Steroid-resistant nephrotic syndrome: past and current perspectives

Outcomes and prognostic factors in childhood-onset steroid-resistant nephrotic syndrome: a retrospective single-center study

BACKGROUND

Steroid-resistant nephrotic syndrome (SRNS) is the second leading cause of chronic kidney disease (CKD) in childhood. It represents a heterogeneous group of diseases with variable kidney outcomes that are still challenging to predict. In this study, our main objective is to describe predictive factors of remission states and kidney survival comparing genetic and non-genetic SRNS.

METHODS

We conducted a retrospective analysis of 65 pediatric patients with SRNS treated at the pediatric outpatient clinic in Berlin between 2000 and 2023. Clinical characteristics, laboratory findings, and treatment strategies were systematically collected at multiple time points. Outcomes were defined by remission status, kidney survival (CKD stage I-IV), or progression to CKD stage V. Statistical analyses included univariate and multivariate logistic and Cox regression models adjusted for monogenic SRNS to identify predictors of remission and kidney survival.

RESULTS

The median age of onset was 4.0 years, with a male predominance of 57%. Patients were followed for a median of 5.9 years. At the last follow-up, 26 patients achieved complete remission, 12 achieved partial remission, and 27 showed no remission. Kidney survival rates at 5 and 10 years were 71% and 56%, respectively. High initial nephrotic-range proteinuria, confirmed genetic diagnoses, reduced eGFR, and hypoalbuminemia at 3-month and 1-year follow-ups were identified as negative predictive factors for complete or partial remission. These factors also correlated strongly with an elevated risk of progression to CKD stage V.

CONCLUSION

Our findings highlight additional prognostic factors influencing remission status and long-term kidney survival in pediatric SRNS, emphasizing the value of detailed early time-point analyses.

Changes in Serum Immunoglobulin Levels Play as Predictors of Treatment Response and Prognosis in Pediatric Idiopathic Nephrotic Syndrome During the Remission Phase

BACKGROUND

Nephrotic syndrome is an immune-mediated renal disorder characterized by T-cell and B-cell dysfunctions with changes in immunoglobulin (Ig) levels and the IgG:IgM ratio. Therefore, this study aimed to determine whether the serum level of Igs can be considered as an index to predict the response to treatment and the prognosis of idiopathic nephrotic syndrome (INS) in children in the remission phase.

METHODS

The study population consisted of 38 children with INS in the remission phase and 38 age- and sex-matched healthy children. Blood samples were collected from participants and serum values of IgG, IgM, IgE, and IgA were measured using EISA KITS from Aptech Services. The IgG:IgM ratio was studied in the participants.

RESULTS

Patients significantly increased IgM and IgE levels compared with healthy subjects, unlike IgG and IgA values (p < 0.001-0.05). Patients with steroid-resistant nephrotic syndrome (SRNS) had a significant increase in IgM levels compared with those with steroid-sensitive nephrotic syndrome (SSNS) (p < 0.05). While, subjects with SRNS showed significant reductions in IgG and IgA values (p < 0.01). There were significant differences in the levels of IgG and IgM between steroid-sensitive patients with and without a history of relapse (p < 0.01). Furthermore, patients with steroid-independent and frequently relapsing NS showed a significant increase in IgE value compared with that of subjects with steroid-dependent and relapse (p < 0.05). The ratio of IgG/IgM was significantly reduced in patients compared with healthy individuals (p < 0.05). Other results indicated that there was a significant difference between patients with steroid-independent and steroid-dependent who had a history of relapse (p < 0.01).

CONCLUSION

Alterations in serum Ig values can be considered as predictors of treatment response and prognosis in pediatric idiopathic nephrotic syndrome during the remission phase.

Quantitative phenotyping of Nphs1 knockout mice as a prerequisite for gene replacement studies

Steroid-resistant nephrotic syndrome (SRNS) is the second most frequent cause of chronic kidney disease before the age of 25 yr. Nephrin, encoded by NPHS1, localizes to the slit diaphragm of glomerular podocytes and is the predominant structural component of the glomerular filtration barrier. Biallelic variants in NPHS1 can cause congenital nephrotic syndrome of the Finnish type, for which, to date, no causative therapy is available. Recently, adeno-associated virus (AAV) vectors targeting the glomerular podocyte have been assessed as a means for gene replacement therapy. Here, we established quantitative and reproducible phenotyping of a published, conditional Nphs1 knockout mouse model (Nphs1tm1.1Pgarg/J and Nphs2-Cre+) in preparation for a gene replacement study using AAV vectors. Nphs1 knockout mice (Nphs1fl/fl Nphs2-Cre+) exhibited 1) a median survival rate of 18 days (range: from 9 to 43 days; males: 16.5 days and females: 20 days); 2) an average foot process (FP) density of 1.0 FP/µm compared with 2.0 FP/µm in controls and a mean filtration slit density of 2.64 µm/µm2 compared with 4.36 µm/µm2 in controls; 3) a high number of proximal tubular microcysts; 4) the development of proteinuria within the first week of life as evidenced by urine albumin-to-creatinine ratios; and 5) significantly reduced levels of serum albumin and elevated blood urea nitrogen and creatinine levels. For none of these phenotypes, significant differences between sexes in Nphs1 knockout mice were observed. We quantitatively characterized five different phenotypic features of congenital nephrotic syndrome in Nphs1fl/fl Nphs2-Cre+ mice. Our results will facilitate future gene replacement therapy projects by allowing for sensitive detection of even subtle molecular effects.NEW & NOTEWORTHY To evaluate potential, even subtle molecular, therapeutic effects of gene replacement therapy (GRT) in a mouse model, prior rigorous quantifiable and reproducible disease phenotyping is necessary. Here, we, therefore, describe such a phenotyping effort in nephrin (Nphs1) knockout mice to establish the basis for GRT for congenital nephrotic syndrome. We believe that our findings set an important basis for upcoming/ongoing gene therapy approaches in the field of nephrology, especially for monogenic nephrotic syndrome.

Assessment of medication discrepancy, medication appropriateness, and cost analysis among patients with pediatric nephrotic syndrome: An ambispective cohort observational study

BACKGROUND

Nephrotic syndrome (NS) is a commonly encountered chronic kidney disease in pediatric populations, with South Asian children being at high risk and requiring long-term pharmacological management. Thus, identifying medication discrepancies and evaluating the appropriateness of therapy and its economic burden are vital for inpatient management. The aim of the study was to assess medication reconciliation, medication appropriateness, and cost analysis in NS cases.

