Asymmetric dimethylarginine and progression of chronic kidney disease: a one-year follow-up study

Increased level of serum asymmetric dimethylarginine in individuals with more severe cognitive impairment, as evaluated using Montreal Cognitive Assessment instead of Mini-Mental State Examination

BACKGROUND

This study aimed to explore the link between cognitive impairment and levels of asymmetric dimethylarginine (ADMA).

METHODS

The study included 172 patients from the Department of Geriatrics and Neurology at the Second Affiliated Hospital of Harbin Medical University. The enrollment period spanned from October 2013 to July 2014. To assess their cognitive function, we used the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). Additionally, automatic biochemical analyzers were employed to measure various biochemical blood indexes, while enzyme-linked immunosorbent assay was used to determine the serum ADMA concentrations.

RESULTS

The participants were categorized into four groups based on the MMSE scale, which reflects cognition (higher scores indicating better cognitive function), and five groups based on the MoCA scale, which also measures cognition (higher scores indicating better cognitive function). Various factors were analyzed for their statistical significance in relation to different cognitive impairment groups determined by each scale. Regarding the MoCA scale, the following factors were found to be statistically significant: Age (P = 0.0001), systolic blood pressure (P = 0.0261), ALT (P = 0.0104), AST (P = 0.0106), endogenous creatinine clearance (P = 0.0006), and serum ADMA concentration (P = 0.0383). For the MMSE scale, the following factors showed statistical significance: Age (P = 0.0008), ALT (P = 0.0002), AST (P = 0.0088), CRP (P = 0.0407), and endogenous creatinine clearance (P = 0.0027). Interestingly, as the scores on the MoCA scale decreased, the serum ADMA concentration increased (P=0.0383), but this trend was not observed in the groups classified based on the MMSE scale (P > 0.05).

CONCLUSION

The level of sensitivity measured by the MoCA scale indicated the presence of initial cognitive dysfunction. The extent of cognitive impairment showed a direct correlation with ADMA levels, indirectly implying a connection between impaired endothelial function and cognitive dysfunction.

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.

Associations of Biopterins and ADMA with Vascular Function in Peripheral Microcirculation from Patients with Chronic Kidney Disease

We hypothesized that patients with chronic kidney disease (CKD) display an altered plasma amino acid (AA) metabolomic profile that could contribute to abnormal vascular maintenance of peripheral circulation in uremia. The relationships between plasma AAs and endothelial and vascular smooth muscle function in the microcirculation of CKD patients are not well understood. The objective of this study is to investigate to what extent the levels of AAs and its metabolites are changed in CKD patients and to test their relationship with endothelial and vascular smooth muscle function. Patients with CKD stages 3 and 5 and non-CKD controls are included in this study. We report that there was a significant reduction of the biopterin (BH4/BH2) ratio, which was accompanied by increased plasma levels of BH2, asymmetric dimethylarginine (ADMA) and citrulline in patients with CKD-5 vs. CKD-3 vs. controls. In vivo augmentation index measurement showed a positive association with ADMA in all participants. The contribution of nitric oxide, assessed by ex vivo assay, showed a negative association with creatinine, ADMA and citrulline in all participants. In CKD-5, BH4 negatively correlated with ADMA and ornithine levels, and the ex vivo endothelium-mediated dilatation positively correlated with phenylalanine levels. In conclusion, uremia is associated with alterations in AA metabolism that may affect endothelium-dependent dilatation and vascular stiffness in microcirculation. Interventional strategies aiming to normalize the AA metabolism could be of interest as treatment options.

Role of ADMA in the pathogenesis of microvascular complications in type 2 diabetes mellitus

Diabetic microangiopathy is a typical and severe problem in diabetics, including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, and diabetic cardiomyopathy. Patients with type 2 diabetes and diabetic microvascular complications have significantly elevated levels of Asymmetric dimethylarginine (ADMA), which is an endogenous inhibitor of nitric oxide synthase (NOS). ADMA facilitates the occurrence and progression of microvascular complications in type 2 diabetes through its effects on endothelial cell function, oxidative stress damage, inflammation, and fibrosis. This paper reviews the association between ADMA and microvascular complications of diabetes and elucidates the underlying mechanisms by which ADMA contributes to these complications. It provides a new idea and method for the prevention and treatment of microvascular complications in type 2 diabetes.

