Serum uric acid levels and endothelial dysfunction in patients with autosomal dominant polycystic kidney disease

Predictors of autosomal dominant polycystic kidney disease progression: a Brazilian single-center cohort

INTRODUCTION

Identifying risk factors for autosomal dominant polycystic kidney disease (ADPKD) progression is important. However, studies that have evaluated this subject using a Brazilian sample is sparce. Therefore, the aim of this study was to identify risk factors for renal outcomes and death in a Brazilian cohort of ADPKD patients.

METHODS

Patients had the first medical appointment between January 2002 and December 2014, and were followed up until December 2019. Associations between clinical and laboratory variables with the primary outcome (sustained decrease of at least 57% in the eGFR from baseline, need for dialysis or renal transplantation) and the secondary outcome (death from any cause) were analyzed using a multiple Cox regression model. Among 80 ADPKD patients, those under 18 years, with glomerular filtration rate <30 mL/min/1.73 m2, and/or those with missing data were excluded. There were 70 patients followed.

RESULTS

The factors independently associated with the renal outcomes were total kidney length - adjusted Hazard Ratio (HR) with a 95% confidence interval (95% CI): 1.137 (1.057-1.224), glomerular filtration rate - HR (95% CI): 0.970 (0.949-0.992), and serum uric acid level - HR (95% CI): 1.643 (1.118-2.415). Diabetes mellitus - HR (95% CI): 8.115 (1.985-33.180) and glomerular filtration rate - HR (95% CI): 0.957 (0.919-0.997) were associated with the secondary outcome.

CONCLUSIONS

These findings corroborate the hypothesis that total kidney length, glomerular filtration rate and serum uric acid level may be important prognostic predictors of ADPKD in a Brazilian cohort, which could help to select patients who require closer follow up.

Emerging Roles of Xanthine Oxidoreductase in Chronic Kidney Disease

Xanthine Oxidoreductase (XOR) is a ubiquitous, essential enzyme responsible for the terminal steps of purine catabolism, ultimately producing uric acid that is eliminated by the kidneys. XOR is also a physiological source of superoxide ion, hydrogen peroxide, and nitric oxide, which can function as second messengers in the activation of various physiological pathways, as well as contribute to the development and the progression of chronic conditions including kidney diseases, which are increasing in prevalence worldwide. XOR activity can promote oxidative distress, endothelial dysfunction, and inflammation through the biological effects of reactive oxygen species; nitric oxide and uric acid are the major products of XOR activity. However, the complex relationship of these reactions in disease settings has long been debated, and the environmental influences and genetics remain largely unknown. In this review, we give an overview of the biochemistry, biology, environmental, and current clinical impact of XOR in the kidney. Finally, we highlight recent genetic studies linking XOR and risk for kidney disease, igniting enthusiasm for future biomarker development and novel therapeutic approaches targeting XOR.

A Systematic Review of Reported Outcomes in ADPKD Studies

Introduction

Methods

Results

Conclusion

Drugs in Clinical Development to Treat Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation that ultimately leads to kidney failure in most patients. Approximately 10% of patients who receive kidney replacement therapy suffer from ADPKD. To date, a vasopressin V2 receptor antagonist (V2RA) is the only drug that has been proven to attenuate disease progression. However, aquaresis-related adverse events limit its widespread use. Data on the renoprotective effects of somatostatin analogues differ largely between studies and medications. This review discusses new drugs that are investigated in clinical trials to treat ADPKD, such as cystic fibrosis transmembrane conductance regulator (CFTR) modulators and micro RNA inhibitors, and drugs already marketed for other indications that are being investigated for off-label use in ADPKD, such as metformin. In addition, potential methods to improve the tolerability of V2RAs are discussed, as well as methods to select patients with (likely) rapid disease progression and issues regarding the translation of preclinical data into clinical practice. Since ADPKD is a complex disease with a high degree of interindividual heterogeneity, and the mechanisms involved in cyst growth also have important functions in various physiological processes, it may prove difficult to develop drugs that target cyst growth without causing major adverse events. This is especially important since long-standing treatment is necessary in this chronic disease. This review therefore also discusses approaches to targeted therapy to minimize systemic side effects. Hopefully, these developments will advance the treatment of ADPKD.

