Tolvaptan in autosomal dominant polycystic kidney disease: three years' experience

Prospective Study on Individualized Dose Adjustment of Tolvaptan Based on Urinary Osmolality in Patients With ADPKD

Introduction

Tolvaptan has been shown to reduce renal volume and delay disease progression in autosomal-dominant polycystic kidney disease (ADPKD). However, no biomarkers are currently available to guide dose adjustment. We aimed to explore the possibility of individualized tolvaptan dose adjustments based on cut-off values for urinary osmolality (OsmU).

Methods

This prospective cohort study included patients with ADPKD, with rapid disease progression. Tolvaptan treatment was initiated at a dose of 45/15 mg and increased based on OsmU, with a limit set at 200 mOsm/kg. Primary renal events (25% decrease in estimated glomerular filtration rate [eGFR] during treatment), within-patient eGFR slope, and side effects were monitored during the 3-year follow-up.

Results

Forty patients participated in the study. OsmU remained below 200 mOsm/kg throughout the study period, and most patients required the minimum tolvaptan dose (mean dose, 64 [±10] mg), with a low discontinuation rate (5%). The mean annual decline in eGFR was -3.05 (±2.41) ml/min per 1.73 m2 during tolvaptan treatment, compared to the period preceding treatment, corresponding to a reduction in eGFR decline of more than 50%. Primary renal events occurred in 20% of patients (mean time to onset, 31 months; 95% confidence interval [CI] = 28-34).

Conclusion

Individualized tolvaptan dose adjustment based on OsmU in patients with ADPKD and rapid disease progression provided benefits in terms of reducing eGFR decline, compared with reference studies, and displayed lower dropout rates and fewer side effects. Further studies are required to confirm optimal strategies for the use of OsmU for tolvaptan dose adjustment in patients with ADPKD.

A child with TSC2/PKD1 contiguous gene deletion syndrome successfully treated with tolvaptan for rapidly enlarging renal cysts

Tolvaptan, a vasopressin receptor antagonist, has been shown to be effective in the treatment of renal cysts in ADPKD. However, tolvaptan is not indicated for pediatric patients, and reports of its use are rare, making its efficacy and adverse reactions unclear. Herein, we present the case of an 11-year-old girl who had vitiligo from birth. She was diagnosed with West syndrome at 6 months of age and tuberous sclerosis at 2 years of age. At the age of 6 years, an abdominal magnetic resonance imaging (MRI) revealed multiple bilateral renal cysts, and she was diagnosed with ADPKD. Abdominal MRI scans performed at 10 years and 11 years showed rapid renal cyst enlargement, and the renal prognosis was judged to be poor. The patient was treated with tolvaptan to delay cyst exacerbation. There were no apparent adverse events after the initiation of treatment, and the MRI performed 12 months after treatment initiation showed that renal cyst enlargement was suppressed. The results suggest that tolvaptan may be effective in pediatric patients with severe ADPKD who have rapidly enlarging renal cysts, although evaluation of renal cyst enlargement and side effects should be continued.

The safety and efficacy of tolvaptan in the treatment of patients with autosomal dominant polycystic kidney disease: A systematic review and meta-analysis

BACKGROUND

The irreversible progression of autosomal dominant polycystic kidney disease (ADPKD) to end-stage renal disease (ESRD) is delayed by tolvaptan. Therefore, we aim to systematically estimate and evaluate the efficacy and safety of tolvaptan in the treatment of ADPKD.

METHODS

Two reviewers independently searched all published randomized controlled trials studies in PubMed, EMBASE, Web of Science and Cochrane databases, extracted data, assessed bias risk and rated the quality of evidence. Data were analyzed by the RevMan software.

RESULTS

We identified 8 trials including 2135 patients. Both of the decline of estimated glomerular filtration rate (eGFR) [MD=1.89, 95% CI (0.74, 3.04), P=0.001] and total kidney volume (TKV) [MD=-3.32, 95% CI (-4.57, -2.07), P<0.001] were delayed in tolvaptan group compared with placebo group in ADPKD patients. The use of tolvaptan delayed TKV progression in the different-month subgroups [MD=-69.99, 95% CI (-91.05, -48.94), P<0.001]. Tolvaptan reduced renal pain [RR=0.66, 95% CI (0.54, 0.81), P<0.001] and hematuria events [RR=0.55, 95% CI (0.41, 0.74), P<0.001] in ADPKD patients. However, the prevalence of thirst [RR=2.75, 95% CI (2.34, 3.24), P<0.001] and nocturia events [RR=3.01, 95% CI (1.27, 7.11), P=0.01] were increased in tolvaptan group. There is no significant difference of hypertension events [RR=0.92, 95% CI (0.82, 1.03), P=0.13] in tolvaptan group compared placebo group.

CONCLUSIONS

This meta-analysis suggests that tolvaptan may improve clinical progression in patients with ADPKD without significantly increasing the risk of adverse reactions.

Utility of new image-derived biomarkers for autosomal dominant polycystic kidney disease prognosis using automated instance cyst segmentation

New image-derived biomarkers for patients affected by autosomal dominant polycystic kidney disease are needed to improve current clinical management. The measurement of total kidney volume (TKV) provides critical information for clinicians to drive care decisions. However, patients with similar TKV may present with very different phenotypes, often requiring subjective decisions based on other factors (e.g., appearance of healthy kidney parenchyma, a few cysts contributing significantly to overall TKV, etc.). In this study, we describe a new technique to individually segment cysts and quantify biometric parameters including cyst volume, cyst number, parenchyma volume, and cyst parenchyma surface area. Using data from the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) study the utility of these new parameters was explored, both quantitatively as well as visually. Total cyst number and cyst parenchyma surface area showed superior prediction of the slope of estimated glomerular filtration rate decline, kidney failure and chronic kidney disease stages 3A, 3B, and 4, compared to TKV. In addition, presentations such as a few large cysts contributing significantly to overall kidney volume were shown to be much better stratified in terms of outcome predictions. Thus, these new image biomarkers, which can be obtained automatically, will have great utility in future studies and clinical care for patients affected by autosomal dominant polycystic kidney disease.

Experimental Models of Polycystic Kidney Disease: Applications and Therapeutic Testing

Polycystic kidney diseases (PKDs) are genetic disorders characterized by the formation and expansion of numerous fluid-filled renal cysts, damaging normal parenchyma and often leading to kidney failure. Although PKDs comprise a broad range of different diseases, with substantial genetic and phenotypic heterogeneity, an association with primary cilia represents a common theme. Great strides have been made in the identification of causative genes, furthering our understanding of the genetic complexity and disease mechanisms, but only one therapy so far has shown success in clinical trials and advanced to US Food and Drug Administration approval. A key step in understanding disease pathogenesis and testing potential therapeutics is developing orthologous experimental models that accurately recapitulate the human phenotype. This has been particularly important for PKDs because cellular models have been of limited value; however, the advent of organoid usage has expanded capabilities in this area but does not negate the need for whole-organism models where renal function can be assessed. Animal model generation is further complicated in the most common disease type, autosomal dominant PKD, by homozygous lethality and a very limited cystic phenotype in heterozygotes while for autosomal recessive PKD, mouse models have a delayed and modest kidney disease, in contrast to humans. However, for autosomal dominant PKD, the use of conditional/inducible and dosage models have resulted in some of the best disease models in nephrology. These have been used to help understand pathogenesis, to facilitate genetic interaction studies, and to perform preclinical testing. Whereas for autosomal recessive PKD, using alternative species and digenic models has partially overcome these deficiencies. Here, we review the experimental models that are currently available and most valuable for therapeutic testing in PKD, their applications, success in preclinical trials, advantages and limitations, and where further improvements are needed.

