Plasma dimethylarginines during the acute inflammatory response

USE OF SYMMETRIC DIMETHYLARGININE TO DETECT RENAL LESIONS IN FISH: A PRELIMINARY STUDY IN BROOK TROUT (SALVELINUS FONTINALIS)

Symmetric dimethylarginine (SDMA) is an early marker for renal lesions in mammals. The objectives of this study were 1) to establish a reference interval of SDMA in healthy brook trout, Salvelinus fontinalis (Mitchill, 1814), and 2) to assess its sensibility as a marker of renal pathology. Plasma SDMA was quantified by liquid chromatography-mass spectrometry in 25 adult brook trout, including 20 fish displaying no renal histologic lesions, and five fish displaying chronic nonactive microscopic granulomas. The fish size (P = 0.30) and weight (P = 0.12) were not statistically different among groups, nor were SDMA values (P = 0.22). However, brook trout without microscopic renal lesions tended to have lower SDMA values (no lesions: mean = 24.9 µg/dL; lesions: mean = 31.4 µg/dL). The reference interval (90% confidence interval [90% CI]) for SDMA concentration in brook trout ranged between 10.0 µg/dL (90% CI: 5.4-14.7) and 39.8 µg/dL (90% CI: 34.8-43.9). These values were higher than those previously reported in other vertebrate species. Further research is needed to evaluate the use of SDMA as a marker of renal function in fishes.

ANALGESIC EFFECT OF TRAMADOL IS NOT ALTERED BY POSTOPERATIVE SYSTEMIC INFLAMMATION AFTER MAJOR ABDOMINAL SURGERY

Tramadol is a commonly used analgesic in intensive care units (ICUs) for acute postoperative pain. Conversion of tramadol into active metabolites may be impaired in inflammatory states. Catechol-O-methyltransferase may influence pain. The aim of the study was to examine differences in the analgesic effect of tramadol between ICU patients with and without signs of systemic inflammation. Forty-three patients were admitted to ICU after a major abdominal surgery. The patients received a dose of 100 mg of tramadol intravenously every 6 hours during the first 24 hours after surgical procedure. Pain scores were measured by the Numeric Rating Scale before and 30 minutes after tramadol administration in awake patients. Systemic inflammation was considered when at least two of the following postoperative parameters were present in the first 24 hours of ICU admission: fever or hypothermia, tachycardia, pCO₂ <4.3 kPa, white blood cells >12000/mm³ or <4000/mm³, or preoperative value of C-reactive protein (CRP) >50 mg/L or/and procalcitonin (PCT) >0.5 mg/L. Catechol-O-methyltransferase was analyzed postoperatively. Fifteen (34.8%) patients met the criteria for systemic inflammation. Tramadol was proven to be an effective analgesic for the treatment of postoperative pain regardless of the presence of systemic inflammation (p<0.05). Lower perception of pain before tramadol application was observed in patients with systemic inflammation, but the difference was not significant. A negative correlation was observed between the preoperative values of CRP and PCT and the analgesic effect of tramadol assessed at the second measurement point (r=-0.358, p=0.03, and r=-0.364, p=0.02, respectively). Catechol-O-methyltransferase variants were not in correlation with pain and opioid consumption. Based on our findings, tramadol is effective in lowering pain scores after major abdominal surgery irrespective of the presence of systemic inflammation.

A Review of Specific Biomarkers of Chronic Renal Injury and Their Potential Application in Nonclinical Safety Assessment Studies

A host of novel renal biomarkers have been developed over the past few decades which have enhanced monitoring of renal disease and drug-induced kidney injury in both preclinical studies and in humans. Since chronic kidney disease (CKD) and acute kidney injury (AKI) share similar underlying mechanisms and the tubulointerstitial compartment has a functional role in the progression of CKD, urinary biomarkers of AKI may provide predictive information in chronic renal disease. Numerous studies have explored whether the recent AKI biomarkers could improve upon the standard clinical biomarkers, estimated glomerular filtration rate (eGFR), and urinary albumin to creatinine ratio, for predicting outcomes in CKD patients. This review is an introduction to alternative assays that can be utilized in chronic (>3 months duration) nonclinical safety studies to provide information on renal dysfunction and to demonstrate specific situations where these assays could be utilized in nonclinical drug development. Novel biomarkers such as symmetrical dimethyl arginine, dickkopf homolog 3, and cystatin C predict chronic renal injury in animals, act as surrogates for GFR, and may predict changes in GFR in patients over time, ultimately providing a bridge from preclinical to clinical renal monitoring.

