End-stage renal disease in autosomal dominant polycystic kidney disease: a comparison of dialysis-related utilization and costs with other chronic kidney diseases

KLC3 Regulates Ciliary Trafficking and Cyst Progression in CILK1 Deficiency-Related Polycystic Kidney Disease

BACKGROUND

Ciliogenesis-associated kinase 1 (CILK1) is a ciliary gene that localizes in primary cilia and regulates ciliary transport. Mutations in CILK1 cause various ciliopathies. However, the pathogenesis of CILK1-deficient kidney disease is unknown.

METHODS

To examine whether CILK1 deficiency causes PKD accompanied by abnormal cilia, we generated mice with deletion of Cilk1 in cells of the renal collecting duct. A yeast two-hybrid system and coimmunoprecipitation (co-IP) were used to identify a novel regulator, kinesin light chain-3 (KLC3), of ciliary trafficking and cyst progression in the Cilk1-deficient model. Immunocytochemistry and co-IP were used to examine the effect of KLC3 on ciliary trafficking of the IFT-B complex and EGFR. We evaluated the effects of these genes on ciliary trafficking and cyst progression by modulating CILK1 and KLC3 expression levels.

RESULTS

CILK1 deficiency leads to PKD accompanied by abnormal ciliary trafficking. KLC3 interacts with CILK1 at cilia bases and is increased in cyst-lining cells of CILK1-deficient mice. KLC3 overexpression promotes ciliary recruitment of IFT-B and EGFR in the CILK1 deficiency condition, which contributes to the ciliary defect in cystogenesis. Reduction in KLC3 rescued the ciliary defects and inhibited cyst progression caused by CILK1 deficiency.

CONCLUSIONS

Our findings suggest that CILK1 deficiency in renal collecting ducts leads to PKD and promotes ciliary trafficking via increased KLC3.

Serum microRNA profiles in patients with autosomal dominant polycystic kidney disease show systematic dysregulation partially reversible by hemodialysis

INTRODUCTION

The impact of autosomal dominant polycystic kidney disease (ADPKD) on serum microRNAs (miRNA) is unknown.

MATERIAL AND METHODS

For profiling experiment we recruited 30 patients from three equinumerous groups: controls, ADPKD and ADPKD on hemodialysis. From the last group extra samples were collected for in pre-/postdialysis analysis. Additionally, 23 healthy volunteers were used for selected biomarker verification. Real-time PCR arrays were used for quantification of 752 miRNAs. Validation of selected miRNAs was performed in total RNA extracted from the serum and the exosomal fraction in pre-/postdialysis samples.

RESULTS

In total, 37 significant circulating miRNAs were found to differ between ADPKD patients and controls. In validation, 3 miRNAs with the highest fold change in comparison of dialyzed vs non-dialyzed patients (miR-532-3p, miR-320b, miR-144-5p) were not significantly altered by hemodialysis and from the top down-regulated ones, miR-27a-3p was significantly lower after dialysis in both total and exosomal fractions, miR-20a-5p was down-regulated in the exosomal fraction and miR-16-5p was unaltered by hemodialysis. MiR-16-5p was selected as the best circulating biomarker of ADPKD. Circulating representatives of the miR-17 family sharing the same seed region (miR-20a-5p, miR-93-5p and miR-106a-5p) showed significantly lower expression among dialyzed vs. non-dialyzed patients and their exosomal fraction dropped after hemodialysis.

CONCLUSIONS

The serum miRNAs among ADPKD patients differ substantially depending on the stage of CKD. The exosomal fraction of miRNA was more affected by dialysis than the total one. There was a common pattern of down-regulation for circulating miR-17 family members sharing the same seed region.