Markers of endothelial dysfunction and arterial stiffness in patients with early-stage autosomal dominant polycystic kidney disease: A meta-analysis

OBJECTIVES

Autosomal dominant polycystic kidney disease (ADPKD) is characterised by increased rates of cardiovascular complications leading to significant morbidity and mortality. This meta-analysis aims to evaluate whether the disease is linked to endothelial dysfunction and arterial stiffness during its early stages.

METHODS

Medline, Scopus, CENTRAL, Web of Science, Clinicaltrials.gov and Google Scholar databases comparing ADPKD patients with preserved renal function to healthy controls were included. The outcomes of interest were brachial flow-mediated dilatation, carotid-femoral pulse wave velocity, augmentation index, carotid intima-media thickness and central systolic blood pressure, plasma ADMA or homocysteine levels. Standardised mean differences (SMDs) were estimated by a random-effects model in R-3.6.3.

RESULTS

A total of 27 studies were included, comprising 1967 individuals. ADPKD was linked to significantly lower flow-mediated dilatation (SMD: -1.44, 95% CI: [-2.35, -0.53]) and higher pulse wave velocity (SMD: 1.44, 95% CI: [0.22, 2.66]) and carotid intima-media thickness (SMD: 1.02, 95% CI: [0.57, 1.47]). No significant associations were noted regarding augmentation index (SMD: 0.62, 95% CI: [-0.19, 1.43]) and central systolic blood pressure (SMD: 1.84, 95% CI: [-0.12, 3.80]). Plasma homocysteine was significantly higher in ADPKD (SMD: 0.81, 95% CI: [0.16, 1.45]), while no difference was calculated for ADMA levels (SMD: 1.14, 95% CI: [-0.25, 2.53]).

CONCLUSIONS

Early-stage ADPKD patients present increased vascular stiffness and endothelial dysfunction, as reflected by low flow-mediated dilatation and elevated values of pulse wave velocity, carotid intima-media thickness and plasma homocysteine. The exact effects of early arterial stiffness on long-term outcomes remain to be elucidated.

[Cardiovascular disorders in autosomal dominant polycystic kidney disease]

Autosomal dominant polycystic kidney disease is the most frequent genetic kidney disease. Cardiovascular disorders associated with autosomal dominant polycystic kidney disease are multiple and may occur early in life. In autosomal dominant polycystic kidney disease cardiovascular morbidity and mortality are related both to the nonspecific consequences of chronic kidney disease and to the particular phenotype of autosomal dominant polycystic kidney disease. Compared to the general population, patients with autosomal dominant polycystic kidney disease present an increased prevalence of hypertension, left ventricular hypertrophy, atrial fibrillation, valvular diseases, aneurisms and arterial dissections. This review article provides an update on cardiovascular disorders associated with autosomal dominant polycystic kidney disease and recent pathophysiological developments.

Serum Uric Acid and Progression of Autosomal Dominant Polycystic Kidney Disease: Results from the HALT PKD Trials

BACKGROUND

Epidemiological studies have suggested that elevated serum uric acid may contribute to the progression of chronic kidney disease. However, no large prospective study has examined whether hyperuricemia is an independent risk factor for the progression of autosomal dominant polycystic kidney disease (ADPKD).

METHODS

We measured uric acid in stored serum samples from the 2-year study visit of 671 participants from the HALT PKD multicenter trials. Participants were categorized according to uric acid tertiles. For Study A (participants aged 15-49 years with preserved kidney function, n=350), we used linear mixed effects models to examine the association between uric acid and repeated measures of height-adjusted total kidney volume (htTKV), the primary outcome for Study A. For Study B (participants aged 18-64 with decreased kidney function, n=321), we used Cox proportional hazards models to assess the hazard for the combined endpoint of 50% loss in estimated glomerular filtration rate (eGFR), end-stage kidney disease (ESKD), or death, the primary outcome for Study B. To assess the association of uric acid with the slope of eGFR decline (secondary outcome of HALT A and B), we used linear mixed effects models for the combined population of Study A and B.

