Primary hyperoxaluria in adults and children: a nationwide cohort highlights a persistent diagnostic delay

Background

Primary hyperoxalurias (PH) are extremely rare genetic disorders characterized by clinical heterogeneity. Delay in diagnosing these conditions can have detrimental effects on patient outcomes. The primary objective of this study is to assess the current diagnostic delay for PH.

Methods

This nationwide, observational and retrospective study included patients who received a genetic diagnosis of PH types 1, 2 and 3 between 1 January 2015 and 31 December 2019. Diagnostic delay was defined as the duration between the onset of symptoms and the time of genetic diagnosis.

Results

A total of 52 patients (34 children and 18 adults) were included in the study, with 40 PH1 (77%), 3 PH2 (6%) and 9 PH3 (17%). At the time of diagnosis, 12 patients (23%) required dialysis. Among the PH1 patients, the predominant symptom at onset in adults was renal colic (79% of cases), whereas symptoms in children were more diverse (renal colic in 17% of cases). The diagnostic delay was significantly shorter in children compared with adults [median (interquartile range)]: 1.2 (0.1-3.0) versus 30 (17-36) years, respectively (P < .0001). RNA interference was utilized in 23 patients (58%). Five individuals (13%) underwent double liver-kidney transplantation, and five (13%) received isolated kidney transplantation, with lumasiran therapy in four patients. For PH2 and PH3 patients, the diagnostic delay ranges from 0 to 3 years, with renal colic as first symptom in 33% of cases.

Conclusion

This extensive and recent cohort of PH underscores the considerable delay in diagnosing PH, particularly in adults, even in a country with a dedicated organization for enhancing the overall management of rare diseases. These findings reinforce the imperative for increased awareness among relevant specialties regarding the evaluation of urolithiasis.

Acute and Chronic Kidney Dysfunction and Prognosis following Thrombectomy for Ischemic Stroke

INTRODUCTION

Patients with chronic kidney disease (CKD) have an increased risk of stroke, and CKD seems associated with worse outcome after a stroke. The main objective of our study RISOTTO was to evaluate the influence of CKD and acute kidney injury (AKI) on the clinical outcome and mortality of ischemic stroke patients after thrombolysis and/or thrombectomy.

METHODS

This multicenter cohort study included patients in the acute phase of ischemic stroke due to large artery occlusion managed by thrombectomy. Functional outcome at 3 months was assessed by the modified Rankin Scale (mRS).

RESULTS

280 patients were included in the analysis. Fifty-nine patients (22.6%) had CKD. At 3 months, CKD was associated with similar functional prognosis (mRS 3-6: 50.0% vs. 41.7%, p = 0.262) but higher mortality (24.2% versus 9.5%, p = 0.004). In univariate analysis, patients with CKD had a higher burden of white matter hyperintensities (Fazekas score: 1.7 ± 0.8 vs. 1.0 ± 0.8, p = 0.002), lower initial infarct volume with equivalent severity, and lower recanalization success (86.4% vs. 97.0%, p = 0.008) compared to non-CKD patients. Forty-seven patients (20.0%) developed AKI. AKI was associated with poorer 3-month functional outcome (mRS 3-6: 63.8% vs. 49.0%, p = 0.002) and mortality (23.4% versus 7.7%, p = 0.002). In multivariate analysis, AKI appeared as an independent risk factor for poor functional outcome (mRS 3-6: adjOR 2.79 [1.11-7.02], p = 0.029) and mortality (adjOR 2.52 [1.03-6.18], p = 0.043) at 3 months, while CKD was not independently associated with 3-month mortality and poor neurological outcome.

CONCLUSIONS

AKI is independently associated with poorer functional outcome and increased mortality at 3 months. CKD was not an independent risk factor for 3-month mortality or poor functional prognosis.

Beyond the kidney biopsy: genomic approach to undetermined kidney diseases

Background

According to data from large national registries, almost 20%-25% of patients with end-stage kidney disease have an undetermined kidney disease (UKD). Recent data have shown that monogenic disease-causing variants are under-diagnosed. We performed exome sequencing (ES) on UKD patients in our center to improve the diagnosis rate.

Methods

ES was proposed in routine practice for patients with UKD including kidney biopsy from January 2019 to December 2021. Mutations were detected using a targeted bioinformatic customized kidney gene panel (675 genes). The pathogenicity was assessed using American College of Medical Genetics guidelines.

Results

We included 230 adult patients, median age 47.5 years. Consanguinity was reported by 25 patients. A family history of kidney disease was documented in 115 patients (50%). Kidney biopsies were either inconclusive in 69 patients (30.1%) or impossible in 71 (30.9%). We detected 28 monogenic renal disorders in 75 (32.6%) patients. Collagenopathies was the most common genetic kidney diagnosis (46.7%), with COL4A3 and COL4A4 accounting for 80% of these diagnoses. Tubulopathies (16%) and ciliopathies (14.7%) yielded, respectively, the second and third genetic kidney diagnosis category and UMOD-associated nephropathy as the main genetic findings for tubulopathies (7/11). Ten of the 22 patients having ES "first" eventually received a positive diagnosis, thereby avoiding 11 biopsies. Among the 44 patients with glomerular, tubulo-interstitial or vascular nephropathy, 13 (29.5%) were phenocopies. The diagnostic yield of ES was higher in female patients (P = .02) and in patients with a family history of kidney disease (P < .0001), reaching 56.8% when the patient had both first- and second-degree family history of renal disease.