Predictive markers in chronic kidney disease

Chronic kidney disease (CKD) is defined by gradual deterioration of the renal parenchyma and decline of functioning nephrons. CKD is now recognized as a distinct risk factor for cardiovascular disease (CVD). This risk rises in tandem with the decline in kidney function and peaks at the end-stage. It is important to identify individuals with CKD who are at a higher risk of advancing to end-stage renal disease (ESRD) and the beginning of CVD. This will enhance the clinical benefits and so that evidence-based therapy may be started at the initial stages for those individuals. A promising biomarker must represent tissue damage, and be easy to detect using non-invasive methods. Current CKD progression indicators have difficulties in reaching this aim. Hence this review presents an update on markers studied in the last decade, which help in the prediction of CKD progression such as neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, urinary liver-type fatty acid-binding protein, cystatin-C, asymmetric dimethylarginine, symmetric dimethylarginine, endotrophin, methylglyoxal, sclerostin, uric acid, and miRNA-196a. Additional research is needed to determine the predictive usefulness of these indicators in clinical samples for disease development. Their utility as surrogate markers need to be explored further for the early identification of CKD progression.

The role of oxidative stress markers in Indonesian chronic kidney disease patients: a cross sectional study

Background: Several aspects of chronic kidney disease (CKD) such as the incidence rate and mortality rate are concerning. Oxidative stress contributes to progression and mortality in patients with CKD; however, a specific correlation between several markers of oxidative stress and the estimated glomerular filtration rate (eGFR) and albumin-creatinine ratio (ACR) in the Indonesian population has not been sufficiently described yet. Methods: This study was an analytic observational study with a sample of 56 patients with CKD in Universitas Airlangga Hospital, Surabaya, Indonesia, from December 2019 – March 2020. The markers for oxidative stress investigated were urinary 8-hydroxy-2 deoxyguanosine (8-OHdG), serum symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA). The correlations between each variable of oxidative stress and CKD were analyzed using Pearson analysis. Results: There was a positive correlation between 8-OHdG and eGFR (p=0.00, r=0.51); however, there was a negative correlation between 8-OHdG and ACR (p=0.025, r=-0.30). SDMA and eGFR showed a negative correlation (p=0.00, r=-0.648), while SDMA and ACR showed a positive correlation (p=0.03, r=0.349). ADMA showed a negative correlation with eGFR (p=0.00, r=-0.476). There were significantly decreased 8-OHdG but increased ADMA and SDMA as the CKD stage progressed (p=0.001, p=0.00, and p = 0.00, respectively). Higher urine 8-OHdG was detected in patients without history of hemodialysis, whereas ADMA and SDMA showed higher value in patients with hemodialysis (p=0.00, p=0.00, and p=0.004, respectively), patients with history of diabetes mellitus (DM) had higher mean 8-OHdG (p 0.000) yet lower serum ADMA and SDMA (p=0.004 and p=0.003, respectively). Conclusions: In patients with CKD in Indonesia, the markers for oxidative stress 8-OHdG, SDMA, and ADMA are correlated with eGFR and ACR levels. There were also significant difference in 8-OHdG, SDMA, and ADMA levels among CKD stages, between dialysis vs non dialysis, and DM vs non DM patients.

The impact of uremic toxins on Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia, pathologically characterized by accumulation of senile plaques and neurofibrillary tangles. Chronic kidney disease (CKD) is highly prevalent in elderly population closely associated with occurrence of dementia. Recent epidemiological and experimental studies suggest a potential association of CKD with AD. Both diseases share a panel of identical risk factors, such as type 2 diabetes; and hypertension. However, the relationship between CKD and AD is unclear. Lower clearance of a panel of uremic toxin including cystatin-C, guanidine, and adiponectin due to CKD is implied to contribute to AD pathogenesis. In this review we summarize the current evidence from epidemiological, experimental and clinical studies on the potential contribution of uremic toxins to AD pathogenesis. We describe outstanding questions and propose an outlook on the link between uremic toxins and AD.

The Influence of an Acute Bout of Aerobic Exercise on Vascular Endothelial Function in Moderate Stages of Chronic Kidney Disease