Novel glomerular filtration markers

Chronic kidney disease is currently assessed by estimated glomerular filtration rate, a mathematical construct based on creatinine or creatinine and cystatin concentration. Creatinine-based equations have improved with standardization efforts and the Modification of Diet in Renal Disease Study (MDRD) and CKD-Epidemiology Collaboration Study (CKD-EPI). Because the measurement of creatinine is subject to interference from non-GFR determinants, alternative markers have long been sought. These have included cystatin C and low molecular weight proteins like β2-microglobulin and beta trace protein. Tubular disease often occurs before glomerular filtration is impaired and investigators have investigated the excretion of other low molecular weight proteins such as Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Kidney Injury Molecule-1 and N-acetyl-β-d-glucosaminidase. While preliminary, there is some evidence linking these analytes with GFR, disease stage and mortality. Although asymmetrical dimethyl arginine, an inhibitor of nitric oxide, has been shown to be associated with progression of renal disease, symmetric dimethyl arginine may be a better marker. Recent work has also explored the potential of microRNA (miRNA) analysis and metabolomics studies to further elucidate this complex pathophysiologic disease process. Investigators hope to improve our ability to detect CKD by the use of test panels, i.e., various marker combinations thereof. Unfortunately, most of these markers lack standardization unlike traditional measures that rely on creatinine and cystatin C measurement.

Serum Symmetric Dimethylarginine as an Early Marker of Excretory Dysfunction in Canine Leishmaniosis (L. infantum) Induced Nephropathy

The aims of the study were to determine whether symmetric dimethylarginine (SDMA) was increased in dogs with leishmaniosis and to assess its relationship with creatinine concentration and urinary protein : creatinine ratio (UPC) to determine its utility as a marker of early excretory dysfunction. Fifty-three dogs with leishmaniosis classified according to the LeishVet clinical staging (stage I, n = 5, stage II, n = 30; stage III, n = 12; stage IV, n = 6) were selected and compared with 41 clinically healthy dogs. Thirty-nine dogs with leishmaniosis were also followed up for six months. SDMA concentrations on the day of diagnosis were significantly higher in dogs with leishmaniosis with respect to control dogs and in dogs from LeishVet stage IV when compared with the other stages. Increased UPC (>0.5), SDMA (>19 μg/dL), and creatinine concentrations (≥1.4 mg/dL) were found in 47.1%, 15.1%, and 9.4% of dogs with leishmaniosis, respectively. SDMA concentration was increased in 24% of proteinuric dogs, in 7% of nonproteinuric dogs, and in four of five dogs with increased creatinine. SDMA concentration ≥ 25 μg/dL was associated with clinical chronic kidney disease (CKD) after six months. Our results did not demonstrate advantages in using SDMA concentration as an early marker of CKD when compared to creatinine and UPC in canine leishmaniosis.