METHODS

An ambispective cohort observational study was carried out with 150 NS patients where medication discrepancies were identified retrospectively and prospectively using the best possible medication history and following up patients correspondingly. Further, the Medication Appropriateness Index and cost variation analysis were used to assess the prescribed therapy and cost analysis, respectively.

RESULTS

Out of 150 patients with NS included, 67.3% were male and the mean age was 7.2 years. In total, 36.7% medication discrepancies were found at baseline and 6% discrepancies at follow-up. The majority of discrepancies were unintentional and due to dosing error both at baseline and follow-up. Further, in only 2% of the patients was there inappropriately prescribed medication, and the majority of patients spent between INR (Indian Rupees) 500 and 1000.

CONCLUSION

Chronic conditions like NS require continuous monitoring by the specialist pediatric clinical pharmacist, who can contribute significantly by minimizing the medication discrepancies, by assessing the appropriateness of therapy, and lessening the economic burden.

Outcomes of children with idiopathic steroid resistant nephrotic syndrome: a single centre observational study

INTRODUCTION

Idiopathic steroid resistant nephrotic syndrome (SRNS) has variable outcomes in children. The primary objective of the present study was to assess the cumulative remission rate and the secondary objectives were to assess factors affecting the remission status, kidney function survival, and adverse effects of medications.

METHODS

One hundred fourteen patients with SRNS were included. Calcineurin inhibitor-based treatment protocol along with prednisolone and angiotensin-converting enzyme inhibitor were used, and patients were followed over 5 years.

RESULTS

Median age was 4.5 years; 53.5% of cases were between 1 to 5 years of age. Sixty-two patients (54.4%) were at initial stage and 52 (45.6%) were at a late SRNS stage. Median eGFRcr was 83.5 mL/min/1.73m2 at presentation. Of the 110 patients, 63 (57.3%) achieved remission [complete remission 30 (27.3%), partial remission 33 (30%)], and 47 (42.7%) had no remission. Kidney function survival was 87.3% and 14 cases (12.7%) had progression to CKD (G3-8, G4-3, G5-1, and G5D-2). Median duration of follow up was 36 months (IQR 24, 60). Age of onset, cyclosporine/tacrolimus, eGFRcr, and histopathology (MCD/FSGS) did not affect remission. Similarly, remission status in addition to age of onset, drug protocol, and histopathology did not significantly affect kidney function during a period of 5 years. Hypertension, cushingoid facies, short stature, cataract, and obesity were observed in 37.7, 29.8, 25.5, 17.5, and 0.7% of cases, respectively.

CONCLUSION

About half of the cases achieved remission. Age of onset of disease, cyclosporine/tacrolimus use, and histopathological lesion neither affected remission status nor short-term kidney function survival in SRNS.

Association between serum calcium and biochemical parameters among nephrotic syndrome patients: a case-control study

Background

Nephrotic syndrome is characterized by proteinuria, hyperlipidemia, and edema. The annual incidence of nephrotic syndrome is 2–7 cases/100,000 children.

Methods and results

The present study included 32 control, 32 steroid-sensitive nephrotic syndrome cases, and 32 steroid-resistant nephrotic syndrome cases aged ≤ 17 years. Serum samples were handled to check serum albumin, creatinine, calcium, and total cholesterol in SSNS and SRNS. Pearson’s correlation test was performed to investigate the relationship between the parameters. The independent sample t-test was done to compare the mean differences between two parameters by SPSS (Statistical Package for the Social Sciences). We found a significant positive correlation in SSNS in serum albumin, creatinine, calcium, and total cholesterol. In SRNS, we did not find a correlation between serum calcium and total cholesterol.

Conclusions

The combination of serum albumin, creatinine, and total cholesterol with serum calcium improves the diagnostic sensitivity of SSNS and SRNS. Thus, serum calcium may be used as an equivalent marker in the early diagnosis and treatment of nephrotic syndrome in children.

Combined Methylprednisolone Pulse Therapy plus Rituximab for Treating a Rare Juvenile Steroid-Resistant Nephrotic Syndrome with Cerebral Venous Sinus Thrombosis: A Case Report

Background: Cerebral venous sinus thrombosis (CVST) secondary to nephrotic syndrome (NS) is rarely reported. Additionally, treating steroid-sensitive nephrotic syndrome (SSNS) that changes to steroid resistance (SRNS) is difficult, with many relapses and side effects. Case presentation: A 32-month-old SSNS male child turned into SRNS and developed cerebral venous sinus thrombosis (CVST), a rare complication of NS. As a result of the administration of combined pulse methylprednisolone and IV Rituximab (RTX) therapy, the patient showed marked improvement, the results of urine analysis were remarkably improved, and the child started to respond to treatment. Conclusion: Successful treatment of a rare case of juvenile SSNS behaving as SRNS with the development of CVST could be established using combined steroid pulse therapy, Enoxaparin, and the B lymphocytes monoclonal antibodies RTX.

Desfechos de crianças com síndrome nefrótica idiopática córtico-resistente: um estudo observacional de centro único

RESUMO Introdução: A síndrome nefrótica idiopática córtico-resistente (SNICR) apresenta desfechos variáveis em crianças. O objetivo principal deste estudo foi avaliar a taxa de remissão cumulativa. Os objetivos secundários foram avaliar fatores que afetam status de remissão, sobrevida da função renal e efeitos adversos de medicamentos. Métodos: Foram incluídos 114 pacientes com SNCR. Utilizou-se protocolo de tratamento baseado em inibidores de calcineurina juntamente com prednisolona e inibidor da enzima conversora de angiotensina. Os pacientes foram acompanhados durante 5 anos. Resultados: A idade mediana foi 4,5 anos; 53,5% dos casos tinham entre 1 e 5 anos. 62 pacientes (54,4%) estavam em estágio inicial; 52 (45,6%) em estágio tardio da SNCR. A TFGecr mediana foi 83,5 mL/min/1,73 m2 na apresentação. Dos 110 pacientes, 63 (57,3%) alcançaram remissão [remissão completa 30 (27,3%), remissão parcial 33 (30%)], e 47 (42,7%) não apresentaram remissão. A sobrevida da função renal foi 87,3%; 14 casos (12,7%) progrediram para DRC (G3-8, G4-3, G5-1, G5D-2). A duração mediana do acompanhamento foi 36 meses (IIQ 24, 60). Idade no início, ciclosporina/tacrolimus, TFGecr e histopatologia (DLM/GESF) não afetaram a remissão. Igualmente, status de remissão, além da idade no início, protocolo de medicamentos e histopatologia não afetaram significativamente a função renal por 5 anos. Observou-se hipertensão, fácies cushingoide, baixa estatura, catarata e obesidade em 37,7; 29,8; 25,5; 17,5; e 0,7% dos casos, respectivamente. Conclusão: Aproximadamente metade dos casos alcançou remissão. Idade no início, uso de ciclosporina/tacrolimus e lesão histopatológica não afetaram o status de remissão nem a sobrevida da função renal a curto prazo na SNICR.

