Plasma concentration of asymmetrical dimethylarginine and mortality in patients with end-stage renal disease: a prospective study

Novel Perspectives in Chronic Kidney Disease-Specific Cardiovascular Disease

Chronic kidney disease (CKD) affects > 10% of the global adult population and significantly increases the risk of cardiovascular disease (CVD), which remains the leading cause of death in this population. The development and progression of CVD-compared to the general population-is premature and accelerated, manifesting as coronary artery disease, heart failure, arrhythmias, and sudden cardiac death. CKD and CV disease combine to cause multimorbid cardiorenal syndrome (CRS) due to contributions from shared risk factors, including systolic hypertension, diabetes mellitus, obesity, and dyslipidemia. Additional neurohormonal activation, innate immunity, and inflammation contribute to progressive cardiac and renal deterioration, reflecting the strong bidirectional interaction between these organ systems. A shared molecular pathophysiology-including inflammation, oxidative stress, senescence, and hemodynamic fluctuations characterise all types of CRS. This review highlights the evolving paradigm and recent advances in our understanding of the molecular biology of CRS, outlining the potential for disease-specific therapies and biomarker disease detection.

Klotho and lean mass as novel cardiovascular risk factors in hemodialysis patients

Background

Patients with chronic kidney disease (CKD) present a higher risk of cardiovascular (CV) morbidity and mortality compared with the general population. While there are several well-established traditional CV risk factors, few studies have addressed novel potential risk factors such as α-Klotho, asymmetric dimethylarginine (ADMA) and lean mass.

Methods

This was an observational, prospective, single-center, cohort study that included prevalent hemodialysis (online hemodiafiltration) adult patients. By univariate logistic regression models, univariate and multivariate Cox proportional hazards models, and Kaplan-Meier analysis, we evaluated the association between the levels of α-Klotho, ADMA and lean mass, with the risk of peripheral vascular disease (PVD), CV events and all-cause mortality in these patients.

Results

A total of 200 HD patients was included. We found that increased levels of log-α-Klotho were significantly associated with decreased odds of both PVD [odds ratio (OR) 0.521, 95% confidence interval (CI) 0.270-0.954, P = .034] and CV events (OR 0.415, 95% CI 0.203-0.790, P = .01), whereas increased levels of log-ADMA were only significantly associated with increased odds of PVD (OR 13.482, 95% CI 5.055-41.606, P < .001). We also found that the levels of log-α-Klotho (HR 0.357, 95% CI 0.140-0.906, P < .05) and lean mass (HR 0.187, 95% CI 0.042-0.829, P < .05), but not log-ADMA, were significantly associated with the risk of all-cause mortality, even after adjusting for possible confounding variables.

Conclusions

Novel long-term clinical associations were generated that support α-Klotho and lean mass as novel CV risk factors in hemodialysis patients.

Association of urine and plasma ADMA with atherosclerotic risk in DKD cardiovascular disease risk in diabetic kidney disease: findings from the Chronic Renal Insufficiency Cohort (CRIC) study

BACKGROUND

Chronic kidney disease (CKD) is associated with atherosclerotic cardiovascular disease (ASCVD) risk, especially among those with diabetes. Altered metabolism of solutes that accumulate in CKD [asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and trimethylamine N-oxide (TMAO)] may reflect pathways linking CKD with ASCVD.

METHODS

This case-cohort study included Chronic Renal Insufficiency Cohort participants with baseline diabetes, estimated glomerular filtration rate <60 mL/min/1.73 m2, and without prior history for each outcome. The primary outcome was incident ASCVD (time to first myocardial infarction, stroke or peripheral artery disease event) and secondary outcome was incident heart failure. The subcohort comprised randomly selected participants meeting entry criteria. Plasma and urine ADMA, SDMA and TMAO concentrations were determined by liquid chromatography-tandem mass spectrometry. Associations of uremic solute plasma concentrations and urinary fractional excretions with outcomes were evaluated by weighted multivariable Cox regression models, adjusted for confounding covariables.

RESULTS

Higher plasma ADMA concentrations (per standard deviation) were associated with ASCVD risk [hazard ratio (HR) 1.30, 95% confidence interval (CI) 1.01-1.68]. Lower fractional excretion of ADMA (per standard deviation) was associated with ASCVD risk (HR 1.42, 95% CI 1.07-1.89). The lowest quartile of ADMA fractional excretion was associated with greater ASCVD risk (HR 2.25, 95% CI 1.08-4.69) compared with the highest quartile. Plasma SDMA and TMAO concentration and fractional excretion were not associated with ASCVD. Neither plasma nor fractional excretion of ADMA, SDMA and TMAO were associated with incident heart failure.

CONCLUSION

These data suggest that decreased kidney excretion of ADMA leads to increased plasma concentrations and ASCVD risk.

Association of triglyceride-glucose index with coronary severity and mortality in patients on dialysis with coronary artery disease

BACKGROUND

The triglyceride-glucose (TyG) index is validated as a reliable biomarker of insulin resistance and an independent predictor of cardiovascular prognosis. However, the prognostic value of the TyG index in patients on dialysis with coronary artery disease (CAD) remained unexplored. This study aimed to determine the association between the TyG index and CAD severity and mortality in these patients.

METHODS

A total of 1061 dialysis patients with CAD were enrolled in this multi-center cohort study from January 2015 to June 2021. The extent and severity of CAD were evaluated using the multivessel disease and Gensini score (GS). Patients were followed up for all-cause death and cardiovascular death.

RESULTS

The multivariable logistic regression model indicated that the TyG index was significantly associated with multivessel disease (odds ratio [OR] 1.51, 95% confidence interval [CI] 1.18-1.94, P = 0.001), and high GS (OR 1.33, 95% CI 1.10-1.61, P = 0.003). After adjusting for baseline risk factors, the hazards of all-cause death and cardiovascular death were 1.23 (95% CI 1.06-1.43, P = 0.007), and 1.33 (95% CI 1.11-1.59, P = 0.002), independent of CAD severity. Restricted cubic spline analysis identified a dose-response association between the TyG index and both CAD severity and mortality (all P for nonlinearity > 0.05). When modeling the TyG index as a categorical variable, these independent associations remained. Subgroup analyses did not substantially modify the results. Furthermore, incorporating the TyG index into the existing risk prediction model improved the predictive accuracy for all-cause death and cardiovascular death, as evaluated by C-statistic, continuous net reclassification improvement, and integrated discrimination improvement.

CONCLUSIONS

In patients on dialysis with CAD, the TyG index was significantly associated with more severe CAD as well as mortality. These results highlight the clinical importance of the TyG index for assessing CAD severity and risk stratification in patients on dialysis with CAD.

Cardiovascular Manifestations and Management in ADPKD

Cardiovascular disease (CVD) is the major cause of mortality in autosomal dominant polycystic kidney disease (ADPKD) and contributes to significant burden of disease. The manifestations are varied, including left ventricular hypertrophy (LVH), intracranial aneurysms (ICAs), valvular heart disease, and cardiomyopathies; however, the most common presentation and a major modifiable risk factor is hypertension. The aim of this review is to detail the complex pathogenesis of hypertension and other extrarenal cardiac and vascular conditions in ADPKD drawing on preclinical, clinical, and epidemiological evidence. The main drivers of disease are the renin-angiotensin-aldosterone system (RAAS) and polycystin-related endothelial cell dysfunction, with the sympathetic nervous system (SNS), nitric oxide (NO), endothelin-1 (ET-1), and asymmetric dimethylarginine (ADMA) likely playing key roles in different disease stages. The reported rates of some manifestations, such as LVH, have decreased likely due to the use of antihypertensive therapies; and others, such as ischemic cardiomyopathy, have been reported with increased prevalence likely due to longer survival and higher rates of chronic disease. ADPKD-specific screening and management guidelines exist for hypertension, LVH, and ICAs; and these are described in this review.