An Overview of In Vivo and In Vitro Models for Autosomal Dominant Polycystic Kidney Disease: A Journey from 3D-Cysts to Mini-Pigs

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inheritable cause of end stage renal disease and, as of today, only a single moderately effective treatment is available for patients. Even though ADPKD research has made huge progress over the last decades, the precise disease mechanisms remain elusive. However, a wide variety of cellular and animal models have been developed to decipher the pathophysiological mechanisms and related pathways underlying the disease. As none of these models perfectly recapitulates the complexity of the human disease, the aim of this review is to give an overview of the main tools currently available to ADPKD researchers, as well as their main advantages and limitations.

The impact of chronic kidney disease on developed countries from a health economics perspective: A systematic scoping review

Chronic kidney disease (CKD) affects over 10% of the global population and poses significant challenges for societies and health care systems worldwide. To illustrate these challenges and inform cost-effectiveness analyses, we undertook a comprehensive systematic scoping review that explored costs, health-related quality of life (HRQoL) and life expectancy (LE) amongst individuals with CKD. Costs were examined from a health system and societal perspective, and HRQoL was assessed from a societal and patient perspective. Papers published in English from 2015 onward found through a systematic search strategy formed the basis of the review. All costs were adjusted for inflation and expressed in US$ after correcting for purchasing power parity. From the health system perspective, progression from CKD stages 1-2 to CKD stages 3a-3b was associated with a 1.1-1.7 fold increase in per patient mean annual health care cost. The progression from CKD stage 3 to CKD stages 4-5 was associated with a 1.3-4.2 fold increase in costs, with the highest costs associated with end-stage renal disease at $20,110 to $100,593 per patient. Mean EuroQol-5D index scores ranged from 0.80 to 0.86 for CKD stages 1-3, and decreased to 0.73-0.79 for CKD stages 4-5. For treatment with renal replacement therapy, transplant recipients incurred lower costs and demonstrated higher HRQoL scores with longer LE compared to dialysis patients. The study has provided a comprehensive updated overview of the burden associated with different CKD stages and renal replacement therapy modalities across developed countries. These data will be useful for the assessment of new renal services/therapies in terms of cost-effectiveness.

The societal economic burden of autosomal dominant polycystic kidney disease in the United States

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited kidney diseases characterized by progressive development of renal cysts and numerous extra-renal manifestations, eventually leading to kidney failure. Given its chronic and progressive nature, ADPKD is expected to carry a substantial economic burden over the course of the disease. However, there is a paucity of evidence on the impact of ADPKD from a societal perspective. This study aimed to estimate the direct and indirect costs associated with ADPKD in the United States (US).

METHODS

A prevalence-based approach using data from scientific literature, and governmental and non-governmental organizations was employed to estimate direct healthcare costs (i.e., medical services, prescription drugs), direct non-healthcare costs (i.e., research and advocacy, donors/recipients matching for kidney transplants, transportation to/from dialysis centers), and indirect costs (i.e., patient productivity loss from unemployment, reduced work productivity, and premature mortality, caregivers' productivity loss and healthcare costs). The incremental costs associated with ADPKD were calculated as the difference between costs incurred over a one-year period by individuals with ADPKD and the US population. Sensitivity analyses using different sources and assumptions were performed to assess robustness of estimates and account for variability in published estimates.

RESULTS

The estimated total annual costs attributed to ADPKD in 2018 ranged from $7.3 to $9.6 billion in sensitivity analyses, equivalent to $51,970 to $68,091 per individual with ADPKD. In the base scenario, direct healthcare costs accounted for $5.7 billion (78.6%) of the total $7.3 billion costs, mostly driven by patients requiring renal replacement therapy ($3.2 billion; 43.3%). Indirect costs accounted for $1.4 billion (19.7%), mostly driven by productivity loss due to unemployment ($784 million; 10.7%) and reduced productivity at work ($390 million; 5.3%). Total excess direct non-healthcare costs were estimated at $125 million (1.7%).

CONCLUSIONS

ADPKD carries a considerable economic burden, predominantly attributed to direct healthcare costs, the majority of which are incurred by public and private healthcare payers. Effective and timely interventions to slow down the progression of ADPKD could substantially reduce the economic burden of ADPKD.

