, we identified a cohort at high risk of poor kidney-related health outcomes amongst members of the Dunedin Multidisciplinary Health and Development Study (DMHDS). We therefore examined associations between methylarginine metabolites and kidney function in this cohort.

METHODS

ADMA, SDMA, L-arginine and L-citrulline were measured in plasma samples from 45-year-olds in the DMHDS cohort by liquid chromatography-tandem mass spectrometry.

RESULTS

In a healthy DMHDS subset (n = 376), mean concentrations were: ADMA (0.40 ± 0.06 µmol/L), SDMA (0.42 ± 0.06 µmol/L), L-arginine (93.5 ± 23.1 µmol/L) and L-citrulline (24.0 ± 5.4 µmol/L). In the total cohort (n = 857), SDMA correlated positively with serum creatinine (Pearson's r = 0.55) and pCYSC (r = 0.55), and negatively with eGFR (r = 0.52). A separate cohort of 38 patients with stage 3-4 CKD (eGFR 15-60 mL/min/1.73 m2) confirmed significantly higher mean ADMA (0.61 ± 0.11 µmol/L), SDMA (0.65 ± 0.25 µmol/L) and L-citrulline (42.7 ± 11.8 µmol/L) concentrations. DMHDS members classified as high-risk of poor kidney health outcomes had significantly higher mean concentrations of all four metabolites compared with individuals not at risk. ADMA and SDMA individually predicted high-risk of poor kidney health outcomes with areas under the ROC curves (AUCs) of 0.83 and 0.84, and together with an AUC of 0.90.

CONCLUSIONS

Plasma methylarginine concentrations facilitate stratification for risk of CKD progression.

Effects of l-Arginine Plus Vitamin C Supplementation on l-Arginine Metabolism in Adults with Long COVID: Secondary Analysis of a Randomized Clinical Trial

Altered l-arginine metabolism has been described in patients with COVID-19 and has been associated with immune and vascular dysfunction. In the present investigation, we determined the serum concentrations of l-arginine, citrulline, ornithine, monomethyl-l-arginine (MMA), and symmetric and asymmetric dimethylarginine (SDMA, ADMA) in adults with long COVID at baseline and after 28-days of l-arginine plus vitamin C or placebo supplementation enrolled in a randomized clinical trial, compared with a group of adults without previous history of SARS-CoV-2-infection. l-arginine-derived markers of nitric oxide (NO) bioavailability (i.e., l-arginine/ADMA, l-arginine/citrulline+ornithine, and l-arginine/ornithine) were also assayed. Partial least squares discriminant analysis (PLS–DA) models were built to characterize systemic l-arginine metabolism and assess the effects of the supplementation. PLS–DA allowed discrimination of participants with long COVID from healthy controls with 80.2 ± 3.0% accuracy. Lower markers of NO bioavailability were found in participants with long COVID. After 28 days of l-arginine plus vitamin C supplementation, serum l-arginine concentrations and l-arginine/ADMA increased significantly compared with placebo. This supplement may therefore be proposed as a remedy to increase NO bioavailability in people with long COVID.

Neither Trimethylamine-N-Oxide nor Trimethyllysine Is Associated with Atherosclerosis: A Cross-Sectional Study in Older Japanese Adults

Recent evidence suggests that trimethylamine-N-oxide (TMAO), a metabolite of L-carnitine and choline, is linked to atherosclerosis and cardiovascular diseases. As TMAO content is very high in fish, we raised the following question: why do Japanese people, who consume lots of fish, show a low risk of atherosclerosis? To address this question, we investigated the effects of TMAO and other L-carnitine-related metabolites on carotid intima-media thickness (IMT). Participants were recruited from a small island and a mountainous region. Plasma L-carnitine, γ-butyrobetaine (γBB), TMAO, trimethyllysine (TML), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels were measured using liquid or gas chromatography-mass spectrometry. Plasma L-carnitine concentration was higher in men than in women. TMAO and TML were significantly higher in the residents of the island than in the mountainous people. In multiple linear regression analyses in all participants, TML showed a significant inverse association with max-IMT and plaque score (PS), whereas TMAO did not show any associations. In women, L-carnitine was positively associated with max-IMT and PS. TMAO was correlated with both EPA and DHA levels, implying that fish is a major dietary source of TMAO in Japanese people. Our study found that plasma TMAO was not an apparent risk factor for atherosclerosis in elderly Japanese people, whereas a low level of TML might be a potential risk. L-carnitine may be a marker for atherosclerosis in women.

The role of arginine and endothelial nitric oxide synthase in the pathogenesis of Covid-19 complicated by metabolic syndrome

This literature review presents the role of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO), as well as arginine, the enzyme substrate, in the disease of metabolic syndrome and COVID-19 (SARS-CoV-2 virus). Metabolic syndrome is a combination of obesity, insulin resistance, hyperglycemia, dyslipidemia and hypertension. It has been shown that in elderly people, patients with obesity, metabolic syndrome, type 2 diabetes mellitus (DM2), and patients with COVID-19, endothelial dysfunction (ED) and vascular endothelial activation are detected. ED is the main cause of a number of pathological conditions during the development of COVID-19 and earlier in patients with metabolic syndrome, while a sharp drop in the level of nitric oxide (NO) is detected due to a decrease in the expression and activity of eNO synthase and enzyme depletion, which leads to a violation of the integrity of bloodvessels, that is, to vasoconstrictive, inflammatory and thrombotic conditions, followed by ischemia of organs and edema of tissues. It should be noted that metabolic syndrome, DM2, hypertension and obesity, in particular, are age-related diseases, and it is known that blood glucose levels increase with age, which reduces the bioavailability of NO in endothelial cells. Defects in the metabolism of NO cause dysfunction in the pulmonary blood vessels, the level of NO decreases, which leads to impaired lung function and coagulopathy. The review presents possible mechanisms of these disorders associated with ED, the release of eNO synthase, changes in phosphorylation and regulation of enzyme activity, as well as insulin resistance. A modern view of the role of the polymorphism of the eNO synthase gene in the development of these pathologies is presented. To increase the level of endothelial NO, drugs are offered that regulate the bioavailability of NO. These include arginine, agonist NO – minoxidil, steroid hormones, statins, metformin. However, further research and clinical trials are needed to develop treatment strategies that increase NO levels in the endothelium.

Target Metabolome Profiling-Based Machine Learning as a Diagnostic Approach for Cardiovascular Diseases in Adults

Metabolomics is a promising technology for the application of translational medicine to cardiovascular risk. Here, we applied a liquid chromatography/tandem mass spectrometry approach to explore the associations between plasma concentrations of amino acids, methylarginines, acylcarnitines, and tryptophan catabolism metabolites and cardiometabolic risk factors in patients diagnosed with arterial hypertension (HTA) (n = 61), coronary artery disease (CAD) (n = 48), and non-cardiovascular disease (CVD) individuals (n = 27). In total, almost all significantly different acylcarnitines, amino acids, methylarginines, and intermediates of the kynurenic and indolic tryptophan conversion pathways presented increased (p < 0.05) in concentration levels during the progression of CVD, indicating an association of inflammation, mitochondrial imbalance, and oxidative stress with early stages of CVD. Additionally, the random forest algorithm was found to have the highest prediction power in multiclass and binary classification patients with CAD, HTA, and non-CVD individuals and globally between CVD and non-CVD individuals (accuracy equal to 0.80 and 0.91, respectively). Thus, the present study provided a complex approach for the risk stratification of patients with CAD, patients with HTA, and non-CVD individuals using targeted metabolomics profiling.