Chronic kidney disease (CKD) is directly influenced by the deleterious effects of systemic inflammation and oxidative stress. The vascular endothelium may transiently respond to aerobic exercise and improve post-exercise vascular renal function in moderate stages of CKD. Brachial artery flow-mediated dilation (FMD) is a nitric-oxide-dependent measure of endothelial function that is transiently potentiated by exercise. The purpose of the study was to determine the acute influence of a single bout of high-intensity interval exercise (HIIE) or steady-state moderate-intensity exercise (SSE) on endothelial dysfunction in moderate stages of CKD. Twenty participants (n = 6 men; n = 14 women) completed 30 min of SSE (65%) and HIIE (90:20%) of VO_2reserve in a randomized crossover design. FMD measurements and blood samples were obtained before, 1 h, and 24 h post-exercise. FMD responses were augmented 1 h post-exercise in both conditions (p < 0.005). Relative to pre-exercise measures, total antioxidant capacity increased by 4.3% 24 h post-exercise (p = 0.012), while paraoxonase-1 was maintained 1 h and elevated by 6.1% 24 h after SSE, but not HIIE (p = 0.035). In summary, FMD can be augmented by a single episode of either HIIE or SSE in moderate stages of CKD. Modest improvements were observed in antioxidant analytes, and markers of oxidative stress were blunted in response to either SSE or HIIE.

Ventricular arrhythmias in mouse models of diabetic kidney disease

Chronic kidney disease (CKD) affects more than 20 million people in the US, and it is associated with a significantly increased risk of sudden cardiac death (SCD). Despite the significance, the mechanistic relationship between SCD and CKD is not clear and there are few effective therapies. Using optical mapping techniques, we tested the hypothesis that mouse models of progressive diabetic kidney disease (DKD) exhibit enhanced ventricular arrhythmia incidence and underlying arrhythmia substrates. Compared to wild-type mice, both Lepr^db/db eNOS^−/− (2KO) and high fat diet plus low dose streptozotocin (HFD + STZ) mouse models of DKD experienced sudden death and greater arrhythmia inducibility, which was more common with isoproterenol than programmed electrical stimulation. 2KO mice demonstrated slowed conduction velocity, prolonged action potential duration (APD), and myocardial fibrosis; both 2KO and HFD + STZ mice exhibited arrhythmias and calcium dysregulation with isoproterenol challenge. Finally, circulating concentrations of the uremic toxin asymmetric dimethylarginine (ADMA) were elevated in 2KO mice. Incubation of human cardiac myocytes with ADMA prolonged APD, as also observed in 2KO mice hearts ex vivo. The present study elucidates an arrhythmia-associated mechanism of sudden death associated with DKD, which may lead to more effective treatments in the vulnerable DKD patient population.

Asymmetric dimethylarginine level as biomarkers of cardiovascular or all-cause mortality in patients with chronic kidney disease: a meta-analysis

BACKGROUND

Studies have yielded conflicting findings on the association of asymmetric dimethylarginine (ADMA) level with cardiovascular or all-cause mortality in patients with chronic kidney disease (CKD). This meta-analysis sought to evaluate the association of blood ADMA level with cardiovascular or all-cause mortality in CKD patients.

MATERIALS AND METHODS

PubMed and Embase databases were comprehensively searched until September 9, 2020 for studies investigating the association of ADMA level with cardiovascular or all-cause mortality in CKD patients.

RESULTS

Data were collected from nine prospective studies involving 6553 patients. The pooled adjusted risk ratio (RR) of all-cause mortality was 2.06 (95% confidence interval [CI] 1.43-2.96) for the highest versus the lowest ADMA level. Each 0.20 μmol/L ADMA increase was associated with 21% (95% CI 1.09-1.35) higher risk of all-cause mortality but not cardiovascular mortality (RR 1.07; 95% CI 0. 99-1.16). Subgroup analysis showed that each 0.20 μmol/L ADMA increase was significantly associated with all-cause mortality in end-stage renal disease (ESRD) patients (RR 1.22; 95% CI 1.05-1.41) but not in patients with stage 3 to 4 CKD (RR 1.16; 95% CI 0.86-1.56).

CONCLUSIONS

Elevated ADMA level is independently associated with higher risk of all-cause mortality in ESRD patients.

Association Between the Asymmetric Dimethylarginine Levels and Glaucoma Severity: A Cross-Sectional Analysis of the LIGHT Study

Purpose

Asymmetric dimethylarginine (ADMA), a potent endogenous inhibitor of nitric oxide synthase, may be involved in the pathophysiology of glaucoma by dysfunctioning nitric oxide and oxidative stress. The purpose of this study was to determine whether the serum ADMA level is associated with the severity of glaucoma.

Methods

One hundred twenty-five patients with glaucoma (mean age 69.4 years) were analyzed in this cross-sectional study. The severity of glaucoma was determined by the visual field mean deviation in the worse eye; severe, a mean deviation ≤ -12 dB; and mild, a mean deviation > -12 dB. The serum ADMA levels were classified into three groups according to tertiles; low (T1), intermediate (T2), and high group (T3).