Leukocyte 8-hydroxy-2'-deoxyguanosine as an oxidative stress marker to predict cardiovascular events and death in chronic hemodialysis patients

BACKGROUND

Hemodialysis patients have a markedly increased risk of cardiovascular (CV) morbidity and mortality. Oxidative stress plays a pathogenic role in the progression of atherosclerosis and CV disease among chronic hemodialysis patients. The 8-hydroxy-2'-deoxyguanosine (8-OHdG) content in leukocyte deoxyribonucleic acid (DNA) has been shown as a sensitive and well-known biomarker of oxidant-induced DNA damage in chronic hemodialysis patients.

METHODS

We conducted a retrospective cohort study to investigate the association of leukocyte 8-OHdG and CV events and deaths in patients of chronic hemodialysis. In this study, 217 chronic hemodialysis patients were recruited from 2016 to 2021. The 8-OHdG content of leukocyte DNA was measured by a high-performance liquid chromatography electrochemical detection method. Study outcomes were CV events as well as CV and all-cause deaths. The patients were followed until May 2021.

RESULTS

The median follow-up period was 34.8 months. At the end of May 2021, 57 first CV events and 89 all-CV events occurred. Among the first and all CV events, 17 (29.8%) and 32 (36.0%) were fatal, respectively. Multivariate Cox regression analysis showed per 1/10 5 dG increment in leukocyte 8-OHdG values increased risk of CV events (adjusted hazard ratio [aHR], 1.19; 95% CI, 1.10-1.41; p < 0.001), CV death (aHR, 1.27; 95% CI, 1.03-1.72; p = 0.034), and all-cause death (aHR, 1.11; 95% CI, 1.01-1.30; p = 0.038).

CONCLUSION

This is the first study to demonstrate that oxidative stress assessed by 8-OHdG levels of leukocyte DNA predicted CV events as well as CV and all-cause deaths among chronic hemodialysis patients.

Evaluation of plasma sphingolipids as mediators of the relationship between kidney disease and cardiovascular events

BACKGROUND

Sphingolipids are a family of circulating lipids with regulatory and signaling roles that are strongly associated with both eGFR and cardiovascular disease. Patients with chronic kidney disease (CKD) are at high risk for cardiovascular events, and have different plasma concentrations of certain plasma sphingolipids compared to patients with normal kidney function. We hypothesize that circulating sphingolipids partially mediate the associations between eGFR and cardiovascular events.

METHODS

We measured the circulating concentrations of 8 sphingolipids, including 4 ceramides and 4 sphingomyelins with the fatty acids 16:0, 20:0, 22:0, and 24:0, in plasma from 3,463 participants in a population-based cohort (Cardiovascular Health Study) without prevalent cardiovascular disease. We tested the adjusted mediation effects by these sphingolipids of the associations between eGFR and incident cardiovascular disease via quasi-Bayesian Monte Carlo method with 2,000 simulations, using a Bonferroni correction for significance.

FINDINGS

The mean (±SD) eGFR was 70 (±16) mL/min/1.73 m2; 62% of participants were women. Lower eGFR was associated with higher plasma ceramide-16:0 and sphingomyelin-16:0, and lower ceramides and sphingomyelins-20:0 and -22:0. Lower eGFR was associated with risk of incident heart failure and ischemic stroke, but not myocardial infarction. Five of eight sphingolipids partially mediated the association between eGFR and heart failure. The sphingolipids associated with the greatest proportion mediated were ceramide-16:0 (proportion mediated 13%, 95% CI 8-22%) and sphingomyelin-16:0 (proportion mediated 10%, 95% CI 5-17%). No sphingolipids mediated the association between eGFR and ischemic stroke.

INTERPRETATION

Plasma sphingolipids partially mediated the association between lower eGFR and incident heart failure. Altered sphingolipids metabolism may be a novel mechanism for heart failure in patients with CKD.

FUNDING

This study was supported by T32 DK007467 and a KidneyCure Ben J. Lipps Research Fellowship (Dr. Lidgard). Sphingolipid measurements were supported by R01 HL128575 (Dr. Lemaitre) and R01 HL111375 (Dr. Hoofnagle) from the National Heart, Lung, and Blood Institute (NHLBI).

The Association Between Fluid Overload and Endothelial Dysfunction in Chronic Kidney Failure Patients Undergoing Hemodialysis Twice a Week

BACKGROUND

Fluid overload causes excessive systemic vasoconstriction and decreased perfusion of peripheral tissues, leading to abnormalities in cardiopulmonary physiological functions. Prolonged fluid overload caused by inadequate hemodialysis may cause heart dilatation, left ventricular hypertrophy, hypertension, and a decrease in coronary reserves, which later will develop into coronary ischemia, leading to increased morbidity and mortality of cardiovascular disease (CVD). Endothelial dysfunction plays a role in excessive vasoconstriction on fluid overload. Brain natriuretic peptide (BNP) and asymmetric dimethylarginine (ADMA) are used as parameters of fluid overload and endothelial dysfunction, respectively. This study is conducted to describe the relationship between fluid overload with endothelial dysfunction.

METHOD

This study is a cross-sectional study of kidney failure patients who underwent hemodialysis twice weekly for at least three months. BNP and ADMA were used as parameters for fluid overload and taken prior to hemodialysis.

RESULT

From 126 subjects, the proportion with fluid overload (BNP>356 pg/ml) was found to be 64.3% with the median age of subjects being 52 years (47-62). There was 47.6% population with endothelial dysfunction (ADMA>100 ng/ml). Presumptive causes of primary chronic kidney disease (CKD) were hypertension (38.9%), diabetes mellitus (DM) (28.6%), and glomerulonephritis (21.4%). There was no significant association between fluid overload and endothelial dysfunction (PR=1,042, p=0.832 CI 95%=0.714-1.521).

CONCLUSION

There was no relationship between fluid overload and endothelial dysfunction.

A multicentric consortium study demonstrates that dimethylarginine dimethylaminohydrolase 2 is not a dimethylarginine dimethylaminohydrolase

Dimethylarginine dimethylaminohydrolase 1 (DDAH1) protects against cardiovascular disease by metabolising the risk factor asymmetric dimethylarginine (ADMA). However, the question whether the second DDAH isoform, DDAH2, directly metabolises ADMA has remained unanswered. Consequently, it is still unclear if DDAH2 may be a potential target for ADMA-lowering therapies or if drug development efforts should focus on DDAH2's known physiological functions in mitochondrial fission, angiogenesis, vascular remodelling, insulin secretion, and immune responses. Here, an international consortium of research groups set out to address this question using in silico, in vitro, cell culture, and murine models. The findings uniformly demonstrate that DDAH2 is incapable of metabolising ADMA, thus resolving a 20-year controversy and providing a starting point for the investigation of alternative, ADMA-independent functions of DDAH2.