Conclusion

Genetic diagnosis has provided new clinical insights by clarifying or reclassifying kidney disease etiology in over a third of UKD patients. Exome "first" may have a significant positive diagnostic yield, thus avoiding invasive kidney biopsy; moreover, the diagnostic yield remains elevated even when biopsy is impossible or inconclusive. ES provides a clinical benefit for routine nephrological healthcare in patients with UKD.

Indoxyl sulfate inhibits muscle cell differentiation via Myf6/MRF4 and MYH2 downregulation

BACKGROUND

Chronic kidney disease (CKD) is associated with a significant decrease in muscle strength and mass, possibly related to muscle cell damage by uremic toxins. Here, we studied in vitro and in vivo the effect of indoxyl sulfate (IS), an indolic uremic toxin, on myoblast proliferation, differentiation and expression of myogenic regulatory factors (MRF)-myoblast determination protein 1 (MyoD1), myogenin (Myog), Myogenic Factor 5 (Myf5) and myogenic regulatory factor 4 (Myf6/MRF4)-and expression of myosin heavy chain, Myh2.

METHODS

C2C12 myoblasts were cultured in vitro and differentiated in myotubes for 7 days in the presence of IS at a uremic concentration of 200 µM. Myocytes morphology and differentiation was analyzed after hematoxylin-eosin staining. MRF genes' expression was studied using reverse transcription polymerase chain reaction in myocytes and 5/6th nephrectomized mice muscle. Myf6/MRF4 protein expression was studied using enzyme-linked immunosorbent assay; MYH2 protein expression was studied using western blotting. The role of Aryl Hydrocarbon Receptor (AHR)-the cell receptor of IS-was studied by adding an AHR inhibitor into the cell culture milieu.

RESULTS

In the presence of IS, the myotubes obtained were narrower and had fewer nuclei than control myotubes. The presence of IS during differentiation did not modify the gene expression of the MRFs Myf5, MyoD1 and Myog, but induced a decrease in expression of Myf6/MRF4 and MYH2 at the mRNA and the protein level. AHR inhibition by CH223191 did not reverse the decrease in Myf6/MRF4 mRNA expression induced by IS, which rules out the implication of the ARH genomic pathway. In 5/6th nephrectomized mice, the Myf6/MRF4 gene was down-regulated in striated muscles.

CONCLUSION

In conclusion, IS inhibits Myf6/MRF4 and MYH2 expression during differentiation of muscle cells, which could lead to a defect in myotube structure. Through these new mechanisms, IS could participate in muscle atrophy observed in CKD.

Diagnosis of Kidney Diseases of Unknown Etiology Through Biopsy-Genetic Analysis

Introduction

Previous studies have suggested that genetic kidney diseases in adults are often overlooked, representing up to 10% of all cases of chronic kidney disease (CKD). We present data obtained from exome sequencing (ES) analysis of patients with biopsy-proven undetermined kidney disease (UKD).

Methods

ES was proposed during routine clinical care in patients with UKD from January 2020 to December 2021. We used in silico custom kidney genes panel analysis to detect pathological variations using American College of Medical Genetics guidelines in 52 patients with biopsy-proven UKD with histological finding reassessment.

Results

We detected 12 monogenic renal disorders in 21 (40.4%) patients. The most common diagnoses were collagenopathies (8/21,38.1%), COL4A3 and COL4A4 accounting for 80% of these diagnoses, and ciliopathies (5/21, 23.8%). The diagnostic yield of ES was higher in female patients and patients with a family history of kidney disease (57.1% and 71%, respectively). Clinical nephropathy categories matched with the final genetic diagnoses in 72.7% of cases, whereas histological renal lesions matched with the final diagnoses in 92.3% of cases. The genetics diagnoses and histopathological findings were in complete agreement for both glomerular and tubulointerstitial cases. Interstitial inflammation without tubulitis was only observed in tubulopathies or ciliopathies. Isolated CKD, CKD with proteinuria or hematuria, and isolated proteinuria or hematuria yielded the highest diagnostic yields (54.6%, 52.6%, and 42.9%, respectively).

Conclusion

ES done in patients with biopsy-proven UKD should be considered as a first-line tool for CKD patients with a family history of kidney disease. Combination of ES and kidney biopsy may have major impacts on kidney disease ontology.

