Dimethylarginines and inflammation markers in patients with chronic kidney disease undergoing dialysis

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.

The Correlation of Interleukin-6, Malnutrition Inflammation Score and Asymmetric Dimethylarginine in Chronic Kidney Disease Patients Undergoing Routine Hemodialysis

Introduction: Chronic kidney disease (CKD) patients undergoing routine hemodialysis (HD) have a high prevalence of protein-energy malnutrition (PEM) and inflammation. The combination of inflammation and PEM is associated with cardiovascular disease and poor outcomes. Interleukin-6 (IL-6) is an inflammatory factor that runs parallel to endothelial damage and is closely related to the nutritional status of CKD HD patients. The tool to assess nutrition status is Malnutrition Inflammation Score (MIS) and to assess endothelial damage is Asymmetric Dimethylarginine (ADMA). It is currently unclear whether there is a correlation between inflammation, malnutrition, and endothelial dysfunction. Therefore the aim of this study is to determine the correlation between IL-6, MIS and ADMA in CKD HD patients.  Methods: A cross-sectional design with analytic observational study was conducted on end stage renal disease patient who undergo routine hemodialysis for at least 2 years with the duration of hemodialysis is 4-5 hours and at least twice per week. IL-6 was examined by kit (ELISA) and ADMA using LC-MS/MS at a certified laboratory in Manado city. History taking and physical examination were used to calculate MIS. Data analysis was done using SPSS version 22. Results: There were 30 participants consisting of 22 men (72%) and 8 women (28%). The median age of the subjects was 56.50 years. There was a statistically significant positive correlation between IL-6 and ADMA (r = 0.440, p = 0.015), MIS and ADMA (r = 0.378, p = 0.039), and IL-6 and MIS (r = 0.682, p = 0.0001). Conclusion: There was a significant correlation between IL-6, MIS and ADMA.

Plausible diagnostic value of urinary isomeric dimethylarginine ratio for diabetic nephropathy

Altered circulatory asymmetric and symmetric dimethylarginines have been independently reported in patients with end-stage renal failure suggesting their potential role as mediators and early biomarkers of nephropathy. These alterations can also be reflected in urine. Herein, we aimed to evaluate urinary asymmetric to symmetric dimethylarginine ratio (ASR) for early prediction of diabetic nephropathy (DN). In this cross-sectional study, individuals with impaired glucose tolerance (IGT), newly diagnosed diabetes (NDD), diabetic microalbuminuria (MIC), macroalbuminuria (MAC), and normal glucose tolerance (NGT) were recruited from Dr. Mohans’ Diabetes Specialties centre, India. Urinary ASR was measured using a validated high-throughput MALDI-MS/MS method. Significantly lower ASR was observed in MIC (0.909) and MAC (0.741) in comparison to the NGT and NDD groups. On regression models, ASR was associated with MIC [OR: 0.256; 95% CI: 0.158–0.491] and MAC [OR 0.146; 95% CI: 0.071–0.292] controlled for all the available confounding factors. ROC analysis revealed ASR cut-point of 0.95 had C-statistic of 0.691 (95% CI: 0.627-0.755) to discriminate MIC from NDD with 72% sensitivity. Whereas, an ASR cut-point of 0.82 had C-statistic of 0.846 (95% CI: 0.800 - 0.893) had 91% sensitivity for identifying MAC. Our results suggest ASR as a potential early diagnostic biomarker for DN among the Asian Indians.

Symmetric dimethylarginine concentrations in dogs with International Renal Interest Society stage 4 chronic kidney disease undergoing intermittent hemodialysis

BACKGROUND

Symmetric dimethylarginine (SDMA) is a methylated arginine derived from intranuclear methylation of l-arginine by protein-arginine methyltransferase and released into circulation after proteolysis. It is primarily eliminated by renal excretion, and its concentration is highly correlated with glomerular filtration rate (GFR) in animals and humans and is an earlier indicator of kidney dysfunction than serum creatinine concentration (sCr).

OBJECTIVES

To evaluate and quantify the effects of IV fluid therapy (IF) or intermittent hemodialysis (IH) on renal function in a randomized group of dogs previously diagnosed with International Renal Interest Society (IRIS) stage 4 chronic kidney disease (CKD).

ANIMALS

Twenty-four client-owned dogs with naturally occurring CKD.

METHODS

Serum from 14 dogs treated by IH and 10 dogs treated with IF was submitted for measurement of sCr and SDMA. Dogs in each treatment group received up to 5 treatment sessions, administered 48 hours apart.

RESULTS

Significant differences (P ≤ .05) were seen between treatment groups, but dogs from the IH group were the most affected based on SDMA (P < .001), sCr (P < .001), and blood urea (P < .001) concentrations. Furthermore, for each 10% increase in urea reduction ratio, there was a 6.2 μg/dL decrease in SDMA (P = .002).