RESULTS

In the unadjusted model, the annual change in htTKV was 2.7% higher in the highest uric acid tertile compared to the lowest (p<0.001), but this difference became insignificant after adjustment for gender. Men had faster TKV growth than women (p<0.001). There was no difference in eGFR decline between the 3 uric acid tertiles. Hazard ratios for the clinical endpoint were 2.9 (95% confidence interval, 1.9-4.4) and 1.8 (1.1-2.8) respectively in the high and medium uric acid groups in unadjusted and partially adjusted models (p<0.001), but the significance was lost after adjustment for baseline eGFR. Results were similar when uric acid was examined as a continuous variable.

CONCLUSION

Elevated serum uric acid is not an independent risk factor for disease progression in ADPKD.

The haplotype of SLC2A9_rs3733591, PKD2_rs2725220 and ABCG2_rs2231142 increases the hyperuricaemia risk and alcohol, chicken and processed meat intakes and smoking interact with its risk

We determined that a genetic haplotype increased the risk of hyperuricaemia and it interacted with lifestyle factors, including nutrients in 28,445 middle-aged Koreans. ABCG2_rs2231142, PKD2_rs2725220 and SLC2A9_rs3733591 were selected from GWAS based on hyperuricaemia (≥7 mg/dL; p = 6.88E-42, 1.56E-26 and 1.01E-20, respectively). Hyperuricaemia and gout were elevated by 3.93- and 3.23-fold, respectively, by the minor alleles as compared with the major alleles of the haplotype of the selected 3 SNPs after adjusting for covariates. The haplotype significantly interacted with alcohol, chicken and processed meat intakes, and smoking status in the hyperuricaemia risk (p = 0.002-0.007). Minor alleles of the haplotype had an association with hyperuricaemia as compared with major alleles particularly in high intakes of alcohol (2g/day), chicken (6.3g/day), and processed meat (3g/day) and smokers. In conclusion, people carrying minor alleles of the haplotype of SLC2A9_rs3733591, PKD2_rs2725220 and ABCG2_rs2231142 should avoid diets high in chicken and processed meat, alcohol drinking, and cigarette smoking to protect against hyperuricaemia risk.

Hypoxia and Endothelial Dysfunction in Autosomal-Dominant Polycystic Kidney Disease

Autosomal-dominant polycystic kidney disease (ADPKD) is the most prevalent inherited kidney disease, characterized by growth of bilateral renal cysts, hypertension, and multiple extrarenal complications that eventually can lead to renal failure. It is caused by mutations in PKD1 or PKD2 genes encoding the proteins polycystin-1 and polycystin-2, respectively. Over the past few years, studies investigating the role of primary cilia and polycystins, present not only on the surface of renal tubular cells but also on vascular endothelial cells, have advanced our understanding of the pathogenesis of ADPKD and have shown that mechanisms other than cyst formation also contribute to renal functional decline in this disease. Among them, increased oxidative stress, endothelial dysfunction, and hypoxia may play central roles because they occur early in the disease process and precede the onset of hypertension and renal functional decline. Endothelial dysfunction is linked to higher asymmetric dimethylarginine levels and reduced nitric oxide bioavailability, which would cause regional vasoconstriction and impaired renal blood flow. The resulting hypoxia would increase the levels of hypoxia-inducible-transcription factor 1α and other angiogenetic factors, which, in turn, may drive cyst growth. In this review, we summarize the existing evidence for roles of endothelial dysfunction, oxidative stress, and hypoxia in the pathogenesis of ADPKD.

Association between serum uric acid level and endothelial dysfunction in elderly individuals with untreated mild hypertension

Background

Endothelial dysfunction is the initial stage in atherosclerotic formation and progression and is associated with high serum uric acid (SUA) level. We hypothesized that reactive hyperemia index (RHI), which reflects endothelial function, is associated with SUA levels in elderly individuals with untreated mild hypertension.

