Epimeric vitamin D and cardiovascular structure and function in advanced CKD and after kidney transplantation

BACKGROUND

25-hydroxyvitamin D can undergo C-3 epimerization to produce 3-epi-25(OH)D3. 3-epi-25(OH)D3 levels decline in chronic kidney disease (CKD), but its role in regulating the cardiovascular system is unknown. Herein, we examined the relationship between 3-epi-25(OH)D3, and cardiovascular functional and structural endpoints in patients with CKD.

METHODS

We examined n = 165 patients with advanced CKD from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) study cohort, including those who underwent kidney transplant (KTR, n = 76) and waitlisted patients who did not (NTWC, n = 89). All patients underwent cardiopulmonary exercise testing and echocardiography at baseline, 2 months and 12 months. Serum 3-epi-25(OH)D3 was analyzed by liquid chromatography-tandem mass spectrometry.

RESULTS

Patients were stratified into quartiles of baseline 3-epi-25(OH)D3 (Q1: <0.4 ng/mL, n = 51; Q2: 0.4 ng/mL, n = 26; Q3: 0.5-0.7 ng/mL, n = 47; Q4: ≥0.8 ng/mL, n = 41). Patients in Q1 exhibited lower peak oxygen uptake [VO2Peak = 18.4 (16.2-20.8) mL/min/kg] compared with Q4 [20.8 (18.6-23.2) mL/min/kg; P = .009]. Linear mixed regression model showed that 3-epi-25(OH)D3 levels increased in KTR [from 0.47 (0.30) ng/mL to 0.90 (0.45) ng/mL] and declined in NTWC [from 0.61 (0.32) ng/mL to 0.45 (0.29) ng/mL; P < .001]. Serum 3-epi-25(OH)D3 was associated with VO2Peak longitudinally in both groups [KTR: β (standard error) = 2.53 (0.56), P < .001; NTWC: 2.73 (0.70), P < .001], but was not with left ventricular mass or arterial stiffness. Non-epimeric 25(OH)D3, 24,25(OH)2D3 and the 25(OH)D3:24,25(OH)2D3 ratio were not associated with any cardiovascular outcome (all P > .05).

CONCLUSIONS

Changes in 3-epi-25(OH)D3 levels may regulate cardiovascular functional capacity in patients with advanced CKD.

PROphylaxis for paTiEnts at risk of COVID-19 infecTion (PROTECT-V)

BACKGROUND

Despite the introduction of vaccination, there remains a need for pre-exposure prophylactic agents against SARS-CoV-2. Several patient groups are more vulnerable to SARS-CoV-2 infection by virtue of underlying health conditions, treatments received or suboptimal responses to vaccination.

METHODS

PROTECT-V is a platform trial testing pre-exposure prophylactic interventions against SARS-CoV-2 infection in vulnerable patient populations (organ transplant recipients; individuals with oncological/haematological diagnoses, immune deficiency or autoimmune diseases requiring immunosuppression or on dialysis). Multiple agents can be evaluated across multiple vulnerable populations sharing placebo groups, with the option of adding additional treatments at later time points as these become available. The primary endpoint is symptomatic SARS-CoV-2 infection, and each agent will be independently evaluated in real time when the required number of events occurs. Presently, three agents are approved in the platform: intranasal niclosamide, nasal and inhaled ciclesonide and intravenous sotrovimab.

DISCUSSION

Despite the introduction of vaccination, there remains a need for pre-exposure prophylactic agents against SARS-CoV-2. Several patient groups are more vulnerable to COVID-19 disease by virtue of underlying health conditions, treatments received or suboptimal responses to vaccination.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04870333. EudraCT 2020-004144-28.

FGF23 and Cardiovascular Structure and Function in Advanced Chronic Kidney Disease

Background

Fibroblast growth factor 23 (FGF23) is a bone-derived phosphatonin that is elevated in chronic kidney disease (CKD) and has been implicated in the development of cardiovascular disease. It is unknown whether elevated FGF23 in CKD is associated with impaired cardiovascular functional capacity, as assessed by maximum exercise oxygen consumption (VO2Max). We sought to determine whether FGF23 is associated with cardiovascular functional capacity in patients with advanced CKD and after improvement of VO2Max by kidney transplantation.

Methods

We performed secondary analysis of 235 patients from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) cohort, which recruited patients with stage 5 CKD who underwent kidney transplantation or were waitlisted and hypertensive controls. All patients underwent cardiopulmonary exercise testing (CPET) and echocardiography and were followed longitudinally for 1 year after study enrollment.

Results

Patients across FGF23 quartiles differed in BMI (P=0.004) and mean arterial pressure (P<0.001) but did not significantly differ in sex (P=0.5) or age (P=0.08) compared with patients with lower levels of FGF23. Patients with higher FGF23 levels had impaired VO2Max (Q1: 24.2±4.8 ml/min per kilogram; Q4: 18.6±5.2 ml/min per kilogram; P<0.001), greater left ventricular mass index (LVMI; P<0.001), reduced HR at peak exercise (P<0.001), and maximal workload (P<0.001). Kidney transplantation conferred a significant decline in FGF23 at 2 months (P<0.001) before improvement in VO2Max at 1 year (P=0.008). Multivariable regression modeling revealed that changes in FGF23 was significantly associated with VO2Max in advanced CKD (P<0.001) and after improvement after kidney transplantation (P=0.006). FGF23 was associated with LVMI before kidney transplantation (P=0.003), however this association was lost after adjustment for dialysis status (P=0.4). FGF23 was not associated with LVMI after kidney transplantation in all models.

Conclusions

FGF23 levels are associated with alterations in cardiovascular functional capacity in advanced CKD and after kidney transplantation. FGF23 is only associated with structural cardiac adaptations in advanced CKD but this was modified by dialysis status, and was not associated after kidney transplantation.

Initiation of Dialysis Is Associated With Impaired Cardiovascular Functional Capacity

Background

The transition to dialysis period carries a substantial increased cardiovascular risk in patients with chronic kidney disease. Despite this, alterations in cardiovascular functional capacity during this transition are largely unknown. The present study therefore sought to assess ventilatory exercise response measures in patients within 1 year of initiating dialysis.

Methods and Results

We conducted a cross‐sectional study of 241 patients with chronic kidney disease stage 5 from the CAPER (Cardiopulmonary Exercise Testing in Renal Failure) study and from the intradialytic low‐frequency electrical muscle stimulation pilot randomized controlled trial cohorts. Patients underwent cardiopulmonary exercise testing and echocardiography. Of the 241 patients (age, 48.9 [15.0] years; 154 [63.9%] men), 42 were predialytic (mean estimated glomerular filtration rate, 14 mL·min −1 ·1.73 m −2 ), 54 had a dialysis vintage ≤12 months, and 145 had a dialysis vintage >12 months. Dialysis vintage ≤12 months exhibited a significantly impaired cardiovascular functional capacity, as assessed by oxygen uptake at peak exercise (18.7 [5.8] mL·min −1 ·kg −1 ) compared with predialysis (22.7 [5.2] mL·min −1 ·kg −1 ; P <0.001). Dialysis vintage ≤12 months also exhibited reduced peak workload, impaired peak heart rate, reduced circulatory power, and increased left ventricular mass index ( P <0.05 for all) compared with predialysis. After excluding those with prior kidney transplant, dialysis vintage >12 months exhibited a lower oxygen uptake at peak exercise (17.0 [4.9] mL·min −1 ·kg −1 ) compared with dialysis vintage ≤12 months (18.9 [5.9] mL·min −1 ·kg −1 ; P =0.033).