The role of decoy receptor 3 in inflammation and atherosclerosis in patients with chronic kidney disease and renal transplant patients

INTRODUCTION

The cardiovascular risk has been increased in chronic kidney disease associated with chronic inflammation and atherosclerosis. Decoy receptor 3, is a member of the TNF receptor superfamily and associated with inflammation and atherosclerosis. The aim of our study is to determine the relationship, between serum DcR3 levels and inflammatory markers in patients with renal transplantation, those receiving dialysis treatment and cases with chronic renal failure that did not receive replacement therapy, and to evaluate their correlation with USG findings.

MATERIAL AND METHODS

A total of 150 patients aged between 22-86 years, consisting of 4 groups, namely renal transplantation, dialysis, predialysis chronic kidney disease and control groups, were included in the study. Serum decoy receptor 3, VCAM-1, ICAM-1 and IL-8 measured with ELISA method. Carotid intima-media thickness and presence of carotis arter plaque performed by ultrasound probe, non-invasively.

RESULTS

All serum markers were higher in dialysis and pre-dialysis chronic kidney disease groups compared to renal transplant and control groups (p<0.05). Serum decoy receptor 3 level (median(min-max)) of renal transplant group (0.49ng/mL (0.19-1.65)) was higher than control group (0.35ng/mL (0.19-2.22)). There was no difference between patients receiving dialysis (0.89ng/mL (0.41-4.98)) and patients with pre-dialysis chronic kidney disease (0.71ng/mL (0.29-1.68)). There was no difference between patient groups in terms of the presence of plaque.

CONCLUSION

Although renal transplantation provides a significant improvement in the inflammatory process, not return completely. Inflammatory process associated with uremic milieu may predispose to atherosclerosis in patients with pre-dialysis chronic kidney disease and hemodialysis patients.

Improved vascular function and functional capacity following l-citrulline administration in patients with heart failure with preserved ejection fraction: a single-arm, open-label, prospective pilot study

There is accumulating evidence for both peripheral vascular dysfunction and impaired functional capacity in patients with heart failure with a preserved ejection fraction (HFpEF). Although derangements in the l-arginine-nitric oxide (l-Arg-NO) pathway are likely to contribute to these aspects of HFpEF pathophysiology, the impact of increased NO substrate on vascular health and physical capacity has not been evaluated in this patient population. Thus, using a single-arm study design, we evaluated the impact of enteral l-citrulline (l-Cit, 6 g/day for 7 days), a precursor for l-Arg biosynthesis, on vascular function [flow-mediated dilation (FMD), reactive hyperemia (RH), and passive limb movement (PLM)], functional capacity [6-min walk test (6MWT)], and biomarkers of l-Arg-NO signaling in 14 patients with HFpEF (n = 14, 4 M/10 F, 70 ± 10 yr, EF: 66 ± 7%). Compared with baseline (0d), 7 days of l-Cit administration improved FMD (0d: 2.5 ± 1.6%, 7d: 4.5 ± 2.9%), RH (0d: 468 ± 167 mL, 7d: 577 ± 199 mL), PLM blood flow area-under-the-curve (0d: 139 ± 130 mL, 7d: 198 ± 115 mL), and 6MWT distance (0d: 377 ± 27 m, 7d: 397 ± 27 m) (P < 0.05). An increase in plasma l-Cit (0d: 42 ± 11 µM/L, 7d: 369 ± 201 µM/L), l-Arg (0d: 65 ± 8 µM/L, 7d: 257 ± 25 µM/L), and the ratio of l-Arg to asymmetric dimethylarginine (ADMA) (0d: 136 ± 13 AU, 7d: 481 ± 49 AU) (P < 0.05) was also observed. Though preliminary in nature, these functional and biomarker assessments demonstrate a potential benefit of l-Cit administration in patients with HFpEF, findings that provide new insight into the mechanisms that govern vascular and physical dysfunction in this patient group.NEW & NOTEWORTHY The current investigation has demonstrated that l-Cit administration may improve brachial artery endothelium-dependent vasodilation, upper and lower limb microvascular function, and physical capacity in patients with HFpEF, highlighting the potential therapeutic potential of interventions targeting the l-Arg-NO signaling cascade to improve outcomes in this patient group.

N-Acetylcysteine: more than preventing contrast-induced nephropathy in uremic patients-focus on the antioxidant and anti-inflammatory properties

Oxidative stress (OS) has been recognized as a pathophysiologic mechanism underlying the development and progression of chronic kidney disease (CKD). OS, which results from the disturbance of balance among pro-oxidants and antioxidants favoring the pro-oxidants, is present even in early CKD and increases progressively along with deterioration of kidney function to end-stage kidney disease (ESKD). In ESKD, OS is further exacerbated mainly due to dialysis procedures per se and predisposes to increased cardiovascular morbidity and mortality. Therefore, since OS plays a pivotal role in the pathogenesis and progression of atherosclerosis in uremic patients, several strategies aiming to ameliorate OS in these patients have been proposed. Among those, N-acetylcysteine (NAC), a thiol-containing antioxidant agent, has attracted special attention due to its pleiotropic functions and beneficial effect in various OS-related entities including paracetamol overdose and prevention of contrast-induced nephropathy. In this review, we present the currently available literature on the antioxidant and anti-inflammatory properties of NAC in CKD, including hemodialysis and peritoneal dialysis.

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.

Nitric-oxide precursors and dimethylarginines as risk markers for accelerated measured GFR decline in the general population

Introduction

Nitric oxide (NO) deficiency is associated with endothelial dysfunction, hypertension, atherosclerosis, and chronic kidney disease (CKD). Reduced NO bioavailability is hypothesized to play a vital role in kidney function impairment and CKD. We investigated the association of serum levels of endogenous inhibitors of NO, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), and precursors of NO, arginine, citrulline, and ornithine, with a decline in glomerular filtration rate (GFR) and new-onset CKD.

Methods

In a prospective cohort study of 1407 healthy, middle-aged participants of Northern European origin in the Renal Iohexol Clearance Survey (RENIS), GFR was measured repeatedly with iohexol clearance during a median follow-up time of 11 years. GFR decline rates were analyzed using a linear mixed model, new-onset CKD (GFR < 60 ml/min per 1.73 m²) was analyzed with interval-censored Cox regression, and accelerated GFR decline (the 10% with the steepest GFR decline) was analyzed with logistic regression.

Results

Higher SDMA was associated with slower annual GFR decline. Higher levels of citrulline and ornithine were associated with accelerated GFR decline (odds ratio [OR], 1.43; 95% confidence interval [CI] 1.16-1.76 per SD higher citrulline and OR 1.23; 95% CI 1.01 to 1.49 per SD higher ornithine). Higher citrulline was associated with new-onset CKD, with a hazard ratio of 1.33 (95% CI 1.07-1.66) per SD higher citrulline.

Conclusions

Associations between NO precursors and the outcomes suggest that NO metabolism plays a significant role in the pathogenesis of age-related GFR decline and the development of CKD in middle-aged people.