Methods

We recruited 123 patients ≥ 60 years with untreated mild hypertension. The association between SUA level and RHI was analyzed using univariate correlation analysis and multiple regression analysis. The receiver operating characteristic (ROC) curve was performed to validate the cutoff value of SUA that can be used to predict endothelial dysfunction.

Results

The serum uric acid level significantly increased in the RHI < 1.67 group, and this result was still observed in the subgroup of men. RHI was inversely associated with SUA level (P = 0.006) and the association was still observed after adjusting for factors, such as age, sex, smoking status, and creatinine level (P = 0.014). In the subgroup analysis, a positive association was observed only in men. In the ROC curve analysis, the optimal cutoff values of SUA for predicting endothelial dysfunction was 293.5 µmol/L in elderly mild hypertension patients and 287.0 µmol/L in men.

Conclusion

A high SUA level was considered an independent predictor of endothelial dysfunction among elderly individuals, particularly men with untreated mild hypertension.

Clinical burden of autosomal dominant polycystic kidney disease

There are no specific therapies for autosomal dominant polycystic kidney disease (ADPKD), and clinical data evaluating the effects of non-specific therapies on ADPKD patients are scarce. We therefore evaluated those effects using data from a longitudinal health insurance database collected from 2000-2010. We individually selected patients with and without ADPKD from inpatient data files as well as from the catastrophic illness registry in Taiwan based on 1:5 frequency matching for sex, age, and index year. The hazard ratios (HR) of all-cause mortality, ischemic stroke, hemorrhagic stroke and end-stage renal disease (ESRD) in ADPKD inpatients were elevated as compared to the controls. Similarly, ADPKD patients from the catastrophic illness registry had an increased risk of hemorrhagic stroke and ESRD. Allopurinol users also had an increased risk of all-cause mortality. The HR for developing ESRD after medication exposure was 0.47-fold for statin and 1.93-fold for pentoxifylline. These results reveal that patients with ADPKD (either inpatient or from the catastrophic illness registry) are at elevated risk for hemorrhagic stroke and ESRD, and suggest that allopurinol and pentoxifylline should not be prescribed to ADPKD patients due to possible adverse effects.

Identification of Key Genes and Candidated Pathways in Human Autosomal Dominant Polycystic Kidney Disease by Bioinformatics Analysis

Background/Aims: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic form of kidney disease. High-throughput microarray analysis has been applied for elucidating key genes and pathways associated with ADPKD. Most genetic profiling data from ADPKD patients have been uploaded to public databases but not thoroughly analyzed. This study integrated 2 human microarray profile datasets to elucidate the potential pathways and protein-protein interactions (PPIs) involved in ADPKD via bioinformatics analysis in order to identify possible therapeutic targets. Methods: The kidney tissue microarray data of ADPKD patients and normal individuals were searched and obtained from NCBI Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified, and enriched pathways and central node genes were elucidated using related websites and software according to bioinformatics analysis protocols. Seven DEGs were validated between polycystic kidney disease and control kidney samples by quantitative real-time polymerase chain reaction. Results: Two original human microarray datasets, GSE7869 and GSE35831, were integrated and thoroughly analyzed. In total, 6,422 and 1,152 DEGs were extracted from GSE7869 and GSE35831, respectively, and of these, 561 DEGs were consistent between the databases (291 upregulated genes and 270 downregulated genes). From 421 nodes, 34 central node genes were obtained from a PPI network complex of DEGs. Two significant modules were selected from the PPI network complex by using Cytotype MCODE. Most of the identified genes are involved in protein binding, extracellular region or space, platelet degranulation, mitochondrion, and metabolic pathways. Conclusions: The DEGs and related enriched pathways in ADPKD identified through this integrated bioinformatics analysis provide insights into the molecular mechanisms of ADPKD and potential therapeutic strategies. Specifically, abnormal decorin expression in different stages of ADPKD may represent a new therapeutic target in ADPKD, and regulation of metabolism and mitochondrial function in ADPKD may become a focus of future research.

