Amiloride Reduces Urokinase/Plasminogen-Driven Intratubular Complement Activation in Glomerular Proteinuria.

SIGNIFICANCE STATEMENT: Proteinuria predicts accelerated decline in kidney function in CKD. The pathologic mechanisms are not well known, but aberrantly filtered proteins with enzymatic activity might be involved. The urokinase-type plasminogen activator (uPA)-plasminogen cascade activates complement and generates C3a and C5a in vitro / ex vivo in urine from healthy persons when exogenous, inactive, plasminogen, and complement factors are added. Amiloride inhibits uPA and attenuates complement activation in vitro and in vivo . In conditional podocin knockout (KO) mice with severe proteinuria, blocking of uPA with monoclonal antibodies significantly reduces the urine excretion of C3a and C5a and lowers tissue NLRP3-inflammasome protein without major changes in early fibrosis markers. This mechanism provides a link to proinflammatory signaling in proteinuria with possible long-term consequences for kidney function. BACKGROUND: Persistent proteinuria is associated with tubular interstitial inflammation and predicts progressive kidney injury. In proteinuria, plasminogen is aberrantly filtered and activated by urokinase-type plasminogen activator (uPA), which promotes kidney fibrosis. We hypothesized that plasmin activates filtered complement factors C3 and C5 directly in tubular fluid, generating anaphylatoxins, and that this is attenuated by amiloride, an off-target uPA inhibitor. METHODS: Purified C3, C5, plasminogen, urokinase, and urine from healthy humans were used for in vitro / ex vivo studies. Complement activation was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and ELISA. Urine and plasma from patients with diabetic nephropathy treated with high-dose amiloride and from mice with proteinuria (podocin knockout [KO]) treated with amiloride or inhibitory anti-uPA antibodies were analyzed. RESULTS: The combination of uPA and plasminogen generated anaphylatoxins C3a and C5a from intact C3 and C5 and was inhibited by amiloride. Addition of exogenous plasminogen was sufficient for urine from healthy humans to activate complement. Conditional podocin KO in mice led to severe proteinuria and C3a and C5a urine excretion, which was attenuated reversibly by amiloride treatment for 4 days and reduced by >50% by inhibitory anti-uPA antibodies without altering proteinuria. NOD-, LRR- and pyrin domain-containing protein 3-inflammasome protein was reduced with no concomitant effect on fibrosis. In patients with diabetic nephropathy, amiloride reduced urinary excretion of C3dg and sC5b-9 significantly. CONCLUSIONS: In conditions with proteinuria, uPA-plasmin generates anaphylatoxins in tubular fluid and promotes downstream complement activation sensitive to amiloride. This mechanism links proteinuria to intratubular proinflammatory signaling. In perspective, amiloride could exert reno-protective effects beyond natriuresis and BP reduction. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Increased Activity of a Renal Salt Transporter (ENaC) in Diabetic Kidney Disease, NCT01918488 and Increased Activity of ENaC in Proteinuric Kidney Transplant Recipients, NCT03036748 .

Effects of semaglutide, empagliflozin and their combination on renal diffusion-weighted MRI and total kidney volume in patients with type 2 diabetes: a post hoc analysis from a 32 week randomised trial.