Novel Biomarkers in the Diagnosis of Chronic Kidney Disease and the Prediction of Its Outcome

In its early stages, symptoms of chronic kidney disease (CKD) are usually not apparent. Significant reduction of the kidney function is the first obvious sign of disease. If diagnosed early (stages 1 to 3), the progression of CKD can be altered and complications reduced. In stages 4 and 5 extensive kidney damage is observed, which usually results in end-stage renal failure. Currently, the diagnosis of CKD is made usually on the levels of blood urea and serum creatinine (sCr), however, sCr has been shown to be lacking high predictive value. Due to the development of genomics, epigenetics, transcriptomics, proteomics, and metabolomics, the introduction of novel techniques will allow for the identification of novel biomarkers in renal diseases. This review presents some new possible biomarkers in the diagnosis of CKD and in the prediction of outcome, including asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), uromodulin, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), miRNA, ncRNA, and lincRNA biomarkers and proteomic and metabolomic biomarkers. Complicated pathomechanisms of CKD development and progression require not a single marker but their combination in order to mirror all types of alterations occurring in the course of this disease. It seems that in the not so distant future, conventional markers may be exchanged for new ones, however, confirmation of their efficacy, sensitivity and specificity as well as the reduction of analysis costs are required.

Assessment of asymmetrical dimethylarginine metabolism in patients with critical illness

BACKGROUND

Critically ill patients experience metabolic disorders including hypercatabolic state and hyperglycaemia, and these are associated with poor outcome. Hyperglycaemia and asymmetrical dimethylarginine (ADMA) are reported to have significant influences on endothelial dysfunction. The aim of this study was to examine the relationship between plasma ADMA and related arginine metabolism in patients with critical illness.

MATERIALS AND METHOSDS

Two venous blood samples (EDTA) (104 patients), on admission and follow-up sample in the last day in intensive care unit (ICU) (died or discharge sample median 7, interquartile range (IQR) 6-8, range 5-15). Plasma ADMA, arginine, homoarginine and SDMA were measured by high-performance liquid chromatography (HPLC).

RESULT

ADMA (P < 0·01) and SDMA (P < 0·05) were elevated, and homoarginine was decreased (P < 0·05) in nonsurvivors and was directly associated with predicted mortality rate (P < 0·05 and P < 0·001), Sequential Organ Failure Assessment (SOFA) (P < 0·05, P < 0·001), ICU stay (P < 0·05, P < 0·001) and mortality (P < 0·01, P < 0·05). ADMA was directly associated with SDMA (P < 0·001), albumin (P < 0·05), ICU stay and mortality (P < 0·01). SDMA was directly associated with creatinine (P < 0·001) and Acute physiology and Chronic Health Evaluation II score (P < 0·001). In the follow-up measurements, there was a significant decrease in SOFA score (P < 0·01), homoarginine (P < 0·01), aminotransferase (P < 0·01), Laboratory Glucose (P < 0·01) and albumin (P < 0·01). In contrast, there was an increase in arginine (P < 0·01), ADMA (P < 0·01), ADMA:SDMA ratio (P < 0·01) and the norepinephrine administration (P < 0·01).

CONCLUSION

In the present longitudinal study, ADMA metabolism was altered in patients with critical illness and was associated with disease severity and mortality.

Symmetric Dimethylarginine: Improving the Diagnosis and Staging of Chronic Kidney Disease in Small Animals

Chronic kidney disease (CKD) is a common condition in cats and dogs, traditionally diagnosed after substantial loss of kidney function when serum creatinine concentrations increase. Symmetric dimethylarginine (SDMA) is a sensitive circulating kidney biomarker whose concentrations increase earlier than creatinine as glomerular filtration rate decreases. Unlike creatinine SDMA is unaffected by lean body mass. The IDEXX SDMA test introduces a clinically relevant and reliable tool for the diagnosis and management of kidney disease. SDMA has been provisionally incorporated into the International Renal Interest Society guidelines for CKD to aid staging and targeted treatment of early and advanced disease.

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.

Serum Concentrations of Symmetric Dimethylarginine and Creatinine in Dogs with Naturally Occurring Chronic Kidney Disease

Background

Serum concentrations of symmetric dimethylarginine (SDMA) detected chronic kidney disease (CKD) in cats an average of 17.0 months before serum creatinine (Cr) concentrations increased above the reference interval.

Objectives

To report on the utility of measuring serum SDMA concentrations in dogs for detection of CKD before diagnosis by measurement of serum Cr.