Association of OSR-1 With Vascular Dysfunction and Hypertension in Polycystic Kidney Disease

Autosomal-dominant polycystic kidney disease (ADPKD) is associated with oxidative stress and hypertension development before renal function decline and cardiovascular disease development. Oxidative stress-responsive kinase-1 (OSR-1) participates in the signaling regulating Na⁺ transport during oxidative stress and also plays a role in the regulation of cell volume and blood pressure. Therefore, we aimed to investigate the potential role of OSR-1 in ADPKD patients. Eighty ADPKD patients, 80 healthy controls, and 80 non-ADPKD patients with hypertension were enrolled in this cross-sectional study. Twenty-four-hour ambulatory blood pressure monitoring was conducted in all participants. Blood samples were taken after 12-h fasting for the measurement of biochemical parameters and OSR-1 gene expression. Vascular dysfunction was assessed using ischemia-induced forearm flow-mediated vasodilation (FMD). Briefly, of the 80 ADPKD patients, 41(51%) were male, and 53(66%) of them were hypertensive. The mean age of the 80 controls was 35.3 ± 12.6 years, and 37(46%) of them were male. The mean age of the 80 non-ADPKD patients with hypertension was 44.6 ± 11.9 years, and 38(47.5) of them were male. There were significant differences in serum OSR-1 gene expression between the ADPKD patients and the control subjects. Serum OSR-1 gene expression was also significantly increased in hypertensive ADPKD patients in comparison with both normotensive ADPKD counterparts and non-ADPKD hypertensive subjects. Serum OSR-1 gene expression was increased in patients with ADPKD than healthy subjects. Low estimated glomerular filtration rate (eGFR), OSR-1 gene expression, total kidney volume (TKV), and high-density lipoprotein (HDL) were also independently associated with hypertension in ADPKD patients.

Oxidative stress in autosomal dominant polycystic kidney disease: player and/or early predictor for disease progression?

Autosomal dominant polycystic kidney disease (ADPKD), caused by mutations in PKD1 or PKD2 genes, is the most common hereditary renal disease. Renal manifestations of ADPKD are gradual cyst development and kidney enlargement ultimately leading to end-stage renal disease. ADPKD also causes extrarenal manifestations, including endothelial dysfunction and hypertension. Both of these complications are linked with reduced nitric oxide levels related to excessive oxidative stress (OS). OS, defined as disturbances in the prooxidant/antioxidant balance, is harmful to cells due to the excessive generation of highly reactive oxygen and nitrogen free radicals. Next to endothelial dysfunction and hypertension, there is cumulative evidence that OS occurs in the early stages of ADPKD. In the current review, we aim to summarize the cardiovascular complications and the relevance of OS in ADPKD and, more specifically, in the early stages of the disease. First, we will briefly introduce the link between ADPKD and the early cardiovascular complications including hypertension. Secondly, we will describe the potential role of OS in the early stages of ADPKD and its possible importance beyond the chronic kidney disease (CKD) effect. Finally, we will discuss some pharmacological agents capable of reducing reactive oxygen species and OS, which might represent potential treatment targets for ADPKD.

Relationships of Hyperhomocysteinemia and Hyperuricemia With Metabolic Syndrome and Renal Function in Chinese Centenarians