Kidney disease and stroke: epidemiology and potential mechanisms of susceptibility

Patients with chronic kidney disease (CKD) have an increased risk of both ischaemic and haemorrhagic stroke compared with the general population. Both acute and chronic kidney impairment are independently associated with poor outcome after the onset of a stroke, after adjustment for confounders. End-stage kidney disease (ESKD) is associated with a 7- and 9-fold increased incidence of both ischaemic and haemorrhagic strokes, respectively, poorer neurological outcome and a 3-fold higher mortality. Acute kidney injury (AKI) occurs in 12% of patients with stroke and is associated with a 4-fold increased mortality and unfavourable functional outcome. CKD patients seem to have less access to revascularisation techniques like thrombolysis and thrombectomy despite their poorer prognosis. Even if CKD patients could benefit from these specific treatments in acute ischaemic stroke, their prognosis remains poor. After thrombolysis, CKD is associated with a 40% increased risk of intracerebral haemorrhage (ICH), a 20% increase in mortality and poorer functional neurological outcomes. After thrombectomy, CKD is not associated with ICH but is still associated with increased mortality, and AKI with unfavourable outcome and mortality. The beneficial impact of gliflozins on the prevention of stroke is still uncertain. Non-traditional risk factors of stroke, like uraemic toxins, can lead to chronic cerebrovascular disease predisposing to stroke in CKD, notably through an increase in the blood-brain barrier permeability and impaired coagulation and thrombosis mechanisms. Preclinical and clinical studies are needed to specifically assess the impact of these non-traditional risk factors on stroke incidence and outcomes, aiming to optimize and identify potential therapeutic targets.

Weaning Maintenance Therapy in Lupus Nephritis: For Whom, When, and How?

Lupus nephritis (LN) is one of the main determinants of the severity of systemic lupus erythematosus (SLE). LN flares can lead to organ damage with chronic kidney disease (CKD) or even end-stage kidney disease (ESKD) and impair patients' survival. The "treat-to-target" strategy, which aims at obtaining and maintaining remission or low disease activity of SLE to alleviate symptoms and prevent organ damage, also refers to the control of residual activity in the kidney. But damage in SLE can also come from treatments, and toxicities related to long-term use of treatments should be prevented. This may contribute to the frequent nonadherence in patients with SLE. The de-escalation or even weaning of treatments whenever possible, or "think-to-untreat" (T2U) strategy, is to be considered in patients with LN. This possibility of treatment weaning in LN was explored in retrospective cohorts, on the basis of long-term clinical remission. It was also proposed prospectively with a kidney-biopsy-based approach, combining clinical and pathologic remission to secure treatment weaning. The WIN-Lupus trial was the first randomized controlled trial comparing the continuation to the discontinuation of maintenance immunosuppressive therapy (IST) after 2 to 3 years in patients with LN in remission. It showed a higher risk of severe SLE flares in patients who discontinued treatment, but also a possibility of weaning without flare in some patients, who need to be better identified. We propose here a narrative review of the available literature on the weaning of treatment in LN and discuss how to secure a T2U strategy.

VNtyper enables accurate alignment-free genotyping of MUC1 coding VNTR using short-read sequencing data in autosomal dominant tubulointerstitial kidney disease

The human genome comprises approximately 3% of tandem repeats with variable length (VNTR), a few of which have been linked to human rare diseases. Autosomal dominant tubulointerstitial kidney disease-MUC1 (ADTKD-MUC1) is caused by specific frameshift variants in the coding VNTR of the MUC1 gene. Calling variants from VNTR using short-read sequencing (SRS) is challenging due to poor read mappability. We developed a computational pipeline, VNtyper, for reliable detection of MUC1 VNTR pathogenic variants and demonstrated its clinical utility in two distinct cohorts: (1) a historical cohort including 108 families with ADTKD and (2) a replication naive cohort comprising 2,910 patients previously tested on a panel of genes involved in monogenic renal diseases. In the historical cohort all cases known to carry pathogenic MUC1 variants were re-identified, and a new 25bp-frameshift insertion in an additional mislaid family was detected. In the replication cohort, we discovered and validated 30 new patients.

Rheopheresis Performed in Hemodialysis Patients Targets Endothelium and Has an Acute Anti-Inflammatory Effect

Background: Rheopheresis is a double-filtration plasmapheresis that removes a defined spectrum of high-molecular-weight proteins to lower plasma viscosity and improves microcirculation disorders. This technique can be performed in hemodialysis (HD) patients with severe microischemia. Interestingly, some studies showed that rheopheresis sessions improve endothelial function. Methods: Our study evaluated the inflammatory and endothelial biomarker evolution in 23 HD patients treated or not with rheopheresis. A p value ≤ 0.001 was considered statistically significant. Results: Thirteen HD patients treated by rheopheresis either for a severe peripheral arterial disease (N = 8) or calciphylaxis (N = 5) were analyzed. Ten control HD patients were also included in order to avoid any misinterpretation of the rheopheresis effects in regard to the HD circuit. In the HD group without rheopheresis, the circulating endothelial adhesion molecules, cytokines, angiogenic factor concentrations, and circulating levels were not modified. In the HD group with rheopheresis, the circulating endothelial adhesion molecules (sVCAM-1, sP-selectin, and sE-selectin) experienced a significant reduction, except sICAM-1. Among the pro-inflammatory cytokines, TNF-α was significantly reduced by 32.6% [(−42.2)−(−22.5)] (p < 0.0001), while the anti-inflammatory cytokine IL-10 increased by 674% (306−1299) (p < 0.0001). Among the angiogenic factors, only sEndoglin experienced a significant reduction. The CEC level trended to increase from 13 (3−33) cells/mL to 43 (8−140) cells/mL (p = 0.002). We did not observe any difference on the pre-session values of the molecules of interest between the first rheopheresis session and the last rheopheresis session. Conclusion: Rheopheresis immediately modified the inflammation balance and the endothelial injury biomarkers. Further studies are needed to understand the mechanisms underlying these biological observations.