Risks and renal outcomes of severe acute kidney injury in children with steroid-resistant nephrotic syndrome

BACKGROUND

Risks and renal outcomes of severe acute kidney injury (AKI) in children with steroid-resistant nephrotic syndrome (SRNS), particularly those who require dialysis, have not been fully explored.

METHODS

This retrospective cohort study enrolled children who had been diagnosed with idiopathic nephrotic syndrome at the National Center for Child Health and Development between March 2002 and December 2018. Children with steroid-sensitive nephrotic syndrome or SRNS-related gene mutations were excluded.

RESULTS

Sixty-two children with SRNS (37 boys; median age, 3.6 years [interquartile range (IQR) 2.0-10.3]) were enrolled. Sixteen patients (25.8%) had severe AKI, including nine patients (14.5%) who received dialysis. The period from nephrotic syndrome (NS) onset to partial remission (median [IQR]) was not significantly influenced by dialysis status, but tended to be longer in the dialysis group (125 days [74-225] vs. 40 days [28-113]; p = 0.09); notably, no patient developed chronic kidney disease during the follow-up period. Infection and posterior reversible encephalopathy (PRES) were significantly associated with AKI. Patients with AKI tended to require dialysis in the presence of infection, undergo treatment with cyclosporine A, and have PRES. The period from onset of NS to AKI was significantly longer in the dialysis group (26 days [15.5-46.0] vs. 4 days [0.0-14.0]; p = 0.01).

CONCLUSION

Dialysis was commonly required among children with SRNS who exhibited severe AKI. The period from onset of NS to partial remission tended to be longer in patients receiving dialysis, whereas renal prognosis was satisfactory during subsequent follow-up.

Long-Term Study in Children with Steroid-Resistant Nephrotic Syndrome Progressing to End-Stage Renal Disease

Introduction:Steroid-resistant nephrotic syndrome (SRNS) in children is a glomerular disease who often fails to respond to immunosuppressive treatment and is a leading cause for progression to end-stage renal disease (ESRD) and dialysis. Some risk factors, that appear to be common in patients with SRNS and progression to ESRD, have been identified and reported: focal and segmental glomeruloslerosis on kidney biopsy, high range persistent proteinuria, microscopic hematuria, hypertension, episodes of acute kidney injury (AKI) and resistance to immunosuppressive agents. The challenge is to identify these risk factors and improve patients' management, because children with ESRD have many associated complications and a high rate of morbidity and mortality. Objective: The aim of our study is to observe the incidence of SRNS in our patients and identify the presence of common risk factors in those progressing to ESRD with requirement for dialysis or kidney transplant. Material and methods:We studied a total number of 125 pacients who were diagnosed with nephrotic syndrome in the Department of Pediatric Nephrology of "M. S. Curie" Emergency Clinical Hospital for Children, Bucharest, Romania, from January 2013 to December 2020. Twenty six patients diagnosed with SRNS were included in our study; all of them underwent clinical examination and laboratory tests and were regularly monitored to assess the progression of kidney disease to ESRD. Discussion and results:Steroid-resistant nephrotic syndrome is associated with an increased risk for developing ESRD with requirement for dialysis and transplant. Resistance to immunosuppressive agents was associated with ESRD in our patients. Focal segmental glomerulosclerosis (FSGS), the most common histopathologic lesion, had no value for progression to ESRD in our study. Hematuria, persistent high value proteinuria, hypertension and episodes of AKI were found in our patients with SRNS and progressed to ESRD.

Selective modulator of nuclear receptor PPARγ with reduced adipogenic potential ameliorates experimental nephrotic syndrome

Glomerular disease manifests as nephrotic syndrome (NS) with high proteinuria and comorbidities, and is frequently refractory to standard treatments. We hypothesized that a selective modulator of PPARγ, GQ-16, will provide therapeutic advantage over traditional PPARγ agonists for NS treatment. We demonstrate in a pre-clinical NS model that proteinuria is reduced with pioglitazone to 64%, and robustly with GQ-16 to 81% of nephrosis, comparable to controls. Although both GQ-16 and pioglitazone restore glomerular-Nphs1, hepatic-Pcsk9 and serum-cholesterol, only GQ-16 restores glomerular-Nrf2, and reduces hypoalbuminemia and hypercoagulopathy. GQ-16 and pioglitazone restore common and distinct glomerular gene expression analyzed by RNA-seq and induce insulin sensitizing adipokines to various degrees. Pioglitazone but not GQ-16 induces more lipid accumulation and aP2 in adipocytes and white adipose tissue. We conclude that selective modulation of PPARγ by a partial agonist, GQ-16, is more advantageous than pioglitazone in reducing proteinuria, NS associated comorbidities, and adipogenic side effects of full PPARγ agonists.

New Insights into the Treatment of Glomerular Diseases: When Mechanisms Become Vivid

Treatment for glomerular diseases has been extrapolated from the experience of other autoimmune disorders while the underlying pathogenic mechanisms were still not well understood. As the classification of glomerular diseases was based on patterns of juries instead of mechanisms, treatments were typically the art of try and error. With the advancement of molecular biology, the role of the immune agent in glomerular diseases is becoming more evident. The four-hit theory based on the discovery of gd-IgA1 gives a more transparent outline of the pathogenesis of IgA nephropathy (IgAN), and dysregulation of Treg plays a crucial role in the pathogenesis of minimal change disease (MCD). An epoch-making breakthrough is the discovery of PLA2R antibodies in the primary membranous nephropathy (pMN). This is the first biomarker applied for precision medicine in kidney disease. Understanding the immune system's role in glomerular diseases allows the use of various immunosuppressants or other novel treatments, such as complement inhibitors, to treat glomerular diseases more reasonable. In this era of advocating personalized medicine, it is inevitable to develop precision medicine with mechanism-based novel biomarkers and novel therapies in kidney disease.