Effects of tofacitinib therapy on arginine and methionine metabolites in association with vascular pathophysiology in rheumatoid arthritis: A metabolomic approach

Introduction

Rheumatoid arthritis (RA) has been associated with changes in lipid, arginine and NO metabolism with increased cardiovascular (CV) risk. The aim of this study is to evaluate the effect of tofacitinib, a Janus kinase (JAK) inhibitor, on arginine and methionine metabolism in correlation with inflammation, functional and pathological vascular changes during one-year treatment of patients with RA.

Materials and methods

Thirty RA patients with active disease were treated with either 5 mg bid or 10 mg bid tofacitinib for 12 months. We determined DAS28, CRP, IgM rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) levels. We assessed brachial artery flow-mediated vasodilation (FMD), carotid intima-media thickness (IMT) and pulse-wave velocity (PWV) by ultrasound at baseline and after 6 and 12 months. We also determined plasma L-arginine, L-citrulline, L-ornithine, inducible nitric oxide synthase (iNOS), asymmetric (ADMA) and symmetric dimethylarginine (SDMA), L-N-monomethyl-arginine (L-NMMA), cysteine, homocysteine, and methionine levels at these time points.

Results

Twenty-six patients (13 on each arm) completed the study. CRP, ESR and DAS28 decreased significantly during one-year treatment with tofacitinib. Arginine and ADMA showed a negative univariate correlation with CRP but not with FMD, PWV or IMT. Tofacitinib at 10 mg bid significantly increased L-arginine, L-ornithine, iNOS and methionine levels after 12 months. ADMA and SDMA levels did not change in our study. Methionine showed negative correlation with FMD at baseline and positive correlation with PWV after 12 months. No change was observed in FMD and PWV but a significant increase was measured in IMT at 6 and 12 months. Multivariate analysis indicated variable correlations of L-arginine, L-citrulline, ADMA, L-NMMA, homocysteine and methionine with DAS28, CRP, ESR and RF but not with anti-CCP after one-year treatment. With respect to vascular pathophysiology, only PWV and methionine correlated with each other.

Conclusion

One-year tofacitinib treatment suppressed systemic inflammation and improved functional status in RA. FMD, PWV have not been affected by one-year tofacitinib treatment., while IMT increased further despite treatment. Increased arginine and methionine might contribute to the anti-inflammatory effects of tofacitinib. Increased arginine availability with no changing ADMA may protect FMD and PWV from deterioration. The increase of IMT in the anti-inflammatory environment cannot be explained by arginine or methionine metabolism in this study.

Increased Plasma L-Arginine Levels and L-Arginine/ADMA Ratios after Twelve Weeks of Omega-3 Fatty Acid Supplementation in Amateur Male Endurance Runners

It is not fully understood how supplementation with omega-3 fatty acids affects the metabolism of amino acids required for the bioavailability/synthesis of NO, i.e., L-arginine (L-arg), asymmetric dimethylarginine (ADMA), their metabolites, and the L-arg/ADMA ratio and their impact on running economy (RE) in runners. Thus, 26 male amateur endurance runners completed a twelve-week study in which they were divided into two supplemented groups: the OMEGA group (n = 14; 2234 mg and 916 mg of eicosapentaenoic and docosahexaenoic acid daily) or the MCT group (n = 12; 4000 mg of medium-chain triglycerides daily). At the same time, all participants followed an endurance training program. Before and after the 12-week intervention, blood was collected from participants at two time points (at rest and immediately post-exercise) to determine EPA and DHA in red blood cells (RBCs) and plasma levels of L-arg, ADMA, and their metabolites. RBC EPA and DHA significantly increased in the OMEGA group (p < 0.001), which was related to the resting increase in L-arg (p = 0.001) and in the L-arg/ADMA ratio (p = 0.005) with no changes in the MCT group. No differences were found in post-exercise amino acid levels. A total of 12 weeks of omega-3 fatty acid supplementation at a dose of 2234 mg of EPA and 916 mg of DHA daily increased levels of L-arg and the L-arg/ADMA ratio, which indirectly indicates increased bioavailability/NO synthesis. However, these changes were not associated with improved RE in male amateur endurance runners.

Arginase: shedding light on the mechanisms and opportunities in cardiovascular diseases

Arginase, a binuclear manganese metalloenzyme in the urea, catalyzes the hydrolysis of L-arginine to urea and L-ornithine. Both isoforms, arginase 1 and arginase 2 perform significant roles in the regulation of cellular functions in cardiovascular system, such as senescence, apoptosis, proliferation, inflammation, and autophagy, via a variety of mechanisms, including regulating L-arginine metabolism and activating multiple signal pathways. Furthermore, abnormal arginase activity contributes to the initiation and progression of a variety of CVDs. Therefore, targeting arginase may be a novel and promising approach for CVDs treatment. In this review, we give a comprehensive overview of the physiological and biological roles of arginase in a variety of CVDs, revealing the underlying mechanisms of arginase mediating vascular and cardiac function, as well as shedding light on the novel and promising therapeutic approaches for CVDs therapy in individuals.

The interplay between exposure to PAHs and MTHFR C677T polymorphism on cardiovascular risk biomarkers in Mexican women

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Environmental and genetic factors are recognized as risk determinants in the onset and development of CVDs. However, the interaction between both factors on CVDs risk is not still completely clarified. Therefore, the objective of this study was to evaluate the effect of the interaction between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and polycyclic aromatic hydrocarbon (PAH) exposure (gene-environment interaction) on cardiovascular risk biomarkers in Mexican women. A cross-sectional study was completed with the participation of 390 healthy women. For all enrolled women, anthropometric measurements, serum biochemical analyses, atherogenic indexes, and serum concentrations of biomolecules used as CVD risk biomarkers were obtained. 1-Hydroxypyrene (1-OHP) was measured in urine, as an exposure biomarker of PAHs. The mean urinary level of 1-OHP in the assessed population was 1.23 ± 1.40 μmol/mol creatinine. The allelic frequency (MTHFR C677T polymorphism) identified in the registered individuals was 68.0% for the mutant allele (T-allele). Significant positive associations were detected between urinary 1-OHP levels and serum asymmetric dimethylarginine (ADMA) concentrations (p < 0.05) and atherogenic index of plasma (AIP) values (p < 0.05). Also, women with the TT genotype of the MTHFR C677T enzyme have the highest serum ADMA levels (p < 0.05) and AIP values (p < 0.05) compared to women grouped as CC genotype and CT genotype. Besides, the findings in this study suggest an interaction between environmental (PAHs exposure) and genetic (MTHFR C677T polymorphism) factors on cardiovascular risk markers (ADMA and AIP). According to the usefulness of AIP and ADMA, an increased cardiovascular risk is notable in highly exposed individuals to PAHs with the polymorphic genotype (TT) of the MTHFR enzyme. Therefore, intervention programs in the target communities are required to diminish the cardiovascular risk of the assessed individuals.

Developing a robust, fast and reliable measurement method for the analysis of methylarginine derivatives and related metabolites

Background

Nitric oxide (NO) plays an important role in endothelial homeostasis. Asymmetric dimethyl arginine (ADMA), L-N monomethyl arginine (L-NMMA) and symmetric dimethyl arginine (SDMA), which are derivatives of methylarginine, directly or indirectly reduce NO production. Therefore, these metabolites are an important risk factor for various diseases, including cardiovascular diseases. Numerous methods have been developed for the measurement of methylarginine derivatives, but various difficulties have been encountered. This study aimed to develop a reliable, fast and cost-effective method for the analysis and measurement of methylarginine derivatives (ADMA, SDMA, L-NMMA) and related metabolites (arginine, citrulline, homoarginine, ornithine), and to validate this method according to Clinical and Laboratory Standards Institute (CLSI) protocols.