Results

The mean serum ADMA levels in the severe glaucoma group was significantly higher than that in the mild glaucoma group (0.41 vs. 0.39 µmol/L; P = 0.031). A significantly higher prevalence of patients with severe glaucoma was found in the T3 group than that in the T1 group (T1, 44.7% and T3, 68.2%; P = 0.018). In the multivariable logistic regression analysis adjusted for the potential confounders, e.g., age, sex, obesity, smoking, hypertension, diabetes, and renal function, the odds ratio for severe glaucoma in the T3 group was significantly higher than that in the T1 group (odds ratio 3.02; 95% confidence interval 1.04 to 8.79; P = 0.043).

Conclusions

A significant association between higher serum ADMA levels and severe glaucoma was found, and this association remained significant after adjusting for the potential confounders.

Uremic Toxins in the Progression of Chronic Kidney Disease and Cardiovascular Disease: Mechanisms and Therapeutic Targets

Chronic kidney disease (CKD) is a progressive loss of renal function. The gradual decline in kidney function leads to an accumulation of toxins normally cleared by the kidneys, resulting in uremia. Uremic toxins are classified into three categories: free water-soluble low-molecular-weight solutes, protein-bound solutes, and middle molecules. CKD patients have increased risk of developing cardiovascular disease (CVD), due to an assortment of CKD-specific risk factors. The accumulation of uremic toxins in the circulation and in tissues is associated with the progression of CKD and its co-morbidities, including CVD. Although numerous uremic toxins have been identified to date and many of them are believed to play a role in the progression of CKD and CVD, very few toxins have been extensively studied. The pathophysiological mechanisms of uremic toxins must be investigated further for a better understanding of their roles in disease progression and to develop therapeutic interventions against uremic toxicity. This review discusses the renal and cardiovascular toxicity of uremic toxins indoxyl sulfate, p-cresyl sulfate, hippuric acid, TMAO, ADMA, TNF-α, and IL-6. A focus is also placed on potential therapeutic targets against uremic toxicity.

Raised Plasma Levels of Asymmetric Dimethylarginine Are Associated with Pathological Type and Predict the Therapeutic Effect in Lupus Nephritis Patients Treated with Cyclophosphamide

BACKGROUND

Lupus nephritis (LN) is one of the most serious complications of systemic lupus erythematosus (SLE). Asymmetric dimethylarginine (ADMA) has been associated with cardiovascular events in SLE patients and is a strong predictor of the progression of chronic kidney disease. However, whether ADMA can provide a predictive value for the diagnosis and treatment of LN patients remains unclear. This study evaluated the clinical significance of ADMA in LN patients.

METHODS

Blood samples of 114 patients with LN, 52 patients with primary glomerular disease, and 20 healthy people were collected. Plasma ADMA was measured via enzyme-linked immunosorbent assay. The relationship between plasma ADMA levels and pathological types and renal function and efficacy in LN patients were further analyzed.

RESULTS

There was no significant difference in plasma ADMA levels between LN and primary glomerular disease, but both were significantly higher than the values in healthy people (p < 0.05). Plasma ADMA levels in LN patients were negatively correlated with baseline estimated glomerular filtration rate (eGFR) and serum superoxide dismutase and positively correlated with serum cystatin C and serum β2-microglobulin (p < 0.05). The plasma ADMA levels of diffuse proliferative LN patients were significantly higher than those of other histopathological classes of LN. High plasma ADMA levels in LN patients (OR = 1.012; 95% CI 1.003-1.022; p = 0.010) is a risk factor for diffuse proliferative LN. The area under the receiver operating characteristic (ROC) curve of diagnosing diffuse proliferative LN by plasma ADMA was 0.707 (95% CI 0.610-0.805). The area under the ROC curve of combination with plasma ADMA, serum complement C3, and eGFR for diffuse proliferative LN was 0.796 (95% CI 0.713-0.879), which was significantly higher than that of ADMA, complement C3, and eGFR for diffuse proliferative LN alone, respectively (p < 0.05). Low plasma ADMA is an independent protective factor for proliferative LN patients achieving complete remission with cyclophosphamide as induction therapy (OR = 0.978; 95% CI 0.961-0.996; p < 0.05).

CONCLUSION

High plasma ADMA levels in combination with eGFR and complement C3 may be useful to diagnose diffuse proliferative LN. Low plasma ADMA may help to predict complete remission in proliferative LN patients treated with cyclophosphamide as induction therapy. Plasma ADMA may be a new biomarker to determine the pathological type of LN and predict the therapeutic effect.

