HYDROchlorothiazide versus placebo to PROTECT polycystic kidney disease patients and improve their quality of life: study protocol and rationale for the HYDRO-PROTECT randomized controlled trial.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) leads to progressive renal cyst formation and loss of kidney function in most patients. Vasopressin 2 receptor antagonists (V2RA) like tolvaptan are currently the only available renoprotective agents for rapidly progressive ADPKD. However, aquaretic side effects substantially limit their tolerability and therapeutic potential. In a preliminary clinical study, the addition of hydrochlorothiazide (HCT) to tolvaptan decreased 24-h urinary volume and appeared to increase renoprotective efficacy. The HYDRO-PROTECT study will investigate the long-term effect of co-treatment with HCT on tolvaptan efficacy (rate of kidney function decline) and tolerability (aquaresis and quality of life) in patients with ADPKD. METHODS: The HYDRO-PROTECT study is an investigator-initiated, multicenter, double-blind, placebo-controlled, randomized clinical trial. The study is powered to enroll 300 rapidly progressive patients with ADPKD aged ≥ 18 years, with an eGFR of > 25 mL/min/1.73 m2, and on stable treatment with the highest tolerated dose of tolvaptan in routine clinical care. Patients will be randomly assigned (1:1) to daily oral HCT 25 mg or matching placebo treatment for 156 weeks, in addition to standard care. OUTCOMES: The primary study outcome is the rate of kidney function decline (expressed as eGFR slope, in mL/min/1.73 m2 per year) in HCT versus placebo-treated patients, calculated by linear mixed model analysis using all available creatinine values from week 12 until the end of treatment. Secondary outcomes include changes in quality-of-life questionnaire scores (TIPS, ADPKD-UIS, EQ-5D-5L, SF-12) and changes in 24-h urine volume. CONCLUSION: The HYDRO-PROTECT study will demonstrate whether co-treatment with HCT can improve the renoprotective efficacy and tolerability of tolvaptan in patients with ADPKD.

Matrix Metalloproteinase-7 in Urinary Extracellular Vesicles Identifies Rapid Disease Progression in Autosomal Dominant Polycystic Kidney Disease.

SIGNIFICANCE STATEMENT: There is an unmet need for biomarkers of disease progression in autosomal dominant polycystic kidney disease (ADPKD). This study investigated urinary extracellular vesicles (uEVs) as a source of such biomarkers. Proteomic analysis of uEVs identified matrix metalloproteinase 7 (MMP-7) as a biomarker predictive of rapid disease progression. In validation studies, MMP-7 was predictive in uEVs but not in whole urine, possibly because uEVs are primarily secreted by tubular epithelial cells. Indeed, single-nucleus RNA sequencing showed that MMP-7 was especially increased in proximal tubule and thick ascending limb cells, which were further characterized by a profibrotic phenotype. Together, these data suggest that MMP-7 is a biologically plausible and promising uEV biomarker for rapid disease progression in ADPKD. BACKGROUND: In ADPKD, there is an unmet need for early markers of rapid disease progression to facilitate counseling and selection for kidney-protective therapy. Our aim was to identify markers for rapid disease progression in uEVs. METHODS: Six paired case-control groups ( n =10-59/group) of cases with rapid disease progression and controls with stable disease were formed from two independent ADPKD cohorts, with matching by age, sex, total kidney volume, and genetic variant. Candidate uEV biomarkers were identified by mass spectrometry and further analyzed using immunoblotting and an ELISA. Single-nucleus RNA sequencing of healthy and ADPKD tissue was used to identify the cellular origin of the uEV biomarker. RESULTS: In the discovery proteomics experiments, the protein abundance of MMP-7 was significantly higher in uEVs of patients with rapid disease progression compared with stable disease. In the validation groups, a significant >2-fold increase in uEV-MMP-7 in patients with rapid disease progression was confirmed using immunoblotting. By contrast, no significant difference in MMP-7 was found in whole urine using ELISA. Compared with healthy kidney tissue, ADPKD tissue had significantly higher MMP-7 expression in proximal tubule and thick ascending limb cells with a profibrotic phenotype. CONCLUSIONS: Among patients with ADPKD, rapid disease progressors have higher uEV-associated MMP-7. Our findings also suggest that MMP-7 is a biologically plausible biomarker for more rapid disease progression.