Efficacy and safety of tolvaptan in cirrhotic patients: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

Tolvaptan has been approved for the management of cirrhosis-related complications according to the Japanese and Chinese practice guidelines, but not the European or American practice guidelines in view of FDA warning about its hepatotoxicity. This study aimed to systematically evaluate its efficacy and safety in cirrhosis.

METHODS

The PubMed, EMBASE, and Cochrane library databases were searched to identify randomized controlled trials (RCTs) evaluating the efficacy and/or safety of tolvaptan in cirrhosis. Risk ratios (RRs) and weight mean differences (WMDs) were calculated. The incidence of common adverse events (AEs) was pooled.

RESULTS

Eight RCTs were included. Tolvaptan was significantly associated with higher rates of improvement of ascites (RR = 1.49, P < 0.001) and hyponatremia (RR = 1.80, P = 0.005) and incidence of any AEs (RR = 1.18, P = 0.003), but not serious AEs (RR = 0.86, P = 0.410). Tolvaptan was significantly associated with reductions in body weight (WMD = -1.30 kg, P < 0.001) and abdominal circumference (WMD = -1.71 cm, P < 0.001), and increases in daily urine volume (WMD = 1299.84 mL, P < 0.001) and serum sodium concentration (WMD = 2.57 mmol/L, P < 0.001). The pooled incidences of dry mouth, thirst, constipation, and pollakiuria were 16%, 24%, 6%, and 17%, respectively.

CONCLUSION

Short-term use of tolvaptan may be considered in cirrhotic patients with ascites who have inadequate response to conventional diuretics and those with hyponatremia.

Effects of tolvaptan discontinuation in patients with autosomal dominant polycystic kidney disease: a post hoc pooled analysis

BACKGROUND

Tolvaptan slows kidney function decline in patients with autosomal dominant polycystic kidney disease (ADPKD) who are at risk of rapid progression. Given that treatment requires commitment to long-term use, we evaluated the effects of tolvaptan discontinuation on the trajectory of ADPKD progression.

METHODS

This was a post hoc analysis of pooled data from two clinical trials of tolvaptan (TEMPO 2:4 [NCT00413777] and TEMPO 3:4 [NCT00428948]), an extension trial (TEMPO 4:4 [NCT01214421]), and an observational study (OVERTURE [NCT01430494]) that enrolled patients from the other trials. Individual subject data were linked longitudinally across trials to construct analysis cohorts of subjects with a tolvaptan treatment duration > 180 days followed by an off-treatment observation period of > 180 days. For inclusion in Cohort 1, subjects were required have ≥ 2 outcome assessments during the tolvaptan treatment period and ≥ 2 assessments during the follow-up period. For Cohort 2, subjects were required to have ≥ 1 assessment during the tolvaptan treatment period and ≥ 1 assessment during the follow-up period. Outcomes were rates of change in estimated glomerular filtration rate (eGFR) and total kidney volume (TKV). Piecewise-mixed models compared changes in eGFR or TKV in the on-treatment and post-treatment periods.

RESULTS

In the Cohort 1 eGFR population (n = 20), the annual rate of eGFR change (in mL/min/1.73 m2) was -3.18 on treatment and -4.33 post-treatment, a difference that was not significant (P = 0.16), whereas in Cohort 2 (n = 82), the difference between on treatment (-1.89) and post-treatment (-4.94) was significant (P < 0.001). In the Cohort 1 TKV population (n = 11), TKV increased annually by 5.18% on treatment and 11.69% post-treatment (P = 0.06). In Cohort 2 (n = 88), the annual TKV growth rates were 5.15% on treatment and 8.16% post-treatment (P = 0.001).

CONCLUSIONS

Although limited by small sample sizes, these analyses showed directionally consistent acceleration in measures of ADPKD progression following the discontinuation of tolvaptan.

Tolvaptan and Kidney Function Decline in Older Individuals With Autosomal Dominant Polycystic Kidney Disease: A Pooled Analysis of Randomized Clinical Trials and Observational Studies

Rationale & Objective

Tolvaptan is indicated for treatment of patients with autosomal dominant polycystic kidney disease (ADPKD) at risk of rapid progression. Participants aged 56-65 years constituted a small proportion of the Replicating Evidence of Preserved Renal Function: an Investigation of Tolvaptan Safety and Efficacy in ADPKD (REPRISE) trial population. We assessed effects of tolvaptan on estimated glomerular filtration rate (eGFR) decline in participants aged >55 years.

Study Design

This was a pooled data analysis from 8 studies of tolvaptan or non-tolvaptan standard of care (SOC).

Setting & Participants

Participants aged >55 years with ADPKD were included. Data on participants in >1 study were linked longitudinally for maximum follow-up duration, with matching for age, sex, eGFR, and chronic kidney disease (CKD) stage to minimize confounding.

Interventions

Tolvaptan or non-tolvaptan SOC.

Outcomes

Treatment effects on annualized eGFR decline were compared using mixed models with fixed effects for treatment, time, treatment-by-time interaction, and baseline eGFR.

Results

In the pooled studies, 230 tolvaptan-treated and 907 SOC participants were aged >55 years at baseline. Ninety-five participant pairs from each treatment group were matched, all in CKD G3 or G4, ranging from 56.0 to 65.0 years (tolvaptan) or from 55.1 to 67.0 years (SOC). The eGFR annual decline rate was significantly reduced by 1.66 mL/min/1.73 m² (95% CI, 0.43-2.90; P = 0.009) in the tolvaptan group compared with SOC (-2.33 versus -3.99 mL/min/1.73 m²) over 3 years.

Limitations

Limitations include potential bias because of study population differences (bias risk was reduced through matching and multiple regression adjustment); vascular disease history data was not uniformly collected, and therefore not adjusted; and natural history of ADPKD precludes evaluating certain clinical endpoints within the study time frame.

Conclusions

In individuals aged 56-65 years with CKD G3 or G4, compared to a SOC group with mean GFR rate of decline ≥3 mL/min/1.73 m²/year, tolvaptan was associated with efficacy similar to that observed in the overall indication.

Funding

Otsuka Pharmaceutical Development & Commercialization, Inc (Rockville, MD).

Trial Registration

TEMPO 2:4 (NCT00413777); phase 1 tolvaptan trial (no NCT number; trial number 156-06-260); phase 2 tolvaptan trial (NCT01336972); TEMPO 4:4 (NCT01214421); REPRISE (NCT02160145); long-term tolvaptan safety extension trial (NCT02251275); OVERTURE (NCT01430494); HALT Progression of Polycystic Kidney Disease (HALT-PKD) study B (NCT01885559).