Conclusions

Initiating dialysis is associated with a significant impairment in oxygen uptake at peak exercise and overall decrements in ventilatory and hemodynamic exercise responses that predispose patients to functional dependence. The magnitude of these changes is comparable to the differences between low‐risk New York Heart Association class I and higher‐risk New York Heart Association class II to IV heart failure.

Myocardial Cytoskeletal Adaptations in Advanced Kidney Disease

Background The myocardial cytoskeleton functions as the fundamental framework critical for organelle function, bioenergetics and myocardial remodeling. To date, impairment of the myocardial cytoskeleton occurring in the failing heart in patients with advanced chronic kidney disease has been largely undescribed. Methods and Results We conducted a 3-arm cross-sectional cohort study of explanted human heart tissues from patients who are dependent on hemodialysis (n=19), hypertension (n=10) with preserved renal function, and healthy controls (n=21). Left ventricular tissues were subjected to pathologic examination and next-generation RNA sequencing. Mechanistic and interference RNA studies utilizing in vitro human cardiac fibroblast models were performed. Left ventricular tissues from patients undergoing hemodialysis exhibited increased myocardial wall thickness and significantly greater fibrosis compared with hypertension patients (P<0.05) and control (P<0.01). Transcriptomic analysis revealed that the focal adhesion pathway was significantly enriched in hearts from patients undergoing hemodialysis. Hearts from patients undergoing hemodialysis exhibited dysregulated components of the focal adhesion pathway including reduced β-actin (P<0.01), β-tubulin (P<0.01), vimentin (P<0.05), and increased expression of vinculin (P<0.05) compared with controls. Cytoskeletal adaptations in hearts from the hemodialysis group were associated with impaired mitochondrial bioenergetics, including dysregulated mitochondrial dynamics and fusion, and loss of cell survival pathways. Mechanistic studies revealed that cytoskeletal changes can be driven by uremic and metabolic abnormalities of chronic kidney disease, in vitro. Furthermore, focal adhesion kinase silencing via interference RNA suppressed major cytoskeletal proteins synergistically with mineral stressors found in chronic kidney disease in vitro. Conclusions Myocardial failure in advanced chronic kidney disease is characterized by impairment of the cytoskeleton involving disruption of the focal adhesion pathway, mitochondrial failure, and loss of cell survival pathways.

Clinical outcomes associated with the emergency treatment of hyperkalaemia with intravenous insulin-dextrose

BACKGROUND

Hyperkalaemia occurs in up to 10% of hospital admissions but its treatment in the emergency setting is inconsistent.

OBJECTIVES

To describe the emergency management of hyperkalaemia in adults with insulin-dextrose (IDex) and to explore clinical outcomes associated with IDex treatment.

DESIGN AND SETTING

Cohort study using comprehensive electronic health records of all emergency admissions to a large university hospital in the United Kingdom between April 2015 and August 2018.

PARTICIPANTS

Adult patients aged ≥16 years with at least one emergency admission and one blood potassium result during the study period.

MAIN OUTCOMES AND MEASURES

Emergency hyperkalaemia treatment was evaluated including the requirement for re-treatment with IDex, episodes of glucose dysregulation, intensive care (ICU) admission and length of hospital stay. Associations with hyperkalaemia, adverse events and IDex treatment were explored by logistic regression.

RESULTS

Amongst 211,993 patients attending the Emergency Department (ED) we identified 11,107 hyperkalaemic adult patients, of whom 1,284 were treated with IDex. Multiple doses were required in 542 patients (42.2%). Hypoglycaemia (plasma glucose < 4 mmol/L) occurred in 249 patients (19.4%) within 6 hours of IDex. Repeated doses were associated with an increased risk of hypoglycaemia (OR 2.94, 95% CI 2.20 to 3.93) compared to patients receiving a single dose, which, after adjustment was also associated with an increased risk of death (OR 1.56, 95% CI 1.16 to 2.09) during the study period. Patients who received multiple doses of IDex (OR 2.2, 95% CI 1.6-3.1) and those who received a dose of insulin above the guideline recommended limit (OR 5.6 3.1-10.3) were more likely to be admitted to ICU following IDex than those who received a single dose or the guideline recommended dose of insulin.

CONCLUSIONS AND RELEVANCE

This study provides novel insight into the emergency management of hyperkalaemia in a large population, demonstrates the high risk of hypoglycaemia and highlights the urgent need for an improved, evidence-based approach to the emergency management of hyperkalaemia.

Developing a patient-centred tool for pain measurement and evaluation in autosomal dominant polycystic kidney disease

BACKGROUND

Pain affects 60% of the autosomal dominant polycystic kidney disease (ADPKD) population. Despite being an early and debilitating symptom, it is poorly characterized and management is suboptimal. This study aimed to develop an ADPKD-specific pain assessment tool (APAT) to facilitate pain research.

METHODS

Following a systematic review of PATs used in ADPKD studies and against international recommendations for pain trials, our multi-disciplinary team of clinical experts and patients constructed an ADPKD-pain conceptual framework of key pain evaluation themes. We compiled a new APAT covering domains prioritized within our framework using components of questionnaires validated in other chronic pain disorders. The APAT was administered longitudinally within a randomized high-water intake trial (NCT02933268) to ascertain feasibility and provide pilot data on ADPKD pain.

RESULTS

Thirty-nine ADPKD participants with chronic kidney disease Stages 1-4 provided 129 APAT responses. Each participant completed a median of 3 (range 1-10) assessments. Respondents' mean ± standard deviation age was 47 ± 13 years; 59% (23) were female; and 69% (27) had enlarged kidneys with median time from diagnosis 14.2 (interquartile range 7.0-25.9) years. Pain (52%) and associated analgesic use (29%) were common. Pain severity was associated with increasing age [odds ratio (OR) = 1.07, P = 0.009], female gender (OR = 4.34, P = 0.018), estimated glomerular filtration rate <60 mL/min/1.73 m2 (OR = 5.45, P = 0.021) and hypertension (OR = 12.11, P = 0.007), but not with kidney size (P = 0.23). The APAT achieved good internal consistency (Cronbach's alpha coefficient = 0.91) and test-retest reliability (domain intra-class correlation coefficients ranging from 0.62 to 0.90).

CONCLUSIONS

The APAT demonstrated good acceptability and reliability, and following further validation in a larger cohort could represent an invaluable tool for future ADPKD pain studies.