Ciliary exclusion of Polycystin-2 promotes kidney cystogenesis in an autosomal dominant polycystic kidney disease model

The human PKD2 locus encodes Polycystin-2 (PC2), a TRPP channel that localises to several distinct cellular compartments, including the cilium. PKD2 mutations cause Autosomal Dominant Polycystic Kidney Disease (ADPKD) and affect many cellular pathways. Data underlining the importance of ciliary PC2 localisation in preventing PKD are limited because PC2 function is ablated throughout the cell in existing model systems. Here, we dissect the ciliary role of PC2 by analysing mice carrying a non-ciliary localising, yet channel-functional, PC2 mutation. Mutants develop embryonic renal cysts that appear indistinguishable from mice completely lacking PC2. Despite not entering the cilium in mutant cells, mutant PC2 accumulates at the ciliary base, forming a ring pattern consistent with distal appendage localisation. This suggests a two-step model of ciliary entry; PC2 first traffics to the cilium base before TOP domain dependent entry. Our results suggest that PC2 localisation to the cilium is necessary to prevent PKD.

The molecular role of ciliary Polycystin-2 (PC2) in cyst formation and polycystic kidney disease (ADKPD) is unclear. Here, the authors identify a PC2 mutant lacking ciliary localisation but with active Ca2+ channel function in mice, that is sufficient to generate an ADPKD phenotype.

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.

Relationship between caffeine intake and autosomal dominant polycystic kidney disease progression: a retrospective analysis using the CRISP cohort

Background

Caffeine has been proposed, based on in vitro cultured cell studies, to accelerate progression of autosomal dominant polycystic kidney disease (ADPKD) by increasing kidney size. Since ADPKD patients are advised to minimize caffeine intake, we investigated the effect of caffeine on disease progression in the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP), a prospective, observational cohort study.

Methods

Our study included 239 patients (mean age = 32.3 ± 8.9 ys; 188 caffeine consumers) with a median follow-up time of 12.5 years. Caffeine intake reported at baseline was dichotomized (any vs. none). Linear mixed models, unadjusted and adjusted for age, race, sex, BMI, smoking, hypertension, genetics and time, were used to model height-adjusted total kidney volume (htTKV) and iothalamate clearance (mGFR). Cox proportional hazards models and Kaplan-Meier plots examined the effect of caffeine on time to ESRD or death.

Results

Caffeine-by-time was statistically significant when modeling ln(htTKV) in unadjusted and adjusted models (p <  0.01) indicating that caffeine consumers had slightly faster kidney growth (by 0.6% per year), but htTKV remained smaller from baseline throughout the study. Caffeine consumption was not associated with a difference in mGFR, or in the time to ESRD or death (p > 0.05). Moreover the results were similar when outcomes were modeled as a function of caffeine dose.

Conclusion

We conclude that caffeine does not have a significant detrimental effect on disease progression in ADPKD.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1182-0) contains supplementary material, which is available to authorized users.

Global costs attributed to chronic kidney disease: a systematic review

SUMMARY The aim of this study is to discuss the global costs attributed to chronic kidney disease (CKD) and its impact on healthcare systems of developing countries, such as Brazil. This is a systematic review based on data from PubMed/Medline, using the key words “costs” and “chronic kidney disease”, in January 2017. The search was also done in other databases, such as Scielo and Google Scholar, aiming to identify regional studies related to this subject, published in journal not indexed in PubMed. Only papers published from 2012 on were included. Studies on CKD costs and treatment modalities were prioritized. The search resulted in 392 articles, from which 291 were excluded because they were related to other aspects of CKD. From the 101 remaining articles, we have excluded the reviews, comments and study protocols. A total of 37 articles were included, all focusing on global costs related to CKD. Despite methods and analysis were diverse, the results of these studies were unanimous in alerting for the impact (financial and social) of CKD on health systems (public and private) and also on family and society. To massively invest in prevention and measures to slow CKD progression into its end-stages and, then, avoid the requirement for dialysis and transplant, can represent a huge, and not yet calculated, economy for patients and health systems all over the world.