Renal asymmetric dimethylarginine inhibits fibrosis

Chronic kidney disease (CKD) is a worldwide public health problem that is caused by repeated injuries to the glomerulus or renal tubules. Renal fibrosis commonly accompanies CKD, and it is histologically characterized by excessive deposition of extracellular matrix proteins, such as fibronectin and collagen I, in interstitial areas. Indirect in vivo experimental data suggest that renal asymmetric dimethylarginine (ADMA) exerts antifibrotic activity in CKD. In this study, we aimed to demonstrate that renal ADMA has a direct effect on fibrosis in vivo. Normal saline, ADMA, nonsense control siRNA, Ddah1 siRNA or Ddah2 siRNA was administered into the kidney through the left ureter in a mouse model of unilateral ureteral obstruction (UUO). UUO kidneys were harvested at day 1 or 7. Western blotting was performed to assess the expression of ADMA, DDAH1 and DDAH2 and the expression of fibrotic markers, such as fibronectin, collagen I, α-smooth muscle actin, phosphorylation of Smad3 and connective tissue growth factor. Masson's trichrome staining was used to further evaluate renal fibrosis. We observed that intrarenal administration of ADMA increased the renal accumulation of ADMA and attenuated renal fibrosis at days 1 and 7. Knockdown of Ddah1 or Ddah2 increased the amount of ADMA in UUO kidneys and inhibited the expression of fibrotic proteins at days 1 and 7, which was further confirmed by Masson's staining. Thus, our in vivo data suggest that renal ADMA exerts direct antifibrotic effects in a mouse model of UUO.

Evaluation of salivary and serum asymmetric dimethylarginine (ADMA) levels in patients with periodontal and cardiovascular disease as subclinical marker of cardiovascular risk

BACKGROUND

Asymmetric dimethylarginine (ADMA) plays a crucial role in endothelial function and maybe a link for the known interaction of periodontitis and coronary heart disease (CHD). In this pilot study, we compared the impact of gingival health, periodontitis (CP), CHD, or of both diseases (CP + CHD) on salivary and serum ADMA levels.

METHODS

The clinical and periodontal characteristics, serum, and saliva samples were collected from 35 patients with CP, 33 patients with CHD, 35 patients with both CP + CHD, and 35 healthy subjects. Levels of ADMA and C-reactive protein (CRP) were assessed with a commercially available kit.

RESULTS

The median (25% and 75% percentile) concentrations of salivary and serum ADMA were significantly higher in the CHD group [serum: 1.5 (1.2 to 1.8) μmol/L; salivary 1.3 (1 to 1.7) μmol/g protein, P < 0.01] and in the CP + CHD [serum: 1.8 (1.4 to 2.0) μmol/L; salivary 1.5 (1.2 to 1.7) μmol/g protein, P < 0.001] group compared to CP patients and controls. In univariate models, CP (P = 0.034), CHD (P < 0.001), and hs-CRP (P < 0.001) were significantly associated with serum ADMA, whereas in a multivariate model, hs-CRP remained a significant predictor of serum ADMA (P < 0.001). In a multivariate model, the significant predictors of salivary ADMA levels were hs-CRP (P < 0.001) and education socioeconomic status (P = 0.042).

CONCLUSIONS

Patients with CHD and CP + CHD presented higher levels of salivary and serum ADMA compared to healthy subjects and CP patients. hs-CRP was a significant predictor of increased salivary and serum ADMA levels.

Endothelial Dysfunction in Chronic Kidney Disease, from Biology to Clinical Outcomes: A 2020 Update

The vascular endothelium is a dynamic, functionally complex organ, modulating multiple biological processes, including vascular tone and permeability, inflammatory responses, thrombosis, and angiogenesis. Endothelial dysfunction is a threat to the integrity of the vascular system, and it is pivotal in the pathogenesis of atherosclerosis and cardiovascular disease. Reduced nitric oxide (NO) bioavailability is a hallmark of chronic kidney disease (CKD), with this disturbance being almost universal in patients who reach the most advanced phase of CKD, end-stage kidney disease (ESKD). Low NO bioavailability in CKD depends on several mechanisms affecting the expression and the activity of endothelial NO synthase (eNOS). Accumulation of endogenous inhibitors of eNOS, inflammation and oxidative stress, advanced glycosylation products (AGEs), bone mineral balance disorders encompassing hyperphosphatemia, high levels of the phosphaturic hormone fibroblast growth factor 23 (FGF23), and low levels of the active form of vitamin D (1,25 vitamin D) and the anti-ageing vasculoprotective factor Klotho all impinge upon NO bioavailability and are critical to endothelial dysfunction in CKD. Wide-ranging multivariate interventions are needed to counter endothelial dysfunction in CKD, an alteration triggering arterial disease and cardiovascular complications in this high-risk population.