As the first time worldwide, this study aimed to investigate the relationships of hyperhomocysteinemia and hyperuricemia with metabolic syndrome (MetS) and renal function in Chinese centenarians. The China Hainan Centenarian Cohort Study was performed in 18 cities and counties of the Hainan Province. Home interview, physical examination, and blood analysis were performed on 808 centenarians following standard procedures. All centenarians had a median age of 102 (100-115) years. Prevalence of hyperhomocysteinemia and hyperuricemia was 91.6% (740 centenarians) and 28.5% (230 centenarians), respectively. The MetS was present in 117 centenarians (14.5%). In simple correlation analyses, hyperhomocysteinemia and hyperuricemia were significantly correlated with MetS and glomerular filtration rate (GFR) < 60 ml/min/1.73 m² (P < 0.05 for all). Serum homocysteine levels were significantly correlated with GFR, waist circumference (WC), and triglyceride levels, while serum uric acid levels were significantly correlated with these variables plus high-density lipoprotein cholesterol (HDL-C) levels (P < 0.05 for all). In logistic regression analyses, hyperhomocysteinemia and hyperuricemia were significantly associated with MetS and GFR < 60 ml/min/1.73 m² (P < 0.05 for all). In linear regression analyses, serum homocysteine levels were significantly associated with GFR, WC, and triglyceride, while serum uric acid levels were significantly associated with these variables plus HDL-C (P < 0.05 for all). Both hyperhomocysteinemia and hyperuricemia had important relationships with MetS and renal function in Chinese centenarians. Hyperuricemia and hyperhomocysteinemia that could help identify, while also affecting, the development of MetS and renal function may unfold complex relationships between MetS, renal function, and cardiovascular risk and provide effective prevention strategies for these conditions.

Early Markers of Cardiovascular Risk in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND/AIMS

Cardiovascular disease is the most frequent cause of morbidity and mortality in autosomal dominant polycystic kidney disease (ADPKD) patients, often before the onset of renal failure, and the pathogenetic mechanism is not yet well elucidated. The aim of the study was to identify early and noninvasive markers of cardiovascular risk in young ADPKD patients, in the early stages of disease.

METHODS

A total of 26 patients with ADPKD and 24 control group, matched for age and sex, were enrolled, and we have assessed inflammatory indexes, mineral metabolism, metabolic state and markers of atherosclerosis and endothelial dysfunction (carotid intima media thickness (IMT), ankle brachial index (ABI), flow mediated dilation (FMD), renal resistive index (RRI), left ventricular mass index (LVMI)) and cardiopulmonary exercise testing (CPET), maximal O2 uptake (V'O2max), and O2 uptake at lactic acid threshold (V'O2@LT).

RESULTS

The ADPKD patients compared to control group, showed a significant higher mean value of LVMI, RRI, homocysteine (Hcy), Homeostasis Model Assessment-insulin resistance (HOMA-IR), serum uric acid (SUA), Cardiac-troponinT (cTnT) and intact parathyroid hormone (iPTH) (p<0.001, p<0.001, p<0.001, p<0.001, p<0.001, p=0.007, p=0.019; respectively), and a lower value of FMD and 25-hydroxyvitaminD (25-OH-VitD) (p<0.001, p<0.001) with reduced parameters of exercise tolerance, as V'O2max, V'O2max/Kg and V'O2max (% predicted) (p<0.001, p<0.001, p=0.018; respectively), and metabolic response indexes (V'O2@LT, V'O2 @LT%, V'O2@LT/Kg,) (p<0.001, p=0.14, p<0.001; respectively). Moreover, inflammatory indexes were significantly higher in ADPKD patients, and we found a positive correlation between HOMA-IR and C-reactive protein (CRP) (r=0.507, p=0.008), and a negative correlation between HOMA-IR and 25-OH-VitD (r=-0.585, p=0.002).

CONCLUSION

In our study, ADPKD patients, in the early stages of disease, showed a greater insulin resistance, endothelial dysfunction, inflammation and mineral metabolism disorders, respect to control group. Moreover, these patients presented reduced tolerance to stress, and decreased anaerobic threshold to CPET. Our results indicate a major and early cardiovascular risk in ADPKD patients. Therefore early and noninvasive markers of cardiovascular risk and CPET should be carried out, in ADPKD patients, in the early stages of disease, despite the cost implication.

Vasopressin-related copeptin is a novel predictor of early endothelial dysfunction in patients with adult polycystic kidney disease

Background

In this study, we examined the relative usefulness of serum copeptin levels as a surrogate marker of vasopressin (AVP) in adult polycystic kidney disease (ADPKD) by correlating it with baseline and longitudinal changes in markers of both renal function and common CVD manifestations (hypertensive vascular disease, atherosclerosis and endothelial dysfunction) that accompany the progression of this disease.