Animals

CKD dogs (n = 19) included those persistently azotemic for ≥3 months (n = 5), dogs that were azotemic at the time of death (n = 4), and nonazotemic dogs (n = 10). CKD dogs were compared with healthy control dogs (n = 20).

Methods

Retrospective study, whereby serum Cr concentrations were determined by enzymatic colorimetry and serum SDMA concentrations were determined by liquid chromatography‐mass spectrometry in dogs with necropsy confirmed CKD.

Results

Serum SDMA increased before serum Cr in 17 of 19 dogs (mean, 9.8 months; range, 2.2–27.0 months). Duration of elevations in serum SDMA concentrations before the dog developed azotemia (N = 1) or before the dog died (N = 1) was not determined. Serum SDMA and Cr concentrations were linearly related (r = 0.84; P < .001). Serum SDMA (r = −0.80) and serum Cr (r = −0.89) concentrations were significantly related to glomerular filtration rate (both P < .001).

Conclusion and Clinical Importance

Using serum SDMA as a biomarker for CKD allows earlier detection of kidney dysfunction in dogs than does measurement of serum Cr. Earlier detection might be desirable for initiating renoprotective interventions that slow progression of kidney disease.

Asymmetric Dimethylarginine in Adult Falciparum Malaria: Relationships With Disease Severity, Antimalarial Treatment, Hemolysis, and Inflammation

Asymmetric Dimethylarginine (ADMA) and arginine bioavailability are reduced acutely in adult falciparum malaria. ADMA increases following commencement of antimalarial therapy, is associated with arginine and haemolysis, and likely contributes to reduced nitric oxide bioavailability in severe falciparum malaria.

Background. Endothelial nitric oxide (NO) bioavailability is impaired in severe falciparum malaria (SM). Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase (NOS), contributes to endothelial dysfunction and is associated with mortality in adults with falciparum malaria. However, factors associated with ADMA in malaria, including the NOS-substrate l-arginine, hemolysis, and antimalarial treatment, are not well understood.

Methods. In a prospective observational study of Malaysian adults with SM (N = 22) and non-SM (NSM; N = 124) and healthy controls (HCs), we investigated factors associated with plasma ADMA including the effects of antimalarial treatment.

Results. Compared with HCs, ADMA levels were lower in NSM (0.488 µM vs 0.540 µM, P = .001) and in the subset of SM patients enrolled before commencing treatment (0.453 µM [N = 5], P = .068), but levels were higher in SM patients enrolled after commencing antimalarial treatment (0.610 µM [N = 17], P = .026). In SM and NSM, ADMA levels increased significantly to above-baseline levels by day 3. Baseline ADMA was correlated with arginine and cell-free hemoglobin in SM and NSM and inversely correlated with interleukin-10 in NSM. Arginine and the arginine/ADMA ratio (reflective of arginine bioavailability) were lower in SM and NSM compared with HCs, and the arginine/ADMA ratio was lower in SM compared with NSM.

Conclusions. Pretreatment ADMA concentrations and l-arginine bioavailability are reduced in SM and NSM. Asymmetric dimethylarginine increases to above-baseline levels after commencement of antimalarial treatment. Arginine, hemolysis, and posttreatment inflammation all likely contribute to ADMA regulation, with ADMA likely contributing to the reduced NO bioavailability in SM.

Relationship between lean body mass and serum renal biomarkers in healthy dogs

Background

Symmetric dimethylarginine (SDMA) is an accurate and precise biomarker for estimating glomerular filtration rate (GFR) in humans and cats. Serum creatinine (sCr) also correlates with GFR, but has limitations as a biomarker of renal function because nonrenal factors can influence its concentration.

Hypothesis

Differences in lean body mass (LBM) influence sCr, but not serum SDMA concentrations.

Animals

Forty‐one healthy Beagles, mean age 9.9 years (range: 3.1–14.8 years), were studied over a 6 month period.