Asymmetric dimethylarginine and angiopoietin-like protein-2 are independent predictors of cardiovascular risk in pre-dialysis non-diabetic chronic kidney disease patients

BACKGROUND

Chronic kidney disease (CKD) is associated with increased cardiovascular (CVD) morbidity and mortality. Hence, this study was carried out to assess the biomarkers of endothelial dysfunction and inflammation as predictors of CVD risk in Indian patients with CKD.

METHODS

In this case control study, we recruited 43 patients with CKD and 43 healthy control volunteers. Circulating levels of endothelial dysfunction markers [asymmetric dimethylarginine (ADMA), angiopoietin-like protein-2 (ANGPTL2), matrix metallopeptidase 9 (MMP-9)] and systemic inflammation [high-sensitivity C-reactive protein (hs-CRP)] were assessed in the study population. All study participants underwent brachial artery flow mediated dilation (FMD) to estimate endothelial dysfunction. Disease severity (e-GFR) was assessed by a nephrologist.

RESULTS

CKD patients showed markedly elevated levels of ADMA, ANGPTL2, MMP-9, and hs-CRP. FMD and eGFR were significantly decreased in cases, as compared to the controls. ADMA, ANGPTL2, MMP-9 and hs-CRP showed significant positive correlation with one another and significant negative correlation with FMD and disease severity. We also observed a significant negative correlation of FMD with disease severity and duration of CKD. In the multiple linear regression model, ADMA and ANGPTL2 were found to be independent predictors of FMD.

CONCLUSION

In CKD patients, there is significantly increased endothelial dysfunction and systemic inflammation, which showed a positive correlation with disease severity. Thus, the markers of endothelial dysfunction such as ADMA and ANGPTL2 can be used as predictors of CVD risk in CKD.

The Clinician's Guide to Proton Pump Inhibitor Related Adverse Events

A substantial volume of literature exists linking proton pump inhibitor (PPI) use with a multitude of serious adverse events. There is uncertainty, however, over whether these associations are clinically important. Excessive concern about PPI-related adverse events may leave patients at risk of harm by leaving acid-related upper gastrointestinal disease untreated. Conversely, the risk of treatments may outweigh the benefits if any of the purported adverse events are directly caused by PPI use; this is of particular concern where indications for PPI use are not present. In this paper, we review the studies which have reported associations between adverse events and PPI use, discuss the proposed mechanisms of action, grade the confidence in whether these associations are truly causal, and provide advice regarding balancing the benefits of PPI use against their possible harms.

Asymmetric (ADMA) and Symmetric (SDMA) Dimethylarginines in Chronic Kidney Disease: A Clinical Approach

Asymmetric dimethylarginine (ADMA) and its enantiomer, Symmetric dimethylarginine (SDMA), are naturally occurring amino acids that were first isolated and characterized in human urine in 1970. ADMA is the most potent endogenous inhibitor of nitric oxide synthase (NOS), with higher levels in patients with end-stage renal disease (ESRD). ADMA has shown to be a significant predictor of cardiovascular outcome and mortality among dialysis patients. On the other hand, although initially SDMA was thought to be an innocuous molecule, we now know that it is an outstanding marker of renal function both in human and in animal models, with ESRD patients on dialysis showing the highest SDMA levels. Today, we know that ADMA and SDMA are not only uremic toxins but also independent risk markers for mortality and cardiovascular disease (CVD). In this review, we summarize the role of both ADMA and SDMA in chronic kidney disease along with other cardiovascular risk factors.

Asymmetric dimethylarginine: An crucial regulator in tissue fibrosis

Fibrosis is a reparative process with very few therapeutic options to prevent its progression to organ dysfunction. Chronic fibrotic diseases contribute to an estimated 45% of all death in the industrialized world. Asymmetric dimethylarginine (ADMA), an endothelial nitric oxide synthase inhibitor, plays a crucial role in the pathogenesis of various cardiovascular diseases associated with endothelial dysfunction. Recent reports have focused on ADMA in the pathogenesis of tissue fibrosis. This review discusses the current knowledge about ADMA biology, its association with risk factors of established fibrotic diseases and the potential pathophysiological mechanisms implicating ADMA in the process of tissue fibrosis.