Methods

We studied a cohort of young and otherwise healthy ADPKD patients (n = 235) and measured cardiovascular function using flow-mediation dilatation (FMD), carotid intima media thickness (cIMT) and pulse wave velocity (PWV), as well as serum copeptin (commercial ELISA, a stable marker of AVP activity). The same analyses were carried out at baseline and after 3 years of follow-up.

Results

At baseline, median eGFR was 69 mL/min./1.73 m², mean FMD 6.9 ± 0.9%, cIMT 0.7 ± 0.1 mm, and PWV 8.1 ± 1.2 m/s. At follow-up, equivalent values were 65 (44–75) mL/min./1.73 m², 5.8 ± 0.9%, 0.8 ± 0.1 mm. and 8.2 ± 1.3 m/s. with all changes statistically significant. Plasma copeptin also rose from 0.62 ± 0.12 to 0.94 ± 0.19 ng/mL and this change correlated with ΔeGFR (-0.33, p < 0.001), ΔFMD (0.599, p < 0.001), ΔcIMT (0.562, p < 0.001) and ΔPWV (0.27, p < 0.001) also after linear regression modeling to correct for confounders. Finally, ROC analysis was done for a high baseline copeptin with ΔeGFR [cut-off:≤59], ΔFMD [cut-off: ≤7.08], ΔcIMT [cut-off:>0.76], and ΔPWV [cut-off:≤7.80].

Conclusions

Vascular dysfunction as reflected by FMD and cIMT, but not PWV or an altered cardiac geometry, precede most other signs of disease in ADPKD but is predicted by elevated levels of the circulating AVP-marker copeptin.

Diagnostic Evaluation as a Biomarker in Patients with ADPKD

Recently, newer treatments have been introduced for autosomal dominant polycystic kidney disease (ADPKD) patients. Since cysts grow and renal function declines over a long period of time, the evaluation of treatment effects in ADPKD has been very difficult. Therefore, there has been a great interest to find out the "better" surrogate marker or biomarker which reflects disease progression. Biomarkers in ADPKD should have three clinical implications: (1) They should reflect disease severity, (2) they should distinguish patients with poor versus good prognosis to select those who will benefit better from the treatment, and (3) they should be easy to evaluate short-term outcome after treatment, which will demonstrate hard outcome. Herein, we will discuss currently available surrogate biomarkers including the volume of total kidney and urinary molecular markers.

Effects of dialysis solution on the cardiovascular function in peritoneal dialysis patients

Objective Peritoneal dialysis (PD) patients have an increased cardiovascular burden. In this study, we aimed to compare certain PD solutions (Physioneal(®) and Dianeal(®)) in terms of the ambulatory blood pressure, echocardiographic parameters (ECHO), carotid atherosclerosis, endothelial function and serum asymmetric dimethylarginine (ADMA) level. Methods A total of 45 PD patients were enrolled in this prospective randomized controlled study: 23 patients in the Dianeal(®) group and 22 patients in the Physioneal(®) group. Ambulatory blood pressure measurements, echocardiography, carotid artery intima-media thickness measurements and flow mediated dilatation (FMD) and ADMA values were obtained at baseline and 12 months. Results The baseline parameters were similar between the groups with respect to the echocardiographic parameters, 24-hour ambulatory blood monitoring measurements and ADMA and FMD levels. All 24-hour blood pressure monitoring measurements, except for the average daytime systolic blood pressure, were significantly decreased in both groups at the first year. In the Physioneal(®) group, a significant decrease was observed with regard to the ADMA levels. Considering the FMD values, significant augmentation was seen at the end of the first year in both groups. Improvements in the FMD measurements were prominent in the Physioneal(®) group; however, this finding was not statistically significant. Conclusion The use of solutions with a neutral pH in PD patients results in decreased ADMA levels, which may be an important contributor to reductions in the incidence of cardiovascular events and deaths in this population.