Methods

Serum biomarkers of renal function were measured prospectively at baseline, and 1, 3, and 6 months. SDMA concentrations were measured by liquid chromatography‐mass spectroscopy and sCr concentrations by enzymatic colorimetry. Body composition was determined by dual energy x‐ray absorptiometry.

Results

LBM (P < .001) and age (P = .006) were significant explanatory variables for sCr concentration (R² = 0.38), but not SDMA concentration. Time on food was the only significant explanatory variable for SDMA concentration (R² = 0.49). SDMA concentrations decreased across time (P < .001). LBM was affected by sex (males > females; P = .02). Mature adult dogs (<8 years) had greater LBM compared with geriatric dogs (≥8 years; P < .001).

Conclusion and Clinical Importance

sCr concentrations, but not SDMA concentrations, are influenced by LBM, which limits sCr utility as a biomarker for monitoring renal function in dogs with decreased LBM. Reductions in LBM can lower sCr concentration and overestimate GFR. SDMA concentrations, but not sCr concentrations were influenced by time on food. SDMA could have clinical advantages over sCr in monitoring response to nutritional interventions.

Association of dimethylarginines and mediators of inflammation after acute ischemic stroke

Background

Elevated levels of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are accompanied by endothelial dysfunction and predict adverse outcome after ischemic stroke. Via induction of oxidative stress, dimethylarginines are possibly linked to the inflammatory cascade after stroke that is known to considerably contribute to secondary progression of brain injury. We sought to investigate the association between dimethylarginines and inflammatory mediators in patients with acute ischemic stroke.

Methods

Plasma levels of ADMA and SDMA were measured in prospectively collected blood samples of 58 patients with acute ischemic stroke. Blood samples were taken at 6 hours, 12 hours, 24 hours, 3 days and 7 days after onset of symptoms. Analyses of ADMA and SDMA were done by high-performance liquid chromatography-tandem mass spectrometry. Monocyte chemotactic protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), interleukin-6 (IL-6), C-reactive protein (CRP) and S100B as markers of inflammation and brain damage were determined by commercially available immunometric assays. Patient data were compared with control data from 32 age-adjusted healthy volunteers. Baseline stroke severity was evaluated by the National Institutes of Health Stroke Scale (NIHSS) (NIHSS 0 to 1: mild stroke; NIHSS 2 to 8: moderate stroke; NIHSS ≥9: severe stroke).

Results

Plasma ADMA and SDMA levels significantly correlated with blood levels of inflammatory mediators up to day 7 after stroke. On multiple stepwise linear regression analysis ADMA correlated with TIMP-1 at 6 hours, 24 hours, 3 days and 7 days, MMP-9 at 12 hours and IL-6 at 7 days (P <0.05) while SDMA correlated with MCP-1 at 6 hours, 24 hours, 3 days and 7 days as well as IL-6 at 3 days and 7 days (P <0.05).

Conclusions

The levels of the vasoactive compound ADMA as well as levels of its structural isomer SDMA are associated with levels of inflammatory mediators after acute ischemic stroke. Further studies need to elucidate the cause and effect relationship of these crucial players.

Role of dimethylarginine dimethylaminohydrolase activity in regulation of tissue and plasma concentrations of asymmetric dimethylarginine in an animal model of prolonged critical illness

High plasma concentrations of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are associated with adverse outcome in critically ill patients. Asymmetric dimethylarginine is released within cells during proteolysis of methylated proteins and is either degraded by dimethylarginine dimethylaminohydrolase (DDAH) or exported to the circulation via cationic amino acid transporters. We aimed to establish the role of DDAH activity in the regulation of tissue and plasma concentrations of ADMA. In 33 critically ill rabbits, we measured DDAH activity in kidney, liver, heart, and skeletal muscle and related these values to concentrations of ADMA in these tissues and in the circulation. Both DDAH activity and ADMA concentration were highest in kidney and lowest in skeletal muscle, with intermediate values for liver and heart. Whereas ADMA content was significantly correlated between tissues (r = 0.40-0.78), DDAH activity was not. Significant inverse associations between DDAH activity and ADMA content were only observed in heart and liver. Plasma ADMA was significantly associated with ADMA in the liver (r = 0.41), but not in the other tissues. In a multivariable regression model, DDAH activities in muscle, kidney, and liver, but not in heart, were negatively associated with plasma ADMA concentration, together explaining approximately 50% of its variation. In critical illness, plasma ADMA poorly reflects intracellular ADMA. Furthermore, tissue DDAH activity is a stronger predictor of plasma ADMA than of intracellular ADMA, indicating that, compared with DDAH activity, generation of ADMA and cationic amino acid transporter-mediated exchange may be more important regulators of intracellular ADMA.