Clinical and Apoptotic Factors Defining and Predicting Steroid Resistance in Nephrotic Syndrome in Children

Introduction. Nephrotic syndrome (NS) is a kidney disease characterized by albuminuria, hyperlipidemia, edema, and hypoalbuminemia. Above 20 % of nephrotic children do not show response to steroid treatment. Molecular markers controlling apoptosis have not been studied as a predictors of steroid resistant NS (SRNS) and steroid sensitive NS (SSNS) in children. Aim of the Study. To identify clinical and molecular markers which define and predict the steroid-resistance phenomenon in children with NS. Methods. Fifty-six clinical cases of children hospitalized in Pediatric Hospital No. 7 (Kyiv, Ukraine) with NS (26 SSNS and 30 SRNS) studied. Stepwise logistic regression models used to analyze data. Data processed using GraphPad Prism 9.0 Software for Windows (USA, San Diego, CA). Results. Arterial hypertension, WBC and RBC count, serum creatinine, serum urea, serum cholesterol found to be factors defining and predicting SRNS. Apoptosis regulating BcL-xL, Bax but not caspase-8 found to be those defining SRNS. Among transcriptional factors HIF-1alfa selected as a factor predicting steroid resistance phenomenon. For SSNS group significant negative correlation observed between BcL-xL and Bax, BcL-xL and caspase-3, significant positive correlation observed between marker of cellular hypoxia HIF-1alfa and proapoptotic factor caspase-3. For SRNS group significant negative correlation observed between BcL-xL and Bax, BcL-xL and caspase-3 level, significant positive correlation observed between HIF-1alfa and proapoptotic factor caspase-3. Conclusions. Arterial hypertension, serum creatinine level, serum urea level, serum cholesterol level, WBC and RBC count, BcL-xL, Bax, caspase-3, and HIF-1alfa identified as candidate biomarkers to predict and define SRNS in pediatric NS.

Liposorber® LA-15 system for LDL apheresis in resistant nephrotic syndrome patients

BACKGROUND

Steroid-resistant nephrotic syndrome (SRNS) is a major cause of stage 5 chronic kidney disease (CKD 5) in children. LDL apheresis (LDL-A) is now FDA approved for the treatment of pediatric focal segmental glomerulosclerosis (FSGS). Effective management of hyperlipidemia with LDL-A in SRNS patients may prevent progression of kidney disease and lead to remission. We report a case series of patients who received LDL-A for treatment of SRNS METHODS: We describe five children with SRNS who were treated with 12 sessions of LDL-A. Partial remission (PR) is defined as urine protein to creatinine ratio (UPC) of 0.2-2 (g/g) or decrease in UPC ≥ 50%, and complete remission (CR) is defined as UPC < 0.2 (g/g).

RESULTS

One patient achieved CR and three achieved PR. One patient did not respond to therapy. The earliest that a patient achieved PR was at treatment #10 and some did not respond until after LDL-A was completed. Those who responded stayed in either CR or PR for extended periods of time. LDL-A was successful at significantly reducing LDL (p < 0.001), total cholesterol (p < 0.001), and triglyceride (p < 0.001).

CONCLUSIONS

LDL-A was able to significantly decrease the lipid levels in these patients and induce CR and PR in the majority. The current study confirms previous studies showing those with a higher glomerular sclerosis burden were less likely to respond. LDL-A should be considered in patients with treatment-resistant SRNS and should be considered before there is a high burden of glomerular sclerosis to provide the best chance of success.

UK experience of ofatumumab in recurrence of focal segmental glomerulosclerosis post-kidney transplant

BACKGROUND

Steroid-resistant nephrotic syndrome (SRNS), commonly caused by focal segmental glomerulosclerosis (FSGS), is associated with progression to stage 5 chronic kidney disease, requirement for kidney replacement therapy and a risk of disease recurrence post-kidney transplantation. Ofatumumab (OFA) is a fully humanised monoclonal antibody to CD20, with similar mechanisms of action to rituximab (RTX).

METHODS

We report a case series of seven UK patients (five paediatric, two adult), all of whom developed FSGS recurrence after kidney transplantation and received OFA as part of their therapeutic intervention. All also received concomitant plasmapheresis. The 2-year outcome of these seven patients is reported, describing clinical course, kidney function and proteinuria.

RESULTS

Four patients (all paediatric) achieved complete urinary remission with minimal proteinuria 12 months post-treatment. Three of those four also had normal graft function. Two patients showed partial remission-brief improvement to non-nephrotic proteinuria (197 mg/mmol) in one patient, maintained improvement in kidney function (estimated glomerular filtration rate 76 ml/min/1.73 m²) in the other. One patient did not demonstrate any response.

CONCLUSIONS

OFA may represent a useful addition to therapeutic options in the management of FSGS recurrence post-transplantation, including where RTX has shown no benefit. Concomitant plasmapheresis in all patients prevents any definitive conclusion that OFA was the beneficial intervention.

Management of Steroid-Resistant Nephrotic Syndrome in Children

Nephrotic syndrome (NS) affects 115-169 children per 100,000, with rates varying by ethnicity and location. Immune dysregulation, systemic circulating substances, or hereditary structural abnormalities of the podocyte are considered to have a role in the etiology of idiopathic NS. Following daily therapy with corticosteroids, more than 85% of children and adolescents (often aged 1 to 12 years) with idiopathic nephrotic syndrome have full proteinuria remission. Patients with steroid-resistant nephrotic syndrome (SRNS) do not demonstrate remission after four weeks of daily prednisolone therapy. The incidence of steroid-resistant nephrotic syndrome in children varies between 35 and 92 percent. A third of SRNS patients have mutations in one of the important podocyte genes. An unidentified circulating factor is most likely to blame for the remaining instances of SRNS.

The aim of this article is to explore and review the genetic factors and management of steroid-resistant nephrotic syndrome. An all language literature search was conducted on MEDLINE, COCHRANE, EMBASE, and Google Scholar till September 2021. The following search strings and Medical Subject Headings (MeSH) terms were used: “Steroid resistance”, “nephrotic syndrome”, “nephrosis” and “hypoalbuminemia”. We comprehensively reviewed the literature on the epidemiology, genetics, current treatment protocols, and management of steroid-resistant nephrotic syndrome.

We found that for individuals with non-genetic SRNS, calcineurin inhibitors (cyclosporine and tacrolimus) constitute the current mainstay of treatment, with around 70% of patients achieving full or partial remission and an acceptable long-term prognosis. Patients with SRNS who do not react to calcineurin inhibitors or other immunosuppressive medications may have deterioration in kidney function and may develop end-stage renal failure. Nonspecific renal protective medicines, such as angiotensin-converting enzyme inhibitors, angiotensin 2 receptor blockers, and anti-lipid medications, slow the course of the illness. Recurrent focal segmental glomerulosclerosis in the allograft affects around a third of individuals who get a kidney transplant, and it frequently responds to a combination of plasma exchange, rituximab, and increased immunosuppression. Despite the fact that these results show a considerable improvement in outcome, further multicenter controlled studies are required to determine the optimum drugs and regimens to be used.

