Blood pressure in early autosomal dominant polycystic kidney disease

Pharmacotherapy of hypertension in patients with pre-dialysis chronic kidney disease

INTRODUCTION

Hypertension is the most common co-morbidity in patients with chronic kidney disease (CKD), with prevalence gradually increasing across CKD Stages to the extent that about 90% of end-stage renal disease (ESRD) patients are hypertensives. Several factors contribute to blood pressure (BP) elevation and guide the therapeutic interventions that should be employed in these patients.

AREAS COVERED

This review summarizes the existing data for the management of hypertension, regarding optimal BP targets and the use of major antihypertensive classes in patients with CKD.

EXPERT OPINION

Management of hypertension in CKD requires both lowering BP levels and reducing proteinuria to minimize the risk of both CKD progression and cardiovascular disease. In this respect, aggressive control of office BP to levels <130/80 mmHg has long been proposed for patients with proteinuric nephropathies. Following evidence from recent studies that confirmed significant reductions in renal and cardiovascular outcomes with strict BP control, most, but not all, of international guidelines, suggest such BP goals for all hypertensive patients, including those with CKD. Use of renin-angiotensin system (RAS) blockers is the treatment of choice for patients with proteinuric nephropathies, while, in most patients with CKD, combination treatment with two, three, or more antihypertensive agents is often required to control BP.

Creating an academic research organization to efficiently design, conduct, coordinate, and analyze clinical trials: The Center for Clinical Trials & Data Coordination

When properly executed, the randomized controlled trial is one of the best vehicles for assessing the effectiveness of one or more interventions. However, numerous challenges may emerge in the areas of study startup, recruitment, data quality, cost, and reporting of results. The use of well-run coordinating centers could help prevent these issues, but very little exists in the literature describing their creation or the guiding principles behind their inception. The Center for Clinical Trials & Data Coordination (CCDC) was established in 2015 through institutional funds with the intent of 1) providing relevant expertise in clinical trial design, conduct, coordination, and analysis; 2) advancing the careers of clinical investigators and CCDC-affiliated faculty; and 3) obtaining large data coordinating center (DCC) grants. We describe the organizational structure of the CCDC as well as the homegrown clinical trial management system integrating nine crucial elements: electronic data capture, eligibility and randomization, drug and external data tracking, safety reporting, outcome adjudication, data and safety monitoring, statistical analysis and reporting, data sharing, and regulatory compliance. Lastly, we share numerous lessons that can be taken from our experience. Specifically, we focus on 1) funding for DCCs, 2) the importance of DCCs to clinical researchers, 3) the expertise of DCC personnel, and 4) continually striving to improve. In conclusion, the CCDC strives to provide high-quality support for the design, conduct, coordination, and analyses of clinical trials, and we hope this paper will serve as a blueprint for future clinical trialists involved in DCCs.

The role of DNA damage as a therapeutic target in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disease and is caused by heterozygous germ-line mutations in either PKD1 (85%) or PKD2 (15%). It is characterised by the formation of numerous fluid-filled renal cysts and leads to adult-onset kidney failure in ~50% of patients by 60 years. Kidney cysts in ADPKD are focal and sporadic, arising from the clonal proliferation of collecting-duct principal cells, but in only 1-2% of nephrons for reasons that are not clear. Previous studies have demonstrated that further postnatal reductions in PKD1 (or PKD2) dose are required for kidney cyst formation, but the exact triggering factors are not clear. A growing body of evidence suggests that DNA damage, and activation of the DNA damage response pathway, are altered in ciliopathies. The aims of this review are to: (i) analyse the evidence linking DNA damage and renal cyst formation in ADPKD; (ii) evaluate the advantages and disadvantages of biomarkers to assess DNA damage in ADPKD and finally, (iii) evaluate the potential effects of current clinical treatments on modifying DNA damage in ADPKD. These studies will address the significance of DNA damage and may lead to a new therapeutic approach in ADPKD.

Investigation and Treatment of High Blood Pressure in Young People: Too Much Medicine or Appropriate Risk Reduction?

Hypertension among young people is common, affecting 1 in 8 adults aged between 20 and 40 years. This number is likely to increase with lifestyle behaviors and lowering of hypertension diagnostic thresholds. Early-life factors influence blood pressure (BP) although the mechanisms are unclear; BP tracks strongly within individuals from adolescence through to later life. Higher BP at a young age is associated with abnormalities on heart and brain imaging and increases the likelihood of cardiovascular events by middle age. However, diagnosis rates are lower, and treatment is often delayed in young people. This reflects the lack of high-quality evidence that lowering BP in young adults improves cardiovascular outcomes later in life. In this review, we evaluate the current evidence regarding the association between BP in young adult life and adverse cardiovascular outcomes later in life. Following this, we discuss which young people with raised BP should be investigated for secondary causes of hypertension. Third, we assess the current models to assess cardiovascular risk and show a lack of validation in the younger age group. Fourth, we evaluate the evidence for lifestyle interventions in this age group and demonstrate a lack of persistence in BP lowering once the initial intervention has been delivered. Fifth, we address the pros and cons of drug treatment for raised BP in young people. Finally, there are unique life events in young people, such as pregnancy, that require specific advice on management and treatment of BP.

International consensus statement on the diagnosis and management of autosomal dominant polycystic kidney disease in children and young people

These recommendations were systematically developed on behalf of the Network for Early Onset Cystic Kidney Disease (NEOCYST) by an international group of experts in autosomal dominant polycystic kidney disease (ADPKD) from paediatric and adult nephrology, human genetics, paediatric radiology and ethics specialties together with patient representatives. They have been endorsed by the International Pediatric Nephrology Association (IPNA) and the European Society of Paediatric Nephrology (ESPN). For asymptomatic minors at risk of ADPKD, ongoing surveillance (repeated screening for treatable disease manifestations without diagnostic testing) or immediate diagnostic screening are equally valid clinical approaches. Ultrasonography is the current radiological method of choice for screening. Sonographic detection of one or more cysts in an at-risk child is highly suggestive of ADPKD, but a negative scan cannot rule out ADPKD in childhood. Genetic testing is recommended for infants with very-early-onset symptomatic disease and for children with a negative family history and progressive disease. Children with a positive family history and either confirmed or unknown disease status should be monitored for hypertension (preferably by ambulatory blood pressure monitoring) and albuminuria. Currently, vasopressin antagonists should not be offered routinely but off-label use can be considered in selected children. No consensus was reached on the use of statins, but mTOR inhibitors and somatostatin analogues are not recommended. Children with ADPKD should be strongly encouraged to achieve the low dietary salt intake that is recommended for all children.

Rapid Progression of Autosomal Dominant Polycystic Kidney Disease: Urinary Biomarkers as Predictors

BACKGROUND

Markers currently used to predict the likelihood of rapid disease progression in patients with autosomal dominant polycystic kidney disease (ADPKD) are expensive and time consuming to assess and often have limited sensitivity. New, easy-to-measure markers are therefore needed that alone or in combination with conventional risk markers can predict the rate of disease progression. In the present study, we investigated the ability of tubular damage and inflammation markers to predict kidney function decline.

METHODS

At baseline, albumin, immunoglobulin G, kidney injury molecule 1, β2 microglobulin (β2MG), heart-type fatty acid-binding protein, neutrophil gelatinase-associated lipocalin, and monocyte chemotactic protein-1 -(MCP-1) were measured in 24-h urine samples of patients participating in a study investigating the therapeutic efficacy of lanreotide in ADPKD. Individual change in estimated glomerular filtration rate (eGFR) during follow-up was calculated using mixed-model analysis taking into account 13 -eGFRs (chronic kidney disease EPIdemiology) per patient. Logistic regression analysis was used to select urinary biomarkers that had the best association with rapidly progressive disease. The predictive value of these selected urinary biomarkers was compared to other risk scores using C-statistics.

RESULTS

Included were 302 patients of whom 53.3% were female, with an average age of 48 ± 7 years, eGFR of 52 ± 12 mL/min/1.73 m2, and a height-adjusted total kidney volume (htTKV) of 1,082 (736-1,669) mL/m. At baseline, all urinary damage and inflammation markers were associated with baseline eGFR, also after adjustment for age, sex and baseline htTKV. For longitudinal analyses only patients randomized to standard care were considered (n = 152). A stepwise backward analysis revealed that β2MG and MCP-1 showed the strongest association with rapidly progressive disease. A urinary biomarker score was created by summing the ranking of tertiles of β2MG and MCP-1 excretion. The predictive value of this urinary biomarker score was higher compared to that of the Mayo htTKV classification (area under the curve [AUC] 0.73 [0.64-0.82] vs. 0.61 [0.51-0.71], p = 0.04) and comparable to that of the predicting renal outcomes in -ADPKD score (AUC 0.73 [0.64-0.82] vs. 0.65 [0.55-0.75], p = 0.18). In a second independent cohort with better kidney function, similar results were found for the urinary biomarker score.