Efficacy and safety of tolvaptan versus placebo in the treatment of patients with autosomal dominant polycystic kidney disease: a meta-analysis

OBJECTIVE

The objective of this meta-analysis was to compare the efficacy and drug safety of tolvaptan with placebo for autosomal dominant polycystic kidney disease (ADPKD).

METHODS

The PubMed, Embase, and Cochrane Library databases were searched from inception to September 10, 2021. Eligible studies comparing tolvaptan and placebo in the treatment of patients with ADPKD were included. Data were analysed using Review Manager Version 5.3.

RESULTS

Thirteen studies involving 3575 patients were included in the meta-analysis. Compared with placebo, tolvaptan had a better effect on delaying eGFR decline (MD 1.27, 95% CI 1.24-1.29, P < 0.01) and TKV increase (MD - 3.01, 95% CI - 3.55 to - 2.47, P < 0.01) in ADPKD treatment. Additionally, tolvaptan reduced the incidence of complications such as renal pain (OR 0.71, 95% CI 0.58-0.87, P < 0.01), urinary tract infection (OR 0.69, 95% CI 0.54-0.89, P < 0.01), haematuria (OR 0.68, 95% CI 0.51-0.89, P < 0.01), and hypertension (OR 0.66, 95% CI 0.52-0.82, P < 0.01). However, tolvaptan was associated with a higher incidence rate of adverse events such as thirst (OR 8.48 95% CI 4.53-15.87, P < 0.01), polyuria (OR 4.71, 95% CI 2.17-10.24, P < 0.01), and hepatic injury (OR 4.56, 95% CI 2.51-8.29, P < 0.01).

CONCLUSION

Tolvaptan can delay eGFR decline and TKV increase and reduce complications such as renal pain, urinary tract infection, haematuria, and hypertension in the treatment of ADPKD. However, tolvaptan increases the adverse effects of thirst, polyuria and hepatic injury.

Real clinical experience after one year of treatment with tolvaptan in patients with autosomal dominant polycystic kidney disease

Background

Tolvaptan (TV) is the first vasopressin-receptor antagonist approved for the treatment of autosomal dominant polycystic kidney disease (ADPKD). No publications report TV experience in real clinical practice during the first year of treatment.

Methods

A prospective study of an initial cohort of 220 rapidly progressing patients treated with TV for 12 months. The tolerability of TV, the evolution of the estimated glomerular filtration rate (eGFR), analytical parameters, and blood pressure were analyzed.

Results

A total of 163 patients (78.2%) received TV for 1 year. The main causes of treatment withdrawal were the aquaretic effects (11%), eGFR deterioration (5%), and hepatic toxicity (2.3%). eGFR decreased significantly after 1 month of treatment without further changes. The decrease in eGFR in the first month was higher in patients with an initially higher eGFR. The eGFR drop during the first year of treatment with TV was lower than that reported by patients in the 2 years prior to TV treatment (–1.7 ± 7.6 vs. –4.4 ± 4.8 mL/min, p = 0.003). Serum sodium and uric acid concentrations increased, and morning urinary osmolality decreased in the first month, with no further changes. Blood pressure decreased significantly without changes in antihypertensive medication.

Conclusion

TV treatment is well tolerated by most patients. Liver toxicity is very rare and self-limited. TV reduces eGFR in the first month without showing further changes during the first year of treatment. Patients with a higher starting eGFR will suffer a greater initial drop, with a longer recovery. We suggest using the eGFR observed after a month of treatment as the reference for future comparisons and calculating the rate of eGFR decline in patients undergoing TV treatment.

A Systematic Review of Reported Outcomes in ADPKD Studies

Introduction

Methods

Results

Conclusion

A scalable organoid model of human autosomal dominant polycystic kidney disease for disease mechanism and drug discovery

Human pluripotent stem-cell-derived organoids are models for human development and disease. We report a modified human kidney organoid system that generates thousands of similar organoids, each consisting of 1-2 nephron-like structures. Single-cell transcriptomic profiling and immunofluorescence validation highlighted patterned nephron-like structures utilizing similar pathways, with distinct morphogenesis, to human nephrogenesis. To examine this platform for therapeutic screening, the polycystic kidney disease genes PKD1 and PKD2 were inactivated by gene editing. PKD1 and PKD2 mutant models exhibited efficient and reproducible cyst formation. Cystic outgrowths could be propagated for months to centimeter-sized cysts. To shed new light on cystogenesis, 247 protein kinase inhibitors (PKIs) were screened in a live imaging assay identifying compounds blocking cyst formation but not overall organoid growth. Scaling and further development of the organoid platform will enable a broader capability for kidney disease modeling and high-throughput drug screens.

A Shared Nephroprotective Mechanism for Renin-Angiotensin-System Inhibitors, Sodium-Glucose Co-Transporter 2 Inhibitors, and Vasopressin Receptor Antagonists: Immunology Meets Hemodynamics

A major paradigm in nephrology states that the loss of filtration function over a long time is driven by a persistent hyperfiltration state of surviving nephrons. This hyperfiltration may derive from circulating immunological factors. However, some clue about the hemodynamic effects of these factors derives from the effects of so-called nephroprotective drugs. Thirty years after the introduction of Renin-Angiotensin-system inhibitors (RASi) into clinical practice, two new families of nephroprotective drugs have been identified: the sodium-glucose cotransporter 2 inhibitors (SGLT2i) and the vasopressin receptor antagonists (VRA). Even though the molecular targets of the three-drug classes are very different, they share the reduction in the glomerular filtration rate (GFR) at the beginning of the therapy, which is usually considered an adverse effect. Therefore, we hypothesize that acute GFR decline is a prerequisite to obtaining nephroprotection with all these drugs. In this study, we reanalyze evidence that RASi, SGLT2i, and VRA reduce the eGFR at the onset of therapy. Afterward, we evaluate whether the extent of eGFR reduction correlates with their long-term efficacy. The results suggest that the extent of initial eGFR decline predicts the nephroprotective efficacy in the long run. Therefore, we propose that RASi, SGLT2i, and VRA delay kidney disease progression by controlling maladaptive glomerular hyperfiltration resulting from circulating immunological factors. Further studies are needed to verify their combined effects.

Innate Bacteriostatic Mechanisms Defend the Urinary Tract

Urinary tract infection (UTI) is the most common type of urogenital disease. UTI affects the urethra, bladder, ureter, and kidney. A total of 13.3% of women, 2.3% of men, and 3.4% of children in the United States will require treatment for UTI. Traditionally, bladder (cystitis) and kidney (pyelonephritis) infections are considered independently. However, both infections induce host defenses that are either shared or coordinated across the urinary tract. Here, we review the chemical and biophysical mechanisms of bacteriostasis, which limit the duration and severity of the illness. Urinary bacteria attempt to overcome each of these defenses, complicating description of the natural history of UTI.