Podocyte Sphingolipid Signaling in Nephrotic Syndrome

Podocytes play a vital role in the pathogenesis of nephrotic syndrome (NS), which is clinically characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and peripheral edema. The pathogenesis of NS has evolved through several hypotheses ranging from immune dysregulation theory and increased glomerular permeability theory to the current concept of podocytopathy. Podocytopathy is characterized by dysfunction or depletion of podocytes, which may be caused by unknown permeability factor, genetic disorders, drugs, infections, systemic disorders, and hyperfiltration. Over the last two decades, numerous studies have been done to explore the molecular mechanisms of podocyte injuries or NS and to develop the novel therapeutic strategies targeting podocytopathy for treatment of NS. Recent studies have shown that normal sphingolipid metabolism is essential for structural and functional integrity of podocytes. As a basic component of the plasma membrane, sphingolipids not only support the assembly of signaling molecules and interaction of receptors and effectors, but also mediate various cellular activities, such as apoptosis, proliferation, stress responses, necrosis, inflammation, autophagy, senescence, and differentiation. This review briefly summarizes current evidence demonstrating the regulation of sphingolipid metabolism in podocytes and the canonical or noncanonical roles of podocyte sphingolipid signaling in the pathogenesis of NS and associated therapeutic strategies.

Treatment Outcomes of Pediatric Nephrotic Syndrome Patients Treated in Ayder Comprehensive Specialized and Mekelle General Hospitals, Ethiopia

Background

Nephrotic syndrome is a common glomerular disease in children with a relapsing course that leads to complications and steroid-related toxicities. In Ethiopia, data on the outcomes of steroid therapy in pediatric nephrotic syndrome patients are limited.

Objective

The aim of the study was to assess the treatment outcomes of pediatric nephrotic syndrome patients in Ayder Specialized Comprehensive and Mekelle General Hospitals.

Methods

A retrospective study was conducted among children treated for nephrotic syndrome from 2010 to 2017 in Ayder Comprehensive Specialized and Mekelle General Hospitals. Univariate and multivariate logic regression analyses were performed to identify determinants of treatment outcome with a p-value <0.05 considered statistically significant.

Results

A total of 159 pediatric patients treated for nephrotic syndrome in both hospitals were included in this study. The mean age of participants at the initial diagnosis was 5.21 ± 2.66 years. Most of the patients 150 (94.3%) achieved remission within 4 weeks of steroid therapy. Among initial responders, the majority of the patients 117 (78%) encountered relapses of which 65 (40.9%) were developed frequent relapse/steroid-dependent nephrotic syndrome. Also, the majority of patients 102 (64.5%) encountered steroid-related toxicities. The predictors of frequent relapse/steroid-dependent nephrotic syndrome were age of ≤6 years (AOR=3.16; p=0.00), hematuria (AOR=6.74; p=0.00), infection (AOR=3.28; p=0.01), acute renal failure (AOR=6.09; p=0.01), serum albumin below 1.5g/dl (8.38, p=0.01) and lack of remission within 2 weeks (AOR=3.69; p=0.00).

Conclusion

Most of the pediatric NS patients treated in ACSH and MGH have achieved remission with initial to steroid therapy. However, there was a higher relapse rate and steroid-related toxicities among pediatric NS patients who achieved remission. Early age at diagnosis, hematuria, reduced GFR, infection, and remission time were the independent predictors of the frequent relapsing/steroid-dependent nephrotic disease course.

Hypomethylation of NLRP3 gene promoter discriminates glucocorticoid-resistant from glucocorticoid-sensitive idiopathic nephrotic syndrome patients

To assess whether NLRP3 gene promoter methylation was able to discriminate glucocorticoid (GC)-resistant from GC-sensitive idiopathic nephrotic syndrome (INS), patients with minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS), we measured the methylation level of NLRP3 promoter in DNA from peripheral blood cells of 10 adult patients with GC-resistant FSGS already in hemodialysis and 18 patients with GC-sensitive INS (13 MCD/5 FSGS) and in 21 pediatric patients with INS with MCD/FSGS before starting any treatment. Association of NLRP3 inflammasome with GC resistance was recapitulated in vitro in monocytic cell lines (THP-1 and U937). In both adults and pediatric patients, NLRP3 promoter methylation was significantly reduced in GC-resistant compared with GC-sensitive patients. Indeed, NLRP3 methylation distinguished GC-resistant and GC-sensitive patients (area under the receiver operating characteristic curve [AUROC] 86.7% in adults, p = 0.00019, and 73.5% in children, p = 0.00097). NLRP3 knock-down augmented sensitivity to GCs in THP-1 cells, whereas NLRP3 inflammasome activation lowered GC receptor concentration, increasing GC resistance in U937 cells. Our results uncovered a new biological mechanism by which patients with INS may acquire GC resistance, that could be used in future as a novel noninvasive diagnostic tool. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? ☑ Approximately 80% of patients with idiopathic nephrotic syndrome (INS) respond to glucocorticoids, with the remaining 20% being steroid-resistant. WHAT QUESTION DID THIS STUDY ADDRESS? ☑ Whether NLRP3 gene promoter methylation was able to discriminate glucocorticoid-resistant from glucocorticoid (GC)-sensitive INS. WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? ☑ In both adults and children, NLRP3 promoter methylation was significantly reduced in leukocytes of patients with GC-resistant compared with GC-sensitive INS. NLRP3 inflammasome activation lowered GC receptor concentration and augmented GC resistance, whereas NLRP3 knockdown increased sensitivity to GCs in cell lines representative of monocytes (U937 and THP1). HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? ☑ Our findings uncovered a new biological mechanism whereby patients with INS may develop resistance to GCs that could be used in the future as a novel noninvasive diagnostic tool.

Prediction of steroid resistance and steroid dependence in nephrotic syndrome children

Background

Steroid resistant (SR) nephrotic syndrome (NS) affects up to 30% of children and is responsible for fast progression to end stage renal disease. Currently there is no early prognostic marker of SR and studied candidate variants and parameters differ highly between distinct ethnic cohorts.

Methods

Here, we analyzed 11polymorphic variants, 6 mutations, SOCS3 promoter methylation and biochemical parameters as prognostic markers in a group of 124 Polish NS children (53 steroid resistant, 71 steroid sensitive including 31 steroid dependent) and 55 controls. We used single marker and multiple logistic regression analysis, accompanied by prediction modeling using neural network approach.