CONCLUSIONS AND CLINICAL IMPORTANCE

Although SDMA is dialyzable biomarker and despite its removal by IH, SDMA correlates better with renal function than does sCr in dogs with CKD undergoing IF and IH.

A Pilot Study to Examine the Effects of an Anti-inflammatory Supplement on Eicosanoid Derivatives in Patients with Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is a progressive disease with an inverse relationship between kidney function and levels of inflammation and oxidative stress. Curcumin and Boswellia serrata have been reported to exert anti-inflammatory effects on the cyclooxygenase and lipoxygenase pathways. Therefore, the purpose of this study was to study the effects of a supplement containing curcumin and B. serrata on eicosanoid derivatives in early stage CKD patients who had not initiated hemodialysis.

METHODS

Sixteen patients with stage 2 and stage 3 CKD (56.0 ± 16.0 years, 171.4 ± 11.9 cm, 99.3 ± 20.2 kg) were randomized into a treatment group with curcumin and B. serrata or a placebo group. The dependent variables prostaglandin E₂ (PGE₂), 5-hydroxyicosatetraenoic acid, 12-hydroxyicosatetraenoic acid, 15-hydroxyicosatetraenoic acid, and 13-hydroxyoctadecadienoic acid were measured both before and after 8 weeks of supplementation. Results were analyzed by using a repeated-measures analysis of covariance for compliance and body-mass index.

RESULTS

A significant group effect (p = 0.05), and a trend for Group × Time interaction (p = 0.056) were detected for PGE₂. No significant differences were observed for any other variables.

CONCLUSIONS

This is the first article of baseline levels of the dependent variables in early stage CKD, and the first article to show a significant effect of these supplements on PGE₂ in early stage CKD. Further studies are needed to determine whether curcumin and B. serrata may be effective means to reduce inflammation in patients with CKD.

Kidney Disease and the Nexus of Chronic Kidney Disease and Acute Kidney Injury: The Role of Novel Biomarkers as Early and Accurate Diagnostics

Chronic kidney disease (CKD) and acute kidney injury (AKI) are interconnected and the presence of one is a risk for the other. CKD is an important predictor of AKI after exposure to nephrotoxic drugs or major surgery, whereas persistent or repetitive injury could result in the progression of CKD. This brings new perspectives to the diagnosis and monitoring of kidney diseases highlighting the need for a panel of kidney-specific biomarkers that reflect functional as well as structural damage and recovery, predict potential risk and provide prognosis. This article discusses the kidney-specific biomarkers, symmetric dimethylarginine (SDMA), clusterin, cystatin B, and inosine.

Asymmetric dimethylarginine and critical illness

PURPOSE OF REVIEW

Asymmetric dimethylarginine (ADMA) is an analog of arginine and functions as an endogenous inhibitor of the nitric oxide synthase, which forms nitric oxide. Nitric oxide is crucial for perfusion of vital organs and is an important signaling agent in the development of critical illness. The role of ADMA in the pathophysiological mechanisms underlying critical illness is widely studied in the last decades, and recently it has become clear that ADMA should not be overlooked by clinicians working at the ICU. The aim of this review is to describe new insights into the role of ADMA in critical illness and its clinical relevance.

RECENT FINDINGS

High levels of ADMA are found in critically ill patients, because of higher levels of protein methylation, increased rate of protein turnover, decreased activity of dimethylamine dimethylaminohydrolase, and impaired renal and hepatic clearance capacity. These high levels are an independent risk factor for cardiac dysfunction, organ failure, and ICU mortality. The arginine : ADMA ratio in particular is of clinical importance and the restoration of this ratio is expedient to restore several functions that are disturbed during critical illness.

SUMMARY

Elevated ADMA levels occur in critically ill patients, which is detrimental for morbidity and mortality. The arginine : ADMA ratio should be restored to maintain nitric oxide production and therewith improve the clinical outcome of the patient.