Neutrophil:lymphocyte ratio correlates with the uremic toxin indoxyl sulfate and predicts the risk of death in patients on hemodialysis

BACKGROUND

Chronic kidney disease (CKD) is a major public health issue associated with increased cardiovascular, infectious and all-cause mortality. The neutrophil:lymphocyte ratio (NLR) is a predictive marker of the risk of death and cardiovascular events. Uremic toxins, notably indoxyl sulfate (IS), are involved in immune deficiency and cardiovascular complications associated with CKD. The aim of this study was to assess whether the NLR was related to uremic toxins and could predict clinical outcome in hemodialysis (HD) patients.

METHODS

We conducted a prospective cohort study of 183 patients on chronic HD. The main objective was to study the correlation between the NLR and uremic toxin serum levels. The secondary objective was to test if the NLR can predict the incidence of mortality, cardiovascular events and infectious events.

RESULTS

Patients were separated into two groups according to the NLR median value (3.49). The NLR at inclusion was correlated with the NLR at the 6-month (r = 0.55, P < 0.0001) and 12-month (r = 0.62, P < 0.0001) follow-up. Among uremic toxins, IS levels were higher in the group with high NLR (104 µmol/L versus 81 µmol/L; P = 0.004). In multivariate analysis, the NLR remained correlated with IS (P = 0.03). The incidence of death, cardiovascular events and severe infectious events was higher in the group with high NLR [respectively, 38% versus 18% (P = 0.004), 45% versus 26% (P = 0.01) and 33% versus 21% (P = 0.02)] than in the low NLR group. Multivariate analysis showed an independent association of the NLR with mortality (P = 0.02) and cardiovascular events (P = 0.03) but not with severe infectious events.

CONCLUSIONS

In HD patients, the NLR predicted mortality and cardiovascular events but not severe infections and correlated positively with the level of the uremic toxin IS. The NLR could be an interesting marker for monitoring the risk of clinical events in CKD patients.

Protein/Fiber Index Modulates Uremic Toxin Concentrations in Hemodialysis Patients

Background: Indoxyl sulfate (IS) and p-cresyl sulfate (PCS), two uremic toxins (UTs), are associated with increased mortality in patients with chronic kidney disease (CKD). These toxins are produced by the microbiota from the diet and excreted by the kidney. The purpose of this study was to analyze the effect of diet on IS and PCS concentration in hemodialysis (HD) patients. Methods: We performed a prospective monocentric study using a seven-day diet record and determination of serum IS and PCS levels in HD patients. We tested the association between toxin concentrations and nutritional data. Results: A total of 58/75 patients (77%) completed the diet record. Mean caloric intake was 22 ± 9.2 kcal/kg/day. The protein/fiber index was 4.9 ± 1.8. No correlation between IS or PCS concentration and protein/fiber index was highlighted. In the 18 anuric patients (31%) in whom residual renal function could not affect toxin concentrations, IS and PCS concentrations were negatively correlated with fiber intake and positively correlated with the protein/fiber index. In a multivariate analysis, IS serum concentration was positively associated with the protein/fiber index (p = 0.03). Conclusions: A low protein/fiber index is associated with low concentrations of uremic toxins in anuric HD patients. Diets with an increased fiber intake must be tested to determine whether they reduce PCS and IS serum concentrations.

Weaning of maintenance immunosuppressive therapy in lupus nephritis (WIN-Lupus): results of a multicentre randomised controlled trial

Objectives

Lupus nephritis (LN) is a frequent complication of systemic lupus erythematosus (SLE). Severe (proliferative) forms of LN are treated with induction immunosuppressive therapy (IST), followed by maintenance IST, to target remission and avoid relapses. The optimal duration of maintenance IST is unknown. The WIN-Lupus trial tested whether IST discontinuation after 2‒3 years was non-inferior to IST continuation for two more years in proliferative LN.

Methods

WIN-Lupus was an investigator-initiated multicentre randomised controlled trial. Patients receiving maintenance IST with azathioprine or mycophenolate mofetil for 2–3 years, and hydroxychloroquine, were randomised (1:1) into two groups: (1) IST continuation and (2) IST discontinuation. The primary endpoint was the relapse rate of proliferative LN at 24 months. Main secondary endpoints were the rate of severe SLE flares, survival without renal relapse or severe flare, adverse events.