AIMS/HYPOTHESIS: The apparent diffusion coefficient (ADC) derived from diffusion-weighted MRI (DWI-MRI) has been proposed as a measure of changes in kidney microstructure, including kidney fibrosis. In advanced kidney disease, the kidneys often become atrophic; however, in the initial phase of type 2 diabetes, there is an increase in renal size. Glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors both provide protection against progression of kidney disease in diabetes. However, the mechanisms are incompletely understood. To explore this, we examined the effects of semaglutide, empagliflozin and their combination on renal ADC and total kidney volume (TKV). METHODS: This was a substudy of a randomised clinical trial on the effects of semaglutide and empagliflozin alone or in combination. Eighty patients with type 2 diabetes and high risk of CVD were randomised into four groups (n=20 in each) receiving either tablet placebo, empagliflozin, a combination of semaglutide and tablet placebo (herein referred to as the 'semaglutide' group), or the combination of semaglutide and empagliflozin (referred to as the 'combination-therapy' group). The semaglutide and the combination-therapy group had semaglutide treatment for 16 weeks and then had either tablet placebo or empagliflozin added to the treatment, respectively, for a further 16 weeks; the placebo and empagliflozin groups were treated with the respective monotherapy for 32 weeks. We analysed the effects of treatment on changes in ADC (cortical, medullary and the cortico-medullary difference [ΔADC; medullary ADC subtracted from cortical ADC]), as well as TKV measured by MRI. RESULTS: Both semaglutide and empagliflozin decreased cortical ADC significantly compared with placebo (semaglutide: -0.20×10-3 mm2/s [95% CI -0.30, -0.10], p<0.001; empagliflozin: -0.15×10-3 mm2/s [95% CI -0.26, -0.04], p=0.01). No significant change was observed in the combination-therapy group (-0.05×10-3 mm2/s [95%CI -0.15, 0.05]; p=0.29 vs placebo). The changes in cortical ADC were not associated with changes in GFR, albuminuria, TKV or markers of inflammation. Further, there were no changes in medullary ADC in any of the groups compared with placebo. Only treatment with semaglutide changed ΔADC significantly from placebo, showing a decrease of -0.13×10-3 mm2/s (95% CI -0.22, -0.04; p=0.01). Compared with placebo, TKV decreased by -3% (95% CI -5%, -0.3%; p=0.04), -3% (95% CI -5%, -0.4%; p=0.02) and -5% (95% CI -8%, -2%; p<0.001) in the semaglutide, empagliflozin and combination-therapy group, respectively. The changes in TKV were associated with changes in GFR, albuminuria and HbA1c. CONCLUSIONS/INTERPRETATION: In a population with type 2 diabetes and high risk of CVD, semaglutide and empagliflozin significantly reduced cortical ADC compared with placebo, indicating microstructural changes in the kidneys. These changes were not associated with changes in GFR, albuminuria or inflammation. Further, we found a decrease in TKV in all active treatment groups, which was possibly mediated by a reduction in hyperfiltration. Our findings suggest that DWI-MRI may serve as a promising tool for investigating the underlying mechanisms of medical interventions in individuals with type 2 diabetes but may reflect effects not related to fibrosis. TRIAL REGISTRATION: European Union Drug Regulating Authorities Clinical Trials Database (EudraCT) 2019-000781-38.

Proton pump inhibitors and the risk of acute kidney injury in cancer patients receiving immune checkpoint inhibitors: A Danish population-based cohort study.

Previous studies have suggested that the use of proton pump inhibitors (PPIs) more than doubles the risk of acute kidney injury (AKI) in cancer patients receiving immune checkpoint inhibitors (ICIs). However, this association may be confounded. Therefore, we conducted a register-based cohort study to examine the risk of AKI in users and nonusers of PPIs among cancer patients treated with ICIs in Denmark from 2011 through 2021 while accounting for a comprehensive range of potential confounders. PPI use was determined based on redeemed prescriptions of PPIs before ICI initiation. We identified laboratory-recorded AKI events within the first year after ICI initiation. We estimated the risks and hazard ratios (HRs) of AKI while accounting for a comprehensive range of confounders (including comorbidities and comedication) by propensity score weighting. Furthermore, we performed an additional per-protocol analysis while accounting for informative censoring by weighting. We identified 10 200 cancer patients including 2749 (27%) users, 6214 (61%) nonusers, and 1237 (12%) former users of PPIs. PPI users had an increased risk of AKI compared to nonusers (1-year risk, 24.7% vs 19.9%; HR, 1.42 [95% confidence interval (CI), 1.29-1.56]); however, this association attenuated when accounting for confounders (weighted 1-year risk, 24.2% vs 23.8%; weighted HR, 1.06 [95% CI, 0.93-1.21]). In the per-protocol analysis, the crude HR was 1.86 (95% CI, 1.63-2.12), while the weighted HR was 1.24 (95% CI, 1.03-1.49). Thus, the association between PPI use and AKI could largely be explained by confounding, suggesting that previous studies may have overestimated the association.

Daytime Variation in Kidney Perfusion, Oxygenation, and Sodium Concentration Assessed by Multiparametric MRI in Healthy Volunteers.