Pooled Data Analysis of the Long-Term Treatment Effects of Tolvaptan in ADPKD

Introduction

Methods

Results

Conclusion

VX-809 mitigates disease in a mouse model of autosomal dominant polycystic kidney disease bearing the R3277C human mutation

Autosomal dominant polycystic kidney disease (ADPKD) is associated with the formation of renal cysts. We have devised a therapeutic approach, based on reversing the cyst phenotype from secretion to absorption by using VX-809, a modulator of the cystic fibrosis transmembrane regulator trafficking and processing. Our goal is to test VX-809 in RC/RC mice bearing the R3277C human mutation to demonstrate its therapeutic potential. We found that by 5 months of age, RC/RC mice had large cysts and impaired renal function, but when treated with VX-809 between the ages of 3 and 5 months, or 6 and 8 months, the cyst area was reduced in both groups, suggesting that VX-809 had shrunk previously existing cysts. After 2 months of treatment, the cyst size was lower than that of untreated animals of the same age. Our co-localization studies confirmed that cystic fibrosis transmembrane conductance regulator (CFTR) is found predominately at the apical membrane in the untreated animals of each age group, consistent with its role in Cl^- secretion; after VX-809 treatment, the basolateral membrane co-localization of CFTR increased ~4-fold, accompanied by a decrease of ~2-3-fold in its apical co-localization, indicating that VX-809 alters the phenotype to favor fluid absorption. Sodium/hydrogen exchanger and epithelial sodium channel, found in normal kidneys at the apical membrane, were almost absent from the cysts. VX-809 restored both levels toward normal. HSP27 is highly expressed in RC/RC mice and lowered toward normal by VX-809. Our demonstration of cyst reduction, improved renal function, and generation of an absorptive phenotype all strongly support the therapeutic potential of VX-809 as a treatment for ADPKD. We show here in an animal model of slowly progressing cyst formation typical of human ADPKD that VX-809 reduces the growth of already established cysts. The magnitude of the effect in the RC/RC mouse model when compared to previous experiments using the same mouse model to evaluate tolvaptan indicates that CFTR modulators warrant further development as a treatment for ADPKD.

Retarding Progression of Chronic Kidney Disease in Autosomal Dominant Polycystic Kidney Disease with Metformin and Other Therapies: An Update of New Insights

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent single-gene disorder leading to renal failure. Current therapies are aimed to treat renal and extrarenal complications of ADPKD, but improved knowledge of the pathophysiological mechanisms leading to the generation and growth of cysts has permitted the identification of new drug candidates for clinical trials. Among these, in this review, we will examine above all the role of metformin, hypothesized to be able to activate the AMP-activated protein kinase (AMPK) pathway and potentially modulate some mechanisms implicated in the onset and the growth of the cysts.

10-Year Evaluation of Adherence and Satisfaction with Information about Tolvaptan in ADPKD: A Single-Center Pilot Study

PURPOSE

Tolvaptan is the only approved drug for the treatment of autosomal dominant polycystic kidney disease (ADPKD) and causes significant polyuria with secondary polydipsia. Up to now, there is no study that examines tolvaptan adherence and satisfaction with information received about tolvaptan in ADPKD patients 10 years after starting tolvaptan therapy.

PATIENTS AND METHODS

This pilot study includes 12 ADPKD patients that were formerly enrolled in the tolvaptan registration trials and have continued to use tolvaptan thereafter. Data were collected once via questionnaires on patients' self-reported adherence (MARS-D: Medication Adherence Report Scale - German version) and satisfaction with the information received about tolvaptan (SIMS-D: Satisfaction with Information about Medicines Scale - German version) at the time of the present study. In addition, serum creatinine levels and clinical data were evaluated.

RESULTS

The MARS-D demonstrated strong adherence to tolvaptan (range of possible score: 5-25; median: 23.5; range of individual results: 5). The SIMS-D showed a high level of satisfaction with the information received about the action and usage of tolvaptan (SIMS-D AU subscale; range of possible score: 0-9; median: 9, range of individual results: 1), but also revealed dissatisfaction regarding the information received about potential problems of tolvaptan in 42% of the participants (SIMS-D PP subscale; range of possible score: 0-8; median: 8, range of individual results: 6). During treatment with tolvaptan, the eGFR decreased from 78.8 ± 15.9 mL/min/1.73 m2 to 48.3 ± 19.4 mL/min/1.73 m2 (P < 0.0001).

CONCLUSION

Although patients reported strong adherence to tolvaptan, there was still dissatisfaction with the information received about potential problems with tolvaptan. Therefore, our data suggest conduction of at least one patient survey on adherence and satisfaction with the information received about tolvaptan during any tolvaptan treatment to improve patient education regarding the use of tolvaptan in slowing down of ADPKD.

Effectiveness of Tolvaptan in the Treatment for Patients with Autosomal Dominant Polycystic Kidney Disease: A Meta-analysis

AIMS AND OBJECTIVE

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a common chronic kidney disease that leads to End-Stage Renal Disease (ESRD). The key target of this therapy is to prevent the progression of kidney failure. Tolvaptan could slow kidney cyst growth and are proven highly effective. The aims of this analysis are to perform a systematic review, estimate and evaluate the efficacy and safety of tolvaptan in ADPKD patients.

MATERIALS AND METHODS

Randomized controlled trials of tolvaptan in ADPKD were identified in PubMed, Ovid, Web of Science and the Cochrane Library electronic database. The changes observed in kidney function, treatment efficiency and the incidence of adverse events between the tolvaptan and placebo groups were compared. Data were analyzed by the RevMan software.

RESULTS

Eight trials, including 7 double-blinded randomised controlled trials and 1 quasi RCT involving 1,536 patients were extracted. Significant differences in the annual rate of change in the total kidney volume TKV at any stages of CKD (MD = -3.32, 95%CI =-4.57,-2.07, I2 =70%) and the glomerular filtration rate (MD = 1.4, 95%CI = 0.83,1.97, I2 =0%) were observed between the tolvaptan group and the placebo group. Subgroup analysis of patients in different CKD stages also showed the same conclusion. There was an increase in the urine osmolality, and 24-hour urine volume in patients receiving tolvaptan. Tolvaptan reduced the rate of serious hypertension and kidney pain events in ADPKD patients. At higher doses, it increased the rate of adverse events (liver injuries, thirst, pollakiuria, and nocturia). There was no significant risk of bias in the included studies.

CONCLUSION

Tolvaptan has a beneficial effect on ADPKD, but is associated with an increase in adverse events at high doses when compared with the placebo. Further RCTs on tolvaptan may be required to support this conclusion.

Automated total kidney volume measurements in pre-clinical magnetic resonance imaging for resourcing imaging data, annotations, and source code

The objective of this study was to validate a fully automated total kidney volume measurement method for pre-clinical rodent trials that is fast, accurate, reproducible, and to provide these resources to the research community. Rodent studies that involve imaging are crucial for monitoring treatment efficacy in diseases such as polycystic kidney disease. Previous studies utilize manual or semi-automated segmentations, which are time consuming and potentially biased. To develop our automated system, a total of 150 axial magnetic resonance images (MRI) from a variety of mouse models were manually segmented and used to train/validate an automated algorithm. To test the longitudinal application of the model, four mutant and four wild-type mice were imaged sequentially over three to twelve weeks via MRI. Segmentations of the kidneys (excluding the renal pelvis) were generated by the automated method and two different readers, with one reader repeating the measurements. Similarity metrics and longitudinal analysis were calculated to assess the performance of the automated compared to the manual methods. The automated approach required no user input, besides a final visual quality control step. Similarity metrics of the automated method versus the manual segmentations were on par with inter- and intra-reader comparisons. Thus, our fully automated approach described here can be safely used in longitudinal, pre-clinical trials that involve the segmentation of rodent kidneys in T2-weighted MRIs.