Results

Between 2011 and 2016, 96 patients (out of 200 planned) were randomised in WIN-Lupus: IST continuation group (n=48), IST discontinuation group (n=48). Relapse of proliferative LN occurred in 5/40 (12.5%) patients with IST continuation and in 12/44 (27.3%) patients with IST discontinuation (difference 14.8% (95% CI −1.9 to 31.5)). Non-inferiority was not demonstrated for relapse rate; time to relapse did not differ between the groups. Severe SLE flares (renal or extrarenal) were less frequent in patients with IST continuation (5/40 vs 14/44 patients; p=0.035). Adverse events did not differ between the groups.

Conclusions

Non-inferiority of maintenance IST discontinuation after 2‒3 years was not demonstrated for renal relapse. IST discontinuation was associated with a higher risk of severe SLE flares.

Trial registration number

NCT01284725.

OP0280 WEANING OF MAINTENANCE IMMUNOSUPPRESSIVE THERAPY IN LUPUS NEPHRITIS (WIN-Lupus): A MULTICENTER RANDOMIZED CONTROLLED TRIAL

Background

Lupus nephritis (LN) is a frequent complication of systemic lupus erythematosus (SLE). Severe (proliferative) forms of LN are treated with an induction immunosuppressive therapy (IST), followed by a maintenance IST, to target remission and avoid relapses. The optimal duration of maintenance IST for proliferative LN is unknown.

Objectives

The WIN-Lupus trial tested whether IST discontinuation after 2-3 years in proliferative LN was non-inferior to IST continuation for 2 more years.

Methods

WIN-Lupus is an investigator-initiated academic randomized controlled trial, conducted in 28 French centers. Patients on maintenance IST with azathioprine or mycophenolate mofetil for a minimum of 2 years and a maximum of 3 years, and who were taking Hydroxychloroquine, were randomized (1:1) between 2 groups: IST continuation and IST discontinuation. The primary endpoint was the relapse rate of proliferative LN at 24 months. Secondary endpoints were the rate of severe SLE flares, survival without renal relapse or severe flare, adverse events, kidney function, disease activity, corticosteroid exposure, patient-reported outcome and medico-economic impact.

Results

Between 2011 and 2016, 125 patients were screened and 96 were randomized in the trial: 48 in the IST continuation group, 48 in the IST discontinuation group. In the per-protocol population, a relapse of proliferative LN occurred in 5/40 (10.4%) patients with IST continuation, and in 12/44 (25%) patients with IST discontinuation (difference 14.8%, 95%CI [-1.9; 31.5]). Non-inferiority was not demonstrated for relapse rate. Time to renal relapse did not differ between groups (p=0.092). Severe SLE flares (renal or extra-renal) were less frequent in patients with IST continuation compared to IST discontinuation (5/40 vs 14/44 patients, p=0.035). IST discontinuation was associated with lower health-related costs. Adverse events did not differ between groups.

Conclusion

Non-inferiority of maintenance IST discontinuation after 2 to 3 years was not demonstrated for renal relapse. IST discontinuation was associated with a higher risk of severe SLE flare.

References

[1]Moroni G et al. When and how is it possible to stop therapy in patients with lupus nephritis? Clin J Am Soc Nephrol. 2021. CJN.04830421. doi: 10.2215/CJN.04830421.

[2]Fanouriakis A et al. 2019 Update of the Joint European League Against Rheumatism and European Renal Association-European Dialysis and Transplant Association (EULAR/ERA-EDTA) recommendations for the management of lupus nephritis. Ann Rheum Dis. 2020;79(6):713-723.

[3]Jourde-Chiche N et al. Proliferative lupus nephritis treatment: practice survey in nephrology and internal medicine in France. Nephrol Ther. 2014;10(3):170-6.

[4]Zen M et al. Immunosuppressive therapy withdrawal after remission achievement in patients with lupus nephritis. Rheumatology (Oxford). 2021;keab373. doi: 10.1093/rheumatology/keab373.

[5]Malvar A et al. Kidney biopsy-based management of maintenance immunosuppression is safe and may ameliorate flare rate in lupus nephritis. Kidney Int. 2020;97(1):156-162.

Acknowledgements

Groupe Coopératif sur le Lupus Rénal (GCLR)