BACKGROUND: MRI can provide information on kidney structure, perfusion, and oxygenation. Furthermore, it allows for the assessment of kidney sodium concentrations and handling, allowing multiparametric evaluation of kidney physiology. Multiparametric MRI is promising for establishing prognosis and monitoring treatment responses in kidney diseases, but its intraindividual variation during the day is unresolved. PURPOSE: To investigate the variation in multiparametric MRI measurements from the morning to the evening. STUDY TYPE: Prospective. POPULATION: Ten healthy volunteers, aged 29 ± 5 without history of kidney disease. FIELD STRENGTH/SEQUENCE: 3 T/T1 mapping, blood-oxygen level dependent imaging, arterial spin labeling perfusion imaging, diffusion weighted imaging, and sodium imaging. ASSESSMENT: A multiparametric MRI protocol, yielding T1, R2*, ADC, renal blood flow and renal sodium levels, was acquired in the morning, noon, and evening. The participants were fasting prior to the first examination. Urine biochemical analyses were performed to complement MRI data. The cortex and medulla were analyzed separately in a semi-automatic fashion, and gradients of total sodium concentration (TSC) and R2* gradients were calculated from outer cortex to inner medulla. STATISTICAL TEST: Analyses of variance and mixed-effects models to estimate differences from time of day. Coefficients of variation to assess variability within and between participants. A P-value <0.05 was considered statistically significant. RESULTS: The coefficients of variation varied from 5% to 18% for proton-based parametric sequences, while it was 38% for TSC over a day. DATA CONCLUSION: Multiparametric MRI is stable over the day. The coefficients of variation over a day were lower for proton multiparametric MRI, but higher for sodium MRI. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Regional variation in incidence and prognosis of acute kidney injury.

BACKGROUND: Examining regional variation in acute kidney injury (AKI) and associated outcomes may reveal inequalities and possibilities for optimization of the quality of care. Using the Danish medical databases, we examined regional variation in the incidence, follow-up and prognosis of AKI in Denmark. METHODS: Patients with one or more AKI episodes in 2017 were identified using population-based creatinine measurements covering all Danish residents. Crude and sex-and-age-standardized incidence rates of AKI were estimated using census statistics for each municipality. Adjusted hazard ratios (aHR) of chronic kidney disease (CKD), all-cause death, biochemical follow-up and outpatient contact with a nephrology department after AKI were estimated across geographical regions and categories of municipalities, accounting for differences in demographics, comorbidities, medication use, lifestyle and social factors, and baseline kidney function. RESULTS: We identified 63 382 AKI episodes in 58 356 adults in 2017. The regional standardized AKI incidence rates ranged from 12.9 to 14.9 per 1000 person-years. Compared with the Capital Region of Denmark, the aHRs across regions ranged from 1.04 to 1.25 for CKD, from 0.97 to 1.04 for all-cause death, from 1.09 to 1.15 for biochemical follow-up and from 1.08 to 1.49 for outpatient contact with a nephrology department after AKI. Similar variations were found across municipality categories. CONCLUSIONS: Within the uniform Danish healthcare system, we found modest regional variation in AKI incidence. The mortality after AKI was similar; however, CKD, biochemical follow-up and nephrology follow-up after AKI varied across regions and municipality categories.

Risk factor analysis for a rapid progression of chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) is a growing global health concern. Identifying individuals in routine clinical care with new-onset CKD at high risk of rapid progression of the disease is imperative to guide allocation of prophylactic interventions, but community-based data are limited. We aimed to examine the risk of rapid progression, kidney failure, hospitalization and death among adults with incident CKD stage G3 and to clarify the association between predefined risk markers and rapid CKD progression. METHODS: Using plasma creatinine measurements for the entire Danish population from both hospitals and primary care, we conducted a nationwide, population-based cohort study, including adults in Denmark with incident CKD stage G3 in 2017-2020. We estimated 3-year risks of rapid progression (defined by a confirmed decline in estimated glomerular filtration rate of ≥5 mL/min/1.73 m2/year), kidney failure, all-cause hospitalization and death. To examine risk markers, we constructed a heat map showing the risk of rapid progression based on predefined markers: albuminuria, sex, diabetes and hypertension/cardiovascular disease. RESULTS: Among 133 443 individuals with incident CKD stage G3, the 3-year risk of rapid progression was 14.6% [95% confidence interval (CI) 14.4-14.8]. The 3-year risks of kidney failure, hospitalization and death were 0.3% (95% CI 0.3-0.4), 53.3% (95% CI 53.0-53.6) and 18.1% (95% CI 17.9-18.4), respectively. In the heat map, the 3-year risk of rapid progression ranged from 7% in females without albuminuria, hypertension/cardiovascular disease or diabetes, to 46%-47% in males and females with severe albuminuria, diabetes and hypertension/cardiovascular disease. CONCLUSION: This population-based study shows that CKD stage G3 is associated with considerable morbidity in a community-based setting and underscores the need for optimized prophylactic interventions among such patients. Moreover, our data highlight the potential of using easily accessible markers in routine clinical care to identify individuals who are at high risk of rapid progression.

The Cyst Epithelium in Polycystic Kidney Disease Patients Displays Normal Apical-Basolateral Cell Polarity.