CONCLUSION

Measurement of urinary β2MG and MCP-1 excretion allows selection of ADPKD patients with rapidly progressive disease, with a predictive value comparable to or even higher than that of TKV or PKD mutation. Easy and inexpensive to measure urinary markers therefore hold promise to help predict prognosis in ADPKD.

Detection and characterization of mosaicism in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited, progressive nephropathy accounting for 4-10% of end stage renal disease worldwide. PKD1 and PKD2 are the most common disease loci, but even accounting for other genetic causes, about 7% of families remain unresolved. Typically, these unsolved cases have relatively mild kidney disease and often have a negative family history. Mosaicism, due to de novo mutation in the early embryo, has rarely been identified by conventional genetic analysis of ADPKD families. Here we screened for mosaicism by employing two next generation sequencing screens, specific analysis of PKD1 and PKD2 employing long-range polymerase chain reaction, or targeted capture of cystogenes. We characterized mosaicism in 20 ADPKD families; the pathogenic variant was transmitted to the next generation in five families and sporadic in 15. The mosaic pathogenic variant was newly discovered by next generation sequencing in 13 families, and these methods precisely quantified the level of mosaicism in all. All of the mosaic cases had PKD1 mutations, 14 were deletions or insertions, and 16 occurred in females. Analysis of kidney size and function showed the mosaic cases had milder disease than a control PKD1 population, but only a few had clearly asymmetric disease. Thus, in a typical ADPKD population, readily detectable mosaicism by next generation sequencing accounts for about 1% of cases, and about 10% of genetically unresolved cases with an uncertain family history. Hence, identification of mosaicism is important to fully characterize ADPKD populations and provides informed prognostic information.

Native Nephrectomy before and after Renal Transplantation in Patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD)

The aim of this study was 1) to evaluate and compare pre-, peri-, and post-operative data of Autosomal Dominant Polycystic Kidney Disease (ADPKD) patients undergoing native nephrectomy (NN) either before or after renal transplantation and 2) to identify advantages of optimal surgical timing, postoperative outcomes, and economical aspects in a tertiary transplant centre. This retrospective analysis included 121 patients divided into two groups-group 1: patients who underwent NN prior to receiving a kidney transplant (n = 89) and group 2: patients who underwent NN post-transplant (n = 32). Data analysis was performed according to demographic patient details, surgical indication, laboratory parameters, perioperative complications, underlying pathology, and associated mortality. There was no significant difference in patient demographics between the groups, however right-sided nephrectomy was performed predominantly within group 1. The main indication in both groups undergoing a nephrectomy was pain. Patients among group 2 had no postoperative kidney failure and a significantly shorter hospital stay. Higher rates of more severe complications were observed in group 1, even though this was not statistically significant. Even though the differences between both groups were substantial, the time of NN prior or post-transplant does not seem to affect short-term and long-term transplantation outcomes. Retroperitoneal NN remains a low risk treatment option in patients with symptomatic ADPKD and can be performed either pre- or post-kidney transplantation depending on patients' symptom severity.

The pathobiology of polycystic kidney disease from a metabolic viewpoint

Autosomal dominant polycystic kidney disease (ADPKD) affects an estimated 1 in 1,000 people and slowly progresses to end-stage renal disease (ESRD) in about half of these individuals. Tolvaptan, a vasopressin 2 receptor blocker, has been approved by regulatory authorities in many countries as a therapy to slow cyst growth, but additional treatments that target dysregulated signalling pathways in cystic kidney and liver are needed. Metabolic reprogramming is a prominent feature of cystic cells and a potentially important contributor to the pathophysiology of ADPKD. A number of pathways previously implicated in the pathogenesis of the disease, such as dysregulated mTOR and primary ciliary signalling, have roles in metabolic regulation and may exert their effects through this mechanism. Some of these pathways are amenable to manipulation through dietary modifications or drug therapies. Studies suggest that polycystin-1 and polycystin-2, which are encoded by PKD1 and PKD2, respectively (the genes that are mutated in >99% of patients with ADPKD), may in part affect cellular metabolism through direct effects on mitochondrial function. Mitochondrial dysfunction could alter the redox state and cellular levels of acetyl-CoA, resulting in altered histone acetylation, gene expression, cytoskeletal architecture and response to cellular stress, and in an immunological response that further promotes cyst growth and fibrosis.

Can we further enrich autosomal dominant polycystic kidney disease clinical trials for rapidly progressive patients? Application of the PROPKD score in the TEMPO trial

Background

The PROPKD score has been proposed to stratify the risk of progression to end-stage renal disease in autosomal dominant polycystic kidney disease (ADPKD) subjects. We aimed to assess its prognostic value in a genotyped subgroup of subjects from the Tolvaptan Phase 3 Efficacy and Safety Study in Autosomal Dominant Polycystic Kidney Disease (TEMPO3/4) trial.

Methods

In the post hoc analysis, PKD1 and PKD2 were screened in 770 subjects and the PROPKD score was calculated in mutation-positive subjects (male: 1 point; hypertension <35 years: 2 points; first urologic event <35 years: 2 points; nontruncating PKD1 mutation: 2 points; truncating PKD1 mutation: 4 points). Subjects were classified into low-risk (LR; 0-3 points), intermediate-risk (IR; 4-6 points) and high-risk (HR; 7-9 points) groups.

Results

The PROPKD score was calculated in 749 subjects (LR = 132, IR = 344 and HR = 273); age was inversely related to risk (LR = 43.6 years, IR = 39.5 years, HR = 36.2 years; P < 0.001). Subjects from the HR group had significantly higher height-adjusted total kidney volume (TKV) and rates of TKV growth. While baseline renal function was similar across all risk groups, the rate of estimated glomerular filtration rate (eGFR) decline significantly increased from LR to HR in the placebo group. Tolvaptan treatment effectiveness to reduce TKV growth was similar in all three risk categories. While tolvaptan significantly slowed eGFR decline in the IR (tolvaptan = -2.34 versus placebo = -3.33 mL/min/1.73 m2/year; P = 0.008) and HR groups (tolvaptan = -2.74 versus placebo = -3.94 mL/min/1.73 m2/year; P = 0.002), there was no difference in the LR group (tolvaptan = -2.35 versus placebo = -2.50 mL/min/1.73 m2/year; P = 0.72). Excluding the LR subjects from the analysis improved the apparent treatment effect of tolvaptan on eGFR decline.

Conclusion

This study confirms the prognostic value of the PROPKD score and suggests that it could reduce costs and enhance endpoint sensitivity by enriching future study populations for rapidly progressing ADPKD subjects.

European ADPKD Forum multidisciplinary position statement on autosomal dominant polycystic kidney disease care: European ADPKD Forum and Multispecialist Roundtable participants

Autosomal dominant polycystic kidney disease (ADPKD) is a chronic, progressive condition characterized by the development and growth of cysts in the kidneys and other organs and by additional systemic manifestations. Individuals with ADPKD should have access to lifelong, multidisciplinary, specialist and patient-centred care involving: (i) a holistic and comprehensive assessment of the manifestations, complications, prognosis and impact of the disease (in physical, psychological and social terms) on the patient and their family; (ii) access to treatment to relieve symptoms, manage complications, preserve kidney function, lower the risk of cardiovascular disease and maintain quality of life; and (iii) information and support to help patients and their families act as fully informed and active partners in care, i.e. to maintain self-management approaches, deal with the impact of the condition and participate in decision-making regarding healthcare policies, services and research. Building on discussions at an international roundtable of specialists and patient advocates involved in ADPKD care, this article sets out (i) the principles for a patient-centred, holistic approach to the organization and delivery of ADPKD care in practice, with a focus on multispecialist collaboration and shared-decision making, and (ii) the rationale and knowledge base for a route map for ADPKD care intended to help patients navigate the services available to them and to help stakeholders and decision-makers take practical steps to ensure that all patients with ADPKD can access the comprehensive multispecialist care to which they are entitled. Further multispecialty collaboration is encouraged to design and implement these services, and to work with patient organizations to promote awareness building, education and research.

Autosomal dominant polycystic kidney disease: updated perspectives

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited multisystem disorder, characterized by renal and extra-renal fluid-filled cyst formation and increased kidney volume that eventually leads to end-stage renal disease. ADPKD is considered the fourth leading cause of end-stage renal disease in the United States and globally. Care of patients with ADPKD was, for a long time, limited to supportive lifestyle measures, due to the lack of therapeutic strategies targeting the main pathways involved in the pathophysiology of ADPKD. As the first FDA approved treatment of ADPKD, Vasopressin (V2) receptor blocking agent, tolvaptan, is an urgently awaited advance for ADPKD patients. In our review, we also shed some lights on what is beyond Tolvaptan as there are other medications in the pipeline and many medications have been or are currently being studied in clinical trials such as Tesevatinib, Metformin and Pravastatin, with the goal of slowing the rate of progression of ADPKD by reducing the increase in total kidney volume or maintaining eGFR. Here, we review updates in the perspectives and management of ADPKD.