Kidney phosphate wasting predicts poor outcome in polycystic kidney disease.

BACKGROUND AND HYPOTHESIS: Patients with ADPKD have disproportionately high levels of fibroblast growth factor-23 (FGF-23) for their CKD-stage with only a subgroup that develops kidney phosphate wasting. We assessed factors associated with phosphate wasting and hypothesize that it identifies patients with more severe disease and predicts disease progression. METHODS: We included 604 patients with ADPKD from a multi-center prospective observational (DIPAK) cohort in 4 university medical centers in the Netherlands. We measured parathyroid hormone (PTH), total plasma FGF-23 levels and calculated the ratio of tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR) with < 0.8 mmol/L defined as kidney phosphate wasting. We analysed the association of TmP/GFR with eGFR decline over time and the risk for a composite kidney outcome (≥ 30% eGFR decline, kidney failure or kidney replacement therapy). RESULTS: In our cohort (age 48 ± 12 years, 39% male, eGFR 63 ± 28 mL/min/1.73m2), 59% of patients had phosphate wasting. Male sex (coefficient -0.2, 95% confidence interval [CI] -0.2; -0.1), eGFR (0.002, 0.001-0.004), FGF-23 (0.1, 0.03-0.2), PTH(-0.2, -0.3; -0.06) and Copeptin(-0.08, -0.1; -0.08) were associated with TmP/GFR. Corrected for PTH, FGF-23 and eGFR, every 0.1 mmol/L decrease in TmP/GFR was associated with a greater eGFR decline of 0.2 ml/min/1.73m2/year (95% CI 0.01-0.3) and an increased hazard ratio of 1.09 (95% CI 1.01-1.18) of the composite kidney outcome. CONCLUSION: Our study shows that in patients with ADPKD phosphate wasting is prevalent and associated with more rapid disease progression. Phosphate wasting may be a consequence of early proximal tubular dysfunction and insufficient suppression of PTH.

Diversity in the pathway from medical student to specialist in the Netherlands: a retrospective cohort study.

Background: Medical specialist workforces are not representative of the society they serve, partially due to loss of diversity in the path from student to specialist. We investigated which demographic characteristics of bachelor students of medicine (BSM) are associated with becoming a physician and (particular type of) medical specialist; and whether this suggests 'cloning' (reproduction of sameness) of the existing workforce. Methods: We used a retrospective cohort design, based on Statistics Netherlands data of all first-year BSM in 2002-2004 in The Netherlands (N = 4503). We used logistic regression to analyze the impact of sex, migration background, urbanity of residence, parental income and assets categories, and having healthcare professional parents, on being registered as physician or medical specialist in 2021. We compared our results to the national pool of physicians (N = 76,845) and medical specialists (N = 49,956) to identify cloning patterns based on Essed's cultural cloning theory. Findings: Female students had higher odds of becoming a physician (OR 1.87 [1.53-2.28], p < 0.001). Physicians with a migration background other than Turkish, Moroccan, Surinamese, Dutch Caribbean or Indonesian (TMSDI) had lower odds of becoming a specialist (OR 0.55 [0.43-0.71], p < 0.001). This was not significant for TMSDI physicians (OR 0.74 [0.54-1.03], p = 0.073). We found a cloning pattern with regard to sex and migration background. Nationwide, physicians with a Turkish or Moroccan migration background, and female physicians with other migration backgrounds, are least likely to be a medical specialist. Interpretation: In light of equity in healthcare systems, we recommend that every recruitment body increases the representativeness of their particular specialist workforce. Funding: ODISSEI.