Modulation of polycystic kidney disease by G-protein coupled receptors and cyclic AMP signaling

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a systemic disorder associated with polycystic liver disease (PLD) and other extrarenal manifestations, the most common monogenic cause of end-stage kidney disease, and a major burden for public health. Many studies have shown that alterations in G-protein and cAMP signaling play a central role in its pathogenesis. As for many other diseases (35% of all approved drugs target G-protein coupled receptors (GPCRs) or proteins functioning upstream or downstream from GPCRs), treatments targeting GPCR have shown effectiveness in slowing the rate of progression of ADPKD. Tolvaptan, a vasopressin V2 receptor antagonist is the first drug approved by regulatory agencies to treat rapidly progressive ADPKD. Long-acting somatostatin analogs have also been effective in slowing the rates of growth of polycystic kidneys and liver. Although no treatment has so far been able to prevent the development or stop the progression of the disease, these encouraging advances point to G-protein and cAMP signaling as a promising avenue of investigation that may lead to more effective and safe treatments. This will require a better understanding of the relevant GPCRs, G-proteins, cAMP effectors, and of the enzymes and A-kinase anchoring proteins controlling the compartmentalization of cAMP signaling. The purpose of this review is to provide an overview of general GPCR signaling; the function of polycystin-1 (PC1) as a putative atypical adhesion GPCR (aGPCR); the roles of PC1, polycystin-2 (PC2) and the PC1-PC2 complex in the regulation of calcium and cAMP signaling; the cross-talk of calcium and cAMP signaling in PKD; and GPCRs, adenylyl cyclases, cyclic nucleotide phosphodiesterases, and protein kinase A as therapeutic targets in ADPKD.

Sodium and urea excretion as determinants of urine output in autosomal dominant polycystic kidney disease patients on V2 receptor antagonists: impact of dietary intervention

PURPOSE

Tolvaptan, a vasopressin V2 receptor antagonist, slows the decline in renal function in autosomal dominant polycystic kidney disease (ADPKD). However, it increases urine output such that patient adherence could be compromised. In a cohort of patients with ADPKD on tolvaptan, we aimed to identify the contribution of sodium and urea excretion rate to daily urine output, and to evaluate the effectiveness of dietary counseling on sodium and urea excretion rates.

METHODS

Retrospective analysis of 30 ADPKD patients who underwent a single session of personalized dietary counseling to reduce sodium and protein intake before initiation of tolvaptan. Creatinine and 24-h urine were obtained regularly on treatment. Generalized estimation equations were used.

RESULTS

Mean age and median eGFR were 44 ± 11 years and 52 (43-74) ml/min/1.73 m². Tolvaptan increased diuresis from 2.5 to 5.2 l/day. After adjusting for the dose of tolvaptan, an increase in sodium and urea excretion rate by 50 mmol/day was associated with an estimated additional urine volume of 0.6 l/day (95% CI 0.4-0.8 l/day; P < 0.001) and 0.25 l/day (95% CI 0.11-0.39 l/day; P < 0.001), respectively. Dietary counseling resulted in a transient reduction of sodium excretion by 19 mmol/day during the first 4 months (P = 0.016) but resulted in a more sustained reduction in urea excretion by 69 mmol/day (P = 0.008).

CONCLUSION

Both sodium and urea excretion rates contribute significantly to daily urine volume in patients treated with tolvaptan, and a single session of dietary counseling was transiently effective in reducing sodium intake but achieved a more sustained reduction in protein intake. Dietary counseling should be considered in the management of ADPKD patients treated by tolvaptan.

Con: Tolvaptan for autosomal dominant polycystic kidney disease-do we know all the answers?

According to recent literature, tolvaptan ameliorates the natural decline of renal function in autosomal dominant polycystic kidney disease. Tolvaptan is an orally available vasopressin V2 receptor antagonist. We describe herein the remaining questions and problems: it is unclear from the published work what influence tolvaptan has on total kidney volume. The consequences of hepatotoxicity for the subsequent dosing of tolvaptan have not been reported. A vasopressin V2 antagonist will cause polyuria and polydipsia and tolvaptan may influence quality of life (QOL), however, there are no QOL data. The cost-effectiveness of tolvaptan is borderline. It is unknown at which stage of renal failure tolvaptan therapy may have to be stopped. There are no established criteria to determine the ineffectiveness of tolvaptan. It is presently undecided whether a steady high water intake is able to imitate the renal effects of tolvaptan. Finally, the cause of worsening glomerular filtration rate after the start of tolvaptan is unknown.

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.

Sensory primary cilium is a responsive cAMP microdomain in renal epithelia

Primary cilia are hair-like cellular extensions that sense microenvironmental signals surrounding cells. The role of adenylyl cyclases in ciliary function has been of interest because the product of adenylyl cyclase activity, cAMP, is relevant to cilia-related diseases. In the present study, we show that vasopressin receptor type-2 (V2R) is localized to cilia in kidney epithelial cells. Pharmacologic inhibition of V2R with tolvaptan increases ciliary length and mechanosensory function. Genetic knockdown of V2R, however, does not have any effect on ciliary length, although the effect of tolvaptan on ciliary length is dampened. Our study reveals that tolvaptan may have a cilia-specific effect independent of V2R or verapamil-sensitive calcium channels. Live-imaging of single cilia shows that V2R activation increases cilioplasmic and cytoplasmic cAMP levels, whereas tolvaptan mediates cAMP changes only in a cilia-specific manner. Furthermore, fluid-shear stress decreases cilioplasmic, but not cytoplasmic cAMP levels. Our data indicate that cilioplasmic and cytoplasmic cAMP levels are differentially modulated. We propose that the cilium is a critical sensor acting as a responsive cAMP microcompartment during physiologically relevant stimuli.

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.

A Practical Guide for Treatment of Rapidly Progressive ADPKD with Tolvaptan

In the past, the treatment of autosomal dominant polycystic kidney disease (ADPKD) has been limited to the management of its symptoms and complications. Recently, the US Food and Drug Administration (FDA) approved tolvaptan as the first drug treatment to slow kidney function decline in adults at risk of rapidly progressing ADPKD. Full prescribing information approved by the FDA provides helpful guidelines but does not address practical questions that are being raised by nephrologists, internists, and general practitioners taking care of patients with ADPKD, and by the patients themselves. In this review, we provide practical guidance and discuss steps that require consideration before and after prescribing tolvaptan to patients with ADPKD to ensure that this treatment is implemented safely and effectively. These steps include confirmation of diagnosis; identification of rapidly progressive disease; implementation of basic renal protective measures; counseling of patients on potential benefits and harms; exclusions to use; education of patients on aquaresis and its expected consequences; initiation, titration, and optimization of tolvaptan treatment; prevention of aquaresis-related complications; evaluation and management of liver enzyme elevations; and monitoring of treatment efficacy. Our recommendations are made on the basis of published evidence and our collective experiences during the randomized, clinical trials and open-label extension studies of tolvaptan in ADPKD.