Effect of Blood Pressure Control on Long-Term Risk of End-Stage Renal Disease and Death Among Subgroups of Patients With Chronic Kidney Disease

Background Our objective was to explore the effect of intensive blood pressure (BP) control on kidney and death outcomes among subgroups of patients with chronic kidney disease divided by baseline proteinuria, glomerular filtration rate, age, and body mass index. Methods and Results We included 840 MDRD (Modification of Diet in Renal Disease) trial and 1067 AASK (African American Study of Kidney Disease and Hypertension) participants. We used Cox models to examine whether the association between intensive BP control and risk of end-stage renal disease (ESRD) or death is modified by baseline proteinuria (≥0.44 versus <0.44 g/g), glomerular filtration rate (≥30 versus <30 mL/min per 1.73 m2), age (≥40 versus <40 years), or body mass index (≥30 versus <30 kg/m2). The median follow-up was 14.9 years. Strict (versus usual) BP control was protective against ESRD (hazard ratio [HR]ESRD, 0.77; 95% CI, 0.64-0.92) among those with proteinuria ≥0.44 g/g but not proteinuria <0.44 g/g. Strict (versus usual) BP control was protective against death (HRdeath, 0.73; 95% CI, 0.59-0.92) among those with glomerular filtration rate <30 mL/min per 1.73 m2 but not glomerular filtration rate ≥30 mL/min per 1.73 m2 (HRdeath, 0.98; 95% CI, 0.84-1.15). Strict (versus usual) BP control was protective against ESRD among those ≥40 years (HRESRD, 0.82; 95% CI, 0.71-0.94) but not <40 years. Strict (versus usual) BP control was also protective against ESRD among those with body mass index ≥30 kg/m2 (HRESRD, 0.75; 95% CI, 0.61-0.92) but not body mass index <30 kg/m2. Conclusions The ESRD and all-cause mortality benefits of intensive BP lowering may not be uniform across all subgroups of patients with chronic kidney disease. But intensive BP lowering was not associated with increased risk of ESRD or death among any subgroups that we examined.

Cardiac function assessed by myocardial deformation in adult polycystic kidney disease patients

Background

Patients with autosomal dominant polycystic kidney disease (ADPKD) have an increased risk of cardiovascular morbidity and mortality. Impaired left ventricular (LV) global longitudinal strain (GLS) can be a sign of subclinical cardiac dysfunction even in patients with otherwise preserved ejection fraction (EF). Transmitral early filling velocity to early diastolic strain rate (E/SRe) is a novel measure of LV filling pressure, which is often affected early in cardiac disease.

Methods

A total of 110 ADPKD patients not on dialysis were included in this prospective study. All patients underwent an extensive echocardiographic examination including two-dimensional speckle tracking. GLS and strain rates were measured. The distribution of GLS and E/SRe was determined and patient characteristics were compared by median levels of GLS (− 17.8%) and E/SRe (91.4 cm). Twenty healthy participants were included as control group.

Results

There was a significantly worse GLS in the ADPKD patients (mean: − 17.8 ± 2.5%) compared to the healthy controls (mean: − 21.9 ± 1.9%), p < 0.001. The same was true for E/SRe (mean: 10.0 ± 0.3 cm) compared to the control group (mean: 6.5 ± 0.3 cm), p < 0.001. In simple logistic regression, male gender (OR: 4.74 [2.10–10.71], p < 0.001), fasting glucose (odds ratio (OR) 1.05 [1.01–1.10], p = 0.024), htTKV (OR: 1.07 [1.01–1.13], p = 0.013), HDL cholesterol (OR: 0.97 [0.94, 0.996], p = 0.025), triglycerides (OR: 1.01 [1.00–1.02], p = 0.039), hemoglobin (OR: 1.50 [1.11–2.04], p = 0.009), and β-blocker use (OR: 1.07 [1.01, 1.13], p = 0.013) were all associated with higher GLS. After multivariate logistic regression with backward model selection, only male gender (OR: 5.78 [2.27–14.71], p < 0.001) and β-blocker use (OR: 14.00 [1.60, 122.51], p = 0.017) remained significant. In simple logistic regression models, BMI (OR: 1.11 [1.02–1.20], p = 0.015), systolic blood pressure (OR: 1.03 [1.00–1.06], p = 0.027) and β-blocker use (OR: 17.12 [2.15–136.20], p = 0.007) were associated with higher E/SRe - a novel measure of left ventricular filling pressure. After backward elimination, only β-blocker use (OR: 17.22 [2.16, 137.14], p = 0.007) remained significant.

Conclusion

Higher GLS and E/SRe are common in ADPKD patients, even in patients with preserved eGFR and normal left ventricular EF. GLS and E/SRe may aid in cardiovascular risk stratification in patients with ADPKD as they represent early markers of cardiac dysfunction.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1500-1) contains supplementary material, which is available to authorized users.

Presymptomatic Screening for Intracranial Aneurysms in Patients with Autosomal Dominant Polycystic Kidney Disease

BACKGROUND AND OBJECTIVES

Intracranial aneurysm rupture is the most devastating complication of autosomal dominant polycystic kidney disease. Whether selective or widespread intracranial aneurysm screening is indicated remains controversial.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

Records of 3010 patients with autosomal dominant polycystic kidney disease evaluated at the Mayo Clinic between 1989 and 2017 were reviewed. Those who had presymptomatic magnetic resonance angiography screening were included.

RESULTS

Ninety-four intracranial aneurysms were diagnosed in 75 of 812 (9%) patients who underwent magnetic resonance angiography screening. Sex, age, race, and genotype were similar in the groups with and without aneurysms; hypertension and history of smoking were more frequent in the aneurysm group. Twenty-nine percent of patients with aneurysms compared with 11% of those without aneurysms had a family history of subarachnoid hemorrhage (P<0.001). Most aneurysms were small (median diameter =4 mm; range, 2-12 mm); 85% were in the anterior circulation. During a total imaging follow-up of 469 patient-years, de novo intracranial aneurysms were detected in five patients; eight intracranial aneurysms grew (median =2 mm; range, 1-3 mm). During a total clinical follow-up of 668 patient-years, seven patients had preemptive clipping or coil embolization; no intracranial aneurysms ruptured. During a total clinical follow-up of 4783 patient-years in 737 patients with no intracranial aneurysm detected on the first magnetic resonance angiography screening, two patients had an intracranial aneurysm rupture (0.04 per 100 person-years; 95% confidence interval, 0 to 0.10). The rate of intracranial aneurysm rupture in large clinical trials of autosomal dominant polycystic kidney disease was 0.04 per 100 patient-years (95% confidence interval, 0.01 to 0.06).

CONCLUSIONS

Intracranial aneurysms were detected by presymptomatic screening in 9% of patients with autosomal dominant polycystic kidney disease, more frequently in those with familial history of subarachnoid hemorrhage, hypertension, or smoking. None of the patients with and two of the patients without aneurysm detection on screening suffered aneurysmal ruptures. The overall rupture rate in our autosomal dominant polycystic kidney disease cohort was approximately five times higher than that in the general population.

Evaluating Glomerular Filtration Rate Slope as a Surrogate End Point for ESKD in Clinical Trials: An Individual Participant Meta-Analysis of Observational Data

BACKGROUND

Decline in eGFR is a biologically plausible surrogate end point for the progression of CKD in clinical trials. However, it must first be tested to ensure strong associations with clinical outcomes in diverse populations, including patients with higher eGFR.

METHODS

To investigate the association between 1-, 2-, and 3-year changes in eGFR (slope) with clinical outcomes over the long term, we conducted a random effects meta-analysis of 3,758,551 participants with baseline eGFR≥60 ml/min per 1.73 m² and 122,664 participants with eGFR<60 ml/min per 1.73 m² from 14 cohorts followed for an average of 4.2 years.

RESULTS

Slower eGFR decline by 0.75 ml/min per 1.73 m² per year over 2 years was associated with lower risk of ESKD in participants with baseline eGFR≥60 ml/min per 1.73 m² (adjusted hazard ratio, 0.70; 95% CI, 0.68 to 0.72) and eGFR<60 ml/min per 1.73 m² (0.71; 95% CI, 0.68 to 0.74). The relationship was stronger with 3-year slope. For a rapidly progressing population with predicted 5-year risk of ESKD of 8.3%, an intervention that reduced eGFR decline by 0.75 ml/min per 1.73 m² per year over 2 years would reduce the ESKD risk by 1.6%. For a hypothetical low-risk population with a predicted 5-year ESKD risk of 0.58%, the same intervention would reduce the risk by only 0.13%.

CONCLUSIONS

Slower decline in eGFR was associated with lower risk of subsequent ESKD, even in participants with eGFR≥60 ml/min per 1.73 m², but those with the highest risk would be expected to benefit the most.