Prostaglandin E2, Osmoregulation, and Disease Progression in Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: Prostaglandin E2 (PGE2) plays a physiological role in osmoregulation, a process that is affected early in autosomal dominant polycystic kidney disease (ADPKD). PGE2 has also been implicated in the pathogenesis of ADPKD in preclinical models, but human data are limited. Here, we hypothesized that urinary PGE2 excretion is associated with impaired osmoregulation, disease severity, and disease progression in human ADPKD. METHODS: Urinary excretions of PGE2 and its metabolite (PGEM) were measured in a prospective cohort of patients with ADPKD. The associations between urinary PGE2 and PGEM excretions, markers of osmoregulation, eGFR and height-adjusted total kidney volume were assessed using linear regression models. Cox regression and linear mixed models were used for the longitudinal analysis of the associations between urinary PGE2 and PGEM excretions and disease progression defined as 40% eGFR loss or kidney failure, and change in eGFR over time. In two intervention studies, we quantified the effect of starting tolvaptan and adding hydrochlorothiazide to tolvaptan on urinary PGE2 and PGEM excretions. RESULTS: In 562 patients with ADPKD (61% female, eGFR 63±28 ml/min per 1.73 m 2 ), higher urinary PGE2 or PGEM excretions were independently associated with higher plasma copeptin, lower urine osmolality, lower eGFR, and greater total kidney volume. Participants with higher baseline urinary PGE2 and PGEM excretions had a higher risk of 40% eGFR loss or kidney failure (hazard ratio, 1.28; 95% confidence interval [CI], 1.13 to 1.46 and hazard ratio, 1.50; 95% CI, 1.26 to 1.80 per two-fold higher urinary PGE2 or PGEM excretions) and a faster change in eGFR over time (-0.39 [95% CI, -0.59 to -0.20] and -0.53 [95% CI, -0.75 to -0.31] ml/min per 1.73 m 2 per year). In the intervention studies, urinary PGEM excretion was higher after starting tolvaptan, while urinary PGE2 excretion was higher after adding hydrochlorothiazide to tolvaptan. CONCLUSIONS: Higher urinary PGE2 and PGEM excretions in patients with ADPKD are associated with impaired osmoregulation, disease severity, and progression.

Urinary extracellular vesicles and tubular transport.

Tubular transport is a key function of the kidney to maintain electrolyte and acid-base homeostasis. Urinary extracellular vesicles (uEVs) harbor water, electrolyte, and acid-base transporters expressed at the apical plasma membrane of tubular epithelial cells. Within the uEV proteome, the correlations between kidney and uEV protein abundances are strongest for tubular transporters. Therefore, uEVs offer a noninvasive approach to probing tubular transport in health and disease. Here, we review how kidney tubular physiology is reflected in uEVs and, conversely, how uEVs may modify tubular transport. Clinically, uEV tubular transporter profiling has been applied to rare diseases, such as inherited tubulopathies, but also to more common conditions, such as hypertension and kidney disease. Although uEVs hold the promise to advance the diagnosis of kidney disease to the molecular level, several biological and technical complexities must still be addressed. The future will tell whether uEV analysis will mainly be a powerful tool to study tubular physiology in humans or whether it will move forward to become a diagnostic bedside test.

Urinary Citrate Is Associated with Kidney Outcomes in Early Polycystic Kidney Disease.

Low urinary citrate and crystal deposition accelerated cystogenesis in an experimental model of polycystic kidney disease (PKD).Hypocitraturia, frequently observed in patients with autosomal dominant PKD (ADPKD) could contribute to disease progression.Present findings suggest lower urinary citrate in early PKD was associated with faster eGFR decline and worse kidney survival.

Connexin 26 (GJB2) gene mutations linked with autosomal recessive non-syndromic sensor neural hearing loss in the Iraqi population.