Results

We achieved 92% (AUC = 0.778) SR prediction for binomial and 63% for multinomial calculations, with the strongest predictors ABCB1 rs1922240, rs1045642 and rs2235048, CD73 rs9444348 and rs4431401, serum creatinine and unmethylated SOCS3 promoter region. Next, we achieved 80% (AUC = 0.720) in binomial and 63% in multinomial prediction of SD, with the strongest predictors ABCB1 rs1045642 and rs2235048. Haplotype analysis revealed CD73_AG to be associated with SR while ABCB1_AGT was associated with SR, SD and membranoproliferative pattern of kidney injury regardless the steroid response.

Conclusions

We achieved prediction of steroid resistance and, as a novelty, steroid dependence, based on early markers in NS children. Such predictions, prior to drug administration, could facilitate decision on a proper treatment and avoid diverse effects of high steroid doses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02790-w.

Sulfatase 2 Is Associated with Steroid Resistance in Childhood Nephrotic Syndrome

Glucocorticoid (GC) resistance complicates the treatment of ~10-20% of children with nephrotic syndrome (NS), yet the molecular basis for resistance remains unclear. We used RNAseq analysis and in silico algorithm-based approaches on peripheral blood leukocytes from 12 children both at initial NS presentation and after ~7 weeks of GC therapy to identify a 12-gene panel able to differentiate steroid resistant NS (SRNS) from steroid-sensitive NS (SSNS). Among this panel, subsequent validation and analyses of one biologically relevant candidate, sulfatase 2 (SULF2), in up to a total of 66 children, revealed that both SULF2 leukocyte expression and plasma arylsulfatase activity Post/Pre therapy ratios were greater in SSNS vs. SRNS. However, neither plasma SULF2 endosulfatase activity (measured by VEGF binding activity) nor plasma VEGF levels, distinguished SSNS from SRNS, despite VEGF's reported role as a downstream mediator of SULF2's effects in glomeruli. Experimental studies of NS-related injury in both rat glomeruli and cultured podocytes also revealed decreased SULF2 expression, which were partially reversible by GC treatment of podocytes. These findings together suggest that SULF2 levels and activity are associated with GC resistance in NS, and that SULF2 may play a protective role in NS via the modulation of downstream mediators distinct from VEGF.

Plasma Cytokine Profiling to Predict Steroid Resistance in Pediatric Nephrotic Syndrome

Introduction

Glucocorticoids (GCs) are the primary treatment for nephrotic syndrome (NS), although ∼10% to 20% of children develop steroid-resistant NS (SRNS). Unfortunately, there are no validated biomarkers able to predict SRNS at initial disease presentation. We hypothesized that a plasma cytokine panel could predict SRNS at disease presentation, and identify potential pathways regulating SRNS pathogenesis.

Methods

Paired plasma samples were collected from 26 children with steroid-sensitive NS (SSNS) and 14 with SRNS at NS presentation and after ∼7 weeks of GC therapy, when SSNS versus SRNS was clinically determined. Plasma cytokine profiling was performed with a panel of 27 cytokines.

Results

We identified 13 cytokines significantly different in Pretreatment SSNS versus SRNS samples. Statistical modeling identified a cytokine panel (interleukin [IL]-7, IL-9, monocyte chemoattractant protein–1 [MCP-1]) able to discriminate between SSNS and SRNS at disease presentation (receiver operating characteristic [ROC] value = 0.846; sensitivity = 0.643; specificity = 0.846). Furthermore, GC treatment resulted in significant decreases in plasma interferon-γ (IFN-γ), tumor necrosis factor–α (TNF-α), IL-7, IL-13, and IL-5 in both SSNS and SRNS patients.

Conclusions

These studies suggest that initial GC treatment of NS reduces the plasma cytokines secreted by both CD4⁺ T_H1 cells and T_H2 cells, as well as CD8⁺ T cells. Importantly, a panel of 3 cytokines (IL-7, IL-9, and MCP-1) was able to predict SRNS prior to GC treatment at disease presentation. Although these findings will benefit from validation in a larger cohort, the ability to identify SRNS at disease presentation could greatly benefit patients by enabling both avoidance of unnecessary GC-induced toxicity and earlier transition to more effective alternative treatments.

Current understandings in treating children with steroid-resistant nephrotic syndrome

Steroid-resistant nephrotic syndrome (SRNS) remains a challenge for paediatric nephrologists. SRNS is viewed as a heterogeneous disease entity including immune-based and monogenic aetiologies. Because SRNS is rare, treatment strategies are individualized and vary among centres of expertise. Calcineurin inhibitors (CNI) have been effectively used to induce remission in patients with immune-based SRNS; however, there is still no consensus on treating children who become either CNI-dependent or CNI-resistant. Rituximab is a steroid-sparing agent for patients with steroid-sensitive nephrotic syndrome, but its efficacy in SRNS is controversial. Recently, several novel monoclonal antibodies are emerging as treatment option, but their efficacy remains to be seen. Non-immune therapies, such as angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, have been proven efficacious in children with SRNS and are recommended as adjuvant agents. This review summarizes and discusses our current understandings in treating children with idiopathic SRNS.

Time to Relapse and Its Predictors among Children with Nephrotic Syndrome in Comprehensive Specialized Hospitals, Tigray, Ethiopia, 2019

Background

Relapse in children with nephrotic syndrome leads to a variety of complications due to prolonged treatment and potential dependency on steroids. However, there is no study conducted to determine the incidence and predictive factors of relapse for nephrotic syndrome in Ethiopia, especially in children. Thus, this study aimed to assess the incidence of relapse and its predictors among children with nephrotic syndrome in Ethiopia.