Polycystin-1 Assembles With Kv Channels to Govern Cardiomyocyte Repolarization and Contractility

BACKGROUND

Polycystin-1 (PC1) is a transmembrane protein originally identified in autosomal dominant polycystic kidney disease where it regulates the calcium-permeant cation channel polycystin-2. Autosomal dominant polycystic kidney disease patients develop renal failure, hypertension, left ventricular hypertrophy, and diastolic dysfunction, among other cardiovascular disorders. These individuals harbor PC1 loss-of-function mutations in their cardiomyocytes, but the functional consequences are unknown. PC1 is ubiquitously expressed, and its experimental ablation in cardiomyocyte-specific knockout mice reduces contractile function. Here, we set out to determine the pathophysiological role of PC1 in cardiomyocytes.

METHODS

Wild-type and cardiomyocyte-specific PC1 knockout mice were analyzed by echocardiography. Excitation-contraction coupling was assessed in isolated cardiomyocytes and human embryonic stem cell-derived cardiomyocytes, and functional consequences were explored in heterologous expression systems. Protein-protein interactions were analyzed biochemically and by means of ab initio calculations.

RESULTS

PC1 ablation reduced action potential duration in cardiomyocytes, decreased Ca²⁺ transients, and myocyte contractility. PC1-deficient cardiomyocytes manifested a reduction in sarcoendoplasmic reticulum Ca²⁺ stores attributable to a reduced action potential duration and sarcoendoplasmic reticulum Ca²⁺ ATPase (SERCA) activity. An increase in outward K⁺ currents decreased action potential duration in cardiomyocytes lacking PC1. Overexpression of full-length PC1 in HEK293 cells significantly reduced the current density of heterologously expressed Kv4.3, Kv1.5 and Kv2.1 potassium channels. PC1 C terminus inhibited Kv4.3 currents to the same degree as full-length PC1. Additionally, PC1 coimmunoprecipitated with Kv4.3, and a modeled PC1 C-terminal structure suggested the existence of 2 docking sites for PC1 within the N terminus of Kv4.3, supporting a physical interaction. Finally, a naturally occurring human mutant PC1^R4228X manifested no suppressive effects on Kv4.3 channel activity.

CONCLUSIONS

Our findings uncover a role for PC1 in regulating multiple Kv channels, governing membrane repolarization and alterations in SERCA activity that reduce cardiomyocyte contractility.

Modern approaches to conservative therapy of polycystic kidney disease

Polycystic kidney disease (PKD) is a genetically determined pathological process associated with the formation and growth of cysts originating from the epithelial cells of the tubules and/or collecting tubes. PBP is represented by two main types - autosomal dominant (ADPKD) and autosomal recessive PKD (ARPKD), which are different diseases. The main causes of ADPKD are mutations of the PKD1 and PKD2 genes, which encode the formation of polycystin-1 and polycystin-2 proteins. ARPKD-linked mutation in the gene PKHD1, leads to total absence or defective synthesis of receptor protein primary cilia - fibrocystin. There are relationships between the structural and functional defects in the primary cilia and PBP. Mechanisms of cysts formation and growth include a) mutations of polycystines genes located on the cilia; b) increased activity of renal intracellular cAMP; c) vasopressin V2 receptors activation; d) violation of the tubular epithelium polarity (translocation of Na,K-ATPasa from basolateral to apical membrane); e) increased mTOR activity in epithelial cells lining renal cyst. The most promising directions of ADPKD therapy are blockade of vasopressin V2 receptors activation, inhibition of mTOR signaling pathways and reduction of intracellular cAMP level. The review presents clinical studies that assessed the effectiveness of named drugs in ADPKD.

Soluble Urokinase Plasminogen Activator Receptor and Decline in Kidney Function in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Levels of soluble urokinase plasminogen activator receptor (suPAR), an inflammation marker, are strongly predictive of incident kidney disease. Patients with autosomal dominant polycystic kidney disease (ADPKD) experience progressive decline in renal function, but rates of decline and outcomes vary greatly. Whether suPAR levels are predictive of declining kidney function in patients with ADPKD is unknown.

METHODS

We assessed suPAR levels in 649 patients with ADPKD who underwent scheduled follow-up for at least 3 years, with repeated measurements of height-adjusted total kidney volume and creatinine-derived eGFR. We used linear mixed models for repeated measures and Cox proportional hazards to characterize associations between baseline suPAR levels and follow-up eGFR or incident ESRD.

RESULTS

The median suPAR level was 2.47 ng/ml and median height-adjusted total kidney volume was 778, whereas mean eGFR was 84 ml/min per 1.73 m². suPAR levels were associated with height-adjusted total kidney volume (β=0.02; 95% confidence interval, 0.01 to 0.03), independent of age, sex, race, hypertension, and eGFR. Patients in the lowest suPAR tertile (<2.18 ng/ml) had a 6.8% decline in eGFR at 3 years and 22% developed CKD stage 3, whereas those in the highest tertile (suPAR>2.83 ng/ml) had a 19.4% decline in eGFR at 3 years and 68% developed CKD stage 3. suPAR levels >2.82 ng/ml had a 3.38-fold increase in the risk of incident ESRD.

CONCLUSIONS

suPAR levels were associated with progressive decline in renal function and incident ESRD in patients with ADPKD, and may aid early identification of patients at high risk of disease progression.

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.

Recent advances in management of autosomal-dominant polycystic kidney disease

PURPOSE

Promising developments in the search for effective pharmacotherapies for autosomal-dominant polycystic kidney disease (ADPKD) are reviewed.

SUMMARY

The formation and development of cysts characteristic of ADPKD result in inexorable renal and extrarenal manifestations that give rise to more rapid disease progression and more widespread complications than are seen with other forms of chronic kidney disease. To date, no agent has gained Food and Drug Administration marketing approval for use in patients with ADPKD, complicating efforts to meet the medical needs of this population. Although definitive ultrasonographic diagnostic strategies are available, molecular screening approaches lack sufficient evidence and patient outcomes data to support broad clinical application. Recently completed and ongoing clinical trials point to a number of encouraging platforms for evidence-based ADPKD management. Tolvaptan therapy significantly improved cyst burden and slowed disease progression among patients with early-stage ADPKD in a large-scale trial, while somatostatin therapies may also be useful in halting disease progression and managing comorbid polycystic liver disease. Stem cell research and nanomedicine might represent novel approaches to gaining comprehensive insights on ADPKD and, ultimately, to targeting the disease's origins, thereby making restoration of kidney function possible.

CONCLUSION

A number of pharmacotherapy approaches to ADPKD management show promise but are unlikely to be curative, fueling interest among researchers in finding new applications for nanomedicine and stem cell technologies that can slow ADPKD progression and better control complications of the disease.

ADPedKD: A Global Online Platform on the Management of Children With ADPKD

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic cause of renal failure. For several decades, ADPKD was regarded as an adult-onset disease. In the past decade, it has become more widely appreciated that the disease course begins in childhood. However, evidence-based guidelines on how to manage and approach children diagnosed with or at risk of ADPKD are lacking. Also, scoring systems to stratify patients into risk categories have been established only for adults. Overall, there are insufficient data on the clinical course during childhood. We therefore initiated the global ADPedKD project to establish a large international pediatric ADPKD cohort for deep characterization.

Methods

Global ADPedKD is an international multicenter observational study focusing on childhood-diagnosed ADPKD. This collaborative project is based on interoperable Web-based databases, comprising 7 regional and independent but uniformly organized chapters, namely Africa, Asia, Australia, Europe, North America, South America, and the United Kingdom. In the database, a detailed basic data questionnaire, including genetics, is used in combination with data entry from follow-up visits, to provide both retrospective and prospective longitudinal data on clinical, radiologic, and laboratory findings, as well as therapeutic interventions.

Discussion

The global ADPedKD initiative aims to characterize in detail the most extensive international pediatric ADPKD cohort reported to date, providing evidence for the development of unified diagnostic, follow-up, and treatment recommendations regarding modifiable disease factors. Moreover, this registry will serve as a platform for the development of clinical and/or biochemical markers predicting the risk of early and progressive disease.

Determinants of Progression in Early Autosomal Dominant Polycystic Kidney Disease: Is it Blood Pressure or Renin-Angiotensin-Aldosterone-System Blockade?

Background

The HALT PKD trial in early autosomal dominant polycystic kidney disease (ADPKD) showed that intensive control of systolic blood pressure to 95-110 mmHg was associated with a 14% slower rate of kidney volume growth compared to standard control. It is unclear whether this result was due to greater blockade of the renin-angiotensin-aldosterone system (RAAS) by allowing the use of higher drug doses in the low blood pressure arm, or due to the lower blood pressure per se.

Methods

In this secondary analysis of HALT PKD Study A, we categorized participants into high and low dose groups based on the median daily equivalent dose of RAAS blocking drugs used after the initial dose titration period. Using linear mixed models, we compared the percent change in total kidney volume and the slope of estimated glomerular filtration rate (eGFR) between the 2 groups. We also assessed the effects of time-varying dose and time-varying blood pressure parameters on these outcomes.