Deafness is a total or partial hearing loss that may appear at any age and with different degrees of severity. Approximately 50% of hearing loss have a genetic origin, and among them, non-syndromic sensorineural deafness represents about 70% of the cases. From them, 80% correspond to autosomal recessive inheritance deafness. Autosomal recessive deafness was not studied enough at the molecular level in Iraq. This study aimed to verify the frequency of three GJB2 mutations in non-syndromic sensorineural deafness in the Iraqi population. The current case-control study was conducted from January 2018 to January 2020. The study included 95 deafness patients (55 males and 40 females) and 110 healthy control group. Age and sex were matched between the two groups. In order to detect c.35delG, 235delC, and 167delT mutations in the GJB2 gene, we employed the PCR-RFLP technique. The c.35delG was the main frequent mutation encountered with the GJB2 gene among patients with autosomal recessive non-syndromic sensorineural hearing loss. Among them, 35 (36.8%) were homozygous, 40 (42.1%) were heterozygous, and 20 (21.1%) were wild genotypes. The second-degree mutation in the GJB2 gene was c.235delC mutation, which from the 95 deaf patients, there were 20 (21.1%) with homozygous, 33 (34.7%) heterozygous, and 42 (44.2%) wild genotypes. None of the 95 deaf patients showed the c.167delT mutation, and no mutations appeared in the control group. Our data concluded that the GJB2 c.35delG and c.235delC gene mutations were the main cause of autosomal recessive non-syndromic sensorineural hearing loss in the Iraqi deaf population.

Lanreotide Reduces Liver Growth In Patients With Autosomal Dominant Polycystic Liver and Kidney Disease.

BACKGROUND & AIMS: Polycystic liver disease is the most common extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD). There is need for robust long-term evidence for the volume-reducing effect of somatostatin analogues. We made use of data from an open-label, randomized trial to determine the effects of lanreotide on height-adjusted liver volume (hTLV) and combined height-adjusted liver and kidney volume (hTLKV) in patients with ADPKD. METHODS: We performed a 120-week study comparing the reno-protective effects of lanreotide vs standard care in 305 patients with ADPKD (the DIPAK-1 study). For this analysis, we studied the 175 patients with polycystic liver disease with hepatic cysts identified by magnetic resonance imaging and liver volume ≥2000 mL. Of these, 93 patients were assigned to a group that received lanreotide (120 mg subcutaneously every 4 weeks) and 82 to a group that received standard care (blood pressure control, a sodium-restricted diet, and antihypertensive agents). The primary endpoint was percent change in hTLV between baseline and end of treatment (week 120). A secondary endpoint was change in hTLKV. RESULTS: At 120 weeks, hTLV decreased by 1.99% in the lanreotide group (95% confidence interval [CI], -4.21 to 0.24) and increased by 3.92% in the control group (95% CI, 1.56-6.28). Compared with the control group, lanreotide reduced the growth of hTLV by 5.91% (95% CI, -9.18 to -2.63; P < .001). Growth of hTLV was still reduced by 3.87% at 4 months after the last injection of lanreotide compared with baseline (95% CI, -7.55 to -0.18; P = .04). Lanreotide reduced growth of hTLKV by 7.18% compared with the control group (95% CI, -10.25 to -4.12; P < .001). CONCLUSIONS: In this subanalysis of a randomized trial of patients with polycystic liver disease due to ADPKD, lanreotide for 120 weeks reduced the growth of liver and combined liver and kidney volume. This effect was still present 4 months after the last injection of lanreotide. ClinicalTrials.gov, Number: NCT01616927.

Identifying cystogenic paracrine signaling molecules in cyst fluid of patients with polycystic kidney disease.

In autosomal dominant polycystic kidney disease (ADPKD) paracrine signaling molecules in cyst fluid can induce proliferation and cystogenesis of neighboring renal epithelial cells. However, the identity of this cyst-inducing factor is still unknown. The aim of this study was to identify paracrine signaling proteins in cyst fluid using a 3D in vitro cystogenesis assay. We collected cyst fluid from 15 ADPKD patients who underwent kidney or liver resection (55 cysts from 13 nephrectomies, 5 cysts from 2 liver resections). For each sample, the ability to induce proliferation and cyst formation was tested using the cystogenesis assay (RPTEC/TERT1 cells in Matrigel with cyst fluid added for 14 days). Kidney cyst fluid induced proliferation and cyst growth of renal epithelial cells in a dose-dependent fashion. Liver cyst fluid also induced cystogenesis. Using size exclusion chromatography, 56 cyst fluid fractions were obtained of which only the fractions between 30 and 100 kDa showed cystogenic potential. Mass spectrometry analysis of samples that tested positive or negative in the assay identified 43 candidate cystogenic proteins. Gene ontology analysis showed an enrichment for proteins classified as enzymes, immunity proteins, receptors, and signaling proteins. A number of these proteins have previously been implicated in ADPKD, including secreted frizzled-related protein 4, S100A8, osteopontin, and cysteine rich with EGF-like domains 1. In conclusion, both kidney and liver cyst fluids contain paracrine signaling molecules that drive cyst formation. Using size exclusion chromatography and mass spectrometry, we procured a candidate list for future studies. Ultimately, cystogenic paracrine signaling molecules may be targeted to abrogate cystogenesis in ADPKD.