Effects of Spironolactone and Chlorthalidone on Cardiovascular Structure and Function in Chronic Kidney Disease: A Randomized, Open-Label Trial

BACKGROUND AND OBJECTIVES

In a randomized double-blind, placebo-controlled trial, treatment with spironolactone in early-stage CKD reduced left ventricular mass and arterial stiffness compared with placebo. It is not known if these effects were due to BP reduction or specific vascular and myocardial effects of spironolactone.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A prospective, randomized, open-label, blinded end point study conducted in four UK centers (Birmingham, Cambridge, Edinburgh, and London) comparing spironolactone 25 mg to chlorthalidone 25 mg once daily for 40 weeks in 154 participants with nondiabetic stage 2 and 3 CKD (eGFR 30-89 ml/min per 1.73 m²). The primary end point was change in left ventricular mass on cardiac magnetic resonance imaging. Participants were on treatment with an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker and had controlled BP (target ≤130/80 mm Hg).

RESULTS

There was no significant difference in left ventricular mass regression; at week 40, the adjusted mean difference for spironolactone compared with chlorthalidone was -3.8 g (95% confidence interval, -8.1 to 0.5 g, P=0.08). Office and 24-hour ambulatory BPs fell in response to both drugs with no significant differences between treatment. Pulse wave velocity was not significantly different between groups; at week 40, the adjusted mean difference for spironolactone compared with chlorthalidone was 0.04 m/s (-0.4 m/s, 0.5 m/s, P=0.90). Hyperkalemia (defined ≥5.4 mEq/L) occurred more frequently with spironolactone (12 versus two participants, adjusted relative risk was 5.5, 95% confidence interval, 1.4 to 22.1, P=0.02), but there were no patients with severe hyperkalemia (defined ≥6.5 mEq/L). A decline in eGFR >30% occurred in eight participants treated with chlorthalidone compared with two participants with spironolactone (adjusted relative risk was 0.2, 95% confidence interval, 0.05 to 1.1, P=0.07).

CONCLUSIONS

Spironolactone was not superior to chlorthalidone in reducing left ventricular mass, BP, or arterial stiffness in nondiabetic CKD.

Cardiovascular Functional Reserve Before and After Kidney Transplant

Importance

Restitution of kidney function by transplant confers a survival benefit in patients with end-stage renal disease. Investigations of mechanisms involved in improved cardiovascular survival have relied heavily on static measures from echocardiography or cardiac magnetic resonance imaging and have provided conflicting results to date.

Objectives

To evaluate cardiovascular functional reserve in patients with end-stage renal disease before and after kidney transplant and to assess functional and morphologic alterations of structural-functional dynamics in this population.

Design, Setting, and Participants

This prospective, nonrandomized, single-center, 3-arm, controlled cohort study, the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) study, included patients with stage 5 chronic kidney disease (CKD) who underwent kidney transplant (KTR group), patients with stage 5 CKD who were wait-listed and had not undergone transplant (NTWC group), and patients with hypertension only (HTC group) seen at a single center from April 1, 2010, to January 1, 2013. Patients were followed up longitudinally for up to 1 year after kidney transplant. Clinical data collection was completed February 2014. Data analysis was performed from June 1, 2014, to March 5, 2015. Further analysis on baseline and prospective data was performed from June 1, 2017, to July 31, 2019.

Main Outcomes and Measures

Cardiovascular functional reserve was objectively quantified using state-of-the-art cardiopulmonary exercise testing in parallel with transthoracic echocardiography.

Results

Of the 253 study participants (mean [SD] age, 48.5 [12.7] years; 141 [55.7%] male), 81 were in the KTR group, 85 in the NTWC group, and 87 in the HTC group. At baseline, mean (SD) maximum oxygen consumption (V̇O2max) was significantly lower in the CKD groups (KTR, 20.7 [5.8] mL · min-1 · kg-1; NTWC, 18.9 [4.7] mL · min-1 · kg-1) compared with the HTC group (24.9 [7.1] mL · min-1 · kg-1) (P < .001). Mean (SD) cardiac left ventricular mass index was higher in patients with CKD (KTR group, 104.9 [36.1] g/m2; NTWC group, 113.8 [37.7] g/m2) compared with the HTC group (87.8 [16.9] g/m2), (P < .001). Mean (SD) left ventricular ejection fraction was significantly lower in the patients with CKD (KTR group, 60.1% [8.6%]; NTWC group, 61.4% [8.9%]) compared with the HTC group (66.1% [5.9%]) (P < .001). Kidney transplant was associated with a significant improvement in V̇O2max in the KTR group at 12 months (22.5 [6.3] mL · min-1 · kg-1; P < .001), but the value did not reach the V̇O2max in the HTC group (26.0 [7.1] mL · min-1 · kg-1) at 12 months. V̇O2max decreased in the NTWC group at 12 months compared with baseline (17.7 [4.1] mL · min-1 · kg-1, P < .001). Compared with the KTR group (63.2% [6.8%], P = .02) or the NTWC group (59.3% [7.6%], P = .003) at baseline, transplant was significantly associated with improved left ventricular ejection fraction at 12 months but not with left ventricular mass index.

Conclusions and Relevance

The findings suggest that kidney transplant is associated with improved cardiovascular functional reserve after 1 year. In addition, cardiopulmonary exercise testing was sensitive enough to detect a decline in cardiovascular functional reserve in wait-listed patients with CKD. Improved V̇O2max may in part be independent from structural alterations of the heart and depend more on ultrastructural changes after reversal of uremia.

Impaired arterial vitamin D signaling occurs in the development of vascular calcification

Conflicting data exists as to whether vitamin D receptor agonists (VDRa) are protective of arterial calcification. Confounding this, is the inherent physiological differences between human and animal experimental models and our current fragmented understanding of arterial vitamin D metabolism, their alterations in disease states and responses to VDRa’s. Herein, the study aims to address these problems by leveraging frontiers in human arterial organ culture models. Human arteries were collected from a total of 24 patients (healthy controls, n = 12; end-stage CKD, n = 12). Cross-sectional and interventional studies were performed using arterial organ cultures treated with normal and calcifying (containing 5mmol/L CaCl₂ and 5mmol/L β-glycerophosphate) medium, ex vivo. To assess the role of VDRa therapy, arteries were treated with either calcitriol or paricalcitol. We found that human arteries express a functionally active vitamin D system, including the VDR, 1α-hydroxylase and 24-hydroxylase (24-OHase) components and these were dysregulated in CKD arteries. VDRa therapy increased VDR expression in healthy arteries (p<0.01) but not in CKD arteries. Arterial 1α-OHase (p<0.05) and 24-OHase mRNA and protein expression were modulated differentially in healthy and CKD arteries by VDRa therapy. VDRa exposure suppressed Runx2 and MMP-9 expression in CKD arteries, however only paricalcitol suppressed MMP-2. VDRa exposure did not modulate arterial calcification in all organ culture models. However, VDRa reduced expression of senescence associated β-galactosidase (SAβG) staining in human aortic-smooth muscle cells under calcifying conditions, in vitro. In conclusion, maladaptation of arterial vitamin D signaling components occurs in CKD. VDRa exposure can exert vasculo-protective effects and seems critical for the regulation of arterial health in CKD.

High water vs. ad libitum water intake for autosomal dominant polycystic kidney disease: a randomized controlled feasibility trial

BACKGROUND

Vasopressin stimulates cyst growth in autosomal dominant polycystic kidney disease (ADPKD) and is a key therapeutic target. Evaluation of high water intake as an alternative to pharmacological vasopressin blockade is supported by patients. However feasibility, safety and adherence-promoting strategies required to deliver this remain unknown.