Results

Subjects in the high dose group (n=252) did not experience a slower increase in total kidney volume than those in the low-dose (n=225) group, after adjustment for age, sex, genotype, and BP arm. The chronic slope of eGFR decline was similar in the 2 groups. Higher time-varying systolic blood pressure was associated with a steeper decline in eGFR.

Conclusion

ADPKD progression (as detected by eGFR decline and TKV increase) was ameliorated by intense blood pressure control as opposed to pharmacologic intensity of RAAS blockade.

Effect of Statin Therapy on the Progression of Autosomal Dominant Polycystic Kidney Disease. A Secondary Analysis of the HALT PKD Trials

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) commonly results in end-stage renal disease (ESRD), yet a long-term treatment that is well tolerated is still lacking. In a small randomized trial in children and adolescents pravastatin administration for 3 years was associated with reduced renal cyst growth, but no large trial has tested the effect of statins in adults.

METHODS

We performed a post-hoc analysis of the HALT PKD trials to compare outcomes of participants who never used statins with those who used statin for at least 3 years. Because statins were not randomly allocated, we used propensity score models with inverse probability of treatment weighting to account for imbalances between the groups. For subjects in Study A (preserved renal function, n=438) relevant outcomes were percent change in total kidney and liver volume and the rate of decline in estimated glomerular filtration rate (eGFR); for those in Study B (reduced renal function, n=352) we compared time to the composite endpoint of death, ESRD or 50% decline in eGFR. Follow-up was 5-8 years.

RESULTS

There was no difference in any outcome between the 2 groups. However, limitations of this analysis are the small number of statin users in Study A, different statin drugs and doses used, non-randomized allocation and advanced disease stage in Study B.

CONCLUSION

Although this post-hoc analysis of the HALT PKD trials does not demonstrate a benefit of statin therapy, conclusions remain preliminary. A larger randomized trial in young people with ADPKD is necessary to answer the question whether statins can slow renal cyst growth and preserve kidney function.

Hyperfiltration-mediated Injury in the Remaining Kidney of a Transplant Donor

Kidney donors face a small but definite risk of end-stage renal disease 15 to 30 years postdonation. The development of proteinuria, hypertension with gradual decrease in kidney function in the donor after surgical resection of 1 kidney, has been attributed to hyperfiltration. Genetic variations, physiological adaptations, and comorbidities exacerbate the hyperfiltration-induced loss of kidney function in the years after donation. A focus on glomerular hemodynamics and capillary pressure has led to the development of drugs that target the renin-angiotensin-aldosterone system (RAAS), but these agents yield mixed results in transplant recipients and donors. Recent work on glomerular biomechanical forces highlights the differential effects of tensile stress and fluid flow shear stress (FFSS) from hyperfiltration. Capillary wall stretch due to glomerular capillary pressure increases tensile stress on podocyte foot processes that cover the capillary. In parallel, increased flow of the ultrafiltrate due to single-nephron glomerular filtration rate elevates FFSS on the podocyte cell body. Although tensile stress invokes the RAAS, FFSS predominantly activates the cyclooxygenase 2-prostaglandin E2-EP2 receptor axis. Distinguishing these 2 mechanisms is critical, as current therapeutic approaches focus on the RAAS system. A better understanding of the biomechanical forces can lead to novel therapeutic agents to target FFSS through the cyclooxygenase 2-prostaglandin E2-EP2 receptor axis in hyperfiltration-mediated injury. We present an overview of several aspects of the risk to transplant donors and discuss the relevance of FFSS in podocyte injury, loss of glomerular barrier function leading to albuminuria and gradual loss of renal function, and potential therapeutic strategies to mitigate hyperfiltration-mediated injury to the remaining kidney.

Ciliotherapy: Remote Control of Primary Cilia Movement and Function by Magnetic Nanoparticles

Patients with polycystic kidney disease (PKD) are characterized with uncontrolled hypertension. Hypertension in PKD is a ciliopathy, an abnormal function and/or structure of primary cilia. Primary cilia are cellular organelles with chemo and mechanosensory roles. In the present studies, we designed a cilia-targeted (CT) delivery system to deliver fenoldopam specifically to the primary cilia. We devised the iron oxide nanoparticle (NP)-based technology for ciliotherapy. Live imaging confirmed that the CT-Fe₂O₃-NPs specifically targeted primary cilia in cultured cells in vitro and vascular endothelia in vivo. Importantly, the CT-Fe₂O₃-NPs enabled the remote control of the movement and function of a cilium with an external magnetic field, making the nonmotile cilium exhibit passive movement. The ciliopathic hearts displayed hypertrophy with compromised functions in left ventricle pressure, stroke volume, ejection fraction, and overall cardiac output because of prolonged hypertension. The CT-Fe₂O₃-NPs significantly improved cardiac function in the ciliopathic hypertensive models, in which the hearts also exhibited arrhythmia, which was corrected with the CT-Fe₂O₃-NPs. Intraciliary and cytosolic Ca²⁺ were increased when cilia were induced with fluid flow or magnetic field, and this served as a cilia-dependent mechanism of the CT-Fe₂O₃-NPs. Fenoldopam-alone caused an immediate decrease in blood pressure, followed by reflex tachycardia. Pharmacological delivery profiles confirmed that the CT-Fe₂O₃-NPs were a superior delivery system for targeting cilia more specifically, efficiently, and effectively than fenoldopam-alone. The CT-Fe₂O₃-NPs altered the mechanical properties of nonmotile cilia, and these nano-biomaterials had enormous clinical potential for ciliotherapy. Our studies further indicated that ciliotherapy provides a possibility toward personalized medicine in ciliopathy patients.

Urinary angiotensinogen level is associated with potassium homeostasis and clinical outcome in patients with polycystic kidney disease: a prospective cohort study

Background

Guidelines for general hypertension treatment do not recommend the combined use of renin-angiotensin-aldosterone system (RAAS) inhibitors due to the risk of hyperkalemia. However, a recent clinical trial showed that polycystic kidney disease (PKD) patients had infrequent episodes of hyperkalemia despite receiving combined RAAS inhibitors. Because intrarenal RAAS is a main component for renal potassium handling, we further investigated the association between intrarenal RAAS activity and serum potassium level in patients with chronic kidney disease, particularly in PKD patients, and examined whether intrarenal RAAS activity has a prognostic role in patients with PKD.

Methods

A total of 1788 subjects from the KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD) were enrolled in this study. Intrarenal RAAS activity was assessed by the measurement of urinary angiotensinogen (AGT). The primary outcome was the composite of all-cause mortality and renal function decline.

Results

Patients with PKD had a significantly lower serum potassium level in chronic kidney disease stages 1 to 3b than non-PKD patients. In logistic regression analysis, after adjusting for multiple confounders, PKD patients had a significantly lower risk of hyperkalemia than non-PKD patients. In multivariable linear regression analysis, the urinary AGT/creatinine (Cr) ratio was negatively correlated with the serum potassium level (β = − 0.058, P = 0.017) and positively correlated with the transtubular potassium gradient (TTKG, β = 0.087, P = 0.001). In propensity score matching analysis, after matching factors associated with serum potassium and TTKG, PKD patients had a significantly higher TTKG (P = 0.021) despite a lower serum potassium level (P = 0.004). Additionally, the urinary AGT/Cr ratio was significantly higher in PKD patients than in non-PKD patients (P = 0.011). In 293 patients with PKD, high urinary AGT/Cr ratio was associated with increased risk of the composite outcome (hazard ratio 1.29; 95% confidence interval, 1.07–1.55; P = 0.007).

Conclusions

High activity of intrarenal RAAS is associated with increased urinary potassium excretion and low serum potassium level in patients with PKD. In addition, intrarenal RAAS activity can be a prognostic marker for mortality and renal function decline in these patients.

Effects of antiretroviral therapy in HIV-positive adults on new HIV infections among young women: a systematic review protocol

BACKGROUND

The HIV/AIDS pandemic has struck regions, countries, and populations in different ways. With the introduction of antiretroviral drugs, people living with HIV (PLHIV) have a much better prognosis, even though there are still many new infections in young women. The role of widespread antiretroviral therapy (ART) on the incidence of HIV in young women is unknown.

METHODS

We will conduct a comprehensive search of MEDLINE (PubMed), Excerpta Medica database (EMBASE), Scopus, Google Scholar, Cochrane Central Register of Controlled Trials (CENTRAL), World Health Organization's (WHO's) library database, Latin American and Caribbean Health Sciences Literature (LILACS), conference abstracts, and gray literature sources to identify any relevant literature. We will include randomized and non-randomized clinical trials and cohort studies in which ART was offered to adults aged 18 and above reporting outcomes in females aged 15 to 24 years. The outcomes of interest are HIV incidence, ART initiation, adherence, retention, and viral load suppression. We will screen titles, abstracts, and the full texts of relevant articles in duplicate. Disagreements will be resolved by consensus. We will extract data on the risk of HIV infection in younger females after the use of ART in the adult population.