Disclosure of Interests

Noemie JOURDE-CHICHE Speakers bureau: Vifor Pharma, Grant/research support from: Fresenius Medical Care: grant paid to my institution (AP-HM) for the CINEVAS study in ANCA-associated vasculitis, Nathalie Costedoat-Chalumeau Grant/research support from: AP-HP received a research support from ROCHE for the OBILUP trial, Karine Baumstarck: None declared, LAURENCE BOUILLET Speakers bureau: GSK, novartis, biocryst, takeda, behring, Paid instructor for: takeda, novartis, Consultant of: GSK, novartis, biocryst, takeda, behring, blueprint, Grant/research support from: takeda, gsk, sanofi, biocryst, novartis, Stéphane Burtey: None declared, Valerie Caudwell: None declared, Laurent Chiche Speakers bureau: BMS, Paid instructor for: BMS, Lionel Couzi Speakers bureau: Astellas, Chiesi, Novartis, Sandoz, Ostuka, GSK, Biotest, Consultant of: Biotest, Hansa, Novartis, Grant/research support from: Novartis, Astellas, Christophe DELIGNY: None declared, Bertrand Dussol Speakers bureau: Genzyme, Novonordisk, Grant/research support from: Shire, Stanislas Faguer Speakers bureau: Asahi, Vifor Pharma, Sanofi, Consultant of: Abyonyx Pharma, Pierre Gobert: None declared, Guillaume Gondran Speakers bureau: Pfizer, Novartis, Consultant of: Genzyme, Antoine Huart Speakers bureau: Janssen, Paid instructor for: Pfizer, Aurélie Hummel: None declared, Emilie Kalbacher: None declared, Alexandre Karras Speakers bureau: Vifor, GSK, Astra-Zeneca, Roche, Paid instructor for: Vifor, Sanofi, Alexion, Consultant of: Novartis, GSK, Bohringer-Ingelheim, Marc Lambert Speakers bureau: CHUGAI-ROCHE, BAYER, PFIZER, LEOPHARMA, Paid instructor for: CHUGAI-ROCHE, Consultant of: CHUGAI-ROCHE, BAYER, PFIZER, LEOPHARMA, Grant/research support from: CHUGAI-ROCHE, Véronique LE GUERN: None declared, Sandrine Loubiere: None declared, Helene Maillard: None declared, Francois Maurier: None declared, Micheline Pha: None declared, Viviane Queyrel Paid instructor for: GSK, Consultant of: Boehringer Ingelheim, Francoise Sarrot-Reynauld: None declared, David Verhelst: None declared, Eric Hachulla Speakers bureau: Johnson & Johnson, GSK, Roche-Chugai, Consultant of: Johnson & Johnson, Boehringer Ingelheim, Bayer, GSK, Roche-Chugai, Sanofi-Genzyme, Grant/research support from: CSL Behring, GSK, Roche-Chugai and Johnson & Johnson, Zahir Amoura Speakers bureau: GSK, CSL Behring, Consultant of: GSK, Grant/research support from: GSK, Eric Daugas Speakers bureau: GSK, Amgen, Paid instructor for: GSK, Astra Zeneca, Consultant of: GSK, Astra Zeneca, Amgen, Grant/research support from: ROCHE for the OBILUP trial (AP-HP)

MO420: Effects of Indoxyl Sulfate and Apixaban in Liver Gene Expression

BACKGROUND AND AIMS

Uraemic toxins accumulate in the blood and tissues of patients with chronic kidney disease (CKD). Previous animal studies have shown that chronic kidney disease (CKD) not only alters the elimination of drugs excreted by the kidneys, but it also impacts the metabolism of drugs subject to non-renal clearance, which involves mainly the liver and the gut. The use of apixaban, an oral anticoagulant, has been approved in the USA for dialysis patients. However, the coexistence of thrombotic and haemorrhagic risk in patients with CKD makes dose adjustment difficult. The liver has a major role in drug metabolization. Hepatocytes express high levels of AhR, a ligand-inducible transcription factor that mediates the induction of various liver cytochrome P450 enzymes by xeno and endobiotic. Tryptophan-derived uraemic toxins (TDUT) are AhR agonists. Indoxyl sulfate (IS) is the main TDUT involved in uraemic syndrome. IS increases the expression and activity of P-glycoprotein (P-gp) in the liver. Apixaban metabolism is mediated by P-gp and Cyp3a4 (Cyp3a11 in mice). We aim to study the effect of apixaban and IS in the expression of drug metabolism genes. Our hypothesis is that AhR activation by IS could severely modify drug metabolism during CKD.

METHOD

C57BL/6J Wild-type mice purchased from The Jackson Laboratory were fed ad libitum with a standard diet. At 10 weeks of age, mice drinking water was substituted with a 5% sucrose water solution with either 0.1% indoxyl sulphate or KCl (control) added at equivalent concentrations. 48-h before sacrifice some mice were gavaged with an apixaban solution (0.6 mg/mL) twice a day with the last dose given 4 h prior to sacrifice. All mice were sacrificed at 11 weeks of age. Liver samples were stored in an RNA-later solution at −20°C. Samples were thawed and lysed in Trizol using the Tissue-Ruptor system (Qiagen). RNA was extracted and purified with chloroform and precipitated with isopropanol. RNA concentration was estimated by spectrophotometry. Gene expression was analysed by q-RT-PCR using Gusb as a housekeeping gene. Apixaban levels were quantified by LC-MS. Kruskal–Wallis followed by a two-stage linear step-up procedure of Benjamini, Krieger and Yekutieli (q &lt; 0.05) was performed using GraphPad Prism 9.2.1.

RESULTS

Four groups of mice per sex were thus created: WT-KCl, WT-IS, WT-KCl Apix, WT-IS Apix. In the IS/KCl model we observe higher mRNA basal expression of Abcb1a (q = 0.008) and Sult1a1 (q = 0.006) and lower basal expression of Abcg2 (q = 0.0005) in females compared to males when treated with KCl. IS treatment increases Cyp1a2 expression in females (q = 0.0139) and Cyp1a1 in both males (q = 0.0145) and females (q = 0.026). In the IS/KCl-Apix model the same sex-related differences are maintained for Abcb1a (q = 0.0031), Sult1a1 (q = 0.0316) and Abcg2 (q &lt; 0.0001). In males, CYP2e1 expression is increased by apixaban in KCl (q = 0.067) and IS (q = 0.0278) treated mice. Moreover, apixaban counteracts the increased expression of Cyp1a1 induced by IS (q = 0.0177). The expression of Cyp3a11 is augmented in males treated with KCl-apixaban (q = 0.0143), an effect that seems to be reversed by IS (q = 0.0066). In females, apixaban has no effect in gene expression. Apixaban serum concentration is higher in KCl (q = 0.0350) and IS (q = 0.0019) treated females when compared to males.