ADMA and C-reactive protein as mortality predictors in dialysis patients

There is a higher mortality between patients with end-stage renal disease than patients in the general population. These circumstances have led to a search for risk factors as predictors of mortality in dialysis patients. Amongst those, inhibitors of the nitric-oxide (NO) synthesis deserve special attention, since patients with end-stage renal disease are also characterized by accelerated atherosclerosis. Asymmetric-dimethylarginine (ADMA) and symmetric-dimethylarginine (SDMA), as well as C-reactive protein (CRP), have also been recognized as predictors of mortality in patients on dialysis. The aim of our study was to compare the prediction power of ADMA, SDMA and CRP for all-cause mortality in patients with end stage renal disease during the fourteen month follow-up. In total 162 patients on hemodialysis were included. ADMA and SDMA were measured by the high-performance liquid chromatography (HPLC); CRP was measured using immunonephelometric assays. During the 14-month period 28 patients (34.1%) died from all-cause mortality. Using univariate analysis, hazard ratios (HR) of the potential independent predictors of mortality in hemodialysis patients were ADMA (HR 1.39 (1.01–1.91) p=0.043) and CRP (HR 1.024 (1.009–1.1.040) p=0.001). Further, multivariate analysis (MVA), however, showed that ADMA is the only predictor of all-cause mortality (HR 1.76 (1.002–3.11) P=0.049), while SDMA failed to predict death in this population. Therefore, our data shows that ADMA is an independent and better marker of all-cause mortality compared with CRP.

Methylated arginines and nitric oxide in end-stage renal disease: impact of inflammation, oxidative stress and haemodialysis

OBJECTIVES

To determine whether inflammation (C-reactive protein, CRP), oxidative stress (malondialdehyde, MDA) or haemodialysis (HD) affect associations between asymmetric (ADMA), symmetric (SDMA) dimethylarginine, NG-monomethyl-L-arginine (L-NMMA) and nitrite/nitrate (NOx) in end-stage renal disease (ESRD).

METHOD

Metabolites were measured pre-HD, after 1 hour and end-HD in 40 ESRD patients (age 63 ± 14 years).

RESULTS

Positive associations between NOx and ADMA (p = 0.04), SDMA (p < 0.001) and L-NMMA (p = 0.04) were observed pre-HD. Associations weakened during HD but were not significantly influenced by CRP or MDA.

CONCLUSIONS

HD, oxidative stress or inflammation did not significantly affect the positive associations between methylated arginines and NOx in ESRD.

Effects of asymmetric dimethylarginine on inflammatory cytokines (TNF-α, IL-6 and IL-10) in rats

This study is intended to examine the effects of administration of asymmetric dimethylarginine (ADMA) on the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-10. A total of 30 Wistar adult albino rats were used. Group I was administrated ( n = 10) with 1 mg/kg/day of ADMA, group II ( n = 10) was administrated with 2 mg/kg/day of ADMA and the control group was administrated ( n = 10) with 0.9% sodium chloride. ADMA was intraperitoneally administrated for 7 days. The serum levels of IL-6, TNF-α and IL-10 were measured. There was a significant decrease in the levels of TNF-α, IL-6 and IL-10 in group I compared with that of the control group ( p < 0.001 ). There was also a significant decrease in the levels of IL-10 in group II compared with that of the control group ( p < 0.05) but the increase was much more distinct in the levels of IL-6 and TNF-α ( p < 0.001). When comparing the groups by the doses given, no difference between the levels of IL-6 and IL-10 in groups I and II ( p > 0.05) was observed; the levels of TNF-α in group II were significantly lower than those of group I (p < 0.05). A significant decrease in the serum levels of inflammatory cytokines IL-6, TNF-α and IL-10, after administration of 1 mg/kg/day and 2 mg/kg/day of ADMA, indicates that ADMA has an effect on inflammation. Increase in ADMA levels in the rats shows that the effects of inflammatory cytokines were suppressed.

Asymmetric dimethyarginine as marker and mediator in ischemic stroke

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, is known as mediator of endothelial cell dysfunction and atherosclerosis. Circulating ADMA levels are correlated with cardiovascular risk factors such as hypercholesterolemia, arterial hypertension, diabetes mellitus, hyperhomocysteinemia, age and smoking. Accordingly, clinical studies found evidence that increased ADMA levels are associated with a higher risk of cerebrovascular events. After the acute event of ischemic stroke, levels of ADMA and its analog symmetric dimethylarginine (SDMA) are elevated through augmentation of protein methylation and oxidative stress. Furthermore, cleavage of ADMA through dimethylarginine dimethylaminohydrolases (DDAHs) is reduced. This increase of dimethylarginines might be predictive for adverse clinical outcome. However, the definite role of ADMA after acute ischemic stroke still needs to be clarified. On the one hand, ADMA might contribute to brain injury by reduction of cerebral blood flow. On the other hand, ADMA might be involved in NOS-induced oxidative stress and excitotoxic neuronal death. In the present review, we highlight the current knowledge from clinical and experimental studies on ADMA and its role for stroke risk and ischemic brain injury in the hyperacute stage after stroke. Finally, further studies are warranted to unravel the relevance of the close association of dimethylarginines with stroke.