Cardiac arrest by inhalation of deodorant spray.

Drug abuse by inhalation of volatile household product substances is uncommon, however, it can have devastating consequences. This case report describes the fatal outcome of deodorant inhalation by a 19-year-old patient in a detoxification clinic who developed a cardiac arrest after inhaling butane from a deodorant spray. Despite initial successful resuscitation, he developed a postanoxic encephalopathy with a status epilepticus resistant to extensive treatment. Inhalant abuse can be a cause of death in young patients.

Effect of Lanreotide on Kidney Function in Patients With Autosomal Dominant Polycystic Kidney Disease: The DIPAK 1 Randomized Clinical Trial.

Importance: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation in both kidneys and loss of renal function, eventually leading to a need for kidney replacement therapy. There are limited therapeutic management options. Objective: To examine the effect of the somatostatin analogue lanreotide on the rate of kidney function loss in patients with later-stage ADPKD. Design, Setting, and Participants: An open-label randomized clinical trial with blinded end point assessment that included 309 patients with ADPKD from July 2012 to March 2015 at 4 nephrology outpatient clinics in the Netherlands. Eligible patients were 18 to 60 years of age and had an estimated glomerular filtration rate (eGFR) of 30 to 60 mL/min/1.73 m2. Follow-up of the 2.5-year trial ended in August 2017. Interventions: Patients were randomized to receive either lanreotide (120 mg subcutaneously once every 4 weeks) in addition to standard care (n = 153) or standard care only (target blood pressure <140/90 mm Hg; n = 152). Main Outcomes and Measures: Primary outcome was annual change in eGFR assessed as slope through eGFR values during the 2.5-year treatment phase. Secondary outcomes included change in eGFR before vs after treatment, incidence of worsening kidney function (start of dialysis or 30% decrease in eGFR), change in total kidney volume and change in quality of life (range: 1 [not bothered] to 5 [extremely bothered]). Results: Among the 309 patients who were randomized (mean [SD] age, 48.4 [7.3] years; 53.4% women), 261 (85.6%) completed the trial. Annual rate of eGFR decline for the lanreotide vs the control group was -3.53 vs -3.46 mL/min/1.73 m2 per year (difference, -0.08 [95% CI, -0.71 to 0.56]; P = .81). There were no significant differences for incidence of worsening kidney function (hazard ratio, 0.87 [95% CI, 0.49 to 1.52]; P = .87), change in eGFR (-3.58 vs -3.45; difference, -0.13 mL/min/1.73 m2 per year [95% CI, -1.76 to 1.50]; P = .88), and change in quality of life (0.05 vs 0.07; difference, -0.03 units per year [95% CI, -0.13 to 0.08]; P = .67). The rate of growth in total kidney volume was lower in the lanreotide group than the control group (4.15% vs 5.56%; difference, -1.33% per year [95% CI, -2.41% to -0.24%]; P = .02). Adverse events in the lanreotide vs control group included injection site discomfort (32% vs 0.7%), injection site papule (5.9% vs 0%), loose stools (91% vs 6.6%), abdominal discomfort (79% vs 20%), and hepatic cyst infections (5.2% vs 0%). Conclusions and Relevance: Among patients with later-stage autosomal dominant polycystic kidney disease, treatment with lanreotide compared with standard care did not slow the decline in kidney function over 2.5 years of follow-up. These findings do not support the use of lanreotide for treatment of later-stage autosomal dominant polycystic kidney disease. Trial Registration: ClinicalTrials.gov Identifier: NCT01616927.