Endogenous Glycosaminoglycans in Various Pathologic Plasma Samples as Measured by a Fluorescent Quenching Method

Endogenous glycosaminoglycans (GAGs) with a similar structure to heparin are widely distributed in various tissues. A fluorescence probe, namely Heparin Red, can detect polyanionic GAGs in plasma samples. The purpose of this study is to measure endogenous GAGs in various plasma samples obtained from different pathologic states in comparison to healthy controls utilizing this method. Plasma samples were obtained from patient groups including atrial fibrillation (AF), end-stage-renal-disease (ESRD), diabetes mellitus (DM), sepsis, cancer, liver disease (LD), and pulmonary embolism (PE). Normal human plasma (NHP) was used as healthy controls. The Heparin Red kit from Red Probes (Münster, Germany) was used for the quantification of endogenous GAGs in each sample before and after heparinase I degradation. All results were compiled as group means  ±  SD for comparison. NHP was found to have relatively low levels of endogenous GAGs with a mean concentration of 0.06 μg/mL. The AF, ESRD, DM, and sepsis patient samples had a mean endogenous GAG concentration of 0.55, 0.72, 0.92, and 0.94 μg/mL, respectively. The levels of endogenous GAGs were highest in cancer, LD, and PE patient plasma samples with a mean concentration of 1.95, 2.78, and 2.83 μg/mL, respectively. Heparinase I degradation resulted in a decline in GAG levels in plasma samples. These results clearly show that detectable Heparin Red sensitive endogenous GAGs are present in circulating plasma at varying levels in various patient groups. Additional studies are necessary to understand this complex pathophysiology.

Examination of the emerging role of transporters in the assessment of nephrotoxicity

INTRODUCTION

The kidney is vulnerable to various injuries based on its function in the elimination of many xenobiotics, endogenous substances and metabolites. Since transporters are critical for the renal elimination of those substances, it is urgent to understand the emerging role of transporters in nephrotoxicity.

AREAS COVERED

This review summarizes the contribution of major renal transporters to nephrotoxicity induced by some drugs or toxins; addresses the role of transporter-mediated endogenous metabolic disturbances in nephrotoxicity; and discusses the advantages and disadvantages of in vitro models based on transporter expression and function.

EXPERT OPINION

Due to the crucial role of transporters in the renal disposition of xenobiotics and endogenous substances, it is necessary to further elucidate their renal transport mechanisms and pay more attention to the underlying relationship between the transport of endogenous substances and nephrotoxicity. Considering the species differences in the expression and function of transporters, and the low expression of transporters in general cell models, in vitro humanized models, such as humanized 3D organoids, shows significant promise in nephrotoxicity prediction and mechanism study.

Hypertension in chronic kidney disease: What lies behind the scene

Hypertension is a frequent condition encountered during kidney disease development and a leading cause in its progression. Hallmark factors contributing to hypertension constitute a complexity of events that progress chronic kidney disease (CKD) into end-stage renal disease (ESRD). Multiple crosstalk mechanisms are involved in sustaining the inevitable high blood pressure (BP) state in CKD, and these play an important role in the pathogenesis of increased cardiovascular (CV) events associated with CKD. The present review discusses relevant contributory mechanisms underpinning the promotion of hypertension and their consequent eventuation to renal damage and CV disease. In particular, salt and volume expansion, sympathetic nervous system (SNS) hyperactivity, upregulated renin–angiotensin–aldosterone system (RAAS), oxidative stress, vascular remodeling, endothelial dysfunction, and a range of mediators and signaling molecules which are thought to play a role in this concert of events are emphasized. As the control of high BP via therapeutic interventions can represent the key strategy to not only reduce BP but also the CV burden in kidney disease, evidence for major strategic pathways that can alleviate the progression of hypertensive kidney disease are highlighted. This review provides a particular focus on the impact of RAAS antagonists, renal nerve denervation, baroreflex stimulation, and other modalities affecting BP in the context of CKD, to provide interesting perspectives on the management of hypertensive nephropathy and associated CV comorbidities.

Divergent Dimethylarginine Dimethylaminohydrolase Isoenzyme Expression in the Central Nervous System

The endogenous methylated derivative of ʟ-arginine, Nω,Nω'-dimethyl-ʟ-arginine (asymmetric dimethylarginine, ADMA), an independent risk factor in many diseases, inhibits the activity of nitric oxide synthases and, consequently, modulates the availability of nitric oxide. While most studies on the biological role of ADMA have focused on endothelial and inducible nitric oxide synthases modulation and its contribution to cardiovascular, metabolic, and renal diseases, a role in regulating neuronal nitric oxide synthases and pathologies of the central nervous system is less understood. The two isoforms of dimethylarginine dimethylaminohydrolase (DDAH), DDAH1 and DDAH2, are thought to be the main enzymes responsible for ADMA catabolism. A current impediment is limited knowledge on specific tissue and cellular distribution of DDAH enzymes within the brain. In this study, we provide a detailed characterization of the regional and cellular distribution of DDAH1 and DDAH2 proteins in the adult murine and human brain. Immunohistochemical analysis showed a wide distribution of DDAH1, mapping to multiple cell types, while DDAH2 was detected in a limited number of brain regions and exclusively in neurons. Our results provide key information for the investigation of the pathophysiological roles of the ADMA/DDAH system in neuropsychiatric diseases and pave the way for the development of novel selective therapeutic approaches.

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.

Hyperphosphatemia and its relationship with blood pressure, vasoconstriction, and endothelial cell dysfunction in hypertensive hemodialysis patients

Background

Hyperphosphatemia occurs frequently in end-stage renal disease patients on hemodialysis and is associated with increased mortality. Hyperphosphatemia contributes to vascular calcification in these patients, but there is emerging evidence that it is also associated with endothelial cell dysfunction.

Methods

We conducted a cross-sectional study in hypertensive hemodialysis patients. We obtained pre-hemodialysis measurements of total peripheral resistance index (TPRI, non-invasive cardiac output monitor) and plasma levels of endothelin-1 (ET-1) and asymmetric dimethylarginine (ADMA). We ascertained the routine peridialytic blood pressure (BP) measurements from that treatment and the most recent pre-hemodialysis serum phosphate levels. We used generalized linear regression analyses to determine independent associations between serum phosphate with BP, TPRI, ET-1, and ADMA while controlling for demographic variables, parathyroid hormone (PTH), and interdialytic weight gain.

Results

There were 54 patients analyzed. Mean pre-HD supine and seated systolic and diastolic BP were 164 (27), 158 (21), 91.5 (17), and 86.1 (16) mmHg. Mean serum phosphate was 5.89 (1.8) mg/dL. There were significant correlations between phosphate with all pre-hemodialysis BP measurements (r = 0.3, p = .04; r = 0.4, p = .002; r = 0.5, p < .0001; and r = 0.5, p = .0003.) The correlations with phosphate and TPRI, ET-1, and ADMA were 0.3 (p = .01), 0.4 (p = .007), and 0.3 (p = .04). In our final linear regression analyses controlling for baseline characteristics, PTH, and interdialytic weight gain, independent associations between phosphate with pre-hemodialysis diastolic BP, TPRI, and ET-1 were retained (β = 4.33, p = .0002; log transformed β = 0.05, p = .005; reciprocal transformed β = -0.03, p = .047).

Conclusions

Serum phosphate concentration is independently associated with higher pre-HD BP, vasoconstriction, and markers of endothelial cell dysfunction. These findings demonstrate an additional negative impact of hyperphosphatemia on cardiovascular health beyond vascular calcification.

Trial registration

The study was part of a registered clinical trial, NCT01862497 (May 24, 2013).