[Hyponatremia in Liver Cirrhosis]

Hyponatremia is a commonly observed complication that is related to hypoalbuminemia and portal hypertension in patients with advanced liver cirrhosis. Hyponatremia in patients with liver cirrhosis is mostly dilutional hyponatremia and is defined when the serum sodium concentration is below 130 meq/L. The risk of complications increases significantly in cirrhotic patients with hyponatremia, which includes spontaneous bacterial peritonitis, hepatorenal syndrome, and hepatic encephalopathy. In addition, hyponatremia is associated with increased morbidity and mortality in patients with cirrhosis, and is an important prognostic factor before and after liver transplantation. The conventional therapies of hyponatremia are albumin infusion, fluid restriction and loop diuretics, but these are frequently ineffective. This review investigates the pathophysiology and various therapeutic modalities, including selective vasopressin receptor antagonists, for the management of hyponatremia in patients with liver cirrhosis.

Long-Term Administration of Tolvaptan in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND AND OBJECTIVES

In the 3-year Tolvaptan Efficacy and Safety in Management of ADPKD and Its Outcomes (TEMPO) 3:4 and 1-year Replicating Evidence of Preserved Renal Function: an Investigation of Tolvaptan Safety and Efficacy in ADPKD (REPRISE) trials, tolvaptan slowed the decline of eGFR in patients with autosomal dominant polycystic kidney disease at early and later stages of CKD, respectively. Our objective was to ascertain whether the reduction associated with the administration of tolvaptan is sustained, cumulative, and likely to delay the need for kidney replacement therapy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

One hundred and twenty-eight patients with autosomal dominant polycystic kidney disease participated in clinical trials of tolvaptan at the Mayo Clinic. All had the opportunity to enroll into open-label extension studies. Twenty participated in short-term studies or received placebo only. The remaining 108 were analyzed for safety. Ninety seven patients treated with tolvaptan for ≥1 year (mean±SD, 4.6±2.8; range, 1.1-11.2) were analyzed for efficacy using three approaches: (1) comparison of eGFR slopes and outcome (33% reduction from baseline eGFR) to controls matched by sex, age, and baseline eGFR; (2) Stability of eGFR slopes with duration of follow-up; and (3) comparison of observed and predicted eGFRs at last follow-up.

RESULTS

Patients treated with tolvaptan had lower eGFR slopes from baseline (mean±SD, -2.20±2.18 ml/min per 1.73 m2 per year) and from month 1 (mean±SD, -1.97±2.44 ml/min per 1.73 m2 per year) compared with controls (mean±SD, -3.50±2.09 ml/min per 1.73 m2 per year; P<0.001), and lower risk of a 33% reduction in eGFR (risk ratio, 0.63; 95% confidence interval, 0.38 to 0.98 from baseline; risk ratio, 0.53; 95% confidence interval, 0.31 to 0.85 from month 1). Annualized eGFR slopes of patients treated with tolvaptan did not change during follow-up and differences between observed and predicted eGFRs at last follow-up increased with duration of treatment.

CONCLUSIONS

Follow-up for up to 11.2 years (average 4.6 years) showed a sustained reduction in the annual rate of eGFR decline in patients treated with tolvaptan compared with controls and an increasing separation of eGFR values over time between the two groups.

Prognostic enrichment design in clinical trials for autosomal dominant polycystic kidney disease: the HALT-PKD clinical trial

Background

Patients with mild autosomal dominant polycystic kidney disease (ADPKD) are less likely to be informative in randomized clinical trials (RCTs). We previously developed an imaging classification of ADPKD (typical diffuse cyst distribution Class 1A-E and atypical cyst distribution Class 2) for prognostic enrichment design in RCTs. We investigated whether using this classification would have increased the power to detect a beneficial treatment effect of rigorous blood pressure (BP) control on HALT-PKD participants with early disease (Study A).

Methods

Post hoc analysis of the early disease HALT-PKD study, an RCT that studied the effect of rigorous versus standard BP control on rates of total kidney volume (TKV) increase and estimated glomerular filtration rate (eGFR) decline in ADPKD patients with eGFR >60 mL/min/1.73 m2.

Results

Five hundred and fifty-one patients were classified by two observers (98.2% agreement) into Class 1A (6.2%), 1B (20.3%), 1C (34.1%), 1D (22.1%), 1E (11.8%) and 2 (5.4%). The TKV increase and eGFR decline became steeper from Class 1A through 1E. Rigorous BP control had been shown to be associated with slower TKV increase, without a significant overall effect on the rate of eGFR decline (faster in the first 4 months and marginally slower thereafter). Merging Classes 1A and 2 (lowest severity), 1B and 1C (intermediate severity) and 1D and 1E (highest severity) detected stronger beneficial effects on TKV increase and eGFR decline in Class 1D and E with a smaller number of patients.

Conclusions

Strategies for prognostic enrichment, such as image classification, should be used in the design of RCTs for ADPKD to increase their power and reduce their cost.

Expanding the role of vasopressin antagonism in polycystic kidney diseases: From adults to children?

Polycystic kidney disease (PKD) encompasses a group of genetic disorders that are common causes of renal failure. The two classic forms of PKD are autosomal recessive polycystic kidney disease (ARPKD) and autosomal dominant polycystic kidney disease (ADPKD). Despite their clinical differences, ARPKD and ADPKD share many similarities. Altered intracellular Ca²⁺ and increased cyclic adenosine monophosphate (cAMP) concentrations have repetitively been described as central anomalies that may alter signaling pathways leading to cyst formation. The vasopressin V2 receptor (V2R) antagonist tolvaptan lowers cAMP in cystic tissues and slows renal cystic progression and kidney function decline when given over 3 years in adult ADPKD patients. Tolvaptan is currently approved for the treatment of rapidly progressive disease in adult ADPKD patients. On the occasion of the recent initiation of a clinical trial with tolvaptan in pediatric ADPKD patients, we aim to describe the most important aspects in the literature regarding the AVP-cAMP axis and the clinical use of tolvaptan in PKD.

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.

Actualización en enfermedad renal poliquística

Introducción. La enfermedad renal poliquística (PKD, por su sigla en inglés) es una enfermedad genética frecuente en la que se desarrollan de forma progresiva lesiones quísticas que reemplazan el parénquima renal. Es una causa de insuficiencia renal terminal y una indicación común para diálisis y trasplante renal. Existen dos presentaciones de esta enfermedad que se distinguen por sus patrones de herencia: la enfermedad renal poliquística dominante (ADPKD, por su sigla en inglés) y la enfermedad renal poliquística recesiva (ARPKD, por su sigla en inglés).Objetivo. Resumir los aspectos más relevantes de la enfermedad renal: epidemiología, fisiopatología, diagnóstico, manifestaciones clínicas, tratamiento y pronóstico.Materiales y métodos. Revisión sistemática de la literatura en las bases de datos PubMed, Lilacs, UptoDate y Medline con los siguientes términos: enfermedades renales poliquísticas, riñón poliquístico autosómico dominante y riñón poliquístico autosómico recesivo.Resultados. Se encontraron 271 artículos y se escogieron 64 con base en su importancia.Conclusiones. Todo paciente con enfermedad renal poliquística en insuficiencia renal grado V debe ser estudiado para un trasplante renal; en la gran mayoría de los casos no se encontrará contraindicación para realizarlo.