The main characteristic of polycystic kidney disease is the development of multiple fluid-filled renal cysts. The discovery of mislocalized sodium-potassium pump (Na,K-ATPase) in the apical membrane of cyst-lining epithelia alluded to reversal of polarity as a possible explanation for the fluid secretion. The topic of apical Na,K-ATPase in cysts remains controversial. We investigated the localization of the Na,K-ATPase and assessed the apical-basolateral polarization of cyst-lining epithelia by means of immunohistochemistry in kidney tissue from six polycystic kidney disease patients undergoing nephrectomy. The Na,K-ATPase α1 subunit was conventionally situated in the basolateral membrane of all immunoreactive cysts. Proteins of the Crumbs and partitioning defective (Par) complexes were localized to the apical membrane domain in cyst epithelial cells. The apical targeting protein Syntaxin-3 also immunolocalized to the apical domain of cyst-lining epithelial cells. Proteins of the basolateral Scribble complex immunolocalized to the basolateral domain of cysts. Thus, no deviations from the typical epithelial distribution of basic cell polarity proteins were observed in the cysts from the six patients. Furthermore, we confirmed that cysts can originate from virtually any tubular segment with preserved polarity. In conclusion, we find no evidence of a reversal in apical-basolateral polarity in cyst-lining epithelia in polycystic kidney disease.

Amiloride evokes significant natriuresis and weight loss in kidney transplant recipients with and without albuminuria.

Albuminuria in kidney transplant recipients (KTRs) is associated with hypertension and aberrant glomerular filtration of serine proteases that may proteolytically activate the epithelial Na+ channel (ENaC). The present nonrandomized, pharmacodynamic intervention study aimed to investigate if inhibition of ENaC increases Na+ excretion and reduces extracellular volume in KTRs dependent on the presence of albuminuria. KTRs with and without albuminuria (albumin-to-creatinine ratio > 300 mg/g, n = 7, and <30 mg/g, n = 7, respectively) were included and ingested a diet with fixed Na+ content (150 mmol/day) for 5 days. On the last day, amiloride at 10 mg was administered twice. Body weight, 24-h urine electrolyte excretion, body water content, and ambulatory blood pressure as well as plasma renin, angiotensin II, and aldosterone concentrations were determined before and after amiloride. Amiloride led to a significant decrease in body weight, increase in 24-h urinary Na+ excretion, and decrease in 24-h urinary K+ excretion in both groups. Urine output increased in the nonalbuminuric group only. There was no change in plasma renin, aldosterone, and angiotensin II concentrations after amiloride, whereas a significant decrease in nocturnal systolic blood pressure and increase in 24-h urine aldosterone excretion was observed in albuminuric KTRs only. There was a significant correlation between 24-h urinary albumin excretion and amiloride-induced 24-h urinary Na+ excretion. In conclusion, ENaC activity contributes to Na+ and water retention in KTRs with and without albuminuria. ENaC is a relevant pharmacological target in KTRs; however, larger and long-term studies are needed to evaluate whether the magnitude of this effect depends on the presence of albuminuria.NEW & NOTEWORTHY Amiloride has a significant natriuretic effect in kidney transplant recipients (KTRs) that relates to urinary albumin excretion. The epithelial Na+ channel may be a relevant direct pharmacological target to counter Na+ retention and hypertension in KTRs. Epithelial Na+ channel blockers should be further investigated as a mean to mitigate Na+ and water retention and to potentially obtain optimal blood pressure control in KTRs.

Proprotein convertase subtilisin/kexin type 9 targets megalin in the kidney proximal tubule and aggravates proteinuria in nephrotic syndrome.

Proteinuria is a prominent feature of chronic kidney disease. Interventions that reduce proteinuria slow the progression of chronic kidney disease and the associated risk of cardiovascular disease. Here, we propose a mechanistic coupling between proteinuria and proprotein convertase subtilisin/kexin type 9 (PCSK9), a regulator of cholesterol and a therapeutic target in cardiovascular disease. PCSK9 undergoes glomerular filtration and is captured by megalin, the receptor responsible for driving protein reabsorption in the proximal tubule. Accordingly, megalin-deficient mice and patients carrying megalin pathogenic variants (Donnai Barrow syndrome) were characterized by elevated urinary PCSK9 excretion. Interestingly, PCSK9 knockout mice displayed increased kidney megalin while PCSK9 overexpression resulted in its reduction. Furthermore, PCSK9 promoted trafficking of megalin to lysosomes in cultured proximal tubule cells, suggesting that PCSK9 is a negative regulator of megalin. This effect can be accelerated under disease conditions since either genetic destruction of the glomerular filtration barrier in podocin knockout mice or minimal change disease (a common cause of nephrotic syndrome) in patients resulted in enhanced tubular PCSK9 uptake and urinary PCSK9 excretion. Pharmacological PCSK9 inhibition increased kidney megalin while reducing urinary albumin excretion in nephrotic mice. Thus, glomerular damage increases filtration of PCSK9 and concomitantly megalin degradation, resulting in escalated proteinuria.