Effects of Ramipril on Biomarkers of Endothelial Dysfunction and Inflammation in Hypertensive Children on Maintenance Hemodialysis: the SEARCH Randomized Placebo-Controlled Trial

BACKGROUND

Hypertension, endothelial dysfunction, and inflammation are associated with increased cardiovascular mortality in end-stage kidney disease. We evaluated the effects of ACE (angiotensin-converting enzyme) inhibition on biomarkers of endothelial dysfunction and inflammation in hypertensive children with end-stage kidney disease on maintenance hemodialysis.

METHODS

In a randomized, double-blind, placebo-controlled trial, 135 (72 males/63 females) children and adolescents (age 7-15 years) were randomly assigned to treatment with either 2.5 mg once daily ramipril (n=68) or placebo (n=67) for 16 weeks. Primary outcome were the serum concentrations of asymmetrical dimethylarginine, a marker of endothelial dysfunction and hs-CRP (high-sensitivity C-reactive protein), a marker of inflammation. Changes in IL-6 (interleukin-6), TNF-α (tumor necrosis factor-alpha), systolic (S), and diastolic (D) blood pressure were secondary outcomes. Change in potassium levels and incidence of hyperkalemia were among the safety parameters.

RESULTS

Ramipril, but not placebo, significantly reduced serum levels of asymmetrical dimethylarginine (-79.6%; P<0.001), hs-CRP (-46.5%; P<0.001), IL-6 (-27.1%; P<0.001), and TNF-α (-51.7%; P<0.001). Systolic blood pressure and diastolic blood pressure were significantly lowered in both groups with a greater reduction in children receiving ramipril (median between-group differences -12.0 [95% CI -18.0 to -9.5] and -9.0 [95% CI -12.0 to -4.5]; P<0.001, respectively). Changes in asymmetrical dimethylarginine, hs-CRP, IL-6, or TNF-α in the ramipril group did not significantly correlate with blood pressure reductions. No severe cases of hyperkalemia or other serious treatment-associated adverse events were observed.

CONCLUSIONS

Ramipril improves biomarkers of endothelial dysfunction and inflammation in hypertensive children on maintenance hemodialysis in addition to its efficacious and safe potential to lower blood pressure.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04582097.

Far-Infrared Therapy Improves Arteriovenous Fistula Patency and Decreases Plasma Asymmetric Dimethylarginine in Patients with Advanced Diabetic Kidney Disease: A Prospective Randomized Controlled Trial

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and plays a significant role in the pathogenesis of arteriovenous fistula (AVF) dysfunction. The aim of this study is to evaluate the effect of far-infrared (FIR) therapy on the maturation and patency of newly-created AVFs in patients with advanced diabetic kidney disease (DKD) as well as the concurrent change in plasma ADMA. The study enrolled 144 participants with advanced DKD where 101 patients were randomly allocated to the FIR therapy group (N = 50) and control group (N = 51). Patients receiving FIR therapy had a decreased AVF failure rate within 12 months (16% versus 35.3%; p = 0.027); decreased incremental change of ADMA concentration at the 3rd and 12th month; increased AVF blood flow at the 1st, 3rd, and 12th month; increased 3-month physiologic maturation rate (88% versus 68.6%; p = 0.034); increased 1-year unassisted AVF patency rate (84% versus 64.7%; p = 0.017); and increased clinical AVF maturation rate within 12 months (84% versus 62.7%; p = 0.029) compared to the control group. The study demonstrates that FIR therapy can reduce the incremental changes in plasma ADMA concentration, which may be associated with the improvement of AVF prognosis in patients with advanced DKD.

Comparison of the Surgical Resection and Infarct 5/6 Nephrectomy Rat Models of Chronic Kidney Disease

The 5/6 nephrectomy rat remnant kidney model is commonly employed to study chronic kidney disease (CKD). This model requires removal of one whole kidney and two-thirds of the other. The two most common ways of producing the remnant kidney are surgical resection of poles, known as the polectomy (Pol) model, or ligation of upper and lower renal arterial branches, resulting in pole infarction (Inf). These models have much in common, but also major phenotypic differences, and thus respectively model unique aspects of human CKD. The purpose of this review is to summarize phenotypic similarities and differences between these two models and their relation to human CKD, while emphasizing their vascular phenotype. In this article we review studies that have evaluated arterial blood pressure, the renin-angiotensin-aldosterone-system (RAAS), autoregulation, nitric oxide, single nephron physiology, angiogenic and anti-angiogenic factors, and capillary rarefaction in these two models. Phenotypic similarities: both models spontaneously develop hallmarks of human CKD including uremia, fibrosis, capillary rarefaction, and progressive renal function decline. They both undergo whole-organ hypertrophy, hyperfiltration of functional nephrons, reduced renal expression of angiogenic factor VEGF, increased renal expression of the anti-angiogenic thrombospondin-1, impaired renal autoregulation, and abnormal vascular nitric oxide physiology. Key phenotypic differences: the Inf model develops rapid-onset, moderate-to-severe systemic hypertension, and the Pol model early normotension followed by mild-to-moderate hypertension. The Inf rat has a markedly more active renin-angiotensin-aldosterone-system. Comparison of these two models facilitates understanding of how they can be utilized for studying CKD pathophysiology (e.g., RAAS dependent or independent pathology).

Diabetes acts on mortality in hemodialysis patients predicted by asymmetric dimethylarginine and inflammation

BACKGROUND

The mortality rate of diabetic patients on dialysis is higher than that of non-diabetic patients. Asymmetric dimethylarginine and inflammation are strong predictors of death in hemodialysis. This study aimed to evaluate asymmetric dimethylarginine and C-reactive protein interaction in predicting mortality in hemodialysis according to the presence or absence of diabetes.

METHODS

Asymmetric dimethylarginine and C-reactive protein were measured in 202 patients in maintenance hemodialysis assembled from 2011 to 2012 and followed for four years. Effect modification of C-reactive protein on the relationship between asymmetric dimethylarginine and all-cause mortality was investigated dividing the population into four categories according to the median of asymmetric dimethylarginine and C-reactive protein.

RESULTS

Asymmetric dimethylarginine and C-reactive protein levels were similar between diabetics and non-diabetics. Asymmetric dimethylarginine - median IQR μM - (1.95 1.75-2.54 versus 1.03 0.81-1.55 P=0.000) differed in non-diabetics with or without evolution to death (HR 2379 CI 1.36-3.68 P=0.000) and was similar in diabetics without or with evolution to death. Among non-diabetics, the category with higher asymmetric dimethylarginine and C-reactive protein levels exhibited the highest mortality (69.0% P=0.000). No differences in mortality were seen in diabetics. A joint effect was found between asymmetric dimethylarginine and C-reactive protein, explaining all-cause mortality (HR 15.21 CI 3.50-66.12 P=0.000).

CONCLUSIONS

Asymmetric dimethylarginine is an independent predictor of all-cause mortality in non-diabetic patients in hemodialysis. Other risk factors may overlap asymmetric dimethylarginine in people with diabetes. Inflammation dramatically increases the risk of death associated with high plasma asymmetric dimethylarginine in hemodialysis.

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

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

Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance

The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.