Methods

A retrospective study was conducted by reviewing all charts of children with an initial diagnosis of the nephrotic syndrome in tertiary hospitals from 2011 to 2018. Charts of children with a diagnosis of steroid-resistant cases were excluded. The extraction tool was used for data collection, Epi-data manager V-4.4.2 for data entry, and Stata V-14 for cleaning and analysis. Kaplan-Meier curve, log-rank test, life table, and crude hazard ratios were used to describe the data and adjusted hazard ratios with 95% CI and P value for analysis. Median relapse time, incidence rate of relapse, and cumulative relapse probabilities at a certain time interval were computed. Bivariable and multivariate analyses were performed using the Cox proportional hazard regression to identify the factors associated with relapse. Any variable at P < 0.25 in the bivariable analysis was transferred to multivariate analysis. Then, the adjusted hazard ratio with 95% CI and P ≤ 0.05 was used to report the association and to test the statistical significance, respectively. Finally, texts, tables, and graphs were used to present the results. Results and Conclusion. Majority, 64.5% (40/66), of relapses were recorded in the first 12 months of follow-up. The incidence rate of relapse was 42.6 per 1000 child-month-observations with an overall 1454 child-month-observations and the median relapse time of 16 months. Having undernutrition [AHR = 3.44; 95% CI 1.78-6.65], elevated triglyceride [AHR = 3.37; 95% CI 1.04-10.90], decreased serum albumin level [AHR = 3.51; 95% CI 1.81-6.80], and rural residence [AHR = 4.00; 95% CI 1.49-10.76] increased the hazard of relapse. Conclusion and Recommendation. Relapse was higher in the first year of the follow-up period. Undernutrition, hypoalbuminemia, hypertriglyceridemia, and being from rural areas were independent predictors of relapse. A focused evaluation of those predictors during the initial diagnosis of the disease is compulsory.

Mild electrical stimulation with heat shock attenuates renal pathology in adriamycin-induced nephrotic syndrome mouse model

Nephrotic syndrome (NS) is a renal disorder that is characterized by massive proteinuria, hypoalbuminemia and edema. One of the main causes of NS is focal segmental glomerulosclerosis (FSGS), which has extremely poor prognosis. Although steroids and immunosuppressants are the first line of treatment, some FSGS cases are refractory, prompting the need to find new therapeutic strategies. We have previously demonstrated that an optimized combination treatment of mild electrical stimulation (MES) and heat shock (HS) has several biological benefits including the amelioration of the pathologies of the genetic renal disorder Alport syndrome. Here, we investigated the effect of MES + HS on adriamycin (ADR)-induced NS mouse model. MES + HS suppressed proteinuria and glomerulosclerosis induced by ADR. The expressions of pro-inflammatory cytokines and pro-fibrotic genes were also significantly downregulated by MES + HS. MES + HS decreased the expression level of cleaved caspase-3 and the number of TUNEL-positive cells, indicating that MES + HS exerted anti-apoptotic effect. Moreover, MES + HS activated the Akt signaling and induced the phosphorylation and inhibition of the apoptotic molecule BAD. In in vitro experiment, the Akt inhibitor abolished the MES + HS-induced Akt-BAD signaling and anti-apoptotic effect in ADR-treated cells. Collectively, our study suggested that MES + HS modulates ADR-induced pathologies and has renoprotective effect against ADR-induced NS via regulation of Akt-BAD axis.

Nuclear receptors in podocyte biology and glomerular disease

Nuclear receptors have a broad spectrum of biological functions in normal physiology and in the pathology of various diseases, including glomerular disease. The primary therapies for many glomerular diseases are glucocorticoids, which exert their immunosuppressive and direct podocyte protective effects via the glucocorticoid receptor (GR). As glucocorticoids are associated with important adverse effects and a substantial proportion of patients show resistance to these therapies, the beneficial effects of selective GR modulators are now being explored. Peroxisome proliferator-activated receptor-γ (PPARγ) agonism using thiazolidinediones has potent podocyte cytoprotective and nephroprotective effects. Repurposing of thiazolidinediones or identification of novel PPARγ modulators are potential strategies to treat non-diabetic glomerular disease. Retinoic acid receptor-α is the key mediator of the renal protective effects of retinoic acid, and repair of the endogenous retinoic acid pathway offers another potential therapeutic strategy for glomerular disease. Vitamin D receptor, oestrogen receptor and mineralocorticoid receptor modulators regulate podocyte injury in experimental models. Further studies are needed to better understand the mechanisms of these nuclear receptors, evaluate their synergistic pathways and identify their novel modulators. Here, we focus on the role of nuclear receptors in podocyte biology and non-diabetic glomerular disease.

Treatment of nephrotic syndrome: going beyond immunosuppressive therapy

It is indisputable that immunosuppressive therapy and pathological diagnosis of renal biopsy have greatly improved the prognosis of childhood nephrotic syndrome. Unfortunately, there is no "one-size-fits-all" approach for precise patient stratification and treatment when facing the huge challenges posed by steroid-resistant nephrotic syndrome (SRNS). But genomic medicine has brought a glimmer of light, and the cognition of SRNS has entered a new stage. Based on this, identification of single genetic variants of SRNS has recognized the key role of podocyte injury in its pathogenesis. Targeted treatment of podocyte injury is paramount, and immunosuppressant with podocyte-targeted therapy seems to be more suitable as the first choice for SRNS, that is, we need to pay attention to their additional non-immunosuppressive effects. In the same way, other effect factors of nephrotic syndrome and the related causes of immunosuppressive therapy resistance require us to select reasonable and targeted non-immunosuppressive therapies, instead of only blindly using steroids and immunosuppressants, which may be ineffective and bring significant side effects. This article provides a summary of the clinical value of identification of genetic variants in podocytes and non-immunosuppressive therapy for nephrotic syndrome in children.

Predicting and Defining Steroid Resistance in Pediatric Nephrotic Syndrome Using Plasma Proteomics

INTRODUCTION

Nephrotic syndrome (NS) is a characterized by massive proteinuria, edema, hypoalbuminemia, and dyslipidemia. Glucocorticoids (GCs), the primary therapy for >60 years, are ineffective in approximately 50% of adults and approximately 20% of children. Unfortunately, there are no validated biomarkers able to predict steroid-resistant NS (SRNS) or to define the pathways regulating SRNS.

METHODS

We performed proteomic analyses on paired pediatric NS patient plasma samples obtained both at disease presentation before glucocorticoid initiation and after approximately 7 weeks of GC therapy to identify candidate biomarkers able to either predict steroid resistance before treatment or define critical molecular pathways/targets regulating steroid resistance.

RESULTS

Proteomic analyses of 15 paired NS patient samples identified 215 prevalent proteins, including 13 candidate biomarkers that predicted SRNS before GC treatment, and 66 candidate biomarkers that mechanistically differentiated steroid-sensitive NS (SSNS) from SRNS. Ingenuity Pathway Analyses and protein networking pathways approaches further identified proteins and pathways associated with SRNS. Validation using 37 NS patient samples (24 SSNS/13 SRNS) confirmed vitamin D binding protein (VDB) and APOL1 as strong predictive candidate biomarkers for SRNS, and VDB, hemopexin (HPX), adiponectin (ADIPOQ), sex hormone-binding globulin (SHBG), and APOL1 as strong candidate biomarkers to mechanistically distinguish SRNS from SSNS. Logistic regression analysis identified a candidate biomarker panel (VDB, ADIPOQ, and matrix metalloproteinase 2 [MMP-2]) with significant ability to predict SRNS at disease presentation (P = 0.003; area under the receiver operating characteristic curve = 0.78).