Defining measures of kidney function in observational studies using routine health care data: methodological and reporting considerations.

The availability of electronic health records and access to a large number of routine measurements of serum creatinine and urinary albumin enhance the possibilities for epidemiologic research in kidney disease. However, the frequency of health care use and laboratory testing is determined by health status and indication, imposing certain challenges when identifying patients with kidney injury or disease, when using markers of kidney function as covariates, or when evaluating kidney outcomes. Depending on the specific research question, this may influence the interpretation, generalizability, and/or validity of study results. This review illustrates the heterogeneity of working definitions of kidney disease in the scientific literature and discusses advantages and limitations of the most commonly used approaches using 3 examples. We summarize ways to identify and overcome possible biases and conclude by proposing a framework for reporting definitions of exposures and outcomes in studies of kidney disease using routinely collected health care data.

In a real-life setting, risk factors, coronary artery calcium score, and coronary stenosis at computed tomography angiography are associated with major adverse cardiovascular events and all-cause mortality among kidney transplant candidates.

Kidney failure is associated with an increased risk of cardiovascular disease and death. This single-center, a retrospective study evaluated the association between risk factors, coronary artery calcium score (CACS), coronary computed tomography angiography (CTA), major adverse cardiovascular events (MACEs), and all-cause mortality in kidney transplant candidates. Data on clinical risk factors, MACE, and all-cause mortality were collected from patient records. A total of 529 kidney transplant candidates were included (median follow-up of 4.7 years). CACS was evaluated in 437 patients and CTA in 411. Both the presence of ≥3 risk factors, CACS of ≥400, as well as multiple-vessel stenoses or left main artery disease predicted MACE (hazard ratio, 2.09; [95% confidence interval, 1.35-3.23]; 4.65 [2.20-9.82]; 3.70 [1.81-7.57]; 4.90 [2.40-10.01]) and all-cause mortality (harad ratio, 4.44; [95% confidence interval, 2.54-7.76]; 4.47 [2.22-9.02]; 2.82 [1.34-5.94]; 5.41 [2.81-10.41]) in univariate analyses. Among patients eligible for CACS and CTA (n = 376), only CACS and CTA were associated with both MACE and all-cause mortality. In conclusion, risk factors, CACS, and CTA provide information on the risk of MACE and mortality in kidney transplant candidates. An additional value of CACS and CTA compared with risk factors was observed for the prediction of MACE in a subpopulation undergoing both CACS and CTA.

Twenty-four-Year Trends in Incidence and Mortality of Nephrotic Syndrome: A Population-Based Cohort Study.

BACKGROUND: With the increasing prevalence of risk factors for nephrotic syndrome, updated epidemiologic data on the syndrome are needed. We examined its age- and sex-specific incidence, histopathology, and mortality over 24 years. METHODS: This nationwide cohort study included all adults with first-time-recorded nephrotic syndrome in Denmark during 1995-2018 using the Danish National Patient Registry. We obtained data on age, sex, hospital-diagnosed comorbidities, and histopathologic findings. We computed overall, and age- and sex-specific, incidence rates of nephrotic syndrome, 1- and 5-year mortality by calendar period, and 1-year hazard ratios (HRs) of death using Cox models. RESULTS: We identified 3,970 adults with first-time nephrotic syndrome diagnosis. Incidence was highest in men and increased with age to 11.77 per 100,000 person-years (95% confidence interval [CI]: 10.21-13.32) in men aged 80+ years, and 6.56 per 100,000 person-years (95% CI: 5.71-7.41) in women aged 80+ years. Incidence of nephrotic syndrome increased from 3.35 per 100,000 person-years (95% CI: 3.12-3.58) in 1995-2000 to 4.30 per 100,000 person-years (95% CI: 4.05-4.54) in 2013-2018. Over time, 1-year mortality of nephrotic syndrome was stable at 13%-16%, but HR of death was 0.54 (95% CI: 0.42-0.69), adjusted for age, sex, and comorbidities, in 2013-2018 compared with 1995-2000. Subdistribution of glomerulopathies was stable over time with membranous nephropathy and minimal change disease being the most common. CONCLUSION: During 1995-2018, the incidence of recorded adult nephrotic syndrome increased slightly, and the adjusted mortality of nephrotic syndrome decreased markedly. Whether these findings reflect changes in epidemiology or awareness and coding of nephrotic syndrome, remains to be clarified.