Methods

For the analysis of ADMA, SDMA, L-NMMA, arginine, homoarginine, citrulline, ornithine, 200 Âµl of serum were precipitated with methanol, and subsequently derivatized with a butanol solution containing 5% acetyl chloride. Butyl derivatives were separated using a C18 reverse phase column with a 5 min run time. Detection of analytes was achieved by utilising the specific fragmentation patterns identified through tandem mass spectrometry.

Results

The method was linear for ADMA, SDMA, L-NMMA, ornithine, arginine, homoarginine and citrulline in the ranges of 0.023–6.0, 0.021–5.5, 0.019–5.0, 0.015–250, 0.015–250, 0.019–5 and 0.015–250 µM, respectively. The inter-assay CV% values for all analytes was less than 9.8%.

Conclusions

Data obtained from method validation studies shows that the developed method is highly sensitive, precise and accurate. Short analysis time, cost-effectiveness, and multiplexed analysis of these metabolites, with the same pretreatment steps, are the main advantages of the method.

Reduced L-Arginine and L-Arginine-ADMA-Ratio, and Increased SDMA after Norseman Xtreme Triathlon

Endothelial vasodilatory function is dependent on the NO synthesis from L-arginine by endothelial NO-synthetase (eNOS). eNOS can be inhibited by asymmetric dimethylarginine (ADMA) by competitive inhibition on the binding site, and symmetric dimethylarginine (SDMA) can reduce the L-arginine availability intracellularly through competing for transport over the cellular membrane. To study the NO synthesis after prolonged exercise, we assessed circulatory L-arginine, the L-arginine/ADMA ratio, and SDMA before, after, and on the day after the Norseman Xtreme triathlon, an Ironman distance triathlon. We found significantly reduced levels of L-arginine and the L-arginine/ADMA ratio and increased levels of SDMA after the race (all p < 0.05). L-arginine rose toward baseline levels the day after the race, but ADMA increased beyond baseline levels, and SDMA remained above baseline the day after the race. The reduced levels of L-arginine and the L-arginine/ADMA ratio, and increased SDMA, after the race indicate a state of reduced capability of NO production. Increased levels of ADMA and SDMA, and reduced L-arginine/ADMA ratio, as seen the day after the race, are known risk markers of atherosclerosis and warrant further studies.

The shifted balance of arginine metabolites in acute myocardial infarction patients and its clinical relevance

The arginine metabolism as a target for cardioprotection in patients with ST-segment elevation myocardial infarction (STEMI) remains insufficiently understood. Arginine, ornithine, citrulline, asymmetric dimethylarginine (ADMA) and proline plasma levels were measured using liquid chromatography and tandem mass spectrometry in 70 consecutive STEMI patients upon admission and at 6-month follow-up and were compared with left ventricular function, volumes, and infarct characteristics determined by cardiac magnetic resonance imaging, and with 5-year clinical outcomes. Baseline median concentration of arginine was higher by 49% (P = 0.002) when compared to 6-month measurements and was correlated with an ischemia risk area (R = 0.34, P = 0.004) and infarct size (R = 0.33, P = 0.006). Following ischemia median citrulline/arginine index decreased when compared with 6-month result (P = 0.002), while citrulline/ornithine and arginine/ADMA ratios maintained unchanged indicating a shift of arginine metabolism from nitric oxide synthase (NOS) towards arginase. The 6-month arginine concentration reached the area under the ROC curve of 0.67 (95% confidence interval 0.54–0.81) for prediction of death, myocardial infarction or heart failure hospitalization and its value of < 29 µM was associated with lower event free survival (P = 0.02). In STEMI patients, during ischemia conversion of elevated plasma arginine was shifted from NOS towards arginase. Decreased 6-month arginine concentrations were associated with worse long-term outcomes.

Arginine and Arginine/ADMA Ratio Predict 90-Day Mortality in Patients with Out-of-Hospital Cardiac Arrest-Results from the Prospective, Observational COMMUNICATE Trial

(1) Background: In patients with shock, the L-arginine nitric oxide pathway is activated, causing an elevation of nitric oxide, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) levels. Whether these metabolites provide prognostic information in patients after out-of-hospital cardiac arrest (OHCA) remains unclear. (2) Methods: We prospectively included OHCA patients, recorded clinical parameters and measured plasma ADMA, SDMA and Arginine levels by liquid chromatography tandem mass spectrometry (LC-MS). The primary endpoint was 90-day mortality. (3) Results: Of 263 patients, 130 (49.4%) died within 90 days after OHCA. Compared to survivors, non-survivors had significantly higher levels of ADMA and lower Arginine and Arginine/ADMA ratios in univariable regression analyses. Arginine levels and Arginine/ADMA ratio were significantly associated with 90-day mortality (OR 0.51 (95%CI 0.34 to 0.76), p < 0.01 and OR 0.40 (95%CI 0.26 to 0.61), p < 0.001, respectively). These associations remained significant in several multivariable models. Arginine/ADMA ratio had the highest predictive value with an area under the curve (AUC) of 0.67 for 90-day mortality. Results for secondary outcomes were similar with significant associations with in-hospital mortality and neurological outcome. (4) Conclusion: Arginine and Arginine/ADMA ratio were independently associated with 90-day mortality and other adverse outcomes in patients after OHCA. Whether therapeutic modification of the L-arginine-nitric oxide pathway has the potential to improve outcome should be evaluated.

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.

[Asymmetric dimethylarginine (ADMA) in retinal vein occlusion-Results from the Gutenberg RVO study]

BACKGROUND

Asymmetric dimethylarginine (ADMA) is considered an independent cardiovascular risk factor (cvRF) and thus represents a potential new biomarker for retinal vein occlusion (RVO).

METHODS

Overall, 92 patients with RVO and the same number of matched controls were included in the Gutenberg RVO study. All patients underwent a standardized examination for cvRF at the study center of the population-based Gutenberg health study (GHS) as well as ophthalmological examinations and intensive laboratory tests. This article presents a substudy of patients (≤65 years old) and the controls in whom ADMA was additionally determined by high performance liquid chromatography (HPLC) at baseline and 4-6 weeks later.

RESULTS

Out of 44 patients with RVO 22 had central retinal vein occlusion (CRVO), 15 had branch retinal vein occlusion (BRVO) and 7 had hemiretinal vein occlusion (hemi-RVO). The ADMA levels were 0.383 ± 0.094 µM (mean ± standard deviation) in RVO patients at baseline and 0.380 ± 0.093 µM (p = 0.514, initial vs. follow-up) after the follow-up period versus 0.360 ± 0.077 µM (p = 0.175, controls vs. RVO) in controls (n = 44). Arterial hypertension was the most prevalent risk factor in 22 (50%) of the patients and in 11 (25%) of the controls (odds ratio, OR 2.77, 95% confidence interval, CI 0.97-7.95; p = 0.058). The ADMA values above the 95th percentile (>0.530 µM) were detected in 4 patients with RVO (9.1%) but not in any of the controls (p = 0.041, RVO vs. controls).

CONCLUSION

Hypertension is the most important risk factor for RVO. Due to the high number of hypertensive patients in the cohort, the relevance of ADMA as an independent risk factor could neither be confirmed nor disproved.