Increased Urinary Extracellular Vesicle Sodium Transporters in Cushing Syndrome With Hypertension.

Context: Increased renal sodium reabsorption contributes to hypertension in Cushing syndrome (CS). Renal sodium transporters can be analyzed noninvasively in urinary extracellular vesicles (uEVs). Objective: To analyze renal sodium transporters in uEVs of patients with CS and hypertension. Design: Observational study. Setting: University hospital. Participants: The uEVs were isolated by ultracentrifugation and analyzed by immunoblotting in 10 patients with CS and 7 age-matched healthy participants. In 7 patients with CS, uEVs were analyzed before and after treatment. Main Outcome Measure: Abundance of protein in uEVs. Results: The 10 patients with CS were divided in those with suppressed and nonsuppressed renin-angiotensin-aldosterone system (RAAS; n = 5 per group). Patients with CS with suppressed RAAS had similar blood pressure but significantly lower serum potassium than patients with CS with nonsuppressed RAAS. Compared with healthy participants, only patients with suppressed RAAS had higher phosphorylated Na+-K+-Cl- cotransporter type 2 (pNKCC2) and higher total and phosphorylated Na+-Cl- cotransporter (pNCC) in uEVs. Serum potassium but not urinary free cortisol correlated with pNKCC2, pNCC, and Na+-Cl- cotransporter (NCC) in uEVs. Treatment of CS reversed the increases in pNKCC2, NCC, and pNCC. Conclusions: CS increases renal sodium transporter abundance in uEVs in patients with hypertension and suppressed RAAS. Potassium has recently been identified as an important driver of NCC activity, and low serum potassium may also contribute to increased renal sodium reabsorption and hypertension in CS. These results may also be relevant for hypertension induced by exogenous glucocorticoids.

Effects of Thyroid Hormone on Urinary Concentrating Ability.

BACKGROUND: Hypothyroidism has been associated with impaired urinary concentrating ability. However, previous reports on thyroid hormone and urinary concentrating ability in humans only studied a limited number of patients with autoimmune thyroid disease or used healthy controls instead of paired analysis within the same patients. OBJECTIVE: To study the urinary concentrating ability in athyreotic patients with differentiated thyroid cancer on and off levothyroxine treatment as they are exposed to different thyroid states as part of their treatment in the absence of an autoimmune disease. DESIGN AND METHODS: We studied 9 patients (mean age of 42.7 years) during severe hypothyroid state (withdrawal of levothyroxine before radioactive iodine therapy) and TSH-suppressed state (on levothyroxine therapy). At these two points, serum and urine samples were collected after 14 h of overnight fasting without any food or drink. RESULTS: Serum and urine osmolality were not significantly different between on and off levothyroxine treatment. Serum creatinine levels were significantly higher in patients off versus on levothyroxine treatment (87.0 vs. 71.0 µmol/L, respectively; p = 0.044) and, correspondingly, the estimated glomerular filtration rate was significantly lower (89.6 vs. 93.1 mL/min, respectively; p = 0.038). CONCLUSION: Short-term, severe hypothyroidism has no effect on urinary concentrating ability. Our study confirms the well-known effects of thyroid hormone on serum creatinine concentrations.