Asymmetric dimethylarginine, endothelial dysfunction and renal disease

l-Arginine (Arg) is oxidized to l-citrulline and nitric oxide (NO) by the action of endothelial nitric oxide synthase (NOS). In contrast, protein-incorporated Arg residues can be methylated with subsequent proteolysis giving rise to methylarginine compounds, such as asymmetric dimethylarginine (ADMA) that competes with Arg for binding to NOS. Most ADMA is degraded by dimethylarginine dimethyaminohydrolase (DDAH), distributed widely throughout the body and regulates ADMA levels and, therefore, NO synthesis. In recent years, several studies have suggested that increased ADMA levels are a marker of atherosclerotic change, and can be used to assess cardiovascular risk, consistent with ADMA being predominantly absorbed by endothelial cells. NO is an important messenger molecule involved in numerous biological processes, and its activity is essential to understand both pathogenic and therapeutic mechanisms in kidney disease and renal transplantation. NO production is reduced in renal patients because of their elevated ADMA levels with associated reduced DDAH activity. These factors contribute to endothelial dysfunction, oxidative stress and the progression of renal damage, but there are treatments that may effectively reduce ADMA levels in patients with kidney disease. Available data on ADMA levels in controls and renal patients, both in adults and children, also are summarized in this review.

Symmetric dimethylarginine as a proinflammatory agent in chronic kidney disease

BACKGROUND & OBJECTIVES

Chronic kidney disease (CKD) is characterized by chronic inflammation, considered a nontraditional risk factor for cardiovascular disease, the major cause of death in CKD. Symmetric dimethylarginine (SDMA) was recently demonstrated to induce reactive oxygen species in monocytes. The present study further investigates the inflammatory character of SDMA compared with its structural counterpart asymmetric dimethylarginine (ADMA).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In vitro, the effect of SDMA on intracellular monocytic expression of IL-6 and TNF-α was studied followed by an evaluation of nuclear factor (NF)-κB activation. Additionally, an association of SDMA with inflammatory parameters in consecutive stages of CKD was evaluated in vivo.

RESULTS

Monocytes incubated with SDMA showed increased IL-6 and TNF-α expression and a rise in active NF-κB. N-acetylcysteine abrogated both these effects. No significant effects were observed with ADMA. In vivo, 142 patients (67 ± 12 years) at different stages of CKD showed an inverse association between serum SDMA and ADMA and renal function. Correlations between SDMA and IL-6, TNF-α, and albumin were more significant than for ADMA, while multiple regression analysis only retained TNF-α at a high significance for SDMA (P < 0.0001). In receiver operating characteristic analysis for inflammation, defined as an IL-6 level above 2.97 pg/ml (median), the discriminative power of SDMA (area under the curve [AUC]: 0.69 ± 0.05) directly followed that of C-reactive protein (AUC: 0.82 ± 0.04) and albumin (AUC: 0.72 ± 0.05; for all, P < 0.0001) and preceded that of ADMA (P = 0.002).

CONCLUSIONS

The present study shows that SDMA is involved in the inflammatory process of CKD, activating NF-κB and resulting in enhanced expression of IL-6 and TNF-α, which is corroborated by the clinical data pointing to an in vivo association of SDMA with inflammatory markers in CKD at different stages.

The role of asymmetric and symmetric dimethylarginines in renal disease

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases. By inhibiting nitric oxide formation, ADMA causes endothelial dysfunction, vasoconstriction, elevation of blood pressure, and aggravation of experimental atherosclerosis. Levels of ADMA and its isomer symmetric dimethylarginine (SDMA), which does not inhibit nitric oxide synthesis, are both elevated in patients with kidney disease. Currently available data from prospective clinical trials in patients with chronic kidney disease suggest that ADMA is an independent marker of progression of renal dysfunction, vascular complications and death. High SDMA levels also negatively affect survival in populations at increased cardiovascular risk, but the mechanisms underlying this effect are currently only partly understood. Beyond glomerular filtration, other factors influence the plasma concentrations of ADMA and SDMA. Elevated plasma concentrations of these dimethylarginines might also indirectly influence the activity of nitric oxide synthases by inhibiting the uptake of cellular L-arginine. Other mechanisms may exist by which SDMA exerts its biological activity. The biochemical pathways that regulate ADMA and SDMA, and the pathways that transduce their biological function, could be targeted to treat renal disease in the future.

Cell biological and physicochemical aspects of arterial calcification

Processes similar to endochondral or intramembranous bone formation occur in the vascular wall. Bone and cartilage tissue as well as osteoblast- and chondrocyte-like cells are present in calcified arteries. As in bone formation, apoptosis and matrix vesicles play an important role in the initiation of vascular calcification. Recent evidence indicates that nanocrystals initially formed in the vessel wall may actively be involved in the progression of the calcification process. This review focuses on the cellular and structural similarities between bone formation and vascular calcification and discusses the initial events in this pathological mineralization process.