Arginine and Endothelial Function

Arginine (L-arginine), is an amino acid involved in a number of biological processes, including the biosynthesis of proteins, host immune response, urea cycle, and nitric oxide production. In this systematic review, we focus on the functional role of arginine in the regulation of endothelial function and vascular tone. Both clinical and preclinical studies are examined, analyzing the effects of arginine supplementation in hypertension, ischemic heart disease, aging, peripheral artery disease, and diabetes mellitus.

The effect of Channa striata extract and standard eradication regimen on asymmetric dimethylarginine in Helicobacter pylori gastritis rat model

BACKGROUND AND AIM

The presence of gastric mucosa or submucosa inflammation due to Helicobacter pylori leads to histological changes. Gastric injury, pro-inflammatory factors, and oxidative stress in H. pylori infection produce asymmetric dimethylarginine (ADMA), which are a competitive inhibitor of nitric oxide synthase. Investigations were carried out aimed at finding new drugs derived from natural products for the treatment of H. pylori. Channa striata is known to have in vitro anti-inflammatory and antimicrobial properties. This study aimed to investigate the effect of C. striata extract and a standard eradication regimen on ADMA levels and histological changes in the H. pylori gastritis rat model.

MATERIALS AND METHODS

Thirty-five male rats were randomly and equally divided into five groups. Group-1 was the negative control group and Groups-2 to 5 were H. pylori-infected groups. Groups-3 to 5 were administered C. striata extract, a standard eradication regimen, and a combination of standard eradication regimen and C. striata extract, respectively. Histological examination and serum ADMA levels were analyzed. The difference between groups was analyzed using the Kruskal-Wallis and one-way analysis of variance tests. The significance was p<0.05.

RESULTS

Serum ADMA levels and severity of gastritis were higher in infected groups compared to the negative control group (p<0.05). The severity of gastritis and mean ADMA levels in the group that received a single administration of the C. striata extract was higher than the others (p<0.05). Serum ADMA levels and severity of gastritis were significantly reduced in the group that received a combination of standard eradication regimen and C. striata extract (p<0.05).

CONCLUSION

Single administration of C. striata extract worsens the severity of gastritis and increased serum ADMA levels in the H. pylori gastritis rat model. The administration of a combination of standard eradication regimen and C. striata extract reduces serum ADMA levels and significantly improves the severity of H. pylori gastritis rat model.

Metabolic Pathways Fueling the Endothelial Cell Drive

Endothelial cell (EC) metabolism is important for health and disease. Metabolic pathways, such as glycolysis, fatty acid oxidation, and amino acid metabolism, determine vasculature formation. These metabolic pathways have different roles in securing the production of energy and biomass and the maintenance of redox homeostasis in vascular migratory tip cells, proliferating stalk cells, and quiescent phalanx cells, respectively. Emerging evidence demonstrates that perturbation of EC metabolism results in EC dysfunction and vascular pathologies. Here, we summarize recent insights into EC metabolic pathways and their deregulation in vascular diseases. We further discuss the therapeutic implications of targeting EC metabolism in various pathologies.

Arginine Derivatives in Cerebrovascular Diseases: Mechanisms and Clinical Implications

The amino acid L-arginine serves as substrate for the nitric oxide synthase which is crucial in vascular function and disease. Derivatives of arginine, such as asymmetric (ADMA) and symmetric dimethylarginine (SDMA), are regarded as markers of endothelial dysfunction and have been implicated in vascular disorders. While there is a variety of studies consolidating ADMA as biomarker of cerebrovascular risk, morbidity and mortality, SDMA is currently emerging as an interesting metabolite with distinct characteristics in ischemic stroke. In contrast to dimethylarginines, homoarginine is inversely associated with adverse events and mortality in cerebrovascular diseases and might constitute a modifiable protective risk factor. This review aims to provide an overview of the current evidence for the pathophysiological role of arginine derivatives in cerebrovascular ischemic diseases. We discuss the complex mechanisms of arginine metabolism in health and disease and its potential clinical implications in diverse aspects of ischemic stroke.

Targeted metabolomic analysis of nitric oxide/L-arginine pathway metabolites in dementia: association with pathology, severity, and structural brain changes

L-Arginine/NO pathway is altered in Alzheimer disease (AD). Its clinical relevance and pathway status in vascular dementia (VaD) are unknown. Using targeted metabolomics (a liquid chromatography-mass spectrometry) we assessed L-arginine, L-citrulline, dimethylamine (DMA), asymmetric dimethyl arginine (ADMA) and symmetric dimethylarginine (SDMA) in AD (n = 48), mixed-type dementia (MD; n = 34), VaD (n = 40) and non-demented individuals (n = 140) and determined their clinical relevance (the association with dementia pathology, cognitive impairment, and structural brain damage). L-Arginine, ADMA, L-arginine/ADMA, and L-citrulline levels were decreased in dementia and L-arginine, L-citrulline, age and sex were its independent predictors correctly classifying 91% of cases. L-Arginine and L-arginine/ADMA were differentiating between VaD and AD with moderate accuracy. L-Arginine, L-arginine/ADMA, SDMA, and DMA reflected structural brain changes. DMA and L-citrulline were elevated in patients with strategic infarcts and SDMA, L-arginine/ADMA, and DMA were independent predictors of Hachinski ischemic score. ADMA and SDMA accumulation reflected severity of cognitive impairment. In summary, L-Arginine/NO pathway is altered in neurodegenerative and vascular dementia in association with neurodegenerative and vascular markers of brain damage and severity of cognitive impairment.

Increased plasma concentration of 4-pyridone-3-carboxamide-1-ß-D-ribonucleoside (4PYR) in lung cancer. Preliminary studies

4-pyridone-3-carboxamide-1-β-D-ribonucleoside (4PYR) is a new nicotinamide derivative, which is potentially toxic to the endothelium. Dysfunction of the endothelium promotes cancer cell proliferation, invasiveness, and inflammatory signaling. The aim of this study was to analyze 4PYR concentration in the plasma of lung cancer patients and its relationship to other known biochemical parameters associated with the endothelium function. The concentration of 4PYR, nicotinamide, 1-methylnicotinamide (MNA), amino acids, and their derivatives were measured in samples obtained from patients with primary squamous cell carcinoma (n = 48) and control group (n = 100). The concentration of 4PYR and 4PYR/MNA ratio were significantly higher in lung cancer patients as compared to controls (0.099 ± 0.009 vs. 0.066 ± 0.006 µmol/L and 1.10 ± 0.08 vs. 1.97 ± 0.15, respectively). The plasma arginine/asymmetric dimethylarginine (Arg/ADMA) ratio was considerably lower in lung cancer patients (253 ± 17 vs. 369 ± 19) as well as plasma MNA (0.057 ± 0.004 vs. 0.069 ± 0.003 µmol/L). There was no difference in the plasma concentrations of nicotinamide and nicotinamide riboside in both groups (0.116 ± 0.019 vs. 0.131 ± 0.014 and 0.102 ± 0.006 vs. 0.113 ± 0.011, respectively). In this study, a higher 4PYR concentration was observed for the first time in patients with squamous cell carcinoma. This change may be related to the endothelial dysfunction that promote cancer progression since 4PYR and its derivatives are known to disrupt glycolytic pathway.