The Association of Combined Total Kidney and Liver Volume with Pain and Gastrointestinal Symptoms in Patients with Later Stage Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: There is an ongoing debate if and how kidney and liver volume are associated with pain and gastrointestinal (GI) symptoms in autosomal dominant polycystic kidney disease (ADPKD) patients. Since both kidney and liver volume could interact, we investigated whether combined total kidney and liver volume had stronger associations with ADPKD-related pain and GI symptoms than the volumes of the organs separately. METHODS: We used baseline data from the DIPAK-1 study, which included ADPKD patients with an estimated glomerular filtration rate (eGFR) between 30 and 60 mL/min/1.73 m2. MR imaging was performed to measure height-adjusted total kidney volume (hTKV), height-adjusted total liver volume (hTLV) and the combination of both (height-adjusted total kidney liver volume [hTKLV]). RESULTS: Three hundred nine ADPKD patients were included with a mean age of 48 ± 7 years, 53% female, eGFR 50 ± 11 mL/min/1.73 m2 and median hTKV, hTLV and hTKLV of 1,095 (758-1,669), 1,173 (994-1,523) and 2,496 (1,972-3,352) mL/m, respectively. ADPKD-related pain and GI symptoms were present in, respectively, 27.5 and 61.2% of patients. Gender was no effect modifier in the association between kidney and/or liver volume, and symptom burden, indicating that all models could be tested in the overall study population. hTKLV and hTLV were significantly associated with pain and GI symptoms, whereas hTKV was not. Model testing revealed that the associations of pain and GI symptoms with hTKLV were significantly stronger than with hTKV (p = 0.04 and p = 0.04, respectively) but not when compared to hTLV (p = 0.2 and p = 0.5, respectively). CONCLUSIONS: This study indicates that combined kidney and liver volume was associated with the presence and severity of pain and GI symptoms in ADPKD, with a more prominent role for hTLV than for hTKV.

Urinary renin-angiotensin markers in polycystic kidney disease.

In autosomal dominant polycystic kidney disease (ADPKD), activation of the renin-angiotensin aldosterone system (RAAS) may contribute to hypertension and disease progression. Although previous studies have focused on circulating RAAS components, preliminary evidence suggests that APDKD may increase urinary RAAS components. Therefore, our aim was to analyze circulating and urinary RAAS components in ADPKD. We cross-sectionally compared 60 patients with ADPKD with 57 patients with non-ADPKD chronic kidney disease (CKD). The two groups were matched by sex, estimated glomerular filtration rate (eGFR), blood pressure, and RAAS inhibitor use. Despite similar plasma levels of angiotensinogen and renin, urinary angiotensinogen and renin excretion were five- to sixfold higher in ADPKD (P < 0.001). These differences persisted when adjusting for group differences and were present regardless of RAAS inhibitor use. In multivariable analyses, ADPKD, albuminuria, and the respective plasma concentrations were independent predictors for urinary angiotensinogen and renin excretion. In ADPKD, both plasma and urinary renin correlated negatively with eGFR. Total kidney volume correlated with plasma renin and albuminuria but not with urinary renin or angiotensinogen excretions. Albuminuria correlated positively with urinary angiotensinogen and renin excretions in ADPKD and CKD. In three ADPKD patients who underwent nephrectomy, the concentrations of albumin and angiotensinogen were highest in plasma, followed by cyst fluid and urine; urinary renin concentrations were higher than cyst fluid. In conclusion, this study shows that, despite similar circulating RAAS component levels, higher urinary excretions of angiotensinogen and renin are a unique feature of ADPKD. Future studies should address the underlying mechanism and whether this may contribute to hypertension or disease progression in ADPKD.

A Missense Mutation in the Extracellular Domain of αENaC Causes Liddle Syndrome.

Liddle syndrome is an autosomal dominant form of hypokalemic hypertension due to mutations in the ß- or γ-subunit of the epithelial sodium channel (ENaC). Here, we describe a family with Liddle syndrome due to a mutation in αENaC. The proband was referred because of resistant hypokalemic hypertension, suppressed renin and aldosterone, and no mutations in the genes encoding ß- or γENaC. Exome sequencing revealed a heterozygous, nonconservative T>C single-nucleotide mutation in αENaC that substituted Cys479 with Arg (C479R). C479 is a highly conserved residue in the extracellular domain of ENaC and likely involved in a disulfide bridge with the partner cysteine C394. In oocytes, the C479R and C394S mutations resulted in similar twofold increases in amiloride-sensitive ENaC current. Quantification of mature cleaved αENaC in membrane fractions showed that the number of channels did not increase with these mutations. Trypsin, which increases open probability of the channel by proteolytic cleavage, resulted in significantly higher currents in the wild type than in C479R or C394S mutants. In summary, a mutation in the extracellular domain of αENaC causes Liddle syndrome by increasing intrinsic channel activity. This mechanism differs from that of the ß- and γ-mutations, which result in an increase in channel density at the cell surface. This mutation may explain other cases of patients with resistant hypertension and also provides novel insight into ENaC activation, which is relevant for kidney sodium reabsorption and salt-sensitive hypertension.