Is the light at the end of the tunnel nigh? A review of ADPKD focusing on the burden of disease and tolvaptan as a new treatment

Autosomal dominant polycystic kidney disease (ADPKD) causes pathological cystic changes to the kidney and is characterized by numerous renal and systemic manifestations. ADPKD is the fourth most common renal disease requiring renal replacement therapy. In this report, we present a detailed review of ADPKD, with a particular focus on its major economic, psychological, and social burden in affected patients. Treatment of this disease has been based on prophylactic and supportive measures. However, in recent years, new drugs have emerged as promising agents that may retard the progression of ADPKD, such as tolvaptan. In this report, we provide an in-depth discussion of tolvaptan, which has shown an effect in decreasing annual total kidney volume growth and renal function decline, thus slowing disease progression. The mechanism of action, side effects, and available data on cost-effectiveness are discussed together with the results of the first clinical trials and the most recent trials with regard to its efficacy and safety. Tolvaptan has recently received approval and been granted marketing authorization in Japan, Canada, Korea, Switzerland, and Europe. A demand for widely accepted guidelines for its use has emerged since its approval. The currently available series of recommendations and guidelines as to when to start treatment with tolvaptan, as well as which patients should be treated, are also reviewed in this report. We lastly offer some considerations for future trials, and raise unanswered questions.

Heterozygosity analysis of polycystic kidney disease 1 gene microsatellite markers for linkage analysis of autosomal dominant polycystic kidney disease type 1 in the Iranian population

Background:

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic cause of end-stage renal disease. Although imaging techniques are a means of accurate diagnosis when the cysts appear in the third or fourth decades of the patient's life, they are of little value for early diagnosis. Genetic tests are required for preimplantation genetic diagnosis, decision-making for kidney donation to an affected relative. Although mutation of the polycystic kidney disease (PKD1) gene is solely responsible for the most cases of ADPKD, direct genetic testing is limited by the large size of this gene and the presence of many mutations without hot spots. Therefore, indirect diagnosis with linkage analysis using informative microsatellite markers has been suggested.

Materials and Methods:

In this study, we assessed the informativeness of the PKD1 gene markers D16S475, D16S291, and D16S3252 in Iranian population. Using specific primers, fluorescent polymerase chain reaction (PCR) was performed on genomic DNA extracted from fifty unrelated individuals. PCR products were analyzed by the ALFexpress DNA sequencer system, and the number and frequency of alleles were determined to calculate the heterozygosity (HET) and polymorphism information content (PIC) values.

Results:

We found that the HET and PIC values for the D16S475 marker are 0.92 and 0.91, respectively. These two values are 0.82 and 0.80 for D16S291 and 0.50 and 0.47 for D16S3252, respectively.

Conclusion:

Based on this data, D16S475 and D16S291 are highly and D16S3252 is moderately informative for indirect genetic diagnosis of PKD1 mutations in this population.

Real-world costs of autosomal dominant polycystic kidney disease in the Nordics

Background

There is limited real-world data on the economic burden of patients with autosomal dominant polycystic kidney disease (ADPKD). The objective of this study was to estimate the annual direct and indirect costs of patients with ADPKD by severity of the disease: chronic kidney disease (CKD) stages 1–3; CKD stages 4–5; transplant recipients; and maintenance dialysis patients.

Methods

A retrospective study of ADPKD patients was undertaken April–December 2014 in Denmark, Finland, Norway and Sweden. Data on medical resource utilisation were extracted from medical charts and patients were asked to complete a self-administered questionnaire.

Results

A total of 266 patients were contacted, 243 (91%) of whom provided consent to participate in the study. Results showed that the economic burden of ADPKD was substantial at all levels of the disease. Lost wages due to reduced productivity were large in absolute terms across all disease strata. Mean total annual costs were highest in dialysis patients, driven by maintenance dialysis care, while the use of immunosuppressants was the main cost component for transplant care. Costs were twice as high in patients with CKD stages 4–5 compared to CKD stages 1–3.