The iridoid loganic acid and anthocyanins from the cornelian cherry (Cornus mas L.) fruit increase the plasma l-arginine/ADMA ratio and decrease levels of ADMA in rabbits fed a high-cholesterol diet

BACKGROUND

Although fruit and vegetable-rich diets have beneficial effects on cardiovascular diseases, we have little knowledge of the impact of fruits and their constituents, iridoids and anthocyanins, on the l-arginine-ADMA-DDAH pathway. Our previous study demonstrated the modulation of those factors by the oral administration of the cornelian cherry fruit.

HYPOTHESIS/PURPOSE

We have assessed the effects of the oral administration of two main constituents isolated from the cornelian cherry fruit, iridoid loganic acid and anthocyanins, on l-arginine, its derivatives (ADMA, SDMA), metabolites (DMA, l-citrulline), and the hepatic DDAH activity and its isoform expression in rabbits fed a high-cholesterol diet. We have also analyzed eNOS expression in the thoracic aorta as well as the redox status in blood.

STUDY DESIGN

In the present study, we used an animal model of diet induced atherosclerosis. For 60 days, white New Zealand rabbits were fed a standard diet, a 1% cholesterol enriched diet, or concomitantly with the investigated substances. l-arginine, ADMA, SDMA, DMA, and l-citrulline were assessed using the LC-MS/MS method. DDAH activity and redox parameters were analyzed spectrophotometrically. DDAH1 and DDAH2 isoform expressions were assessed by western blotting, mRNA expression of eNOS was quantified by real-time PCR.

RESULTS

We demonstrated that the administration of loganic acid (20 mg/kg b.w.), and to a lesser extent of anthocyanins (10 mg/kg b.w.), caused an increase in the l-arginine level and the l-arginine/ADMA ratio. Also, both substances decreased ADMA, DMA, and l-citrulline, but not SDMA levels. Anthocyanins, but not loganic acid, enhanced the activity of DDAH in the liver. Anthocyanins also significantly enhanced both DDAH1 and DDAH2 expression, while loganic acid to a lesser extent enhanced DDAH1 but not DDAH2 expression. Both loganic acid and anthocyanins pronouncedly increased mRNA expression of eNOS in thoracic aortas. Both loganic acid and anthocyanins reversed the blood glutathione level depleted by dietary cholesterol. Cholesterol feeding decreased the blood GPx level, and the change was not reversed by anthocyanins or loganic acid. We did not observe any significant differences in the blood levels of MDA or SOD among the groups.

CONCLUSION

Iridoids and anthocyanins may modulate the l-arginine-ADMA pathway in subjects fed a high-cholesterol diet.

Cholesterol crystals in periapical lesions of root filled teeth

AIM

To determine the prevalence of cholesterol crystals in periapical biopsies and to evaluate the correlation between cholesterol crystals in periapical biopsies and age, gender, location of the periapical lesion, pathologic diagnosis and lesion size.

METHODOLOGY

The biopsy report database (Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand) during 2005-2014 was reviewed. The prevalence of cholesterol crystals in the periapical lesions of root filled teeth was determined. Pathological diagnosis, patients' age, gender and the location (maxilla or mandible) of the periapical lesion were obtained from treatment records. The area of the lesion from the periapical radiograph before surgery was calculated using ImageJ software. Univariate and multivariate logistic regression analyses were used to determine the association between independent variables and the presence of cholesterol crystals.

RESULTS

The overall prevalence of cholesterol crystals was 20.31%. The periapical biopsies >100 mm² in size on periapical films had a significantly greater prevalence of cholesterol crystals than those <100 mm² (P = 0.005). The biopsies diagnosed as radicular cysts had a significantly greater prevalence of cholesterol crystals than the biopsies with other diagnoses (P < 0.001). A pathological diagnosis of radicular cyst was the variable with the strongest association with the presence of cholesterol crystals (P < 0.001; adjusted OR, 12.39).

CONCLUSIONS

Presence of cholesterol crystals was associated with periapical lesion diagnosed as a radicular cyst and lesion >100 mm² in area. Age, gender and location of the lesion did not influence the presence of cholesterol crystals.

AGXT2 and DDAH-1 genetic variants are highly correlated with serum ADMA and SDMA levels and with incidence of coronary artery disease in Egyptians

Dimethylarginine aminodehydrolase (DDAH1) and alanine glyoxylate aminotransferase2 (AGXT2) are two enzymes that contribute in asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) metabolism. Hence they affect production and bioavailability of eNOS-derived nitric oxide (NO) and consequently healthy blood vessels. The major aims of the current study were to investigate the association of genetic variants of AGXT2 rs37369, AGXT2 rs16899974 and DDAH1 rs997251 SNPs with incidence of coronary artery disease (CAD) in Egyptians and to correlate these variants with the serum levels of ADMA and SDMA. The study included 150 subjects; 100 CAD patients and 50 healthy controls. Genotyping was performed by qPCR while the ADMA and SDMA concentrations were assayed by ELISA. Both serum ADMA and SDMA concentrations were significantly higher in CAD patients compared to controls (both p < 0.0001). Genotype distributions for all studied SNPs were significantly different between CAD patients and controls. Carriers of AGXT2 rs37369-T allele (CT + TT genotypes) and AGXT2 rs16899974-A allele (CA + AA genotypes) had 2.4- and 2.08-fold higher risk of having CAD than CC genotype in both SNPs (p = 0.0050 and 0.0192, respectively). DDAH1 rs997251 TC + CC genotypes were associated with 2.3-fold higher risk of CAD than TT genotype (p = 0.0063). Moreover, the AGXT2 rs37369 TT and AGXT2 rs16899974 AA genotypes were associated with the highest serum ADMA and SDMA while DDAH1 rs997251 CC genotype was associated with the highest ADMA. AGXT2 rs37369-T, AGXT2 rs16899974-A, and DDAH1 rs997251-C alleles represent independent risk factors for CAD in the Egyptians.

Homoarginine/ADMA ratio and homoarginine/SDMA ratio as independent predictors of cardiovascular mortality and cardiovascular events in lower extremity arterial disease

Endothelial dysfunction plays a key role in development of atherosclerosis and lower extremity arterial disease (LEAD). Homoarginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are sensitive markers for endothelial dysfunction and independent risk factors for cardiovascular death. However, homoarginine may influence the proatherogenic effects of ADMA and SDMA suggesting homoarginine/ADMA ratio or homoarginine/SDMA ratio as further predictors for cardiovascular mortality. Therefore, we investigated the predictive value of homoarginine/ADMA ratio and homoarginine/SDMA ratio related to cardiovascular mortality and cardiovascular events in claudicant patients with LEAD. 151 patients with intermittent claudication were included in a prospective observational study (observation time 7.7 ± 2.5 years) with cardiovascular mortality as main outcome parameter and the occurrence of cardiovascular events as secondary outcome parameter. Homoarginine, ADMA and SDMA were measured by high-performance liquid chromatography at baseline. Low homoarginine/ADMA ratio and homoarginine/SDMA ratio were independently associated with higher cardiovascular mortality (HR 2.803 [95% CI 1.178–6.674], p = 0.020; HR 2.782 [95% CI 1.061–7.290], p = 0.037, respectively) and higher incidence of cardiovascular events (HR 1.938 [95% CI 1.015–3.700], p = 0.045; HR 2.397 [95% CI 1.243–4.623], p = 0.009, respectively). We observed that homoarginine/ADMA ratio and homoarginine/SDMA ratio are independent predictors for long-term cardiovascular mortality and events in claudicant patients with LEAD.