CONCLUSION

The effect of IS as an agonist of AhR in the liver is confirmed by the increased expression of Cyp1a1. Apixaban provokes a remarkable increase of Cyp3a11 in male mice, which could lead to higher degradation rates decreasing its activity. IS seems to reverse this effect. This could lead to increased activity of apixaban during CKD which could derive in an increased risk of bleeding. Higher BCRP rates could explain lower rates of apixaban in male serum. Apixaban did not alter gene expression in females. Clinical trials in CKD are generally biased regarding sex (fewer women represented) possibly masking important sex-dependent drug adverse effects. Our results show great differences in basal expression of various genes, confirming the importance to study men and women separately with respect to drug metabolism.

Mechanisms of myostatin and activin A accumulation in chronic kidney disease

BACKGROUND

Myostatin and activin A induce muscle wasting by activating the ubiquitin proteasome system and inhibiting the Akt/mTOR pathway. In chronic kidney disease (CKD), myostatin and activin A plasma concentrations are increased, but it is not clear if there is an increased production or a decreased renal clearance.

METHODS

We measured myostatin and activin A concentrations in 232 CKD patients and studied their correlation with estimated glomerular filtration rate (eGFR). We analyzed the myostatin gene (MSTN) expression in muscle biopsies of hemodialysis (HD) patients. We then measured circulating myostatin and activin A in plasma and the Mstn and Inhba expression in muscles, kidney, liver and heart of two CKD mice models (adenine and 5/6th nephrectomy models). Finally, we analyzed whether the uremic toxin indoxyl sulfate (IS) increased Mstn expression in mice and cultured muscle cells.

RESULTS

In patients, myostatin and activin A were inversely correlated with eGFR. MSTN expression was lower in HD patients' muscles (vastus lateralis) than in controls. In mice with CKD, myostatin and activin A blood concentrations were increased. Mstn was not up-regulated in CKD mice tissues. Inha was up-regulated in kidney and heart. Exposure to IS did not induce Mstn up-regulation in mice muscles and in cultured myoblasts and myocytes.

CONCLUSION

During CKD, myostatin and activin A blood concentrations are increased. Myostatin is not overproduced, suggesting only an impaired renal clearance, but activin A is over produced in kidney and heart. We propose to add myostatin and activin A to the list of uremic toxins.

Kidney biopsy in very elderly patients: indications, therapeutic impact and complications

BACKGROUND

Few data is available on the risk/benefit balance of native kidney biopsy (KB) in very elderly patients.

METHODS

Multicenter retrospective cohort study in the Aix-Marseille area: the results of KB and medical charts of all patients over 85 years biopsied between January 2010 and December 2018 were reviewed.

RESULTS

104 patients were included. Median age was 87 years. Indications for KB were: acute kidney injury (AKI) in 69.2% of patients, nephrotic syndrome (NS) with AKI in 13.5%, NS without AKI in 12.5%, and proteinuria in 4.8%. Median serum creatinine was 262 μmol/L, 21% of patients required dialysis at the time of KB. Significant bleeding occurred in 7 (6.7%) patients, requiring blood cell transfusion in 4 (3.8%), and radiological embolization in 1 (1%). The most frequent pathological diagnoses were: non-diabetic glomerular diseases (29.8%, including pauci-immune crescentic glomerulonephritis in 9.6%), hypertensive nephropathy (27.9%), acute interstitial nephritis (16.3%), renal involvement of hematological malignancy (8.7%), and acute tubular necrosis (6.7%). After KB, 51 (49%) patients received a specific treatment: corticosteroids (41.3%), cyclophosphamide (6.7%), rituximab (6.7%), bortezomib (3.8%), other chemotherapies (3.8%). Median overall survival was 31 months.

CONCLUSIONS

KB can reveal a diagnosis with therapeutic impact even in very elderly patients. Severe bleeding was not frequent in this cohort, but KB may have not been performed in more vulnerable patients.

Disease Activity and Adverse Events in Patients with ANCA-Associated Vasculitides Undergoing Long-Term Dialysis

BACKGROUND AND OBJECTIVES

Kidney impairment of ANCA-associated vasculitides can lead to kidney failure. Patients with kidney failure may suffer from vasculitis relapses but are also at high risk of infections and cardiovascular events, which questions the maintenance of immunosuppressive therapy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with ANCA-associated vasculitides initiating long-term dialysis between 2008 and 2012 in France registered in the national Renal Epidemiology and Information Network registry and paired with the National Health System database were included. We analyzed the proportion of patients in remission off immunosuppression over time and overall and event-free survival on dialysis (considering transplantation as a competing risk). We compared the incidence of vasculitis relapses, serious infections, cardiovascular events, and cancers before and after dialysis initiation.