AIMS

Assess the feasibility of a definitive randomized high water intake trial in ADPKD.

METHODS

In this prospective open-label randomized trial, adult ADPKD patients with eGFR ≥ 20 ml/min/1.73 m2 were randomized to prescribed high water (HW) intake targeting urine osmolality (UOsm) ≤270 mOsm/kg, or ad libitum (AW) intake (UOsm >300 mOsm/kg). Self-management strategies including home-monitoring of urine-specific gravity (USG) were employed to promote adherence.

RESULTS

We enrolled 42 participants, baseline median eGFR (HW 68.4 [interquartile range (IQR) 35.9-107.2] vs. AW 75.8 [IQR 59.0-111.0 ml/min/1.73 m2, P = 0.22) and UOsm (HW 353 [IQR 190-438] vs. AW 350 [IQR 240-452] mOsm/kg, P = 0.71) were similar between groups. After 8 weeks, 67% in the HW vs. 24% in AW group achieved UOsm ≤270 mOsm/kg, P = 0.001. HW group achieved lower UOsm (194 [IQR 190-438] vs. 379 [IQR 235-503] mOsm/kg, P = 0.01) and higher urine volumes (3155 [IQR 2270-4295] vs. 1920 [IQR 1670-2960] ml/day, P = 0.02). Two cases of hyponatraemia occurred in HW group. No acute GFR effects were detected. In total 79% (519/672) of USG were submitted and 90% (468/519) were within target. Overall, 17% withdrew during the study.

CONCLUSION

DRINK demonstrated successful recruitment and adherence leading to separation between treatment arms in primary outcomes. These findings suggest a definitive trial assessing the impact of high water on kidney disease progression in ADPKD is feasible.

Assessing the role of ketogenic dietary therapy in ring chromosome 20 syndrome: A patient-led approach

Ring chromosome 20 syndrome (r(20)) is an ultra‐rare disease characterized by drug‐refractory epilepsy, cognitive impairment, and behavioral problems. Nonpharmacological treatments alongside antiepileptic drugs early after diagnosis may help reduce seizure frequency and preserve cognition. Ketogenic dietary therapy (KDT) has benefitted children with complex, refractory epilepsies, but its efficacy in r(20) is unknown. We assessed clinical prescription, implementation, and patient experience of KDT in r(20) through online surveys and a workshop. Forty‐two patients, families, carers, and 23 healthcare professionals completed the surveys. While nearly all patients were familiar with KDT, only half had tried it. Significant improvement in seizure activity, cognition, and alertness was reported; side effects were typically mild but with one report of increased seizure frequency. A high rate of co‐morbidity, older age at presentation, behavioral problems, and cognitive impairment can make implementing KDT in r(20) challenging. In the UK, NHS KDT services are predominantly available to pediatric patients, with very limited adult access. A health economic analysis illustrating reduced acute care costs or improved quality of life may support more widespread KDT implementation. Growing evidence supports KDT as an effective and safe intervention, but further research is needed to understand the mechanisms of r(20) and its interaction with ketosis.

Legal and ethical framework for global health information and biospecimen exchange - an international perspective

Background

The progress of electronic health technologies and biobanks holds enormous promise for efficient research. Evidence shows that studies based on sharing and secondary use of data/samples have the potential to significantly advance medical knowledge. However, sharing of such resources for international collaboration is hampered by the lack of clarity about ethical and legal requirements for transfer of data and samples across international borders.

Main text

Here, the International Clinical Trial Center Network (ICN) reports the legal and ethical requirements governing data and sample exchange (DSE) across four continents. The most recurring requirement is ethical approval, whereas only in specific conditions approval of national health authorities is required. Informed consent is not required in all sharing situations. However, waiver of informed consent is only allowed in certain countries/regions and under certain circumstances. The current legal and ethical landscape appears to be very complex and under constant evolution. Regulations differ between countries/regions and are often incomplete, leading to uncertainty.

Conclusion

With this work, ICN illuminates the unmet need for a single international collaborative framework to facilitate DSE. Harmonising requirements for global DSE will reduce inefficiency and waste in research. There are many challenges to realising this ambitious vision, including inconsistent terminology and definitions, and heterogeneous and dynamic legal constraints. Here, we identify areas of agreement and significant difference as a necessary first step towards facilitating international collaboration. We propose the establishment of a working group to continue the comparison across jurisdictions, create a standardised glossary and define a set of basic principles and fundamental requirements for DSE.

Mycophenolate mofetil versus cyclophosphamide for remission induction in ANCA-associated vasculitis: a randomised, non-inferiority trial

OBJECTIVES

Cyclophosphamide induction regimens are effective for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), but are associated with infections, malignancies and infertility. Mycophenolate mofetil (MMF) has shown high remission rates in small studies of AAV.

METHODS

We conducted a randomised controlled trial to investigate whether MMF was non-inferior to cyclophosphamide for remission induction in AAV. 140 newly diagnosed patients were randomly assigned to MMF or pulsed cyclophosphamide. All patients received the same oral glucocorticoid regimen and were switched to azathioprine following remission. The primary endpoint was remission by 6 months requiring compliance with the tapering glucocorticoid regimen. Patients with an eGFR <15 mL/min were excluded from the study.

RESULTS

At baseline, ANCA subtype, disease activity and organ involvement were similar between groups. Non-inferiority was demonstrated for the primary remission endpoint, which occurred in 47 patients (67%) in the MMF group and 43 patients (61%) in the cyclophosphamide group (risk difference 5.7%, 90% CI -7.5% to 19%). Following remission, more relapses occurred in the MMF group (23 patients, 33%) compared with the cyclophosphamide group (13 patients, 19%) (incidence rate ratio 1.97, 95% CI 0.96 to 4.23, p=0.049). In MPO-ANCA patients, relapses occurred in 12% of the cyclophosphamide group and 15% of the MMF group. In PR3-ANCA patients, relapses occurred in 24% of the cyclophosphamide group and 48% of the MMF group. Serious infections were similar between groups (26% MMF group, 17% cyclophosphamide group) (OR 1.67, 95% CI 0.68 to 4.19, p=0.3).

CONCLUSION

MMF was non-inferior to cyclophosphamide for remission induction in AAV, but resulted in higher relapse rate.

TRIAL REGISTRATION NUMBER

NCT00414128.

Randomised controlled trial of high versus ad libitum water intake in patients with autosomal dominant polycystic kidney disease: rationale and design of the DRINK feasibility trial

INTRODUCTION

Vasopressin stimulates cyst growth in autosomal dominant polycystic kidney disease (ADPKD) leading to enlarged kidneys, hypertension and renal failure. Vasopressin receptor blockade slows disease progression. Physiological suppression of vasopressin secretion through high water (HW) intake could achieve a similar effect, necessitating a definitive large-scale trial of HW intake in ADPKD. The objective of the DRINK trial is to answer the key design and feasibility questions required to deliver a successful definitive water intake trial.