Herpes Virus Infections in Kidney Transplant Patients (HINT) - a prospective observational cohort study.

BACKGROUND: Kidney transplant recipients receive maintenance immunosuppressive therapy to avoid allograft rejection resulting in increased risk of infections and infection-related morbidity and mortality. Approximately 98% of adults are infected with varicella zoster virus, which upon reactivation causes herpes zoster. The incidence of herpes zoster is higher in kidney transplant recipients than in immunocompetent individuals, and kidney transplant recipients are at increased risk of severe herpes zoster-associated disease. Vaccination with adjuvanted recombinant glycoprotein E subunit herpes zoster vaccine (RZV) prevents herpes zoster in older adults with excellent efficacy (90%), and vaccination of kidney transplant candidates is recommended in Danish and international guidelines. However, the robustness and duration of immune responses after RZV vaccination, as well as the optimal timing of vaccination in relation to transplantation remain unanswered questions. Thus, the aim of this study is to characterize the immune response to RZV vaccination in kidney transplant candidates and recipients at different timepoints before and after transplantation. METHODS: The Herpes Virus Infections in Kidney Transplant Patients (HINT) study is a prospective observational cohort study. The study will include kidney transplant candidates on the waiting list for transplantation (n = 375) and kidney transplant recipients transplanted since January 1, 2019 (n = 500) from all Danish kidney transplant centers who are offered a RZV vaccine as routine care. Participants are followed with repeated blood sampling until 12 months after inclusion. In the case of transplantation or herpes zoster disease, additional blood samples will be collected until 12 months after transplantation. The immune response will be characterized by immunophenotyping and functional characterization of varicella zoster virus-specific T cells, by detection of anti-glycoprotein E antibodies, and by measuring cytokine profiles. DISCUSSION: The study will provide new knowledge on the immune response to RZV vaccination in kidney transplant candidates and recipients and the robustness and duration of the response, potentially enhancing preventive strategies against herpes zoster in a population at increased risk. TRIAL REGISTRATION: ClinicalTrials.gov (NCT05604911).

Prediction of CKD Progression and Cardiovascular Events Using Albuminuria and Pulse Wave Velocity.

INTRODUCTION: Chronic kidney disease (CKD) is associated with cardiovascular disease (CVD) and death. Albuminuria is an established risk factor, but additional biomarkers predicting CKD progression or CVD are needed. Arterial stiffness is an easily measurable parameter that has been associated with CVD and mortality. We evaluated the ability of carotid-femoral pulse wave velocity (PWV) and urine albumin-creatinine (UAC) ratio to predict CKD progression, cardiovascular events, and mortality in a cohort of CKD patients. METHODS: In CKD stage 3-5 patients, PWV and UAC were measured at baseline. CKD progression was defined as 50% decline in estimated glomerular filtration rate (eGFR), initiation of dialysis, or renal transplantation. A composite endpoint was defined as CKD progression, myocardial infarction, stroke, or death. Endpoints were analyzed using Cox regression analysis adjusted for possible confounders. RESULTS: We included 181 patients (median age 69 [interquartile range 60-75] years, 67% males) with a mean eGFR of 37 ± 12 mL/min/1.73 m2 and UAC 52 (5-472) mg/g. Mean PWV was 10.6 m/s. Median follow-up until first event was 4 (3-6) years with 44 and 89 patients reaching a CKD progression or composite endpoint, respectively. UAC (g/g) significantly predicted both CKD progression (HR 1.5 [1.2; 1.8]) and composite endpoints (HR 1.4 [1.1; 1.7]) in adjusted Cox regression. In contrast, PWV (m/s) was not associated with neither CKD progression (HR 0.99 [0.84; 1.18]) nor the composite endpoint (HR 1.03 [0.92; 1.15]). CONCLUSION: In an aging CKD population, UAC predicted both CKD progression and a composite endpoint of CKD progression, cardiovascular events, or death, while PWV did not.

Proteinuria is accompanied by intratubular complement activation and apical membrane deposition of C3dg and C5b-9 in kidney transplant recipients.