Development of a novel UHPLC-MS/MS-based platform to quantify amines, amino acids and methylarginines for applications in human disease phenotyping

Amine quantification is an important strategy in patient stratification and personalised medicine. This is because amines, including amino acids and methylarginines impact on many homeostatic processes. One important pathway regulated by amine levels is nitric oxide synthase (NOS). NOS is regulated by levels of (i) the substrate, arginine, (ii) amino acids which cycle with arginine and (iii) methylarginine inhibitors of NOS. However, biomarker research in this area is hindered by the lack of a unified analytical platform. Thus, the development of a common metabolomics platform, where a wide range of amino acids and methylarginines can be measured constitutes an important unmet need. Here we report a novel high-throughput ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) platform where ≈40 amine analytes, including arginine and methylarginines can be detected and quantified on a molar basis, in a single sample of human plasma. To validate the platform and to generate biomarkers, human plasma from a well-defined cohort of patients before and after coronary artery bypass surgery, who developed systemic inflammatory response syndrome (SIRS), were analysed. Bypass surgery with SIRS significantly altered 26 amine analytes, including arginine and ADMA. Consequently, pathway analysis revealed significant changes in a range of pathways including those associated with NOS.

The clinical effects of l-arginine and asymmetric dimethylarginine: implications for treatment in secondary Raynaud's phenomenon

Secondary Raynaud's phenomenon (RP) is often the sentinel clinical finding in systemic sclerosis and may precede systemic disease by several years. Altered nitric oxide metabolism plays a critical role in both fibrosis and severe secondary RP phenotypes in these patients. Increased flux through inducible nitric oxide synthase (iNOS) drives cutaneous fibrosis. Failure of flux through endothelial nitric oxide synthase (eNOS) contributes to increased vasoconstriction and decreased vasorelaxation. The underproduction of nitric oxide by eNOS is in part due to increased levels of asymmetric dimethylarginine (ADMA), an endogenous competitive inhibitor of nitric oxide synthase. The inhibitory effects of increased ADMA levels may be counteracted increasing serum l‐arginine, which is often an effective treatment strategy in these patients. As such, l‐arginine‐based therapies should be considered in managing secondary RP, particularly given their favourable safety and tolerability profile. While there is no established dosing regimen, studies of oral l‐arginine in secondary RP suggest that divided dosing may begin at 1–2 g/day and may be titrated up to 10 g/day. Conversely, primary RP is not associated with increased ADMA production which likely accounts for the failure of l‐arginine trials to show benefit in primary RP.

Dihydromyricetin Attenuates TNF-α-Induced Endothelial Dysfunction through miR-21-Mediated DDAH1/ADMA/NO Signal Pathway

Accumulating studies demonstrate that dihydromyricetin (DMY), a compound extracted from Chinese traditional herb, Ampelopsis grossedentata, attenuates atherosclerotic process by improvement of endothelial dysfunction. However, the underlying mechanism remains poorly understood. Thus, the aim of this study is to investigate the potential mechanism behind the attenuating effects of DMY on tumor necrosis factor alpha- (TNF-α-) induced endothelial dysfunction. In response to TNF-α, microRNA-21 (miR-21) expression was significantly increased in human umbilical vein endothelial cells (HUVECs), in line with impaired endothelial dysfunction as evidenced by decreased tube formation and migration, endothelial nitric oxide synthase (eNOS) (ser1177) phosphorylation, dimethylarginine dimethylaminohydrolases 1 (DDAH1) expression and metabolic activity, and nitric oxide (NO) concentration as well as increased asymmetric dimethylarginine (ADMA) levels. In contrast, DMY or blockade of miR-21 expression ameliorated endothelial dysfunction in HUVECs treated with TNF-α through downregulation of miR-21 expression, whereas these effects were abolished by overexpression of miR-21. In addition, using a nonspecific NOS inhibitor, L-NAME, also abrogated the attenuating effects of DMY on endothelial dysfunction. Taken together, these data demonstrated that miR-21-mediated DDAH1/ADMA/NO signal pathway plays an important role in TNF-α-induced endothelial dysfunction, and DMY attenuated endothelial dysfunction induced by TNF-α in a miR-21-dependent manner.

Serum Methylarginines and Hearing Loss in a Population-based Cohort of Older Adults

OBJECTIVE

Age-related hearing loss is associated with endothelial dysfunction and increased cardiovascular risk, suggesting a vascular etiology. Methylarginines are endogenous nitric oxide synthase inhibitors that cause endothelial dysfunction and increase cardiovascular disease risk. This study is the first to examine the hypothesis that higher serum concentrations of methylarginines are associated with greater hearing loss prevalence.

STUDY DESIGN/PATIENTS

Cross-sectional audiometric data on hearing levels, and serum methylarginines were collected from a population-based sample of 630 older community-dwelling adults.

RESULTS

Linear regression analysis showed a statistically significant association between higher serum concentrations of asymmetric dimethylarginine (ADMA) and L-arginine and greater degrees of hearing loss for males, particularly over 75 years. Higher body mass index and previous history of stroke were also associated with hearing loss. For females, ADMA concentration was not associated with hearing loss, but higher serum L-arginine concentrations were associated with reduced hearing loss prevalence in older females. Antihypertensive medication use was also associated with reduced hearing loss prevalence. LDL cholesterol and previous myocardial infarction were associated with greater hearing loss.

CONCLUSION

This study showed a significant association between serum concentrations of ADMA and hearing loss for males, consistent with the association between endothelial dysfunction and hearing loss. The opposite effect of L-arginine on hearing loss in males versus females might reflect a different role of this precursor toward nitric oxide versus methylated arginines synthesis. These findings are potentially clinically significant if the association between ADMA and hearing loss is causal, as serum methylarginine levels are modifiable through pharmacotherapeutic/lifestyle interventions.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

Plasma L-arginine levels distinguish pulmonary arterial hypertension from left ventricular systolic dysfunction

Pulmonary arterial hypertension (PAH) is a life-threatening condition, characterized by an imbalance of vasoactive substances and remodeling of pulmonary vasculature. Nitric oxide, formed from L-arginine, is essential for homeostasis and smooth muscle cell relaxation in PAH. Our aim was to compare plasma concentrations of L-arginine, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) in PAH compared to left ventricular systolic dysfunction (LVSD) and healthy subjects. This was an observational, multicenter study comparing 21 patients with PAH to 14 patients with LVSD and 27 healthy subjects. Physical examinations were obtained and blood samples were collected. Plasma levels of ADMA, SDMA, L-arginine, L-ornithine, and L-citrulline were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Plasma levels of ADMA and SDMA were higher, whereas L-arginine and L-arginine/ADMA ratio were lower in PAH patients compared to healthy subjects (p < 0.001). Patients with PAH also had lower levels of L-arginine than patients with LVSD (p < 0.05). L-Arginine correlated to 6 min walking distance (6MWD) (r _s = 0.58, p = 0.006) and L-arginine/ADMA correlated to WHO functional class (r _s = -0.46, p = 0.043) in PAH. In conclusion, L-arginine levels were significantly lower in treatment naïve PAH patients compared to patients with LVSD. Furthermore, L-arginine correlated with 6MWD in PAH. L-arginine may provide useful information in differentiating PAH from LVSD.