METHODS AND ANALYSIS

We describe the design of a single-centre, open-label, prospective, randomised controlled trial. The "Determining feasibility of R andomisation to high vs. ad libitum water In take in Polycystic K idney Disease" (DRINK) trial aims to enrol 50 patients with ADPKD, over the age of 16 years with an estimated glomerular filtration rate (eGFR) ≥20 mL/min/1.73 m². Participants will be randomised 1:1 to HW intake based on an individualised water intake prescription, or to ad libitum (AW) water intake. The HW group will aim for a dilute urine (urine osmolality ≤270 mOsm/kg) as a surrogate marker of vasopressin suppression, and those in the AW group will target more concentrated urine. Participants will have an 8-week treatment period, and will be seen at weeks 0, 2, 4 and 8, undergoing assessments of fluid status, renal function and serum and urine osmolalities. They will receive dietary advice, and self-monitor urine specific gravity and fluid intake. The trial employs smartphone technology to permit home monitoring and remote direct data capture. The primary feasibility end points are recruitment rate and separation between arms in measured urinary osmolality. Key secondary assessments include acceptability, adherence, health-related quality of life, acute effects of HW intake on measured (⁵¹Cr-EDTA) and eGFR and ADPKD-related pain.

ETHICS AND DISSEMINATION

Ethical approval was awarded by the East of England Essex Research Ethics Committee (16/EE/0026). The results of DRINK will be submitted to peer-reviewed journals, and presented to patients via the PKD Charity.

TRIAL REGISTRATION NUMBER

NCT02933268 and ISCRTN16794957.

Inverting the patient involvement paradigm: defining patient led research

PLAIN ENGLISH SUMMARY

Patients usually understand their disease and lifestyle needs better than many medical professionals. They also have important ideas about what research would be most beneficial to their lives, especially on how to manage symptoms in a way that improves daily quality of life. In the UK, the National Institute for Health Research has recognised the value of patient insight, and now requires researchers with public funding to involve patients and the public throughout the research process. There are many opportunities for involvement, but these generally focus on improving study design to ensure the trial is acceptable to participants. Some programmes work towards setting research priorities as important to patients, public members, and medical experts, but due to the complexity and cost involved in running clinical trials, the majority of research originates with the pharmaceutical industry or academic institutions. There is a clear mismatch between research ideas that patients prioritise (quality of life), and those actually investigated (drug development).The Patient Led Research Hub (PLRH) is a new initiative hosted by the Cambridge Clinical Trials Unit. The PLRH supports research ideas as proposed by patient organisations, providing resources and expertise in research design and delivery. The PLRH aims to co-produce any technically feasible project, regardless of disease or symptom focus. The proposing patient group maintains ownership of the project with an active role in study management. This method of research has proven to produce credible research studies that are of direct relevance to patients.

ABSTRACT

Patient and Public Involvement has become an indispensable and expected component of healthcare research in the United Kingdom, largely driven by the National Institute of Health Research and other research funders. Opportunities for patients to become involved in research abound, and many organisations now have dedicated 'public involvement' teams. However, its value is often questioned amidst criticism of tokenism and the recognition that a mismatch persists between patient priorities and funded research. Although patients are frequently consulted, evidence that their involvement influences the research agenda remains limited. We propose a novel model that allows patients and the public not only to propose research questions, but to design, initiate and deliver their own research with all the necessary support from research professionals. We demonstrate the feasibility and utility of this approach in reporting the establishment, experiences and progress of the Patient Led Research Hub. Using this resource, patient organisations are now able to initiate and conduct rigorous clinical research unfettered by the constraints of academic or economic agendas.

Long term azathioprine maintenance therapy in ANCA-associated vasculitis: combined results of long-term follow-up data

Objective

We studied whether in ANCA-associated vasculitis patients, duration of AZA maintenance influenced relapse rate during long-term follow-up.

Methods

Three hundred and eighty newly diagnosed ANCA-associated vasculitis patients from six European multicentre studies treated with AZA maintenance were included; 58% were male, median age at diagnosis 59.4 years (interquartile range: 48.3-68.2 years); granulomatosis with polyangiitis, n = 236; microscopic polyangiitis, n = 132; or renal limited vasculitis, n = 12. Patients were grouped according to the duration of AZA maintenance after remission induction: ⩽18 months, ⩽24 months, ⩽36 months, ⩽48 months or > 48 months. Primary outcome was relapse-free survival at 60 months.

Results

During follow-up, 84 first relapses occurred during AZA-maintenance therapy (1 relapse per 117 patient months) and 71 after withdrawal of AZA (1 relapse/113 months). During the first 12 months after withdrawal, 20 relapses occurred (1 relapse/119 months) and 29 relapses >12 months after withdrawal (1 relapse/186 months). Relapse-free survival at 60 months was 65.3% for patients receiving AZA maintenance >18 months after diagnosis vs 55% for those who discontinued maintenance ⩽18 months (P = 0.11). Relapse-free survival was associated with induction therapy (i.v. vs oral) and ANCA specificity (PR3-ANCA vs MPO-ANCA/negative).

Conclusion

Post hoc analysis of combined trial data suggest that stopping AZA maintenance therapy does not lead to a significant increase in relapse rate and AZA maintenance for more than 18 months after diagnosis does not significantly influence relapse-free survival. ANCA specificity has more effect on relapse-free survival than duration of maintenance therapy and should be used to tailor therapy individually.

A randomized, multicenter, open-label, blinded end point trial comparing the effects of spironolactone to chlorthalidone on left ventricular mass in patients with early-stage chronic kidney disease: Rationale and design of the SPIRO-CKD trial

BACKGROUND

Chronic kidney disease (CKD) is associated with increased left ventricular (LV) mass and arterial stiffness. In a previous trial, spironolactone improved these end points compared with placebo in subjects with early-stage CKD, but it is not known whether these effects were specific to the drug or secondary to blood pressure lowering.

AIM

The aim was to investigate the hypothesis that spironolactone is superior to chlorthalidone in the reduction of LV mass while exerting similar effects on blood pressure.

DESIGN

This is a multicenter, prospective, randomized, open-label, blinded end point clinical trial initially designed to compare the effects of 40weeks of treatment with spironolactone 25mg once daily to chlorthalidone 25mg once daily on the co-primary end points of change in pulse wave velocity and change in LV mass in 350 patients with stages 2 and 3 CKD on established treatment with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Because of slow recruitment rates, it became apparent that it would not be possible to recruit this sample size within the funded time period. The study design was therefore changed to one with a single primary end point of LV mass requiring 150 patients. Recruitment was completed on 31 December 2016, at which time 154 patients had been recruited. Investigations included cardiac magnetic resonance imaging, applanation tonometry, 24-hour ambulatory blood pressure monitoring, and laboratory tests. Subjects are assessed before and after 40weeks of randomly allocated drug therapy and at 46weeks after discontinuation of the study drug.

Negative anti-neutrophil cytoplasm antibody at switch to maintenance therapy is associated with a reduced risk of relapse

BACKGROUND

Relapse of disease is frequent in anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV). It is unclear whether persistent ANCA when starting maintenance therapy increases the risk of relapse. We examined the association between ANCA status and relapse in two randomised controlled trials.