Reduced asymmetric dimethylarginine accumulation through inhibition of the type I protein arginine methyltransferases promotes renal fibrosis in obstructed kidneys

The role of asymmetric dimethylarginine (ADMA) in chronic kidney disease (CKD) is unclear. Through inhibition of type I protein arginine methyltransferases (PRMTs), a novel strategy, we aimed to determine the effect of ADMA on renal fibrosis and explore its underlying working mechanisms. After sham or unilateral ureter ligation (UUO) operation, 20-25 g male c57 mice were treated with vehicle or PT1001B, an inhibitor of type I PRMTs, for 13 d. Moreover, human kidney 2 (HK2) and normal rat kidney 49F (NRK-49F) cells were treated with various concentrations of PT1001B or ADMA in the presence of 2.5 ng/ml TGF-β. We found that treatment with PT1001B increased the deposition of extracellular matrix proteins, the expression of α smooth muscle actin, and connective tissue growth factor in UUO-induced fibrotic kidneys, which is correlated with reduced expression of PRMT1, reduced the production of ADMA, and increased expression of uromodulin. In TGF-β-stimulated HK2 and NRK-49F cells, PT1001B dose-dependently inhibited ADMA production, increased NO concentrations, and enhanced the expression of profibrotic proteins. Exogenous addition of ADMA inhibited the expression of profibrotic proteins dose-dependently and attenuated the profibrotic effect of PT1001B. Moreover, ADMA reduced the NO concentration in PT1001B-treated HK2 cells. Finally, we conclude that ADMA has an antifibrotic effect in obstructed kidneys, and future application of type I PRMT inhibitor should be done cautiously for patients with CKD.-Wu, M., Lin, P., Li, L., Chen, D., Yang, X., Xu, L., Zhou, B., Wang, C., Zhang, Y., Luo, C., Ye, C. Reduced asymmetric dimethylarginine accumulation through inhibition of the type I protein arginine methyltransferases promotes renal fibrosis in obstructed kidneys.

Treatment Based on Cinacalcet Reduces Oxidative Stress in Hemodialysis Patients with Secondary Hyperparathyroidism

BACKGROUND/AIMS

Oxidative stress is one of the leading factors contributing to increased mortality in patients with chronic kidney disease (CKD) and secondary hyperparathyroidism (sHPT). Cinacalcet is now commonly used in the treatment of sHPT in patients with CKD. The aim of this study was to assess the influence of treatment with cinacalcet on the oxidative stress markers in patients on hemodialysis with sHPT.

METHODS

In 58 hemodialysed patients with sHPT (parathyroid hormone [PTH] > 300 pg/mL) plasma Advanced Oxidation Protein Products (AOPP), serum total antioxidant capacity - ImAnOx (TAS/TAC), serum PTH, calcium and phosphate concentrations were assessed before the first dose of cinacalcet and after 6 months of treatment.

RESULTS

Serum PTH concentration decreased significantly from 895 (748-1,070) to 384 (289-510) pg/mL after 6 months of treatment; p < 0.0001. Mean serum concentrations of -calcium and phosphate remained stable. Plasma AOPP concentration decreased significantly from 152 (126-185) to 49 -(43-57) µmol/L after 6 months of treatment; p < 0.0001. ImAnOx significantly increased from 260 (251-270) to 272 (264-280) µmol/L; p = 0.04. After 6 months of treatment, a significant, positive correlation was found between ImAnOx and the daily dose of cinacalcet (r = 0.30; p = 0.02). Also, the change of serum ImAnOx during treatment with cinacalcet significantly correlated with the daily dose of cinacalcet r = 0.35; p = 0.01. No significant correlations were found between plasma AOPP concentration or ImAnOx and PTH, or their changes in time.

CONCLUSIONS

(1) Six-month treatment based on cinacalcet seems to reduce oxidative stress markers in maintenance hemodialysis patients with sHPT. (2) This benefit may be related rather to the direct action of cinacalcet than to the serum PTH concentration decrease.

HDL in CKD-The Devil Is in the Detail

The picture of HDL cholesterol (HDL-C) as the "good" cholesterol has eroded. This is even more surprising because there exists strong evidence that HDL-C is associated with cardiovascular disease (CVD) in the general population as well as in patients with impairment of kidney function and/or progression of CKD. However, drugs that dramatically increase HDL-C have mostly failed to decrease CVD events. Furthermore, genetic studies took the same line, as genetic variants that have a pronounced influence on HDL-C concentrations did not show an association with cardiovascular risk. For many, this was not surprising, given that an HDL particle is highly complex and carries >80 proteins and several hundred lipid species. Simply measuring cholesterol might not reflect the variety of biologic effects of heterogeneous HDL particles. Therefore, functional studies and the involvement of HDL components in the reverse cholesterol transport, including the cholesterol efflux capacity, have become a further focus of study during recent years. As also observed for other aspects, CKD populations behave differently compared with non-CKD populations. Although clear disturbances have been observed for the "functionality" of HDL particles in patients with CKD, this did not necessarily translate into clear-cut associations with outcomes.