Proteinuria predicts accelerated decline in kidney function in kidney transplant recipients (KTRs). We hypothesized that aberrant filtration of complement factors causes intraluminal activation, apical membrane attack on tubular cells, and progressive injury. Biobanked samples from two previous studies in albuminuric KTRs were used. The complement-activation split products C3c, C3dg, and soluble C5b-9-associated C9 neoantigen were analyzed by ELISA in urine and plasma using neoepitope-specific antibodies. Urinary extracellular vesicles (uEVs) were enriched by lectin and immunoaffinity isolation and analyzed by immunoblot analysis. Urine complement excretion increased significantly in KTRs with an albumin-to-creatinine ratio of ≥300 mg/g compared with <30 mg/g. Urine C3dg and C9 neoantigen excretion correlated significantly to changes in albumin excretion from 3 to 12 mo after transplantation. Fractional excretion of C9 neoantigen was significantly higher than for albumin, indicating postfiltration generation. C9 neoantigen was detected in uEVs in six of the nine albuminuric KTRs but was absent in non-albuminuric controls (n = 8). In C9 neoantigen-positive KTRs, lectin affinity enrichment of uEVs from the proximal tubules yielded signal for iC3b, C3dg, C9 neoantigen, and Na+-glucose transporter 2 but only weakly for aquaporin 2. Coisolation of podocyte markers and Tamm-Horsfall protein was minimal. Our findings show that albuminuria is associated with aberrant filtration and intratubular activation of complement with deposition of C3 activation split products and C5b-9-associated C9 neoantigen on uEVs from the proximal tubular apical membrane. Intratubular complement activation may contribute to progressive kidney injury in proteinuric kidney grafts.NEW & NOTEWORTHY The present study proposes a mechanistic coupling between proteinuria and aberrant filtration of complement precursors, intratubular complement activation, and apical membrane attack in kidney transplant recipients. C3dg and C5b-9-associated C9 neoantigen associate with proximal tubular apical membranes as demonstrated in urine extracellular vesicles. The discovery suggests intratubular complement as a mediator between proteinuria and progressive kidney damage. Inhibitors of soluble and/or luminal complement activation with access to the tubular lumen may be beneficial.

An update on the use of tolvaptan for autosomal dominant polycystic kidney disease: consensus statement on behalf of the ERA Working Group on Inherited Kidney Disorders, the European Rare Kidney Disease Reference Network and Polycystic Kidney Disease International.

Approval of the vasopressin V2 receptor antagonist tolvaptan-based on the landmark TEMPO 3:4 trial-marked a transformation in the management of autosomal dominant polycystic kidney disease (ADPKD). This development has advanced patient care in ADPKD from general measures to prevent progression of chronic kidney disease to targeting disease-specific mechanisms. However, considering the long-term nature of this treatment, as well as potential side effects, evidence-based approaches to initiate treatment only in patients with rapidly progressing disease are crucial. In 2016, the position statement issued by the European Renal Association (ERA) was the first society-based recommendation on the use of tolvaptan and has served as a widely used decision-making tool for nephrologists. Since then, considerable practical experience regarding the use of tolvaptan in ADPKD has accumulated. More importantly, additional data from REPRISE, a second randomized clinical trial (RCT) examining the use of tolvaptan in later-stage disease, have added important evidence to the field, as have post hoc studies of these RCTs. To incorporate this new knowledge, we provide an updated algorithm to guide patient selection for treatment with tolvaptan and add practical advice for its use.

A comparison of four established GFR formulas to estimate measured GFR and changes in GFR in adult kidney transplant recipients.

The accurate assessment of glomerular filtration rate (GFR) is important in the follow-up of kidney transplant recipients in order to identify graft dysfunction. A number of formulas have been proposed to calculate GFR from endogenous plasma markers such as creatinine or cystatin C since measuring GFR using exogenous markers is troublesome. This study compares and evaluates the ability of four different GFR formulas to estimate kidney graft function and to detect changes in GFR in kidney transplant recipients. The study included patients from the prospective, multicenter CONTEXT trial in kidney transplant recipients. GFR was measured using plasma clearance of 51Cr-EDTA and estimated using the MDRD, CKD-EPI Creatinine, CKD-EPI Cystatin C and CKD-EPI Cystatin C + Creatinine equations at three (n = 83) and twelve (n = 65) months post-transplantation. For each formula mean bias, precision, and accuracy were evaluated. The MDRD equation had the lowest mean bias (0.2 ml/min/1.73 m2), whereas the CKD-EPI Cystatin C + Creatinine equation had the highest precision (8 ml/min/1.73 m2). Accuracy at three months were similar for all equations (P30 > 80%) except for the CKD-EPI Cystatin C equation, which performed poorer (P30 = 55%). None of the formulas evaluated avoided misclassification of changes in GFR. The most optimal combination of precision and accuracy suggests the use of CKD-EPI Creatinine + Cystatin C equation in kidney transplant recipients.