METHODS

ANCA-positive patients in two trials, CYCLOPS and IMPROVE, were switched from cyclophosphamide to maintenance therapy after achieving clinical remission. We classified patients as being either ANCA-positive or ANCA-negative at the time they started maintenance therapy. We compared the risk of relapse in ANCA-positive and ANCA-negative patients.

RESULTS

Of 252 patients included, 102 (40%) experienced at least one relapse during the follow-up period. At the time of the switch from induction to maintenance therapy, 111 were ANCA-positive, of whom 55 (50%) relapsed, compared to 141 patients who were ANCA-negative, of whom 47 (33%) relapsed. In multivariable time-to-event analysis, a reduced risk of relapse was associated with having become ANCA-negative at the time of switching to maintenance therapy (hazard ratio 0.63, 95% confidence interval 0.42-0.95; p = 0.026). In addition, initial proteinase 3 (PR3)-ANCA, younger age, lower serum creatinine, pulsed cyclophosphamide for remission induction, and mycophenolate mofetil for remission maintenance were all associated with an increased risk of relapse.

CONCLUSIONS

Becoming ANCA-negative before the switch to maintenance is associated with a reduced risk of relapse.

TRIAL REGISTRATION

CYCLOPS: ClinicalTrials.gov, NCT00430105 . Registered retrospectively on 31 January 2007.

IMPROVE

ClinicalTrials.gov, NCT00307645 . Registered retrospectively on 27 March 2006.

Patient Survey of current water Intake practices in autosomal dominant Polycystic kidney disease: the SIPs survey

Background: Autosomal dominant polycystic kidney disease (ADPKD) affects 12.5 million worldwide. Vasopressin drives cysts growth and in animal models can be suppressed through high water intake. A randomized controlled trial of 'high' versus 'standard' water intake in ADPKD is essential to determine if this intervention is beneficial. We conducted an ADPKD patient survey to gain an understanding of current fluid intake practices and the design challenges of a randomized water intake trial. Methods: In collaboration with the PKD Charity, we developed and distributed an online survey to ADPKD patients over age 16 years and not on renal replacement therapy. Results: Of the 2377 invited, 89 ADPKD patients completed the Survey of current water Intake practices in autosomal dominant Polycystic kidney disease (SIPs) online questionnaire. Most were female (65, 73%) and white (84, 94%), with a median age group of 45-49 years. The risk of contamination between treatment arms was highlighted by the survey as the majority (70, 79%) routinely discussed ADPKD management with family despite only 17% sharing the same household. More participants reported drinking beyond thirst (65, 73%) than those actually indicating a daily fluid intake of >2 L (54, 61%). This discrepancy emphasizes inaccuracies of fluid intake estimates and the requirement for objective methods of measuring water intake. Overall, only 51% believed high water intake was beneficial, while 91% were willing to participate in research evaluating this. Conclusion: ADPKD poses unique design challenges to a randomized water intake trial. However, the trial is likely to be supported by the ADPKD community and could impact significantly on PKD management and associated healthcare costs.

Arterial Expression of the Calcium-Sensing Receptor Is Maintained by Physiological Pulsation and Protects against Calcification

Vascular calcification (VC) is common in chronic kidney disease (CKD) and contributes to cardiovascular mortality. The calcium-sensing receptor (CaSR) is present in human artery, senses extracellular calcium and may directly modulate VC. Objective: to investigate the association between arterial cyclic strain, CaSR expression and VC. Methods and Results: human aortic smooth muscle cells (HAoSMC) were cultured under static or strained conditions, with exposure to CaSR agonists, the calcimimetic R568, and after CaSR silencing and over-expression. High extracellular calcium reduced CaSR expression and promoted osteochondrogenic transformation and calcium deposition. This was partially prevented by cyclic strain and exposure to R568. CaSR silencing enhanced calcification and osteochondrogenic transformation, whereas CaSR over-expression attenuated this procalcific response, demonstrating a central role for the CaSR in the response to cyclic strain and regulation of VC. In arterial explants from CKD patients (n = 11) and controls (n = 9), exposure to R568 did not significantly alter calcium deposition, osteochondrogenic markers or total artery calcium content. Conclusions: physiological mechanical strain is important for arterial homeostasis and may protect arteries from VC. The beneficial effects of cyclic strain may be mediated via the CaSR.

α-Klotho Expression in Human Tissues

CONTEXT

α-Klotho has emerged as a powerful regulator of the aging process. To date, the expression profile of α-Klotho in human tissues is unknown, and its existence in some human tissue types is subject to much controversy.

OBJECTIVE

This is the first study to characterize systemwide tissue expression of transmembrane α-Klotho in humans. We have employed next-generation targeted proteomic analysis using parallel reaction monitoring in parallel with conventional antibody-based methods to determine the expression and spatial distribution of human α-Klotho expression in health.

RESULTS

The distribution of α-Klotho in human tissues from various organ systems, including arterial, epithelial, endocrine, reproductive, and neuronal tissues, was first identified by immunohistochemistry. Kidney tissues showed strong α-Klotho expression, whereas liver did not reveal a detectable signal. These results were next confirmed by Western blotting of both whole tissues and primary cells. To validate our antibody-based results, α-Klotho-expressing tissues were subjected to parallel reaction monitoring mass spectrometry (data deposited at ProteomeXchange, PXD002775) identifying peptides specific for the full-length, transmembrane α-Klotho isoform.

CONCLUSIONS

The data presented confirm α-Klotho expression in the kidney tubule and in the artery and provide evidence of α-Klotho expression across organ systems and cell types that has not previously been described in humans.

Comparability of patients with ANCA-associated vasculitis enrolled in clinical trials or in observational cohorts

OBJECTIVES

To analyse the differences between patients with granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) entered into randomised clinical trials (RCTs) and those followed in large observational cohorts.

METHODS

The main characteristics and outcomes of patients with generalised and/or severe GPA or MPA with a five-factor score ≥ 1 enrolled in the French Vasculitis Study Group (FVSG) or the US-Canadian-based Vasculitis Clinical Research Consortium cohorts were compared to those enrolled in one of 2 FVSG clinical RCTs (WEG91, WEGENT) or 3 European Vasculitis Society clinical trials (CYCLOPS, CYCAZAREM, IMPROVE).

RESULTS

657 patients (65.3% with GPA) in RCTs were compared to 437 in cohorts (90.6% with GPA). RCT patients were older at diagnosis than the cohort patients (56.6 ± 13.9 vs. 46.8 ± 17.3 years), had higher Birmingham vasculitis activity score (19.5 ± 9.1 vs. 16.9 ± 7.4), and more frequent kidney disease (84.0% vs. 54.9%) but fewer ear, nose, and throat symptoms (56.8% vs. 72.2%). At 56 months post-diagnosis, mortality and relapse rates, adjusted for age and renal function, were higher for patients with GPA in RCTs vs. cohorts (10.7% vs. 2.5% [p=0.001] and 22.5% vs. 15.6% [p=0.03], respectively) but similar for patients with MPA (6.2% vs. 6.6% [p=0.92] and 16.6% vs. 10.1% [p=0.39], respectively).