Conclusions

Costs associated with ADPKD are significant and the progression of the disease is associated with an increased frequency and intensity of medical resource utilisation. Interventions that can slow the progression of the disease have the potential to lead to substantial reductions in costs for the treatment of ADPKD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-017-2513-8) contains supplementary material, which is available to authorized users.

Double inhibition of cAMP and mTOR signalling may potentiate the reduction of cell growth in ADPKD cells

BACKGROUND

ADPKD is a renal pathology caused by mutations of PKD1 and PKD2 genes, which encode for polycystin-1 (PC1) and polycystin-2 (PC2), respectively. PC1 plays an important role regulating several signal transducers, including cAMP and mTOR, which are involved in abnormal cell proliferation of ADPKD cells leading to the development and expansion of kidney cysts that are a typical hallmark of this disease. Therefore, the inhibition of both pathways could potentiate the reduction of cell proliferation enhancing benefits for ADPKD patients.

METHODS

The inhibition of cAMP- and mTOR-related signalling was performed by Cl-IB-MECA, an agonist of A3 receptors, and rapamycin, respectively. Protein kinase activity was evaluated by immunoblot and cell growth was analyzed by direct cell counting.

RESULTS

The activation of A₃AR by the specific agonist Cl-IB-MECA causes a marked reduction of CREB, mTOR, and ERK phosphorylation in kidney tissues of Pkd1 ^flox/-: Ksp-Cre polycystic mice and reduces cell growth in ADPKD cell lines, but not affects the kidney weight. The combined sequential treatment with rapamycin and Cl-IB-MECA in ADPKD cells potentiates the reduction of cell proliferation compared with the individual compound by the inhibition of CREB, mTOR, and ERK kinase activity. Conversely, the simultaneous application of these drugs counteracts their effect on cell growth, because the inhibition of ERK kinase activity is lost.

CONCLUSION

The double treatment with rapamycin and Cl-IB-MECA may have synergistic effects on the inhibition of cell proliferation in ADPKD cells suggesting that combined therapies could improve renal function in ADPKD patients.

The Risk for New-Onset Diabetes Mellitus after Kidney Transplantation in Patients with Autosomal Dominant Polycystic Kidney Disease: A Systematic Review and Meta-Analysis

OBJECTIVES

New-onset diabetes after kidney transplantation (NODAT) is associated with both renal allograft failure and increased rates of mortality. The objective of this meta-analysis was to evaluate the risk for NODAT in patients with autosomal dominant polycystic kidney disease (ADPKD).

METHODS

A literature search was performed using MEDLINE, EMBASE and Cochrane Database of Systematic Reviews from inception through July 2015. Studies that reported relative risks, odd ratios or hazard ratios comparing the risk for NODAT in patients with ADPKD were included. Pooled risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using a random-effect, generic inverse variance method.

RESULTS

Included in the analysis were 12 cohort studies, which comprised 1379 patients with ADPKD of a total of 9849 patients who had undergone kidney transplants. The pooled RRs of NODAT in patients with ADPKD were 1.92 (95% CI, 1.36 to 2.70). When meta-analysis was limited only to studies with confounder-adjusted analysis, the pooled RRs for NODAT were 1.98 (95% CI, 1.33 to 2.94). However, the association between NODAT requiring insulin treatment was insignificant, with pooled RRs of 1.57 (95% CI, 0.75 to 3.27).

CONCLUSIONS

Our meta-analysis demonstrates a significant association between ADPKD and NODAT in recipients of kidney transplants. The findings of this study may impact clinical management and follow up for patients with ADPKD after kidney transplantation.

Comorbidity burden at dialysis initiation and mortality: A cohort study

Background

A high level of comorbidity at dialysis initiation is associated with an increased risk of death. However, contemporary assessments of the validity and prognostic value of comorbidity indices are lacking.