Association Between Proton Pump Inhibitor Use and Risk of Progression of Chronic Kidney Disease

BACKGROUND & AIMS

Proton pump inhibitors (PPI) have been associated with acute kidney injury and recent studies suggest that they may be associated with the risk of chronic kidney disease (CKD).

METHODS

We performed a retrospective analysis using the Stockholm creatinine measurements database, which contains information on diagnoses, dispensation claims, and laboratory test results for all citizens in the Stockholm region from 2007 through 2010. We identified new users of PPIs (n = 105,305) and new users of H₂ blockers (H₂B; n = 9578); data on renal outcomes were collected for a median 2.7 years. The primary outcome was progression CKD, defined as doubling of creatinine or decrease in estimated glomerular filtration rate of 30% or more. Secondary outcomes were end-stage renal disease and acute kidney injury. Complete collection of repeated PPI and H₂B dispensations at pharmacies in Sweden allowed modeling the time-dependent risk associated with cumulative PPI exposure.

RESULTS

Users of PPIs, compared with users of H₂Bs, had an increased risk for doubled levels of creatinine (1985 events; adjusted hazard ratio [HR], 1.26; 95% CI, 1.05-1.51) and decrease in estimated glomerular filtration rate of 30% or more (11,045 events; 1.26; 95% CI, 1.16-1.36). PPI use also associated with development of end-stage renal disease (HR, 2.40; 95% CI, 0.76-7.58) and acute kidney injury (HR, 1.30; 95% CI, 1.00-1.69). There was a graded association between cumulative exposure to PPIs and risk of CKD progression. This was not the case for cumulative H₂B use.

CONCLUSIONS

Initiation of PPI therapy and cumulative PPI exposure is associate with increased risk of CKD progression in a large, North European healthcare system. Although consistent, the association was modest in magnitude, and cannot exclude residual confounding.

Emerging Liver-Kidney Interactions in Nonalcoholic Fatty Liver Disease

Mounting evidence connects non-alcoholic fatty liver disease (NAFLD) to chronic kidney disease (CKD). We review emerging mechanistic links between NAFLD and CKD, including altered activation of angiotensin converting enzyme (ACE)-2, nutrient/energy sensors sirtuin-1 and AMP-activated kinase, as well as impaired antioxidant defense mediated by nuclear factor erythroid 2-related factor-2 (Nrf2). Dietary fructose excess may also contribute to NAFLD and CKD. NAFLD affects renal injury through lipoprotein dysmetabolism and altered secretion of the hepatokines fibroblast growth factor-21, fetuin-A, insulin-like growth factor-1, and syndecan-1. CKD may mutually aggravate NAFLD and associated metabolic disturbances through altered intestinal barrier function and microbiota composition, the accumulation of uremic toxic metabolites, and alterations in pre-receptor glucocorticoid metabolism. We conclude by discussing the implications of these findings for the treatment of NAFLD and CKD.

Biomarkers in chronic kidney disease, from kidney function to kidney damage

Chronic kidney disease (CKD) typically evolves over many years, with a long latent period when the disease is clinically silent and therefore diagnosis, evaluation and treatment is based mainly on biomarkers that assess kidney function. Glomerular filtration rate (GFR) remains the ideal marker of kidney function. Unfortunately measuring GFR is time consuming and therefore GFR is usually estimated from equations that take into account endogenous filtration markers like serum creatinine (SCr) and cystatin C (CysC). Other biomarkers such as albuminuria may precede kidney function decline and have demonstrated to have strong associations with disease progression and outcomes. New potential biomarkers have arisen with the promise of detecting kidney damage prior to the currently used markers. The aim of this review is to discuss the utility of the GFR estimating equations and biomarkers in CKD and the different clinical settings where these should be applied. The CKD-Epidemiology Collaboration equation performs better than the modification of diet in renal disease equation, especially at GFR above 60 mL/min per 1.73 m². Equations combining CysC and SCr perform better than the equations using either CysC or SCr alone and are recommended in situations where CKD needs to be confirmed. Combining creatinine, CysC and urine albumin to creatinine ratio improves risk stratification for kidney disease progression and mortality. Kidney injury molecule and neutrophil gelatinase-associated lipocalin are considered reasonable biomarkers in urine and plasma to determine severity and prognosis of CKD.