Endothelial nitric oxide synthase gene expression is associated with hypertension in autosomal dominant polycystic kidney disease

BACKGROUND/AIMS

Early occurrence of hypertension is the prominent feature of autosomal dominant polycystic kidney disease (ADPKD). The role of angiotensin-converting enzyme (ACE) gene polymorphism and endothelial nitric oxide synthase (eNOS) gene polymorphism in the clinical course of ADPKD is not well understood. However, data about the expression of these genes are lacking. Thus, we aimed to investigate the polymorphisms and expressions of both the ACE and eNOS genes that affect hypertension in ADPKD.

METHODS

Whole blood samples were obtained from all participants. ACE and eNOS gene polymorphisms and their expressions were analyzed in 78 ADPKD patients and 30 controls. Gene expressions were assessed by quantitative real-time PCR. Twenty-four-hour blood pressure monitoring was performed for the diagnosis of hypertension in all study participants.

RESULTS

eNOS expression and the estimated glomerular filtration rate were found to be significantly higher in ADPKD patients without hypertension than in those with hypertension. Each unit of increase in eNOS expression led to a 0.88-fold decrease (95% CI: 0.80-0.96) in the risk of hypertension in multiple logistic regression analysis.

CONCLUSIONS

eNOS gene expression is independently predictive of hypertension in the ADPKD population. This study showed, for the first time, a novel link between eNOS gene expression and hypertension in ADPKD.

Polycystin deficiency induces dopamine-reversible alterations in flow-mediated dilatation and vascular nitric oxide release in humans

Autosomal dominant polycystic kidney disease (ADPKD) is a renal hereditary disorder associated with increased cardiovascular mortality, due to mutations in polycystin-1 and polycystin-2 genes. Endothelial polycystin-deficient cells have an altered mechanosensitivity to fluid shear stress and subsequent deficit in calcium-induced nitric oxide release, prevented by dopamine receptor stimulation. However, the impact of polycystin deficiency on endothelial function in ADPKD patients is still largely unknown. Here we assessed endothelium-dependent flow-mediated dilatation in 21 normotensive ADPKD patients and 21 healthy control subjects, during sustained (hand skin heating) and transient (postischemic hyperemia) flow stimulation. Flow-mediated dilatation was less marked in ADPKD patients than in controls during heating, but it was similar during postischemic hyperemia. There was no difference in endothelium-independent dilatation in response to glyceryl trinitrate. Local plasma nitrite, an indicator of nitric oxide availability, increased during heating in controls but not in patients. Brachial infusion of dopamine in a subset of ADPKD patients stimulated plasma nitrite increase during heating and improved flow-mediated dilatation. Thus, ADPKD patients display a loss of nitric oxide release and an associated reduction in endothelium-dependent dilatation of conduit arteries during sustained blood flow increase. The correction of these anomalies by dopamine suggests future therapeutic strategies that could reduce the occurrence of cardiovascular events in ADPKD.

Predictors of autosomal dominant polycystic kidney disease progression

Autosomal dominant polycystic kidney disease is a genetic disorder associated with substantial variability in its natural course within and between affected families. Understanding predictors for rapid progression of this disease has become increasingly important with the emergence of potential new treatments. This systematic review of the literature since 1988 evaluates factors that may predict and/or effect autosomal dominant polycystic kidney disease progression. Predicting factors associated with early adverse structural and/or functional outcomes are considered. These factors include PKD1 mutation (particularly truncating mutation), men, early onset of hypertension, early and frequent gross hematuria, and among women, three or more pregnancies. Increases in total kidney volume and decreases in GFR and renal blood flow greater than expected for a given age also signify rapid disease progression. Concerning laboratory markers include overt proteinuria, macroalbuminuria, and perhaps, elevated serum copeptin levels in affected adults. These factors and others may help to identify patients with autosomal dominant polycystic kidney disease who are most likely to benefit from early intervention with novel treatments.