CONCLUSIONS

Patients with GPA or MPA in RCTs and those in observational cohorts show important differences that should be remembered when interpreting results based on these study populations.

Successful restoration of arteriovenous dialysis access patency after late intervention

Background

Arteriovenous dialysis access may be lost due to stenosis and thrombosis. Patency may be restored by thrombectomy or thrombolysis, but this is often not undertaken when the presentation is delayed. The success rate of delayed intervention is largely unknown.

Methods

In this single-centre study, we identified all instances of arteriovenous vascular access (VA) failure treated with angioplasty, thrombectomy or thrombolysis between August 2010 and July 2013. Patency rates immediately after intervention, and after 3 months, were assessed using multilevel mixed effects logistic regression.

Results

Sixty failures occurred in 41 accesses (38 patients). The access age at failure was 495 (316–888) days. Intervention was carried out after >48 h in 19 failures (32%). Immediate patency was achieved in 46 failures, of which 32 remained patent after 3 months. Delaying intervention increased the likelihood of achieving immediate patency (OR 0.55, 95% CI 0.31–1.0, P = 0.05). Having lost arteriovenous accesses previously increased the risk of immediate failure (OR 4.0, 95% CI 1.07–14.95, P = 0.04). There was no association between failure-to-intervention-time and 3-month patency rates (P = 0.23). Effect estimates did not differ between arteriovenous fistulae and synthetic arteriovenous grafts.

Conclusion

Delayed intervention for failed arteriovenous VA may result in superior early patency rates and yields equivalent 3-month patency rates.

Human urinary exosomes as innate immune effectors

Exosomes are small extracellular vesicles, approximately 50 nm in diameter, derived from the endocytic pathway and released by a variety of cell types. Recent data indicate a spectrum of exosomal functions, including RNA transfer, antigen presentation, modulation of apoptosis, and shedding of obsolete protein. Exosomes derived from all nephron segments are also present in human urine, where their function is unknown. Although one report suggested in vitro uptake of exosomes by renal cortical collecting duct cells, most studies of human urinary exosomes have focused on biomarker discovery rather than exosome function. Here, we report results from in-depth proteomic analyses and EM showing that normal human urinary exosomes are significantly enriched for innate immune proteins that include antimicrobial proteins and peptides and bacterial and viral receptors. Urinary exosomes, but not the prevalent soluble urinary protein uromodulin (Tamm-Horsfall protein), potently inhibited growth of pathogenic and commensal Escherichia coli and induced bacterial lysis. Bacterial killing depended on exosome structural integrity and occurred optimally at the acidic pH typical of urine from omnivorous humans. Thus, exosomes are innate immune effectors that contribute to host defense within the urinary tract.

Plasma exchange induces vitamin D deficiency

BACKGROUND

Plasma exchange is used in the treatment of diseases mediated by pathogenic circulating proteins, or for transplant desensitization. Its non-targeted nature results in the depletion of physiologically important molecules, and it is often complicated by hypocalcaemia.

AIM

To determine the effects of plasma exchange on vitamin D binding protein (DBP) and associated vitamin D metabolites.

DESIGN

Single-centre prospective cohort study of 11 patients.

METHODS

DBP and vitamin D metabolites were measured before and immediately after five plasma exchanges, and 7 and 28 days after discontinuation of plasma exchange.

RESULTS

Plasma exchange reduced plasma DBP concentration from 196.9 ± 53.2 to 98.5 ± 34 μg/ml (P = 0.0001), 1,25-dihydroxyvitamin D from 103 ± 52 to 42 ± 4 pmol/l (P = 0.003) and 25-hydroxyvitamin D from 49.7 ± 29 to 22 ± 9.4 nmol/l (P = 0.0017), through their removal in effluent. After 7 days, DBP and 1,25-dihydroxyvitamin D were not significantly different from baseline, but 25-hydroxyvitamin D remained significantly lower after 7 days (26.4 ± 9.8 nmol/l, P = 0.02) and 28 days (30.8 ± 15.5 nmol/l, P = 0.048). Corrected calcium decreased from 2.23 ± 0.11 to 1.98 ± 0.08 mmol/l (P = 0.0007) immediately after five treatments. Plasma calcium was significantly associated with 1,25-dihydroxyvitamin D (r(2) = 0.79, P < 0.0001).

CONCLUSION

Plasma exchange induced an acute reversible decrease in plasma 1,25-dihydroxyvitamin D, DBP, calcium and a sustained decrease in plasma 25-hydroxyvitamin D.

Association of calcium, phosphate and parathyroid hormone with renal allograft function: a retrospective cohort study

BACKGROUND

Significant variations in postoperative levels of parathyroid hormone (PTH), calcium and phosphate exist after renal transplantation, but whether they affect allograft function is unknown. We investigated the association between early post-transplant levels of PTH, calcium and phosphate and graft function.

METHODS

We performed a single-centre cohort study of renal transplant recipients from Addenbrooke's Hospital, Cambridge, between April 1997 and March 2007, evaluating the association between plasma calcium, phosphate and PTH 1 month after transplantation and change in epidermal growth factor receptor (eGFR) in the first 12 months after transplantation (estimated using the Modification of Diet in Renal Disease Study equation). Differences in eGFR between 26 and 52 weeks after transplantation were computed using mixed effects linear regression models for repeated measures of eGFR, while adjusting for sociodemographic and biochemical variables.

RESULTS

Three hundred and forty-three patients were eligible for study. The mean age (standard deviation) at transplant was 43 years (13 years). Between 30 and 90 days after transplantation, the median (25th-75th percentile) eGFR was 33 (26-50) ml/min/1.73 m(2), the mean calcium level was 2.4 (0.17) mmol/l and the mean phosphate level was 0.78 (0.23) mmol/l. There was a significant interaction between calcium and phosphate levels (p = 0.006). In patients with low levels of phosphate, higher levels of calcium were associated with declining eGFR over time. However, in patients with a high phosphate level, higher calcium was associated with improved eGFR.

CONCLUSIONS

Higher serum calcium in patients with low serum phosphate after transplantation is associated with a decline in graft function during the first year after transplantation. Disorders of mineral metabolism after transplant may represent an important therapeutic target to preserve allograft function.

Clinical utility of PKD2 mutation testing in a polycystic kidney disease cohort attending a specialist nephrology out-patient clinic

Background

ADPKD affects approximately 1:1000 of the worldwide population. It is caused by mutations in two genes, PKD1 and PKD2. Although allelic variation has some influence on disease severity, genic effects are strong, with PKD2 mutations predicting later onset of ESRF by up to 20 years. We therefore screened a cohort of ADPKD patients attending a nephrology out-patient clinic for PKD2 mutations, to identify factors that can be used to offer targeted gene testing and to provide patients with improved prognostic information.

Methods

142 consecutive individuals presenting to a hospital nephrology out-patient service with a diagnosis of ADPKD and CKD stage 4 or less were screened for mutations in PKD2, following clinical evaluation and provision of a detailed family history (FH).