DISCUSSION

To our knowledge, this is the first systematic review to look at the impact of ART use among adults on HIV incidence in young women. The results of this review will be used in a modeling study to simulate the effects of using ART as an effective tool to prevent sexual transmission of HIV to young women. Our findings will inform the treatment-as-prevention (TasP) strategy to reduce new HIV infections among young women.

SYSTEMATIC REVIEW REGISTRATION

The systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42018099174 .

Long-term trajectory of kidney function in autosomal-dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cyst and kidney growth, which is hypothesized to cause loss of functioning renal mass and eventually end-stage kidney disease. However, the time course of decline in glomerular filtration rate (GFR) is poorly defined. The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease study is a 14-year observational cohort study of 241 adults with ADPKD. As an estimate of the rate of kidney growth, participants were stratified into 5 subclasses based on baseline age and magnetic resonance imaging measurements of total kidney volume (TKV) according to the method of Irazabal. GFR trajectories spanning over four decades of life were reconstructed and fitted using mixed polynomial models, which were validated using data from the HALT-PKD study. GFR trajectories were nonlinear, with a period of relative stability in most participants, followed by accelerating decline. The shape and slope of these trajectories were strongly associated with baseline Irazabal class. Patients with PKD1 mutations had a steeper GFR decline than patients with PKD2 mutations or with no detected mutation, largely mediated by the effect of genotype on Irazabal class. Thus, GFR decline in ADPKD is nonlinear, and its trajectory throughout adulthood can be predicted from a single measurement of kidney volume. These models can be used for clinical prognostication, clinical trial design, and patient selection for clinical interventions. Our findings support a causal link between growth in kidney volume and GFR decline, adding support for the use of TKV as a surrogate endpoint in clinical trials.

Autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and one of the most common causes of end-stage kidney disease. Multiple clinical manifestations, such as enlarged kidneys filled with growing cysts, hypertension, and multiple extrarenal complications, including liver cysts, intracranial aneurysms, and cardiac valvular disease, show that ADPKD is a systemic disorder. New information derived from clinical research using molecular genetics and advanced imaging techniques has provided enhanced tools for assessing the diagnosis and prognosis for individual patients and their families. Phase 3 randomised, placebo-controlled clinical trials have clarified aspects of disease management and a disease-modifying therapeutic drug is now available for patients with high risk of rapid disease progression. These developments provide a strong basis on which to make clear recommendations about the management of affected patients and families. Implementation of these advances has the potential to delay kidney failure, reduce the symptom burden, lessen the risk of cardiovascular complications, and prolong life.

Plasma metabolites and lipids associate with kidney function and kidney volume in hypertensive ADPKD patients early in the disease course

Background

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and is characterized by gradual cyst growth and expansion, increase in kidney volume with an ultimate decline in kidney function leading to end stage renal disease (ESRD). Given the decades long period of stable kidney function while cyst growth occurs, it is important to identify those patients who will progress to ESRD. Recent data from our and other laboratories have demonstrated that metabolic reprogramming may play a key role in cystic epithelial proliferation resulting in cyst growth in ADPKD. Height corrected total kidney volume (ht-TKV) accurately reflects cyst burden and predicts future loss of kidney function. We hypothesize that specific plasma metabolites will correlate with eGFR and ht-TKV early in ADPKD, both predictors of disease progression, potentially indicative of early physiologic derangements of renal disease severity.

Methods

To investigate the predictive role of plasma metabolites on eGFR and/or ht-TKV, we used a non-targeted GC-TOF/MS-based metabolomics approach on hypertensive ADPKD patients in the early course of their disease. Patient data was obtained from the HALT-A randomized clinical trial at baseline including estimated glomerular filtration rate (eGFR) and measured ht-TKV. To identify individual metabolites whose intensities are significantly correlated with eGFR and ht-TKV, association analyses were performed using linear regression with each metabolite signal level as the primary predictor variable and baseline eGFR and ht-TKV as the continuous outcomes of interest, while adjusting for covariates. Significance was determined by Storey’s false discovery rate (FDR) q-values to correct for multiple testing.

Results

Twelve metabolites significantly correlated with eGFR and two triglycerides significantly correlated with baseline ht-TKV at FDR q-value < 0.05. Specific significant metabolites, including pseudo-uridine, indole-3-lactate, uric acid, isothreonic acid, and creatinine, have been previously shown to accumulate in plasma and/or urine in both diabetic and cystic renal diseases with advanced renal insufficiency.

Conclusions

This study identifies metabolic derangements in early ADPKD which may be prognostic for ADPKD disease progression.

Clinical trial

HALT Progression of Polycystic Kidney Disease (HALT PKD) Study A; Clinical www.clinicaltrials.gov identifier: NCT00283686; first posted January 30, 2006, last update posted March 19, 2015.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1249-6) contains supplementary material, which is available to authorized users.

Recent advances in the clinical management of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic systemic disorder causing the development of renal and hepatic cysts and decline in renal function. It affects around 1 in 1,000 live births. Early hypertension and progressive renal failure due to massive enlargement of cysts and fibrosis are hallmarks of the disease. This article reviews recent advances in ADPKD and focuses mainly on diagnosis, management, and prediction of the course of the disease.

Autosomal dominant polycystic kidney disease: Disrupted pathways and potential therapeutic interventions

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic inherited renal cystic disease that occurs in different races worldwide. It is characterized by the development of a multitude of renal cysts, which leads to massive enlargement of the kidney and often to renal failure in adulthood. ADPKD is caused by a mutation in PKD1 or PKD2 genes encoding the proteins polycystin-1 and polycystin-2, respectively. Recent studies showed that cyst formation and growth result from deregulation of multiple cellular pathways like proliferation, apoptosis, metabolic processes, cell polarity, and immune defense. In ADPKD, intracellular cyclic adenosine monophosphate (cAMP) promotes cyst enlargement by stimulating cell proliferation and transepithelial fluid secretion. Several interventions affecting many of these defective signaling pathways have been effective in animal models and some are currently being tested in clinical trials. Moreover, the stem cell therapy can improve nephropathies and according to studies were done in this field, can be considered as a hopeful therapeutic approach in future for PKD. This study provides an in-depth review of the relevant molecular pathways associated with the pathogenesis of ADPKD and their implications in development of potential therapeutic strategies.

Central blood pressure and measures of early vascular disease in children with ADPKD

BACKGROUND

There is growing recognition of hypertension in a significant proportion of children with ADPKD. In this study, we assessed blood pressure and cardiovascular status in children with ADPKD.

METHODS

A prospective two-centre observational study of children (< 18 years) with ADPKD was compared against age- and BMI-matched healthy controls. Children underwent peripheral BP (pBP) measured using an aneroid sphygmomanometer and auscultation, 24-h ambulatory BP monitoring (ABPM), non-invasive central BP (cBP) measurement, carotid-femoral pulse wave velocity (PWVcf) measured using applanation tonometry and measurement of indexed left ventricular mass (LVMI) using echocardiography. This study received independent ethical approval.

RESULTS

Forty-seven children with ADPKD and 49 healthy controls were recruited (median age 11 years vs. 12 years). Children with ADPKD had significantly higher systolic pBP (mean 112 ± 13.5 mmHg vs. 104 ± 11 mmHg, p < 0.001), higher systolic cBP (mean 97 ± 12.8 mmHg vs. 87 ± 9.8 mmHg, p < 0.001) and lower pulse pressure amplification ratio (1.59 ± 0.2 vs. 1.67 ± 0.1, p = 0.04) compared to healthy children. Thirty-five percent of children with ADPKD showed a lack of appropriate nocturnal dipping on 24-h ABPM. There was no difference in PWVcf between children with ADPKD and healthy children (mean 5.74 ± 1 m/s vs. 5.57 ± 0.9 m/s, p = 0.46). Those with ADPKD had a significantly higher LVMI (mean 30.4 ± 6.6 g/m^2.7 vs. 26.2 ± 6.2 g/m^2.7, p = 0.01).

CONCLUSIONS

These data highlight the high prevalence of hypertension in children with ADPKD, also demonstrating early cardiovascular dysfunction with increased LVMI and reduced PP amplification despite preserved PWVcf, when compared with healthy peers. These early cardiovascular abnormalities are likely to be amenable to antihypertensive therapy, reinforcing the need for routine screening of children with ADPKD.

Management of autosomal-dominant polycystic kidney disease-state-of-the-art

Autosomal-dominant polycystic kidney disease (ADPKD) is the most frequent genetic cause of end-stage renal disease in adults. Affected individuals and families face a significant medical and psychosocial burden due to both renal and extrarenal manifestations. Consequently, interventions that ameliorate the course of the disease and specifically slow down the loss of kidney function are of special interest. Major research efforts in both the clinical and pre-clinical setting in the last two decades resulted in a number of pivotal clinical trials aimed to ameliorate the disease. These studies have underlined the important role of specific supportive measures and provided the basis for first targeted pharmacological therapies. Very recently, the concept of repurposing drugs approved for other conditions for a use in ADPKD has gained increasing attention. Here, we review the current best-practice management of ADPKD patients with a focus on interventions that have reached clinical use to maintain kidney function and give an outlook on future trials and potential novel treatment strategies.