AGXT2: An unnegligible aminotransferase in cardiovascular and urinary systems

Cardiovascular diseases (CVDs) and renal impairment interact in a complex and interdependent manner, which makes clarification of possible pathogenesis between CVDs and renal diseases very challenging and important. There is increasing evidence showing that both asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) play a crucial role in the development of CVDs as well as in the prediction of cardiovascular events. Also, the plasma levels of ADMA and SDMA were reported to be significantly associated with renal function. Alanine-glyoxylate aminotransferase 2 (AGXT2) is reported to be involved in ADMA and SDMA metabolism, thus deficiency in the expression or activity of AGXT2 may play a part in the progression of cardiovascular or renal diseases through affecting ADMA/SDMA levels. Here, we focused our attention on AGXT2 and discussed its potential impact on CVDs and renal diseases. Meanwhile, the review also summarized the functions and recent advances of AGXT2, as well as the clinical association studies of AGXT2 in cardiovascular and urinary systems, which might arouse the interest of researchers in these fields.

Plasma Arginine/Asymmetric Dimethylarginine Ratio and Incidence of Cardiovascular Events: A Case-Cohort Study

Context

Arginine, its methylated metabolites, and other metabolites related to the urea cycle have been independently associated with cardiovascular risk, but the potential causal meaning of these associations (positive for some metabolites and negative for others) remains elusive due to a lack of studies measuring metabolite changes over time.

Objective

To examine the association between baseline and 1-year concentrations of urea cycle metabolites and cardiovascular disease (CVD) in a case-cohort setting.

Design

A case-cohort study was nested within the Prevención con Dieta Mediterránea trial. We used liquid chromatography-tandem mass spectrometry to assess metabolite levels at baseline and after 1-year follow-up. The primary CVD outcome was a composite of myocardial infarction, stroke and cardiovascular death. We used weighted Cox regression models (Barlow weights) to estimate multivariable-adjusted hazard ratios (HRs) and their 95% confidence intervals (CIs).

Setting

Multicenter randomized trial in Spain.

Participants

Participants were 984 participants accruing 231 events over 4.7 years' median follow-up.

Main Outcome Measure

Incident CVD.

Results

Baseline arginine/asymmetric dimethylarginine ratio [HR per standard deviation (SD) = 0.80; 95% CI, 0.67 to 0.96] and global arginine availability [arginine / (ornithine + citrulline)] (HR per SD = 0.83; 95% CI, 0.69 to 1.00) were significantly associated with lower risk of CVD. We observed no significant association for 1-year changes in these ratios or any effect modification by the Mediterranean diet (MD) intervention.

Conclusions

A higher baseline arginine/asymmetric dimethylarginine ratio was associated with lower CVD incidence in a high cardiovascular risk population. The intervention with the MD did not change 1-year levels of these metabolites.

Association of High-Density Lipoprotein Subclasses with Carotid Intima-Media Thickness: Shimane CoHRE Study

AIMS

Recent studies suggested that subclasses of high-density lipoprotein (HDL) may be a better biomarker to predict the risk of atherosclerotic disorders. We aimed to examine the association of HDL2- and HDL3-cholesterol (HDL2-C and HDL3-C) with carotid intima-media thickness (IMT) using a new method to quantify the HDL-C subclasses.

METHODS

Participants were 657 Japanese subjects (434 women) who received a health examination (mean age: 73 years). Serum samples were analyzed by the homogenous assay for HDL-C and HDL3-C. HDL2-C was calculated indirectly by subtracting HDL3-C from HDL-C. HDL3-C measured by this assay was well correlated with that measured by ultracentrifugation (r=0.898, p＜0.001). The maximum IMT (max-IMT) and plaque score (PS) were evaluated by ultrasonography following the standard protocol.

RESULTS

HDL3-C was associated with age both in men (r=－0.322, p＜0.0001) and women (r=－0.315, p＜0.0001). In a simple regression analysis, max-IMT showed an inverse association with HDL3-C, whereas no significant association was observed with HDL2-C. A multiple linear regression analysis indicated, however, that the association between HDL3-C and max-IMT was not significant in both aged and younger populations when age was included in the analysis. Further, not only HDL2-C but also HDL3-C was not a significant predictor of 'atherosclerotic arteries' defined as the max-IMT ≥1.5 mm. Similar results were observed in the analysis on PS.

CONCLUSIONS

Neither HDL3-C nor HDL2-C was significantly associated with carotid atherosclerosis in the Japanese population in this study.

Metabolomics for clinical use and research in chronic kidney disease

Chronic kidney disease (CKD) has a high prevalence in the general population and is associated with high mortality; a need therefore exists for better biomarkers for diagnosis, monitoring of disease progression and therapy stratification. Moreover, very sensitive biomarkers are needed in drug development and clinical research to increase understanding of the efficacy and safety of potential and existing therapies. Metabolomics analyses can identify and quantify all metabolites present in a given sample, covering hundreds to thousands of metabolites. Sample preparation for metabolomics requires a very fast arrest of biochemical processes. Present key technologies for metabolomics are mass spectrometry and proton nuclear magnetic resonance spectroscopy, which require sophisticated biostatistic and bioinformatic data analyses. The use of metabolomics has been instrumental in identifying new biomarkers of CKD such as acylcarnitines, glycerolipids, dimethylarginines and metabolites of tryptophan, the citric acid cycle and the urea cycle. Biomarkers such as c-mannosyl tryptophan and pseudouridine have better performance in CKD stratification than does creatinine. Future challenges in metabolomics analyses are prospective studies and deconvolution of CKD biomarkers from those of other diseases such as metabolic syndrome, diabetes mellitus, inflammatory conditions, stress and cancer.

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

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

Investigation of Asymmetric and Symmetric Dimethylarginine Levels after Iloprost Treatment in Patients with Buerger's Disease

OBJECTIVE

The aim of this study was to compare the levels of acetyl-dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and the l-arginine/ADMA ratio before and after iloprost treatment in patients with Buerger's disease.

METHODS

Between January 2011 and December 2015, data from 44 patients (36 males, 8 females, mean age 48.7 ± 18.1 years) with the diagnosis of Fontaine Stage III-IV Buerger's disease were included. Iloprost infusion was administered intravenously through the forearm veins for 7 days at a dose of 0.5-1.5 ng/kg/min over 16 h. Blood samples were collected before and after treatment for measurement of ADMA, SDMA, and l-arginine. ADMA, SDMA, l-arginine levels were measured using high performance liquid chromatography (HPLC).

RESULTS

After iloprost treatment, ADMA and SDMA levels significantly decreased (p = .001). The increase in the l-arginine levels was not significant (p = .16). However, the l-arginine/ADMA ratio increased significantly (p = .001).

CONCLUSION

Iloprost treatment decreases ADMA and SDMA, which are associated with endothelial dysfunctions in patients with Buerger's disease. Of note, the still higher than normal range of SDMA levels after iloprost treatment suggests that treatment should continue until SDMA levels are within the normal range in this patient population.

Admission levels of asymmetric and symmetric dimethylarginine predict long-term outcome in patients with community-acquired pneumonia

BACKGROUND

During infection, there is an activation of the L-arginine-nitric-oxide pathway, with a shift from nitric oxide synthesis to a degradation of L-arginine to its metabolites, asymmetric and symmetric dimethylarginine (ADMA and SDMA). However, the prognostic implications for short-term or long-term survival remains unclear. We investigated the association of L-arginine, ADMA, and SDMA with adverse clinical outcomes in a well-defined cohort of patients with community-acquired pneumonia (CAP).

METHODS

We measured L-arginine, ADMA, and SDMA in 268 CAP patients from a Swiss multicenter trial by mass spectrometry and used Cox regression models to investigate associations between blood marker levels and disease severity as well as mortality over a period of 6 years.