Inflammatory-induced hibernation in the fetus: priming of fetal sheep metabolism correlates with developmental brain injury

Prenatal inflammation is considered an important factor contributing to preterm birth and neonatal mortality and morbidity. The impact of prenatal inflammation on fetal bioenergetic status and the correlation of specific metabolites to inflammatory-induced developmental brain injury are unknown. We used a global metabolomics approach to examine plasma metabolites differentially regulated by intrauterine inflammation. Preterm-equivalent sheep fetuses were randomized to i.v. bolus infusion of either saline-vehicle or LPS. Blood samples were collected at baseline 2 h, 6 h and daily up to 10 days for metabolite quantification. Animals were killed at 10 days after LPS injection, and brain injury was assessed by histopathology. We detected both acute and delayed effects of LPS on fetal metabolism, with a long-term down-regulation of fetal energy metabolism. Within the first 3 days after LPS, 121 metabolites were up-regulated or down-regulated. A transient phase (4–6 days), in which metabolite levels recovered to baseline, was followed by a second phase marked by an opposing down-regulation of energy metabolites, increased pO₂ and increased markers of inflammation and ADMA. The characteristics of the metabolite response to LPS in these two phases, defined as 2 h to 2 days and at 6–9 days, respectively, were strongly correlated with white and grey matter volumes at 10 days recovery. Based on these results we propose a novel concept of inflammatory-induced hibernation of the fetus. Inflammatory priming of fetal metabolism correlated with measures of brain injury, suggesting potential for future biomarker research and the identification of therapeutic targets.

Unilateral nephrectomy causes an abrupt increase in inflammatory mediators and a simultaneous decrease in plasma ADMA: a study in living kidney donors

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases (NOS). Reducing inducible NOS activity in acute inflammation seems to be desirable. In vitro data show that ADMA increases in response to inflammatory mediators, yet the effect of acute inflammation in vivo is scarcely studied. The aim of the study was to evaluate ADMA plasma levels before, during, and after the acute (nonbacterial) inflammatory-like state. Plasma ADMA, l-arginine, C-reactive protein, and IL-6 were determined in 24 healthy subjects undergoing living related kidney donation before as well as 1, 6, 12, 24, 72, and 168 h thereafter. Six hours after nephrectomy, ADMA levels decreased compared with baseline (0.488 ± 0.075 vs. 0.560 ± 0.060 μmol/l, P < 0.05). This difference became even more marked 24 h after the operation (0.478 ± 0.083 μmol/l, P < 0.01 vs. baseline), when the proinflammatory cytokine IL-6 peaked. Seven days after unilateral nephrectomy, ADMA levels were elevated above baseline (0.63 ± 0.05 μmol/l, P < 0.001 vs. baseline). l-Arginine levels decreased already 1 h after nephrectomy (97.5 ± 22.5 μmol/l, P < 0.01 vs. baseline) and paralleled the change in ADMA thereafter. At the end of the observation period when inflammation markers were regressing, l-arginine levels were significantly elevated above baseline (160.6 ± 25.1 μmol/l, P < 0.001 vs. baseline). In summary, this is the first study showing that both ADMA and l-arginine decrease temporarily after unilateral nephrectomy coinciding with the increase in inflammatory mediators. The l-arginine/ADMA ratio, a surrogate for NO production capacity, was only altered for <24 h.