The Myth of Water and Salt: From Aquaretics to Tenapanor

The impact of water intake has been studied in several renal diseases. For example, increasing water intake is useful to prevent primary and secondary nephrolithiasis. In autosomal dominant polycystic kidney disease, arginine vasopressin (AVP) is involved in the progression of the disease, and water intake could play a therapeutic role by inhibiting the synthesis of AVP, but its efficacy is still controversial. Conversely, the use of aquaretics, which are antagonists of AVP V2 receptors, results in the reduction of the increase rate of total kidney volume with a slower decline of glomerular filtration rate. In chronic kidney disease, AVP contributes to glomerular hyperfiltration, arterial hypertension, and synthesis of renin, resulting in renal sclerosis. Increased water intake could reduce AVP activation determining a potential protective effect on the kidney, but its efficacy has not yet been clearly demonstrated. On the other side, sodium and potassium play an important role in the control of arterial blood pressure and are involved in the development and progression of chronic kidney disease. Reduction of sodium intake and increase of potassium intake determine a decrease of arterial blood pressure with a beneficial effect on the kidney; however, adherence to sodium restriction is very poor. Regarding this, sodium-hydrogen exchanger isoform 3 inhibitors may reduce sodium absorption in the gut. The most recent sodium-hydrogen exchanger isoform 3 inhibitor, known as tenapanor, reduces extracellular fluid volume, left ventricular hypertrophy, albuminuria, and blood pressure in experimental studies and increases fecal loss of sodium in humans.

The vasopressin system: new insights for patients with kidney diseases: Epidemiological evidence and therapeutic perspectives

People with chronic kidney disease (CKD) are at risk of severe outcomes, such as end-stage renal disease or cardiovascular disease, and CKD is a globally increasing health burden with a high personal and economic cost. Despite major progresses in prevention and therapeutics in last decades, research is still needed to reverse this epidemic trend. The regulation of water balance and the state of activation of the vasopressin system have emerged as factors tightly associated with kidney health, in the general population but also in specific conditions; among them, various stages of CKD, diabetes and autosomal dominant polycystic kidney disease (ADPKD). Basic science findings and also epidemiological evidence have justified important efforts towards interventional studies supporting causality, and opening therapeutic avenues. On the basis of recent clinical data, the blockade of V2 vasopressin receptors using tolvaptan in patients with rapidly progressing ADPKD has been granted in several countries, and a long-term randomized trial evaluating the effect of an increase in water intake in patients with CKD is on-going.

Neonatal renal cystic diseases

PURPOSE

Neonatal renal cystic diseases have a great impact on the morbidity and mortality of the affected neonates and infants. A good insight into the pathophysiology, diagnosis and treatment options of various neonatal renal cystic diseases aid in early diagnosis and intervention, thereby preventing complications.

METHODS

PubMed search was done for articles on "neonatal renal cystic diseases" and relevant publications including reviews were considered for our article.

RESULTS

Both hereditary and nonhereditary causes of cystic kidney diseases can result in severe morbidity and mortality. The main diagnostic modality is ultrasound imaging and most of the neonatal renal cystic diseases are detected during prenatal ultrasound screening. Commonly encountered neonatal renal cystic diseases are autosomal dominant polycystic kidney disease, autosomal recessive polycystic kidney disease and multicystic dysplastic kidney.

CONCLUSIONS

A thorough knowledge of various renal cystic diseases can be of extreme prognostic value. Physicians should be aware of the impact of early diagnosis and intervention on the lives of those affected. Further research about treatment of these diseases is ongoing and can result in breakthrough therapies for these patients.

Electrolyte and Acid-Base Disturbances in End-Stage Liver Disease: A Physiopathological Approach

Electrolyte and acid-base disturbances are frequent in patients with end-stage liver disease; the underlying physiopathological mechanisms are often complex and represent a diagnostic and therapeutic challenge to the physician. Usually, these disorders do not develop in compensated cirrhotic patients, but with the onset of the classic complications of cirrhosis such as ascites, renal failure, spontaneous bacterial peritonitis and variceal bleeding, multiple electrolyte, and acid-base disturbances emerge. Hyponatremia parallels ascites formation and is a well-known trigger of hepatic encephalopathy; its management in this particular population poses a risky challenge due to the high susceptibility of cirrhotic patients to osmotic demyelination. Hypokalemia is common in the setting of cirrhosis: multiple potassium wasting mechanisms both inherent to the disease and resulting from its management make these patients particularly susceptible to potassium depletion even in the setting of normokalemia. Acid-base disturbances range from classical respiratory alkalosis to high anion gap metabolic acidosis, almost comprising the full acid-base spectrum. Because most electrolyte and acid-base disturbances are managed in terms of their underlying trigger factors, a systematic physiopathological approach to their diagnosis and treatment is required.

Effect of tolvaptan on renal water and sodium excretion and blood pressure during nitric oxide inhibition: a dose-response study in healthy subjects

Background

Tolvaptan is a selective vasopressin receptor antagonist. Nitric Oxide (NO) promotes renal water and sodium excretion, but the effect is unknown in the nephron’s principal cells. In a dose-response study, we measured the effect of tolvaptan on renal handling of water and sodium and systemic hemodynamics, during baseline and NO-inhibition with L-NMMA (L-NG-monomethyl-arginine).

Methods

In a randomized, placebo-controlled, double blind, cross over study, 15 healthy subjects received tolvaptan 15, 30 and 45 mg or placebo. L-NMMA was given as a bolus followed by continuous infusion during 60 min. We measured urine output (UO), free water clearance (C_H2O), fractional excretion of sodium (FE_Na), urinary aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma vasopressin (p-AVP) and central blood pressure (cBP).

Results

During baseline, FE_Na was unchanged. Tolvaptan decreased u-ENaC_γ dose-dependently and increased p-AVP threefold, whereas u-AQP2 was unchanged. During tolvaptan with NO-inhibition, UO and C_H2O decreased dose-dependently. FE_Na decreased dose-independently and u-ENaC_γ remained unchanged. Central BP increased equally after all treatments.

Conclusions

During baseline, fractional excretion of sodium was unchanged. During tolvaptan with NO-inhibition, renal water excretion was reduced dose dependently, and renal sodium excretion was reduced unrelated to the dose, partly via an AVP dependent mechanism. Thus, tolvaptan antagonized the reduction in renal water and sodium excretion during NO-inhibition. Most likely, the lack of decrease in AQP2 excretion by tolvaptan could be attributed to a counteracting effect of the high level of p-AVP.

Trial registration

Clinical Trial no: NCT02078973. Registered 1 March 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0501-1) contains supplementary material, which is available to authorized users.