Polycystic kidney disease

Cystic kidneys are common causes of end-stage renal disease, both in children and in adults. Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are cilia-related disorders and the two main forms of monogenic cystic kidney diseases. ADPKD is a common disease that mostly presents in adults, whereas ARPKD is a rarer and often more severe form of polycystic kidney disease (PKD) that usually presents perinatally or in early childhood. Cell biological and clinical research approaches have expanded our knowledge of the pathogenesis of ADPKD and ARPKD and revealed some mechanistic overlap between them. A reduced 'dosage' of PKD proteins is thought to disturb cell homeostasis and converging signalling pathways, such as Ca²⁺, cAMP, mechanistic target of rapamycin, WNT, vascular endothelial growth factor and Hippo signalling, and could explain the more severe clinical course in some patients with PKD. Genetic diagnosis might benefit families and improve the clinical management of patients, which might be enhanced even further with emerging therapeutic options. However, many important questions about the pathogenesis of PKD remain. In this Primer, we provide an overview of the current knowledge of PKD and its treatment.

Unmet needs and challenges for follow-up and treatment of autosomal dominant polycystic kidney disease: the paediatric perspective

Awareness is growing that the clinical course of autosomal dominant polycystic kidney disease (ADPKD) already begins in childhood, with a broad range of both symptomatic and asymptomatic features. Knowing that parenchymal destruction with cyst formation and growth starts early in life, it seems reasonable to assume that early intervention may yield the best chances for preserving renal outcome. Interventions may involve lifestyle modifications, hypertension control and the use of disease-modifying treatments once these become available for the paediatric population with an acceptable risk and side-effect profile. Until then, screening of at-risk children is controversial and not generally recommended since this might cause psychosocial and financial harm. Also, the clinical and research communities are facing important questions as to the nature of potential interventions and their optimal indications and timing. Indeed, challenges include the identification and validation of indicators, both measuring and predicting disease progression from childhood, and the discrimination of slow from rapid progressors in the paediatric population. This discrimination will improve both the cost-effectiveness and benefit-to-risk ratio of therapies. Furthermore, we will need to define outcome measures, and to evaluate the possibility of a potential therapeutic window of opportunity in childhood. The recently established international register ADPedKD will help in elucidating these questions. In this review, we provide an overview of the current knowledge on paediatric ADPKD as a future therapeutic target population and its unmet challenges.

Emerging targeted strategies for the treatment of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a widespread genetic disease that leads to renal failure in the majority of patients. The very first pharmacological treatment, tolvaptan, received Food and Drug Administration approval in 2018 after previous approval in Europe and other countries. However, tolvaptan is moderately effective and may negatively impact a patient's quality of life due to potentially significant side effects. Additional and improved therapies are still urgently needed, and several clinical trials are underway, which are discussed in the companion paper Müller and Benzing (Management of autosomal-dominant polycystic kidney disease-state-of-the-art) Clin Kidney J 2018; 11: i2-i13. Here, we discuss new therapeutic avenues that are currently being investigated at the preclinical stage. We focus on mammalian target of rapamycin and dual kinase inhibitors, compounds that target inflammation and histone deacetylases, RNA-targeted therapeutic strategies, glucosylceramide synthase inhibitors, compounds that affect the metabolism of renal cysts and dietary restriction. We discuss tissue targeting to renal cysts of small molecules via the folate receptor, and of monoclonal antibodies via the polymeric immunoglobulin receptor. A general problem with potential pharmacological approaches is that the many molecular targets that have been implicated in ADPKD are all widely expressed and carry out important functions in many organs and tissues. Because ADPKD is a slowly progressing, chronic disease, it is likely that any therapy will have to continue over years and decades. Therefore, systemically distributed drugs are likely to lead to potentially prohibitive extra-renal side effects during extended treatment. Tissue targeting to renal cysts of such drugs is one potential way around this problem. The use of dietary, instead of pharmacological, interventions is another.

Blood Pressure Goals in Patients with CKD: A Review of Evidence and Guidelines

Hypertension affects the vast majority of patients with CKD and increases the risk of cardiovascular disease, ESKD, and death. Over the past decade, a number of hypertension guidelines have been published with varying recommendations for BP goals in patients with CKD. Most recently, the American College of Cardiology/American Heart Association 2017 hypertension guidelines set a BP goal of <130/80 mm Hg for patients with CKD and others at elevated cardiovascular risk. These guidelines were heavily influenced by the landmark Systolic Blood Pressure Intervention Trial (SPRINT), which documented that an intensive BP goal to a systolic BP <120 mm Hg decreased the risk of cardiovascular disease and mortality in nondiabetic adults at high cardiovascular risk, many of whom had CKD; the intensive BP goal did not retard CKD progression. It is noteworthy that SPRINT measured BP with automated devices (5-minute wait period, average of three readings) often without observers, a technique that potentially results in BP values that are lower than what is typically measured in the office. Still, results from SPRINT along with long-term follow-up data from the Modification of Diet in Renal Disease and the African American Study of Kidney Disease and Hypertension suggest that a BP goal <130/80 mm Hg will reduce mortality in patients with CKD. Unfortunately, data are more limited in patients with diabetes or stage 4-5 CKD. Increased adverse events, including electrolyte abnormalities and decreased eGFR, necessitate careful laboratory monitoring. In conclusion, a BP goal of <130/80 is a reasonable, evidence-based BP goal in patients with CKD. Implementation of this intensive BP target will require increased attention to measuring BP accurately, assessing patient preferences and concurrent medical conditions, and monitoring for adverse effects of therapy.

Recent Advances in the Management of Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic cause of ESKD, is characterized by relentless development of kidney cysts, hypertension, and destruction of the kidney parenchyma. Over the past few years, major advancements in diagnosing, prognosticating, and understanding the pathogenesis and natural course of the disease have been made. Currently, no kidney disease is more suitable for nephron-protective strategies. Early nephrology referral and implementation of these strategies may have a substantial effect. Total kidney volume is a good prognostication marker and allows stratification of patients into slow or rapid progressing disease, with implications for their management. Measurement of total kidney volume, disease stratification, and prognostication are possible using readily available tools. Although some patients require only monitoring and basic optimized kidney protective measures, such as rigorous BP control and various lifestyle and dietary changes, others will benefit from disease-modifying treatments. Vasopressin V2 receptor antagonists, a likely disease-modifying treatment, has been approved in several countries and recently by the US Food and Drug Administration; other therapies, such as somatostatin analogs and other novel agents, are currently in clinical trials. The purpose of this article is to present our views on the optimal management to delay kidney disease progression in ADPKD.

Antihypertensive treatment and renal protection: Is there a J-curve relationship?

A bidirectional relationship between hypertension and kidney disease, with one exacerbating the effect of the other, is well established. Elevated blood pressure (BP) is a well-recognized, modifiable risk factor for cardiovascular (CV) disease as well as for development and progression of chronic kidney disease and, therefore, the identification of optimal BP target is a key issue in the management of renal patients. Recent large trials and real life cohort studies have indicated that below a definite BP value renal protection seems to plateau and too low levels may even be associated with a paradoxical increase in renal morbidity, thus reviving the debate about the so called BP -renal function J-curve relationship. Existing evidence supports a systolic target around 130 mm Hg to combine both renal and CV protection and possibly lower levels in the presence of overt proteinuria.

Systematic Review for the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines

Objective

To review the literature systematically and perform meta-analyses to address these questions: 1) Is there evidence that self-measured blood pressure (BP) without other augmentation is superior to office-based measurement of BP for achieving better BP control or for preventing adverse clinical outcomes that are related to elevated BP? 2) What is the optimal target for BP lowering during antihypertensive therapy in adults? 3) In adults with hypertension, how do various antihypertensive drug classes differ in their benefits and harms compared with each other as first-line therapy?

Methods

Electronic literature searches were performed by Doctor Evidence, a global medical evidence software and services company, across PubMed and EMBASE from 1966 to 2015 using key words and relevant subject headings for randomized controlled trials that met eligibility criteria defined for each question. We performed analyses using traditional frequentist statistical and Bayesian approaches, including random-effects Bayesian network meta-analyses.

Results

Our results suggest that: 1) There is a modest but significant improvement in systolic BP in randomized controlled trials of self-measured BP versus usual care at 6 but not 12 months, and for selected patients and their providers self-measured BP may be a helpful adjunct to routine office care. 2) systolic BP lowering to a target of <130 mm Hg may reduce the risk of several important outcomes including risk of myocardial infarction, stroke, heart failure, and major cardiovascular events. No class of medications (ie, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, calcium channel blockers, or beta blockers) was significantly better than thiazides and thiazide-like diuretics as a first-line therapy for any outcome.

Updated Canadian Expert Consensus on Assessing Risk of Disease Progression and Pharmacological Management of Autosomal Dominant Polycystic Kidney Disease

PURPOSE

The purpose of this article is to update the previously published consensus recommendations from March 2017 discussing the optimal management of adult patients with autosomal dominant polycystic kidney disease (ADPKD). This document focuses on recent developments in genetic testing, renal imaging, assessment of risk regarding disease progression, and pharmacological treatment options for ADPKD.