Association of Variability in the DDAH1, DDAH2, AGXT2 and PRMT1 Genes with Circulating ADMA Concentration in Human Whole Blood

Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthesis and a cardiovascular risk factor. Its regulation has been studied extensively in experimental models, but less in humans. We studied common single-nucleotide polymorphisms (SNPs) in genes encoding for enzymes involved in ADMA biosynthesis and metabolism, i.e., PRMT1, DDAH1, DDAH2, and AGXT2, and assessed their associations with blood ADMA concentration in 377 unselected humans. The minor allele of DDAH1 SNP rs233112 was significantly more frequent in individuals with ADMA in the highest tertile or in the highest quartile, as was the major allele of DDAH2 rs805304. A combined genotype comprising both SNPs showed a significant genotype–phenotype association, with increasing ADMA concentration by an increasing number of inactive alleles. SNPs in the AGXT2 and PRMT1 genes showed no significant associations with blood ADMA concentration. Our study provides comprehensive evidence that DDAH1 and DDAH2 are the major enzymes regulating blood ADMA concentration, whilst PRMT1 indirectly affects ADMA, and AGXT2 may act as a back-up enzyme in ADMA metabolism under pathophysiological conditions only.

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.

Effect of amlodipine versus bisoprolol in hypertensive patients on maintenance hemodialysis: A randomized controlled trial

BACKGROUND

Left ventricular hypertrophy and asymmetric dimethylarginine (ADMA) are surrogate markers of cardiovascular disease (CVD) in the dialysis population. This study aimed to evaluate the effect of a calcium channel blocker-based antihypertensive regimen compared to a beta-blocker-based antihypertensive regimen on left ventricular mass index (LVMI) and ADMA levels in hypertensive patients on hemodialysis (HD).

METHODS

This was a parallel-design, open-label, single-center randomized controlled trial on 46 hypertensive patients on maintenance HD, with no history of CVD. Patients were randomly assigned to receive amlodipine 10 mg/d (n = 23) or bisoprolol 10 mg/d (n = 23). Office-based blood pressure (BP) was targeted to ≤ 140/ 90 mm Hg. The outcome was the change in LVMI and ADMA from baseline to 6 months.

RESULTS

Baseline demographic and clinical characteristics did not vary between groups. After 6 months of treatment, amlodipine-based therapy induced a greater reduction in LVMI from baseline than bisoprolol-based treatment (35 ± 34.2 vs 9.8 ± 35.9 gm/m2; P = .017). A similar reduction in the mean BP occurred with treatment in both groups. ADMA concentration decreased significantly from baseline in the amlodipine group (0.75 ± 0.73 to 0.65 ± 0.67 nmol/mL; P = .001), but increased nonsignificantly in the bisoprolol group (0.64 ± 0.61 to 0.78 ± 0.64 nmol/mL; P = .052).

CONCLUSION

This study showed that compared to a bisoprolol-based regimen, an amlodipine-based antihypertensive regimen resulted in a significantly greater reduction in LVMI and ADMA levels from baseline in hypertensive patients on HD despite similar BP reduction in both groups. These findings support the re-evaluation of amlodipine as a potential first-line antihypertensive treatment in patients on HD without previous CVD.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT04085562, registered September 2019.

Identification of ceRNA (lncRNA-miRNA-mRNA) Regulatory Network in Myocardial Fibrosis After Acute Myocardial Infarction

Purpose

Materials and Methods

Results

Conclusion

Plasmatic Dimethylarginines in Dogs With Myxomatous Mitral Valve Disease

Plasmatic dimethylarginines, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are considered biomarkers of endothelial and renal dysfunction, respectively, in humans. We hypothesize that plasmatic concentration of dimethylarginines in dogs with myxomatous mitral valve disease (MMVD) is influenced by heart disease stage. Eighty-five client-owned dogs with MMVD, including 39, 19, and 27 dogs in ACVIM stages B1, B2, and C+D, respectively, and a control group of 11 clinically healthy dogs were enrolled. A prospective, multicentric, case-control study was performed. Each dog underwent a complete clinical examination, arterial blood pressure measurement, thoracic radiography, six-lead standard electrocardiogram, transthoracic echocardiography, CBC, biochemical profile, and urinalysis. Plasmatic concentration of dimethylarginines was determined through high-performance liquid chromatography coupled with tandem mass spectrometry. Median ADMA was significantly increased in dogs of group C+D (2.5 μmol/L [2.1–3.0]) compared to those of group B1 (1.8 μmol/L [1.6–2.3]; p < 0.001) and healthy dogs (1.9 μmol/L [1.7–2.3]; p = 0.02). Median SDMA was significantly increased in dogs of group C+D (0.7 μmol/L [0.5–0.9]) compared to those of groups B1 (0.4 μmol/L [0.3–0.5]; p < 0.001), B2 (0.4 μmol/L [0.3–0.6]; p < 0.01), and the control group (0.4 μmol/L [0.35–0.45]; p = 0.001). In the final multivariable analysis, ADMA and SDMA were significantly associated with left atrium to aorta ratio (p < 0.001), and creatinine (p < 0.001), respectively. Increased plasmatic concentrations of dimethylarginines suggest a possible role as biomarkers of disease severity in dogs with decompensated MMVD.

Association of Serum Asymmetric Dimethylarginine with the Severity of Coronary Artery Disease: A Pilot Study

Background

Asymmetric dimethylarginine (ADMA), an inhibitor of nitric oxide synthase (NOS), has been implicated in endothelial dysfunction and atherogenesis. Though there is much evidence linking ADMA with atherosclerosis and adverse cardiovascular events, only a few studies have established the independent relationship between elevated ADMA and the angiographic extent of coronary artery disease (CAD). The aim of the study was to analyze serum ADMA levels in patients with varied extent and severity of coronary atherosclerosis and to see whether the levels of ADMA in male and female participants vary significantly.

Methods

We analyzed 40 individuals with obstructive CAD, including men and women, between the ages of 30 and 60. According to their coronary angiographic reports, the participants were divided into four groups: minor CAD, single vessel disease (SVD), double vessel disease (DVD) group and triple vessel disease (TVD). Then, serum ADMA levels was measured and compared among these groups.

Results

ADMA level was significantly higher in patients with TVD (167.74±16.69) than those in the DVD (159.46±10.40), SVD (149.54±16.39) and minor CAD (144.5± 24.16) group (p-value= 0.0001). There was no significant difference in ADMA levels between male and female participants (p= 0.534).

Conclusion

ADMA concentration in the serum may be useful in identifying whether CAD correlates significantly to the extent and severity of coronary atherosclerosis.

Vasodilator use in precapillary pulmonary hypertension with end stage kidney disease: A single center experience

BACKGROUND AND OBJECTIVES

Pulmonary hypertension is commonly seen in end stage kidney disease and is most commonly due to elevated left heart pressures. There is limited data about vasodilator use during the management of Group 1 pulmonary arterial hypertension in the context of those who also have or later developed end stage kidney disease. The objective of this study was to determine safety and efficacy of vasodilator therapy in precapillary pulmonary hypertension requiring renal replacement therapy.

DESIGN

This was a single-center retrospective case series. Patients were identified from our Pulmonary Hypertension Clinic using a historical roster from 2012 to 2020. Patients were included if they >18 years of age, had Group 1 or Group 4 (precapillary) pulmonary hypertension on right heart catheterization, and also had end stage kidney disease requiring either intermittent hemodialysis or peritoneal dialysis.