Safety and effectiveness of direct oral anticoagulants in patients with nephrotic syndrome: a report of 21 cases.

BACKGROUND: Nephrotic syndrome (NS) is associated with increased risk of thromboembolic events (TE) adding to the morbidity and mortality. International guidelines recommend prophylactic anticoagulation in patients with NS and high risk of TE, but no studies have identified the optimal type of anticoagulation in NS. We aimed to assess the effectiveness and safety of direct oral anticoagulant (DOAC) by analyzing the thromboembolic and bleeding events in NS patients prescribed DOAC as primary prophylaxis to prevent TE or as treatment for TE occurring in relation to NS. METHODS: We performed a single-center, retrospective study including patients with NS, a plasma albumin less than 25 g/L and prophylactic anticoagulation treatment with DOAC at the Department of Renal Medicine at Aarhus University Hospital, Denmark from July 2016 to June 2021. Patients treated with DOAC as thromboprophylaxis for other indications than NS were excluded. Baseline characteristics and outcomes, including TE, bleeding and other adverse effects associated with DOAC were obtained from medical records. RESULTS: We identified 268 patients treated with DOAC of which 21 patients with NS were included in the study. Nineteen patients were prescribed DOAC as thromboprophylaxis and two patients received DOAC due to previous TE, which was considered associated with the NS. The type of DOAC prescribed was apixaban (n = 10) and rivaroxaban (n = 11). No patients experienced TE during DOAC treatment, while five patients had a minor bleeding episode. Patients who experienced bleeding episodes were older (median 62 vs 51 years), more often female (80%) and had been on DOAC for a longer period (204 days vs 47 days). Neither the HAS-BLED score nor GN-risk-score predicted the risk of minor bleedings in this population. CONCLUSIONS: In this case series, no new TE and only minor bleeding complications were observed among adult NS patients treated with DOAC.

Is the risk of cardiovascular disease increased in living kidney donors? A Danish population-based cohort study.

Reduced renal function is associated with cardiovascular disease (CVD); however, how living donor nephrectomy affects the risk of CVD remains controversial. We conducted a nationwide cohort study including living kidney donors in Denmark from 1996 to 2018 to assess the risk of hypertension, atrial fibrillation/flutter (AF), major adverse cardiovascular events (MACE; composite of myocardial infarction, ischemic stroke, and death) and death after living kidney donation. As comparisons we identified: a cohort of healthy individuals from the general population and an external blood donor cohort. We followed kidney donors (1,103 when compared with the general population cohort; 1,007 when compared with blood donors) for a median of 8 years. Kidney donors had an increased risk of initiating treatment for hypertension when compared with blood donors (standardized incidence ratio [SIR], 1.40; 95% confidence interval [CI], 1.17-1.66) but they did not have increased risk of MACE neither when compared with the general population cohort (hazard ratio, 0.68; 95% CI, 0.52-0.89) nor with blood donors (SIR, 1.17; 95% CI, 0.88-1.55). Neither did they have increased risks of AF and death. Thus, living kidney donation may be associated with increased risk of hypertension; however, we did not identify increased risks of CVD or death.

Dynamics of circulating dendritic cells and cytokines after kidney transplantation-No effect of remote ischaemic conditioning.

Inflammation resulting from ischaemia/reperfusion injury can cause kidney graft dysfunction, increase the risk of delayed graft function and possibly reduce long-term graft survival. Remote ischaemic conditioning may protect against ischaemia/reperfusion injury and mitigate the immunological response to the graft. We investigated the immunological effects of remote ischaemic conditioning on kidney transplantation from deceased donors in the randomized CONTEXT study. Three circulating dendritic cell (DC) subtypes identified in peripheral blood from kidney transplant recipients [myeloid DCs, plasmacytoid DCs and immunoglobulin-like transcript (ILT)3+ DCs] were measured at baseline, days 1, 3 and 5 and 1 and 3 months after transplantation. We also quantified 21 cytokines at baseline, days 1 and 5 and 3 months after transplantation. Neither DC counts nor cytokine levels differed between patients receiving remote ischaemic conditioning and controls; however, several parameters exhibited dynamic and parallel alterations in the two groups over time, reflecting the immunological response to the kidney transplantation and immunosuppression.