SOURCES OF INFORMATION

Published literature was searched in PubMed, the Cochrane Library, and Google Scholar to identify the latest evidence related to the treatment and management of ADPKD.

METHODS

All pertinent articles were reviewed by the authors to determine if a new recommendation was required, or if the previous recommendation needed updating. The consensus recommendations were developed by the authors based on discussion and review of the evidence.

KEY FINDINGS

The genetics of ADPKD are becoming more complex with the identification of new and rarer genetic variants such as GANAB. Magnetic resonance imaging (MRI) and computed tomography (CT) continue to be the main imaging modalities used to evaluate ADPKD. Total kidney volume (TKV) continues to be the most validated and most used measure to assess disease progression. Since the publication of the previous consensus recommendations, the use of the Mayo Clinic Classification for prognostication purposes has been validated in patients with class 1 ADPKD. Recent evidence supports the benefits of a low-osmolar diet and dietary sodium restriction in patients with ADPKD. Evidence from the Replicating Evidence of Preserved Renal Function: an Investigation of Tolvaptan Safety and Efficacy in ADPKD (REPRISE) trial supports the use of ADH (antidiuretic hormone) receptor antagonism in patients with ADPKD 18 to 55 years of age with eGFR (estimated glomerular filtration rate) of 25 to 65 mL/min/1.73 m2 or 56 to 65 years of age with eGFR of 25 to 44 mL/min/1.73 m2 with historical evidence of a decline in eGFR >2.0 mL/min/1.73 m2/year.

LIMITATIONS

Available literature was limited to English language publications and to publications indexed in PubMed, the Cochrane Library, and Google Scholar.

IMPLICATIONS

Advances in the assessment of the risk of disease progression include the validation of the Mayo Clinic Classification for patients with class 1 ADPKD. Advances in the pharmacological management of ADPKD include the expansion of the use of ADH receptor antagonism in patients 18 to 55 years of age with eGFR of 25 to 65 mL/min/1.73 m2 or 56 to 65 years of age with eGFR of 25 to 44 mL/min/1.73 m2 with historical evidence of a decline in eGFR >2.0 mL/min/1.73 m2/year, as per the results of the REPRISE study.

Renal manifestation of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a tumor predisposition syndrome with significant renal cystic and solid tumor disease. It commonly causes several types of cystic disease and benign tumors (angiomyolipomata) in the kidneys that can both lead to significant premature loss of glomerular filtration rate. The main risks of angiomyolipomata, severe bleeding, loss of renal function, and pulmonary lymphangioleiomyomatosis, can be ameliorated by active surveillance and preemptive therapy with mTOR inhibitors. The cystogenic mechanism may involve primary cilia, but also appears to also involve a majority of normal tubular cells and may be driven by a minority of cells with mutations inactivating both their TSC1 or TSC2 genes. Malignant tumors are rare.

Effects of Intensive Blood Pressure Lowering on Kidney Tubule Injury in CKD: A Longitudinal Subgroup Analysis in SPRINT

BACKGROUND

Random assignment to the intensive systolic blood pressure (SBP) arm (<120mmHg) in the Systolic Blood Pressure Intervention Trial (SPRINT) resulted in more rapid declines in estimated glomerular filtration rates (eGFRs) than in the standard arm (SBP<140mmHg). Whether this change reflects hemodynamic effects or accelerated intrinsic kidney damage is unknown.

STUDY DESIGN

Longitudinal subgroup analysis of clinical trial participants.

SETTINGS & PARTICIPANTS

Random sample of SPRINT participants with prevalent chronic kidney disease (CKD) defined as eGFR<60mL/min/1.73m² by the CKD-EPI (CKD Epidemiology Collaboration) creatinine-cystatin C equation at baseline.

OUTCOMES & MEASUREMENTS

Urine biomarkers of tubule function (β₂-microglobulin [B2M], α₁-microglobulin [A1M]), and uromodulin), injury (interleukin 18, kidney injury molecule 1, and neutrophil gelatinase-associated lipocalin), inflammation (monocyte chemoattractant protein 1), and repair (human cartilage glycoprotein 40) at baseline, year 1, and year 4. Biomarkers were indexed to urine creatinine concentration and changes between arms were evaluated using mixed-effects linear models and an intention-to-treat approach.

RESULTS

978 SPRINT participants (519 in the intensive and 459 in the standard arm) with prevalent CKD were included. Mean age was 72±9 years and eGFR was 46.1±9.4mL/min/1.73m² at baseline. Clinical characteristics, eGFR, urinary albumin-creatinine ratio, and all 8 biomarker values were similar across arms at baseline. Compared to the standard arm, eGFR was lower by 2.9 and 3.3mL/min/1.73m² in the intensive arm at year 1 and year 4. None of the 8 tubule marker levels was higher in the intensive arm compared to the standard arm at year 1 or year 4. Two tubule function markers (B2M and A1M) were 29% (95% CI, 10%-43%) and 24% (95% CI, 10%-36%) lower at year 1 in the intensive versus standard arm, respectively.

LIMITATIONS

Exclusion of persons with diabetes, and few participants had advanced CKD.

CONCLUSIONS

Among participants with CKD in SPRINT, random assignment to the intensive SBP arm did not increase any levels of 8 urine biomarkers of tubule cell damage despite loss of eGFR. These findings support the hypothesis that eGFR declines in the intensive arm of SPRINT predominantly reflect hemodynamic changes rather than intrinsic damage to kidney tubule cells.

Clinical Features of 167 Inpatients with Autosomal Dominant Polycystic Kidney Disease at a Single Center in China

BACKGROUND The aim of this study was to describe the clinical characteristics of Chinese ADPKD inpatients and to identify the factors associated with disease severity. MATERIAL AND METHODS We included 167 hospitalized patients (inpatients) with ADPKD in this study. Multiple regression analyses were conducted to determine factors correlated with estimated glomerular filtration rate (eGFR). Patients were stratified into subgroups according to the presence of symptoms, in which clinical parameters were analyzed and compared. RESULTS The mean age of hospitalized ADPKD patients was 48.7 years old, lumbar and/or abdominal pain was seen in 40.12% of patients, following by nephrolithiasis (38.92%), hematuria (30.54%), and urinary tract infection (24.55%). Serum thrombocyte level and hemoglobin exhibited significant positive correlations with eGFR. Symptomatic patients accounted for 71.26% of the studied population. Patients with hypertension had increased risk of presence of symptoms (OR=2.794, 95%CI=1.341-5.822). Low thrombocyte and hemoglobin levels were observed in patients with hematuria. CONCLUSIONS Thrombocyte level was positively correlated with eGFR but was not associated with presence of PKD-related symptoms, suggesting thrombocyte level might be an independent serum biomarker for disease progression. Hypertension was associated with increased risk of symptom occurrence, indicating the relationship between hypertension and disease progression. This study reveals the clinical characteristics of inpatients with ADPKD in China and provides clinicians with useful insights into this intractable disease.

Standardizing total kidney volume measurements for clinical trials of autosomal dominant polycystic kidney disease

Background

The ability of unstandardized methods to track kidney growth in clinical trials for autosomal dominant polycystic kidney disease (ADPKD) has not been critically evaluated.

Methods

The Tolvaptan Efficacy and Safety Management of ADPKD and its Outcomes (TEMPO) 3:4 study involved baseline and annual magnetic resonance follow-up imaging yearly for 3 years. Total kidney volume (TKV) measurements were performed on these four time points in addition to the baseline imaging in TEMPO 4:4, initially by Perceptive Informatics (Waltham, MA, USA) using planimetry (original dataset) and for this study by the Mayo Translational PKD Center using semiautomated and complementary automated methods (sequential dataset). In the original dataset, the same reader was assigned to all scans of individual patients in TEMPO 3:4, but readers were reassigned in TEMPO 4:4. Two placebo-treated cohorts were included. In the first (n = 158), intervals between the end of TEMPO 3:4 and the start of TEMPO 4:4 scan visits ranged from 12 to 403 days; in the second (n = 95), the same scan (measured twice) visit was used for both.

Results

Growth rates in TEMPO 3:4 were similar in the original and sequential datasets (5.5 and 5.9%/year). Growth rates during the TEMPO 3:4 to TEMPO 4:4 interval were higher in the original (13.7%/year) but were not different in the sequential dataset (4.0%/year). Comparing volumes from the same images, TKVs showed a bias of 2.2% [95% confidence interval (CI) −5.2–9.7] in the original and −0.16% (95% CI −1.91–1.58) in the sequential dataset.

Conclusions

Despite using the same software, TKV and growth rate changes were present, likely due to reader differences in the transition from TEMPO 3:4 to TEMPO 4:4 in the original but not in the sequential dataset. Robust, standardized methods are essential in ADPKD trials to minimize errors in serial TKV measurements.