CONCLUSION

Plasma proteomic analyses and immunoblotting of serial samples in childhood NS identified a candidate biomarker panel able to predict SRNS at disease presentation, as well as candidate molecular targets/pathways associated with clinical steroid resistance.

miR-939-5p decreases the enrichment of RNA polymerase II in the promoter region of CD2AP involved in nephrotic syndrome

The expression changes of CD2-associated protein (CD2AP) can lead to kidney diseases with proteinuria, including nephrotic syndrome (NS). A recent study reported that miRNAs may be important transcriptional regulators. In this study, we found increased expression of miR-939-5p and decreased expression of CD2AP in the peripheral blood of patients with NS. However, miR-939-5p did not show a regulatory effect on the 3'-untranslated region of CD2AP. The expression levels of specific protein 1 and adenovirus E2 promoter-binding factor 1, important transcription regulators in the promoter region of CD2AP, were also not affected by microRNA (miR)-939-5p. We confirmed that miR-939-5p is in the nucleus by fluorescent in situ hybridization and cytoplasmic separation polymerase chain reaction. The promoter plasmid and miR-939-5p were cotransfected into HEK-293 cells, and the luciferase reporter gene assay was used to analyze the promoter activity. We found that miR-939-5p binds to a specific sequence in the CD2AP promoter. miR-939-5p was confirmed to reduce the recruitment of RNA polymerase II to the CD2AP promoter region by chromatin immunoprecipitation. These findings improve our understanding of the mechanism of miR-939-5p in NS and provide potential molecular therapeutic targets for NS.

Prospects of genetic testing for steroid-resistant nephrotic syndrome in Nigerian children: a narrative review of challenges and opportunities

The prevalence of childhood steroid-resistant nephrotic syndrome (SRNS) ranges from 35% to 92%. This steroid resistance among Nigerian children also reflects underlying renal histopathology, revealing a rare minimal-change disease and a varying burden of membranoproliferative glomerulonephritis and focal segmental glomerulosclerosis (FSGS). FSGS tends to progress to end-stage kidney disease, which requires dialysis and/or renal transplantation. While knowledge of the molecular basis of NS is evolving, recent data support the role of mutant genes that otherwise maintain the structural and functional composition of the glomerular filtration barrier to account for many monogenic forms of FSGS. With the advent of next-generation sequencing, >39 genes are currently associated with SRNS, and the number is likely to increase in the near future. Monogenic FSGS is primarily resistant to steroids, and this foreknowledge obviates the need for steroids, other immunosuppressive therapy, and renal biopsy. Therefore, a multidisciplinary collaboration among cell biologists, molecular physiologists, geneticists, and clinicians holds prospects of fine-tuning the management of SRNS caused by known mutant genes. This article describes the genetics of NS/SRNS in childhood and also gives a narrative review of the challenges and opportunities for molecular testing among children with SRNS in Nigeria. For these children to benefit from genetic diagnosis, Nigeria must aspire to have and develop the manpower and infrastructure required for medical genetics and genomic medicine, leveraging on her existing experiences in genomic medicine. Concerted efforts can be put in place to increase the number of enrollees in Nigeria’s National Health Insurance Scheme (NHIS). The scope of the NHIS can be expanded to cater for the expensive bill of genetic testing within or outside the structure of the National Renal Care Policy proposed by Nigerian nephrologists.

Management of steroid-resistant nephrotic syndrome in children and adolescents

More than 85% of children and adolescents (majority between 1-12 years old) with idiopathic nephrotic syndrome show complete remission of proteinuria following daily treatment with corticosteroids. Patients who do not show remission after 4 weeks' treatment with daily prednisolone are considered to have steroid-resistant nephrotic syndrome (SRNS). Renal histology in most patients shows presence of focal segmental glomerulosclerosis, minimal change disease, and (rarely) mesangioproliferative glomerulonephritis. A third of patients with SRNS show mutations in one of the key podocyte genes. The remaining cases of SRNS are probably caused by an undefined circulating factor. Treatment with calcineurin inhibitors (ciclosporin and tacrolimus) is the standard of care for patients with non-genetic SRNS, and approximately 70% of patients achieve a complete or partial remission and show satisfactory long-term outcome. Additional treatment with drugs that inhibit the renin-angiotensin axis is recommended for hypertension and for reducing remaining proteinuria. Patients with SRNS who do not respond to treatment with calcineurin inhibitors or other immunosuppressive drugs can show declining kidney function and are at risk for end-stage renal failure. Approximately a third of those who undergo renal transplantation show recurrent focal segmental glomerulosclerosis in the allograft and often respond to combined treatment with plasma exchange, rituximab, and intensified immunosuppression.

Sphingosine phosphate lyase insufficiency syndrome (SPLIS): A novel inborn error of sphingolipid metabolism

Sphingosine-1-phosphate lyase (SPL) is an intracellular enzyme that controls the final step in the sphingolipid degradative pathway, the only biochemical pathway for removal of sphingolipids. Specifically, SPL catalyzes the cleavage of sphingosine 1-phosphate (S1P) at the C2-3 carbon bond, resulting in its irreversible degradation to phosphoethanolamine (PE) and hexadecenal. The substrate of the reaction, S1P, is a bioactive sphingolipid metabolite that signals through a family of five G protein-coupled S1P receptors (S1PRs) to mediate biological activities including cell migration, cell survival/death/proliferation and cell extrusion, thereby contributing to development, physiological functions and - when improperly regulated - the pathophysiology of disease. In 2017, several groups including ours reported a novel childhood syndrome that featured a wide range of presentations including fetal hydrops, steroid-resistant nephrotic syndrome (SRNS), primary adrenal insufficiency (PAI), rapid or insidious neurological deterioration, immunodeficiency, acanthosis and endocrine abnormalities. In all cases, the disease was attributed to recessive mutations in the human SPL gene, SGPL1. We now refer to this condition as SPL Insufficiency Syndrome, or SPLIS. Some features of this new sphingolipidosis were predicted by the reported phenotypes of Sgpl1 homozygous null mice that serve as vertebrate SPLIS disease models. However, other SPLIS features reveal previously unrecognized roles for SPL in human physiology. In this review, we briefly summarize the biochemistry, functions and regulation of SPL, the main clinical and biochemical features of SPLIS and what is known about the pathophysiology of this condition from murine and cell models. Lastly, we consider potential therapeutic strategies for the treatment of SPLIS patients.