Objectives

To assess the validity of two comorbidity indices and to determine if a high degree of comorbidity is associated with mortality among dialysis patients.

Design

Cohort study.

Setting

QEII Health Sciences Centre (Halifax, Nova Scotia, Canada).

Patients

Incident, chronic dialysis patients between 01 Jan 2006 and 01 Jul 2013.

Measurements

Exposure: The Charlson Comorbidity Index (CCI) and End-Stage Renal Disease Comorbidity Index (ESRD-CI) were used to classify individual comorbid conditions into an overall score. Comorbidities were classified using patient charts and electronic records.

Outcome: All-cause mortality.

Confounders: Patient demographics, dialysis access, cause of ESRD and baseline laboratory data.

Methods

Regression coefficients were estimated on the CCI and ESRD-CI. Discrimination for death was assessed using Harrell’s c-index. Adjusted Cox proportional hazard models were used to calculate relative hazards and 95 % confidence intervals for each category of the CCI and ESRD-CI.

Results

The cohort consisted of 771 ESRD patients from 01 Jan 2006 to 01 Jul 2013. Most were male (62 %) and Caucasian (91 %). The cohort had a high proportion of diabetes (48 %), history of previous myocardial infarction (31 %) and heart failure (22 %). Regression coefficients on the CCI and ESRD-CI were 0.55 and 0.52, respectively. The c-index, for the prediction of death, was 0.61 for the CCI and 0.63 for the ESRD-CI. ESRD-CI scores of 4, 5 and ≥6 were associated with a similar mortality risk (adjusted relative hazard of 1.95, 1.89 and 1.99, respectively). There was a small increased mortality risk for CCI scores of 4, 5 and ≥6 (adjusted relative hazard of 1.86, 2.38 and 2.71, respectively).

Limitations

Classification of comorbidities for each patient was determined by clinical impression.

Conclusions

The CCI and ESRD-CI have a limited ability to discriminate mortality risk for incident dialysis patients. Acknowledging the frequency with which they are used, this study emphasizes the need to re-examine the usefulness of previously derived comorbidity indices in contemporary dialysis cohorts.

Progression of autosomal dominant kidney disease: measurement of the stage transitions of chronic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a progressive genetic disorder characterized by the development of numerous kidney cysts that result in kidney failure. Little is known regarding the key patient characteristics and utilization of healthcare resources for ADPKD patients along the continuum of disease progression. This observational study was designed to describe the characteristics of ADPKD patients and compare them with those of patients with other chronic kidney diseases.

METHODS

This retrospective cohort study involved patients with a claim for ADPKD or PKD unspecified from 1/1/2000-2/28/2013 and ≥6 months of previous continuous enrollment (baseline) within a large database of administrative claims in the USA. A random sample of chronic kidney disease (CKD) patients served as comparators. For a subset of ADPKD patients who had only a diagnosis code of unspecified PKD, abstraction of medical records was undertaken to estimate the proportion of patients who had medical chart-confirmed ADPKD. In patients with linked electronic laboratory data, the estimated glomerular filtration rate was calculated via serum creatinine values to determine CKD stage at baseline and during follow-up. Proportions of patients transitioning to another stage and the mean age at transition were calculated.

RESULTS

ADPKD patients were, in general, younger and had fewer physician visits, but had more specific comorbidities at observation start compared with CKD patients. ADPKD patients had a longer time in the milder stages and longer duration before recorded transition to a more severe stage compared with CKD patients. Patients with ADPKD at risk of rapid progression had a shorter time-to-end-stage renal disease than patients with CKD and ADPKD patients not at risk, but stage duration was similar between ADPKD patients at risk and those not at risk.

CONCLUSIONS

These results suggest that distribution of patients by age at transition to next stage may be useful for identification of ADPKD patients at risk of rapid progression. The results also suggest that medical claims with diagnosis codes for "unspecified PKD", in absence of a diagnosis code for autosomal recessive polycystic kidney disease, may be a good proxy for ADPKD.