RESULTS

18 patients were identified with invasively confirmed Group 1 or Group 4 pulmonary hypertension and end stage kidney disease on renal replacement therapy. Scleroderma was the most common etiology for renal failure. 17 patients were treated with vasodilator therapy. Fifteen patients had paired right heart catheterizations that showed a significant decrease in mean pulmonary artery pressure and pulmonary vascular resistance. Therapy was relatively well tolerated but hypotension was common and midodrine was often helpful. Two patients had successful renal transplantation after starting vasodilator therapy.

CONCLUSION

We found vasodilator therapy was reasonably well tolerated and associated with a drop in mean pressure and pulmonary vascular resistance in patients with end stage kidney disease on dialysis.

Asymmetric Dimethylarginine: a Key Player in the Pathophysiology of Endothelial Dysfunction, Vascular Inflammation and Atherosclerosis in Rheumatoid Arthritis?

Patients with rheumatoid arthritis (RA), a chronic and disabling autoimmune condition that is characterized by articular and extra-articular manifestations and a pro-inflammatory and pro-oxidant state, suffer from premature atherosclerosis and excessive cardiovascular disease burden. A key step in the pathogenesis of atherosclerosis is impaired synthesis of the endogenous messenger nitric oxide (NO) by endothelial cells which, in turn, alters local homeostatic mechanisms and favors vascular damage and plaque deposition. While the exact mechanisms of endothelial dysfunction in RA remain to be established, there is good evidence that RA patients have relatively high circulating concentrations of the methylated arginine asymmetric dimethylarginine (ADMA), a potent endogenous inhibitor of endothelial NO synthase (eNOS). This review discusses the biological and pathophysiological role of ADMA, the interplay between ADMA, inflammation and oxidative stress, and the available evidence on the adverse impact of ADMA on endothelial function and atherosclerosis and potential ADMA-lowering therapies in RA patients.

Εndothelial and microvascular function in CKD: Evaluation methods and associations with outcomes

BACKGROUND

Cardiovascular disease is the major cause of morbidity and mortality in patients with chronic kidney disease (CKD). Endothelial dysfunction, the hallmark of atherosclerosis, is suggested to be involved pathogenetically in cardiovascular and renal disease progression in these patients.

METHODS

This is a narrative review presenting the techniques and markers used for assessment of microvascular and endothelial function in patients with CKD and discussing findings of the relevant studies on the associations of endothelial dysfunction with co-morbid conditions and outcomes in this population.

RESULTS

Venous Occlusion Plethysmography was the first method to evaluate microvascular function; subsequently, several relevant techniques have been developed and used in patients with CKD, including brachial Flow-Mediated Dilatation, and more recently, Near-Infrared Spectroscopy and Laser Speckle Contrast Analysis. Furthermore, several circulating biomarkers are commonly used in clinical research. Studies assessing endothelial function using the above techniques and biomarkers suggest that endothelial dysfunction occurs early in CKD and contributes to the target organ damage, cardiovascular events, death and progression towards end-stage kidney disease.

CONCLUSIONS

Older and newer functional methods and several biomarkers have assessed endothelial dysfunction in CKD; accumulated evidence supports an association of endothelial dysfunction with outcomes. Future research with new, non-invasive and easily applicable methods could further delineate the role of endothelial dysfunction on cardiovascular and renal disease progression in patients with CKD.

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.

Intersection Between Chronic Kidney Disease and Cardiovascular Disease

PURPOSE OF REVIEW

The incidence of chronic kidney disease is increasing worldwide, and the previously decreasing incidence of cardiovascular disease has now plateaued. Understanding the intersection of both heart and kidney disease is crucial.

RECENT FINDINGS

Chronic kidney disease and cardiovascular disease share common risk factors and specific pathogenic mechanisms and impact a significant segment of the population. Patients with chronic kidney disease are more likely to have cardiovascular disease than progress to end-stage kidney disease requiring renal replacement therapy. We discuss shared risk factors and mechanisms for cardiovascular and chronic kidney disease. The following also addresses contemporary cardiovascular treatment considerations in patients with chronic kidney disease with a focus on atherosclerotic cardiovascular disease and heart failure.

Diabetes acts on mortality in hemodialysis patients predicted by asymmetric dimethylarginine and inflammation

BACKGROUND

The mortality rate of diabetic patients on dialysis is higher than that of non-diabetic patients. Asymmetric dimethylarginine and inflammation are strong predictors of death in hemodialysis. This study aimed to evaluate asymmetric dimethylarginine and C-reactive protein interaction in predicting mortality in hemodialysis according to the presence or absence of diabetes.

METHODS

Asymmetric dimethylarginine and C-reactive protein were measured in 202 patients in maintenance hemodialysis assembled from 2011 to 2012 and followed for four years. Effect modification of C-reactive protein on the relationship between asymmetric dimethylarginine and all-cause mortality was investigated dividing the population into four categories according to the median of asymmetric dimethylarginine and C-reactive protein.

RESULTS

Asymmetric dimethylarginine and C-reactive protein levels were similar between diabetics and non-diabetics. Asymmetric dimethylarginine - median IQR μM - (1.95 1.75-2.54 versus 1.03 0.81-1.55 P=0.000) differed in non-diabetics with or without evolution to death (HR 2379 CI 1.36-3.68 P=0.000) and was similar in diabetics without or with evolution to death. Among non-diabetics, the category with higher asymmetric dimethylarginine and C-reactive protein levels exhibited the highest mortality (69.0% P=0.000). No differences in mortality were seen in diabetics. A joint effect was found between asymmetric dimethylarginine and C-reactive protein, explaining all-cause mortality (HR 15.21 CI 3.50-66.12 P=0.000).

CONCLUSIONS

Asymmetric dimethylarginine is an independent predictor of all-cause mortality in non-diabetic patients in hemodialysis. Other risk factors may overlap asymmetric dimethylarginine in people with diabetes. Inflammation dramatically increases the risk of death associated with high plasma asymmetric dimethylarginine in hemodialysis.

Central and peripheral arterial diseases in chronic kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Chronic kidney disease (CKD) affects about 10% of all populations worldwide, with about 2 million people requiring dialysis. Although patients with CKD are at high risk of cardiovascular disease and events, they are often underrepresented or excluded in clinical trials, leading to important knowledge gaps about how to treat these patients. KDIGO (Kidney Disease: Improving Global Outcomes) convened the fourth clinical Controversies Conference on the heart, kidney and vasculature in Dublin, Ireland, in February 2020, entitled Central and Peripheral Arterial Diseases in Chronic Kidney Disease. A global panel of multidisciplinary experts from the fields of nephrology, cardiology, neurology, surgery, radiology, vascular biology, epidemiology, and health economics attended. The objective was to identify key issues related to the optimal detection, management, and treatment of cerebrovascular diseases, central aortic disease, renovascular disease, and peripheral artery disease in the setting of CKD. This report outlines the common pathophysiology of these vascular processes in the setting of CKD, describes best practices for their diagnosis and management, summarizes areas of uncertainty, addresses ongoing controversial issues, and proposes a research agenda to address key gaps in knowledge that, when addressed, could improve patient care and outcomes.

Could Antioxidant Supplementation Delay Progression of Cardiovascular Disease in End-Stage Renal Disease Patients?