Results

PKD2 mutations were identified in one fifth of cases. 12% of non-PKD2 patients progressed to ESRF during this study whilst none with a PKD2 mutation did (median 38.5 months of follow-up, range 16–88 months, p < 0.03). A significant difference was found in age at ESRF of affected family members (non-PKD2 vs. PKD2, 54 yrs vs. 65 yrs; p < 0.0001). No PKD2 mutations were identified in patients with a FH of ESRF occurring before age 50 yrs, whereas a PKD2 mutation was predicted by a positive FH without ESRF.

Conclusions

PKD2 testing has a clinically significant detection rate in the pre-ESRF population. It did not accurately distinguish those individuals with milder renal disease defined by stage of CKD but did identify a group less likely to progress to ESRF. When used with detailed FH, it offers useful prognostic information for individuals and their families. It can therefore be offered to all but those whose relatives have developed ESRF before age 50.

Uromodulin exclusion list improves urinary exosomal protein identification

Advances in mass spectrometry (MS) have encouraged interest in its deployment in urine biomarker studies, but success has been limited. Urine exosomes have been proposed as an ideal source of biomarkers for renal disease. However, the abundant urinary protein, uromodulin, cofractionates with exosomes during isolation and represents a practical contaminant that limits MS sensitivity. Uromodulin depletion has been attempted but is labor- and time-intensive and may remove important protein biomarkers. We describe the application of an exclusion list (ExL) of uromodulin-related peptide ions, coupled with high-sensitivity mass spectrometric analysis, to increase the depth of coverage of the urinary exosomal proteome. Urine exosomal protein samples from healthy volunteers were subjected to tandem MS and abundant uromodulin peptides identified. Samples were run for a second time, while excluding these uromodulin peptides from fragmentation to allow identification of peptides from lower-abundance proteins. Uromodulin exclusion was performed in addition to dynamic exclusion. Results from these two procedures revealed 222 distinct proteins from conventional analysis, compared with 254 proteins after uromodulin exclusion, of which 188 were common to both methods. By unmasking a previously unidentified protein set, adding the ExL increased overall protein identifications by 29.7% to a total of 288 proteins. A fixed ExL, used in combination with conventional methods, effectively increases the depth of urinary exosomal proteins identified by MS, reducing the need for uromodulin depletion.

Mycophenolate mofetil vs azathioprine for remission maintenance in antineutrophil cytoplasmic antibody-associated vasculitis: a randomized controlled trial

CONTEXT

Current remission maintenance therapies for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are limited by partial efficacy and toxicity.

OBJECTIVE

To compare the effects of mycophenolate mofetil with azathioprine on the prevention of relapses in patients with AAV.

DESIGN, SETTING, AND PARTICIPANTS

Open-label randomized controlled trial, International Mycophenolate Mofetil Protocol to Reduce Outbreaks of Vasculitides (IMPROVE), to test the hypothesis that mycophenolate mofetil is more effective than azathioprine for preventing relapses in AAV. The trial was conducted at 42 centers in 11 European countries between April 2002 and January 2009 (42-month study). Eligible patients had newly diagnosed AAV (Wegener granulomatosis or microscopic polyangiitis) and were aged 18 to 75 years at diagnosis.

INTERVENTIONS

Patients were randomly assigned to azathioprine (starting at 2 mg/kg/d) or mycophenolate mofetil (starting at 2000 mg/d) after induction of remission with cyclophosphamide and prednisolone.

MAIN OUTCOME MEASURES

The primary end point was relapse-free survival, which was assessed using a Cox proportional hazards model. The secondary end points were Vasculitis Damage Index, estimated glomerular filtration rate, and proteinuria.

RESULTS

A total of 156 patients were assigned to azathioprine (n = 80) or mycophenolate mofetil (n = 76) and were followed up for a median of 39 months (interquartile range, 0.66-53.6 months). All patients were retained in the analysis by intention to treat. Relapses were more common in the mycophenolate mofetil group (42/76 patients) compared with the azathioprine group (30/80 patients), with an unadjusted hazard ratio (HR) for mycophenolate mofetil of 1.69 (95% confidence interval [CI], 1.06-2.70; P = .03). Severe adverse events did not differ significantly between groups. There were 22 severe adverse events in 13 patients (16%) in the azathioprine group and there were 8 severe adverse events in 8 patients (7.5%) in the mycophenolate mofetil group (HR, 0.53 [95% CI, 0.23-1.18]; P = .12). The secondary outcomes of Vasculitis Damage Index, estimated glomerular filtration rate, and proteinuria did not differ significantly between groups.

CONCLUSIONS

Among patients with AAV, mycophenolate mofetil was less effective than azathioprine for maintaining disease remission. Both treatments had similar adverse event rates.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00307645.

Glyceraldehyde 3-phosphate dehydrogenase is required for band 3 (anion exchanger 1) membrane residency in the mammalian kidney

The mammalian kidney isoform of the essential chloride-bicarbonate exchanger AE1 differs from its erythrocyte counterpart, being shorter at its N terminus. It has previously been reported that the glycolytic enzyme GAPDH interacts only with erythrocyte AE1, by binding to the portion not found in the kidney isoform. (Chu H, Low PS. Biochem J 400:143–151, 2006). We have identified GAPDH as a candidate binding partner for the C terminus of both AE1 and AE2. We show that full-length AE1 and GAPDH coimmunoprecipitated from both human and rat kidney as well as from Madin-Darby canine kidney (MDCK) cells stably expressing kidney AE1, while in human liver, AE2 coprecipitated with GAPDH. ELISA and glutathione S-transferase (GST) pull-down assays using GST-tagged C-terminal AE1 fusion protein confirmed that the interaction is direct; fluorescence titration revealed saturable binding kinetics with K_d 2.3 ± 0.2 μM. Further GST precipitation assays demonstrated that the D⁹⁰²EY residues in the D⁹⁰²EYDE motif located within the C terminus of AE1 are important for GAPDH binding. In vitro GAPDH activity was unaffected by C-terminal AE1 binding, unlike in erythrocytes. Also, differently from red cell N-terminal binding, GAPDH-AE1 C-terminal binding was not disrupted by phosphorylation of AE1 in kidney AE1-expressing MDCK cells. Importantly, small interfering RNA knockdown of GAPDH in these cells resulted in significant intracellular retention of AE1, with a concomitant reduction in AE1 at the cell membrane. These results indicate differences between kidney and erythrocyte AE1/GAPDH behavior and show that in the kidney, GAPDH is required for kidney AE1 to achieve stable basolateral residency.

Coal tar creosote abuse by vapour inhalation presenting with renal impairment and neurotoxicity: a case report

A 56 year old aromatherapist presented with advanced renal failure following chronic coal tar creosote vapour inhalation, and a chronic tubulo-interstitial nephritis was identified on renal biopsy. Following dialysis dependence occult inhalation continued, resulting in seizures, ataxia, cognitive impairment and marked generalised cerebral atrophy. We describe for the first time a case of creosote abuse by chronic vapour inhalation, resulting in significant morbidity. Use of the polycyclic aromatic hydrocarbon-containing wood preservative coal tar creosote is restricted by many countries due to concerns over environmental contamination and carcinogenicity. This case demonstrates additional toxicities not previously reported with coal tar creosote, and emphasizes the health risks of polycyclic aromatic hydrocarbon exposure.