Urine Osmolality, Response to Tolvaptan, and Outcome in Autosomal Dominant Polycystic Kidney Disease: Results from the TEMPO 3:4 Trial

The vasopressin-cAMP-osmolality axis is abnormal in autosomal dominant polycystic kidney disease (ADPKD). In the Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes 3:4 Trial, a 3-year randomized, placebo-controlled trial in adults, the vasopressin V2 receptor antagonist tolvaptan slowed ADPKD progression in patients with preserved GFR. Here, we investigated the determinants of baseline urine osmolality (Uosm) and its value as a severity marker of ADPKD, the factors influencing the response to tolvaptan, and whether change in Uosm associated with key trial end points. At baseline, lower Uosm independently associated with female sex, presence of hypertension, lower eGFR, higher total kidney volume (TKV), and higher age. Tolvaptan consistently reduced Uosm by 200-300 mOsm/kg over 36 months. The Uosm response to tolvaptan depended on baseline eGFR and Uosm. Subjects with greater change in Uosm experienced a significant reduction in clinical progression events. Among subjects receiving tolvaptan, those with a greater suppression of Uosm had slower renal function decline. Assessment at follow-up, off medication, revealed a significant decrease in Uosm in both placebo and treated groups. Tolvaptan significantly increased plasma osmolality, which returned to baseline at follow-up. In conclusion, baseline Uosm in ADPKD reflects age, renal function, and TKV, and baseline Uosm, eGFR, and TKV influence the effect of tolvaptan on Uosm. The greatest renal benefit occurred in subjects achieving greater suppression of Uosm, that is, those with better eGFR at baseline. These results support the link between vasopressin V2 receptor signaling and ADPKD progression.

Technical Evaluation: Identification of Pathogenic Mutations in PKD1 and PKD2 in Patients with Autosomal Dominant Polycystic Kidney Disease by Next-Generation Sequencing and Use of a Comprehensive New Classification System

Genetic testing of PKD1 and PKD2 is expected to play an increasingly important role in determining allelic influences in autosomal dominant polycystic kidney disease (ADPKD) in the near future. However, to date, genetic testing is not commonly employed because it is expensive, complicated because of genetic heterogeneity, and does not easily identify pathogenic variants. In this study, we developed a genetic testing system based on next-generation sequencing (NGS), long-range polymerase chain reaction, and a new software package. The new software package integrated seven databases and provided access to five cloud-based computing systems. The database integrated 241 polymorphic nonpathogenic variants detected in 140 healthy Japanese volunteers aged >35 years, who were confirmed by ultrasonography as having no cysts in either kidney. Using this system, we identified 60 novel and 30 known pathogenic mutations in 101 Japanese patients with ADPKD, with an overall detection rate of 89.1% (90/101) [95% confidence interval (CI), 83.0%–95.2%]. The sensitivity of the system increased to 93.1% (94/101) (95% CI, 88.1%–98.0%) when combined with multiplex ligation-dependent probe amplification analysis, making it sufficient for use in a clinical setting. In 82 (87.2%) of the patients, pathogenic mutations were detected in PKD1 (95% CI, 79.0%–92.5%), whereas in 12 (12.8%) patients pathogenic mutations were detected in PKD2 (95% CI, 7.5%–21.0%); this is consistent with previously reported findings. In addition, we were able to reconfirm our pathogenic mutation identification results using Sanger sequencing. In conclusion, we developed a high-sensitivity NGS-based system and successfully employed it to identify pathogenic mutations in PKD1 and PKD2 in Japanese patients with ADPKD.

An Empirical Biomarker-Based Calculator for Cystic Index in a Model of Autosomal Recessive Polycystic Kidney Disease-The Nieto-Narayan Formula

Autosomal recessive polycystic kidney disease (ARPKD) is associated with progressive enlargement of the kidneys fuelled by the formation and expansion of fluid-filled cysts. The disease is congenital and children that do not succumb to it during the neonatal period will, by age 10 years, more often than not, require nephrectomy+renal replacement therapy for management of both pain and renal insufficiency. Since increasing cystic index (CI; percent of kidney occupied by cysts) drives both renal expansion and organ dysfunction, management of these patients, including decisions such as elective nephrectomy and prioritization on the transplant waitlist, could clearly benefit from serial determination of CI. So also, clinical trials in ARPKD evaluating the efficacy of novel drug candidates could benefit from serial determination of CI. Although ultrasound is currently the imaging modality of choice for diagnosis of ARPKD, its utilization for assessing disease progression is highly limited. Magnetic resonance imaging or computed tomography, although more reliable for determination of CI, are expensive, time-consuming and somewhat impractical in the pediatric population. Using a well-established mammalian model of ARPKD, we undertook a big data-like analysis of minimally- or non-invasive blood and urine biomarkers of renal injury/dysfunction to derive a family of equations for estimating CI. We then applied a signal averaging protocol to distill these equations to a single empirical formula for calculation of CI. Such a formula will eventually find use in identifying and monitoring patients at high risk for progressing to end-stage renal disease and aid in the conduct of clinical trials.

Low-Osmolar Diet and Adjusted Water Intake for Vasopressin Reduction in Autosomal Dominant Polycystic Kidney Disease: A Pilot Randomized Controlled Trial

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) affects millions of people worldwide. Vasopressin promotes disease progression.

STUDY DESIGN

A randomized controlled trial with equal (1:1) allocation.

SETTING & PARTICIPANTS

This trial examined the effect of combining a low-osmolar (low-sodium [1,500mg/d], low-protein [0.8g per kilogram of body weight]) diet and adjusted water intake on vasopressin secretion in 34 patients with ADPKD.

INTERVENTION

Participants were randomly assigned to receive a low-osmolar diet followed by adjusted water intake to achieve urine osmolality ≤ 280mOsm/kg water versus no intervention for 2 weeks.

OUTCOME

The primary outcome of the study was change (delta) in copeptin levels and urine osmolality between the intervention and control groups from baseline to 2 weeks.

MEASUREMENTS

Fasting plasma copeptin level, 24-hour urine osmolality, and total solute intake.

RESULTS

Baseline characteristics of the 2 groups were similar. Mean plasma copeptin levels and urine osmolality declined from 6.2±3.05 (SD) to 5.3±2.5pmol/L (P=0.02) and from 426±193 to 258±117mOsm/kg water (P=0.01), respectively, in the intervention group compared to a nonsignificant change in the control group (from 4.7±3.6 to 5.07±4pmol/L [P=0.2] and 329±159 to 349±139mOsm/kg water [P=0.3], respectively). The change in copeptin levels (primary outcome) and urine osmolality was statistically significant between the intervention and control groups (delta copeptin, -0.86±1.3 vs +0.39±1.2pmol/L [P=0.009]; delta urine osmolality, -167±264 vs +20±80mOsm/kg water [P=0.007], respectively). Total urinary solute decreased in only the intervention group and significantly differed between groups at week 1 (P=0.03), reducing mean water prescription from 3.2 to 2.6L/d.

LIMITATIONS

Small sample size and short follow-up.

CONCLUSIONS

We developed a stepwise dietary intervention that led to a significant reduction in vasopressin secretion in patients with ADPKD. Furthermore, this intervention led to a reduction in water required for vasopressin reduction.