In end-stage renal disease patients, the leading causes of mortality are of cardiovascular (CV) origin. The underlying mechanisms are complex, given that sudden heart failure is more common than acute myocardial infarction. A contributing role of oxidative stress is postulated, which is increased even at early stages of chronic kidney disease, is gradually augmented in parallel to progression to endstage renal disease and is further accelerated by renal replacement therapy. Oxidative stress ensues when there is an imbalance between reactive pro-oxidants and physiologically occurring electron donating antioxidant defence systems. During the last decade, a close association of oxidative stress with accelerated atherosclerosis and increased risk for CV and all-cause mortality has been established. Lipid peroxidation has been identified as a trigger for endothelial dysfunction, the first step towards atherogenesis. In order to counteract the deleterious effects of free radicals and thereby ameliorate, or delay, CV disease, exogenous administration of antioxidants has been proposed. Here, we attempt to summarize existing data from studies that test antioxidants for CV protection, such as vitamins E and C, statins, omega-3 fatty acids and N-acetylcysteine.

Asymmetric dimethylarginine predicts perioperative cardiovascular complications in patients undergoing medium-to-high risk non-cardiac surgery

Objectives

Perioperative cardiovascular events remain an important factor that affects surgery outcome. We assessed if asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthesis, predicts perioperative risk, and if pre-operative supplementation with L-arginine/L-citrulline improves the plasma L-arginine/ADMA ratio.

Methods

In this prospective study, planned thoracic and/or abdominal surgery patients were randomized to receive L-arginine/L-citrulline (5 g/day) or placebo 1 to 5 days before surgery. We measured perioperative plasma ADMA and L-arginine levels. The primary outcome was a 30-day combined cardiovascular endpoint.

Results

Among 269 patients, 23 (8.6%) experienced a major adverse cardiovascular event. ADMA and C-reactive protein were significantly associated with the incidence of cardiovascular complications in the multivariable-adjusted analysis. The L-arginine plasma concentration was significantly higher on the day of surgery with L-arginine/L-citrulline supplementation compared with placebo. In patients with high pre-operative ADMA, there was a non-significant trend towards reduced incidence of the primary endpoint with L-arginine/L-citrulline supplementation (six vs. nine events).

Conclusions

ADMA is a predictor of major adverse cardiovascular complications in the perioperative period for patients who are undergoing major abdominal and/or thoracic surgery. Supplementation with L-arginine/L-citrulline increased the L-arginine plasma concentration, enhanced the L-arginine/ADMA ratio, and induced a trend towards fewer perioperative events.

Biomarkers representing key aging-related biological pathways are associated with subclinical atherosclerosis and all-cause mortality: The Framingham Study

BACKGROUND

Increased oxidative stress, leukocyte telomere length (LTL) shortening, endothelial dysfunction, and lower insulin-like growth factor (IGF)-1 concentrations reflect key molecular mechanisms of aging. We hypothesized that biomarkers representing these pathways are associated with measures of subclinical atherosclerosis and all-cause mortality.

METHODS AND RESULTS

We evaluated up to 2,314 Framingham Offspring Study participants (mean age 61 years, 55% women) with available biomarkers of aging: LTL, circulating concentrations of IGF-1, asymmetrical dimethylarginine (ADMA), and urinary F2-Isoprostanes indexed to urinary creatinine. We evaluated the association of each biomarker with coronary artery calcium [ln (CAC+1)] and carotid intima-media thickness (IMT). In multivariable-adjusted linear regression models, higher ADMA levels were associated with higher CAC values (βADMA per 1-SD increase 0.25; 95% confidence interval [CI] [0.11, 0.39]). Additionally, shorter LTL and lower IGF-1 values were associated with higher IMT values (βLTL -0.08, 95%CI -0.14, -0.02, and βIGF-1 -0.04, 95%CI -0.08, -0.01, respectively). During a median follow-up of 15.5 years, 593 subjects died. In multivariable-adjusted Cox regression models, LTL and IGF-1 values were inversely associated with all-cause mortality (hazard ratios [HR] per SD increase in biomarker, 0.85, 95% CI 0.74-0.99, and 0.90, 95% CI 0.82-0.98 for LTL and IGF-1, respectively). F2-Isoprostanes and ADMA values were positively associated with all-cause mortality (HR per SD increase in biomarker, 1.15, 95% CI, 1.10-1.22, and 1.10, 95% CI, 1.02-1.20, respectively).

CONCLUSION

In our prospective community-based study, aging-related biomarkers were associated with measures of subclinical atherosclerosis cross-sectionally and with all-cause mortality prospectively, supporting the concept that these biomarkers may reflect the aging process in community-dwelling adults.

Changes in the Risk of Stroke in Dialysis Patients: A Retrospective Analysis over the Last 40 Years

The stroke incidence in hemodialysis (HD) patients is high, but the associated factors remain largely unknown. This study aimed to analyze stroke incidence in HD patients and changes in risk factors. Data of 291 patients were retrospectively analyzed. The cumulative stroke incidences were 21.6% at 10 years and 31.5% at 20. Diabetic nephropathy (DN) significantly increased overall stroke (hazard ratio (HR), 2.24; 95% confidence interval (CI), 1.21-4.12; p = 0.001) and ischemic stroke (HR, 2.16; 95% CI, 1.00-4.64; p = 0.049). Patients treated with online HDF were less likely to have overall stroke (HR, 0.13; 95% CI, 0.03-0.56; p = 0.006) and ischemic stroke (HR, 0.08; 95% CI, 0.01-0.60; p = 0.014). DN (HR, 1.56; 95% CI, 1.08-2.27; p = 0.019) and age >80 years at HD initiation (20-49 years old; HR 0.13, 95% CI, 0.05-0.35, p < 0.001 and age 50-79 years; HR 0.42, 95% CI, 0.26-0.66, p < 0.001 (reference: age >80 years)) were significantly associated with stroke and/or death events. Over time, stroke risk increased in HD patients, due to the increasing number of DN. Although dialysis technology has advanced over time, these advances could not overcome other risk factors for stroke. Further increase in stroke and mortality due to aging remains a concern.

Elevated serum SDMA and ADMA at hospital admission predict in-hospital mortality of COVID-19 patients

COVID-19 is a disease with a variable clinical course ranging from mild symptoms to critical illness, organ failure, and death. Prospective biomarkers may help to predict the severity of an individual’s clinical course and mortality risk. We analyzed asymmetric (ADMA) and symmetric dimethylarginine (SDMA) in blood samples from 31 patients hospitalized for COVID-19. We calculated associations of ADMA and SDMA with mortality and organ failure, and we developed a predictive algorithm based upon these biomarkers to predict mortality risk. Nine patients (29%) experienced in-hospital death. SDMA and ADMA serum concentrations were significantly higher at admission in COVID-19 patients who died than in survivors. Cut-offs of 0.90 µmol/L for SDMA (AUC, 0.904, p = 0.0005) and 0.66 µmol/L for ADMA (AUC, 0.874, p = 0.0013) were found in ROC analyses to best discriminate both subgroups of patients. Hazard ratio for in-hospital mortality was 12.2 (95% CI: 2.2–31.2) for SDMA and 6.3 (1.1–14.7) for ADMA above cut-off. Sequential analysis of both biomarkers allowed discriminating a high-risk group (87.5% mortality) from an intermediate-risk group (25% mortality) and a low-risk group (0% mortality). Elevated circulating concentrations of SDMA and ADMA may help to better identify COVID-19 patients with a high risk of in-hospital mortality.