RESULTS

In total, 229 patients were included: 142 with granulomatous polyangiitis and 87 with microscopic polyangiitis. Mean follow-up after dialysis initiation was 4.6±2.7 years; 82 patients received a kidney transplant. The proportion of patients in remission off immunosuppression increased from 23% at dialysis initiation to 62% after 5 years. Overall survival rates on dialysis were 86%, 69%, and 62% at 1, 3, and 5 years, respectively. Main causes of death were infections (35%) and cardiovascular events (26%) but not vasculitis flares (6%). The incidence of vasculitis relapses decreased from 57 to seven episodes per 100 person-years before and after dialysis initiation (P=0.05). Overall, during follow-up, 45% of patients experienced a serious infection and 45% had a cardiovascular event, whereas 13% experienced a vasculitis relapse.

CONCLUSIONS

The proportion of patients with ANCA-associated vasculitis in remission off immunosuppression increases with time spent on dialysis. In this cohort, patients were far less likely to relapse from their vasculitis than to display serious infectious or cardiovascular events.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_11_08_CJN03190321.mp3.

Systemic autoimmune disorders associated with thrombotic microangiopathy: A cross-sectional analysis from the French National TMA registry: Systemic autoimmune disease-associated TMA

CONTEXT

The management of systemic auto-immune diseases (SAID) -associated thrombotic microangiopathies (TMA) [SAID-TMA] remains debated.

OBJECTIVES

To provide a demographic, clinical and therapeutic picture of SAID-TMA.

METHODS

A cross-sectional analysis was conducted on adult patients presenting with SAID and TMA from the French National TMA Registry over a 20-year period. Clinical features were extracted and compared to those from a historical cohort of atypical haemolytic and uremic syndrome (aHUS) patients.

RESULTS

Forty-one patients with SAID-TMA were compared to 78 patients with aHUS from a historical cohort. Connective tissue diseases (CTD) were systemic lupus erythematosus (n=18), primary Sjögren's syndrome (n=7), systemic sclerosis (n=11), mixed CTD (n=2) and 2 cases of vasculitides, including 7 overlapping forms and 8 cases of primary antiphospholipid syndromes (APLS). Patients with SAID-TMA generally had pre-existing chronic kidney failure (OR= 3.17, 95%CI: 1.204 to 7.923; p= 0.016) compared to aHUS patients, though creatinine levels were significantly lower (216 [IQR, 108-334] µmol/L vs. 368 [IQR, 170-722] µmol/L; p= 0.002). Patients were less likely to recover if renal replacement therapy was needed at onset (OR= 0.07; 0.02 to 0.34; p <0.0005). Two patients died. Thirty patients responded to immunosuppressive treatment and complete remission was achieved in 25 cases. By contrast, therapeutic plasma exchange (TPE) did not have an early effect on TMA features at Day-7 nor Day-15 (p >0.05).

CONCLUSION

The management of SAID-TMA implies an early initiation of immunosuppressive drugs for flares of the associated SAID, whereas TPE seem ineffective. KEY MESSAGES.

mTOR-Activating Mutations in RRAGD Are Causative for Kidney Tubulopathy and Cardiomyopathy

BACKGROUND

Over the last decade, advances in genetic techniques have resulted in the identification of rare hereditary disorders of renal magnesium and salt handling. Nevertheless, approximately 20% of all patients with tubulopathy lack a genetic diagnosis.

METHODS

We performed whole-exome and -genome sequencing of a patient cohort with a novel, inherited, salt-losing tubulopathy; hypomagnesemia; and dilated cardiomyopathy. We also conducted subsequent in vitro functional analyses of identified variants of RRAGD, a gene that encodes a small Rag guanosine triphosphatase (GTPase).

RESULTS

In eight children from unrelated families with a tubulopathy characterized by hypomagnesemia, hypokalemia, salt wasting, and nephrocalcinosis, we identified heterozygous missense variants in RRAGD that mostly occurred de novo. Six of these patients also had dilated cardiomyopathy and three underwent heart transplantation. We identified a heterozygous variant in RRAGD that segregated with the phenotype in eight members of a large family with similar kidney manifestations. The GTPase RagD, encoded by RRAGD, plays a role in mediating amino acid signaling to the mechanistic target of rapamycin complex 1 (mTORC1). RagD expression along the mammalian nephron included the thick ascending limb and the distal convoluted tubule. The identified RRAGD variants were shown to induce a constitutive activation of mTOR signaling in vitro.

CONCLUSIONS

Our findings establish a novel disease, which we call autosomal dominant kidney hypomagnesemia (ADKH-RRAGD), that combines an electrolyte-losing tubulopathy and dilated cardiomyopathy. The condition is caused by variants in the RRAGD gene, which encodes Rag GTPase D; these variants lead to an activation of mTOR signaling, suggesting a critical role of Rag GTPase D for renal electrolyte handling and cardiac function.