RESULTS

Six-year mortality was 44.8%. Admission levels of ADMA and SDMA (μmol/L) were correlated with CAP severity as assessed by the pneumonia severity index (r = 0.32, p < 0.001 and r = 0.56, p < 0.001 for ADMA and SDMA, respectively) and higher in 6-year non-survivors versus survivors (median 0.62 vs. 0.48; p < 0.001 and 1.01 vs. 0.85; p < 0.001 for ADMA and SDMA, respectively). Both ADMA and SDMA were significantly associated with long-term mortality (hazard ratios [HR] 4.44 [95% confidence intervals (CI) 1.84 to 10.74] and 2.81 [95% CI 1.45 to 5.48], respectively). The effects were no longer significant after multivariate adjustment for age and comorbidities. No association of L-arginine with severity and outcome was found.

CONCLUSIONS

Both ADMA and SDMA show a severity-dependent increase in patients with CAP and are strongly associated with mortality. This association is mainly explained by age and comorbidities.

TRIAL REGISTRATION

ISRCTN95122877 . Registered 31 July 2006.

12-months metabolic changes among gender dysphoric individuals under cross-sex hormone treatment: a targeted metabolomics study

Metabolomic analyses in epidemiological studies have demonstrated a strong sexual dimorphism for most metabolites. Cross-sex hormone treatment (CSH) in transgender individuals enables the study of metabolites in a cross-gender setting. Targeted metabolomic profiling of serum of fasting transmen and transwomen at baseline and following 12 months of CSH (N = 20/group) was performed. Changes in 186 serum metabolites and metabolite ratios were determined by targeted metabolomics analysis based on ESI-LC-MS/MS. RandomForest (RF) analysis was applied to detect metabolites of highest interest for grouping of transwomen and transmen before and after initiation of CSH. Principal component analysis (PCA) was performed to check whether group differentiation was achievable according to these variables and to see if changes in metabolite levels could be explained by a priori gender differences. PCA predicted grouping of individuals-determined by the citrulline/arginine-ratio and the amino acids lysine, alanine and asymmetric dimethylarginine - in addition to the expected grouping due to changes in sex steroids and body composition. The fact that most of the investigated metabolites did, however, not change, indicates that the majority of sex dependent differences in metabolites reported in the literature before may primarily not be attributable to sex hormones but to other gender-differences.

Changes in Biliary Levels of Arginine and its Methylated Derivatives after Hepatic Ischaemia/Reperfusion

Arginine (Arg) can be methylated to form symmetrical dimethylarginine (SDMA) and asymmetrical dimethylarginine (ADMA), the latter an endogenous inhibitor of nitric oxide synthase (NOS). SDMA is excreted in the urine, while ADMA is mainly subjected to degradation in the liver. Arg competes with ADMA and SDMA for cellular transport across cationic amino-acid transporters (CATs). We evaluated the changes in serum, tissue and biliary levels of Arg, citrulline (Cit), ADMA and SDMA and the modifications in CATs after ischaemia-reperfusion (I/R). Male Wistar rats were subjected to 30-min. partial-hepatic ischaemia or sham-operated. After 60-min. reperfusion, the concentrations of ADMA, SDMA, Arg and Cit in serum, tissue and bile were measured. Serum levels of AST, ALT and alkaline phosphatase (AP) levels were determined. mRNA of cationic transporter 2A (CAT-2A) and 2B (CAT-2B) were also quantified. An increase in ADMA and a decrease in SDMA were observed in bile at the end of reperfusion. On the contrary, lower tissue ADMA levels and higher SDMA levels were quantified. No serum changes in ADMA and SDMA were found. A decrease in Arg and an increase of Cit were detected in serum, bile and tissue after I/R. A marked increase in AST, ALT and AP levels in serum confirmed I/R injury. A decrease in mRNA transporter CAT-2A but not in CAT-2B was detected. This study supported a biliary CAT-2B-dependent transport of ADMA and demonstrated, for the first time, that the liver is also responsible for the biliary excretion of SDMA into the bile.

Relationship between Blood Myostatin Levels and Kidney Function:Shimane CoHRE Study

Objectives

Myostatin (MSTN), a member of TGF-β superfamily, is produced in the skeletal muscle to inhibit myocyte differentiation. MSTN expression is increased in the skeletal muscle in patients with chronic kidney disease (CKD), which may play a role in the pathogenesis of sarcopenia or in the protein energy wasting (PEW). This observation implies that the plasma MSTN level may be correlated with kidney function. Thus, we conducted a cross-sectional study to evaluate the association between the plasma MSTN concentration and the estimated glomerular filtration rate (eGFR).

Subjects and Methods

Subjects were 781 participants of a health examination performed in a rural area in Japan. Among them, 124 subjects were selected by stratified random sampling according to eGFR. Creatinine clearance (ClCr) by the Cockcroft-Gault equation was used as a measure of kidney function. Plasma concentration of MSTN was determined by ELISA.

Results

The plasma MSTN level was not different between men (3.42±1.61 ng/mL) and women (3.27±1.43 ng/mL). In a simple regression analysis, the MSTN level was significantly correlated with eGFR (r = -0.25, p<0.01) and ClCr (r = -0.20, p<0.05) but not with age and BMI. In a multiple linear regression analysis, the MSTN level showed a negative correlation with eGFR (standardized β = -0.31, p<0.01) and ClCr (standardized β = -0.35, p<0.01) under the adjustment with age, sex, BMI and LDL-C. Weak correlation was observed between the MSTN level and BMI / the serum LDL-C level. When the subjects were stratified into 4 groups according to eGFR, MSTN was significantly greater in the groups with the lowest and the 2^nd lowest eGFR (3.55±1.79 and 3.76±1.75 ng/mL, respectively) than the level in the group with the highest eGFR (2.77±0.85 ng/mL).

Conclusion

Plasma MSTN level was elevated in an early stage of CKD, which could be involved in the progression of sarcopenia.

Angiotensin converting enzyme inhibition increases ADMA concentration in patients on maintenance hemodialysis--a randomized cross-over study

Background

Endothelial dysfunction occurs in patients with end-stage renal disease (ESRD) and is associated with increased cardiovascular morbidity and mortality. Asymmetric dimethylarginine (ADMA) contributes to endothelial dysfunction in ESRD. In the general population, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) decrease ADMA levels, but no study has compared the effect of these drugs in patients with ESRD on maintenance hemodialysis (MHD).

Methods

We evaluated the effect of 1-week treatment with ramipril (5 mg/d), valsartan (160 mg/d), and placebo on ADMA levels in 15 patients on MHD in a double-blind, placebo-controlled, three x three cross-over study.

Results

We found that ADMA levels were increased at baseline and throughout the dialysis session during ramipril treatment (p < 0.001 compared to both, placebo and valsartan). Ramipril did not increase ADMA levels in a study of patients without ESRD, suggesting that factors related to ESRD or hemodialysis contribute to the ACE inhibitor-induced increase in ADMA. We have previously shown that ACE inhibition increases bradykinin (BK) levels during hemodialysis. We therefore evaluated the effect of bradykinin on ADMA production in A549 cells; a cell line that expresses BK receptors. Incubation with BK increased intracellular ADMA concentration through BK B2-receptor stimulation.

Conclusion

These data indicate that short-term ACE inhibition increases ADMA in patients on MHD whereas ARBs do not. In vitro studies further suggest that this may occur through BK-mediated increase in ADMA production during ACE inhibition.

Trial registration

Clinicaltrials.gov NCT00732069 August 6 2008 and NCT00607672 February 4 2008

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0162-x) contains supplementary material, which is available to authorized users.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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