Hepatic Cyst Infection During Use of the Somatostatin Analog Lanreotide in Autosomal Dominant Polycystic Kidney Disease: An Interim Analysis of the Randomized Open-Label Multicenter DIPAK-1 Study.

INTRODUCTION AND AIMS: The DIPAK-1 Study investigates the reno- and hepatoprotective efficacy of the somatostatin analog lanreotide compared with standard care in patients with later stage autosomal dominant polycystic kidney disease (ADPKD). During this trial, we witnessed several episodes of hepatic cyst infection, all during lanreotide treatment. We describe these events and provide a review of the literature. METHODS: The DIPAK-1 Study is an ongoing investigator-driven, randomized, controlled, open-label multicenter trial. Patients (ADPKD, ages 18-60 years, estimated glomerular filtration rate 30-60 mL/min/1.73 m2) were randomized 1:1 to receive lanreotide 120 mg subcutaneously every 28 days or standard care during 120 weeks. Hepatic cyst infection was diagnosed by local physicians. RESULTS: We included 309 ADPKD patients of which seven (median age 53 years [interquartile range: 48-55], 71% female, median estimated glomerular filtration rate 42 mL/min/1.73 m2 [interquartile range: 41-58]) developed eight episodes of hepatic cyst infection during 342 patient-years of lanreotide use (0.23 cases per 10 patient-years). These events were limited to patients receiving lanreotide (p < 0.001 vs. standard care). Baseline characteristics were similar between subjects who did or did not develop a hepatic cyst infection during lanreotide use, except for a history of hepatic cyst infection (29 vs. 0.7%, p < 0.001). Previous studies with somatostatin analogs reported cyst infections, but did not identify a causal relationship. CONCLUSIONS: These data suggest an increased risk for hepatic cyst infection during use of somatostatin analogs, especially in ADPKD patients with a history of hepatic cyst infection. The main results are still awaited to fully appreciate the risk-benefit ratio. CLINICALTRIALS. GOV IDENTIFIER: NCT 01616927.

Proteomics of Urinary Vesicles Links Plakins and Complement to Polycystic Kidney Disease.

Novel therapies in autosomal dominant polycystic kidney disease (ADPKD) signal the need for markers of disease progression or response to therapy. This study aimed to identify disease-associated proteins in urinary extracellular vesicles (uEVs), which include exosomes, in patients with ADPKD. We performed quantitative proteomics on uEVs from healthy controls and patients with ADPKD using a labeled approach and then used a label-free approach with uEVs of different subjects (healthy controls versus patients with ADPKD versus patients with non-ADPKD CKD). In both experiments, 30 proteins were consistently more abundant (by two-fold or greater) in ADPKD-uEVs than in healthy- and CKD-uEVs. Of these proteins, we selected periplakin, envoplakin, villin-1, and complement C3 and C9 for confirmation because they were also significantly overrepresented in pathway analysis and were previously implicated in ADPKD pathogenesis. Immunoblotting confirmed higher abundances of the selected proteins in uEVs from three independent groups of patients with ADPKD. Whereas uEVs of young patients with ADPKD and preserved kidney function already had higher levels of complement, only uEVs of patients with advanced stages of ADPKD had increased levels of villin-1, periplakin, and envoplakin. Furthermore, all five proteins correlated positively with total kidney volume. Analysis in kidney tissue from mice with kidney-specific, tamoxifen-inducible Pkd1 deletion demonstrated higher expression in more severe stages of the disease and correlation with kidney weight for each protein of interest. In summary, proteomic analysis of uEVs identified plakins and complement as disease-associated proteins in ADPKD. These proteins are new candidates for evaluation as biomarkers or targets for therapy in ADPKD.