The Effect of a Gluten-Free Diet in Children With Difficult-to-Manage Nephrotic Syndrome

β1-Integrin blockade prevents podocyte injury in experimental models of minimal change disease

INTRODUCTION

Activation of the focal adhesion kinase (FAK) in podocytes is involved in the pathogenesis of minimal change disease (MCD), but the pathway leading to its activation in this disease is unknown. Here, we tested whether podocyte β1 integrin is the upstream modulator of FAK activation and podocyte injury in experimental models of MCD-like injury.

METHODS

We used lipopolysaccharide (LPS) and MCD sera to induce MCD-like changes in vivo and in cultured human podocytes, respectively. We performed functional studies using specific β1 integrin inhibitors in vivo and in vitro, and integrated histological analysis, western blotting, and immunofluorescence to assess for morphological and molecular changes in podocytes. By ELISA, we measured serum LPS levels in 35 children with MCD or presumed MCD (idiopathic nephrotic syndrome [INS]) and in 18 healthy controls.

RESULTS

LPS-injected mice showed morphological (foot process effacement, and normal appearing glomeruli on light microscopy) and molecular features (synaptopodin loss, nephrin mislocalization, FAK phosphorylation) characteristic of human MCD. Administration of a β1 integrin inhibitor to mice abrogated FAK phosphorylation, and ameliorated proteinuria and podocyte injury following LPS. Children with MCD/INS in relapse had higher serum LPS levels than controls. In cultured human podocytes, β1 integrin blockade prevented cytoskeletal rearrangements following exposure to MCD sera in relapse.

CONCLUSIONS

Podocyte β1 integrin activation is an upstream mediator of FAK phosphorylation and podocyte injury in models of MCD-like injury.

A Low-Protein, Plant-Dominant Gluten-Free Diet for Immunoglobulin A Nephropathy and Focal Segmental Glomerulosclerosis

Immunoglobulin A nephropathy is the most common glomerulonephritis syndrome in the world, yet there is currently no cure. While blood pressure control, renin-angiotensin-aldosterone system inhibition, and immunosuppression may slow disease progression, low-protein diets, defined as a daily dietary protein intake of 0.6 to 0.8 g/kg body weight, may also decrease immune complex deposition and disease severity, as evidenced in animal models. The link between secondary immunoglobulin A nephropathy and celiac disease has also led to the rise of gluten-free diets and zinc supplementation as potential lifestyle modifications to help manage common immunoglobulin A nephropathy symptoms such as proteinuria and hematuria. In addition, case reports and prospective studies suggest that patients with focal segmental glomerulosclerosis, which manifests as steroid-resistant nephrotic syndrome may also benefit from a gluten-free diet. We highlight the example of a gluten-free, plant-dominant low-protein diet (a different type of low-protein diet that addresses both protein quantity and quality) for patients with immunoglobulin A nephropathy or focal segmental glomerulosclerosis.

Gut Microbiota Alterations and Primary Glomerulonephritis in Children: A Review

The article summarizes the current evidence on the impact of microbiota alterations on immune-mediated primary glomerulonephritis in children. In particular, the focus is on the link between dysbiosis and the onset or recurrence of idiopathic nephrotic syndrome, immunoglobulin A nephropathy, and membranous nephropathy. The aim is to describe possible pathomechanisms, differences in gut microbiota composition between pediatric patients and healthy controls, and possible usage of microbiota manipulations in supportive therapy. On this basis, we attempt to indicate directions for further research in that field.

Microbiota and glomerulonephritis: An immunological point of view

Glomerular injury is the major cause of chronic kidney diseases (CKD) worldwide and is characterized by proteinuria. Glomerulonephritis (GN) has a wide spectrum of etiologies, the intensity of glomerular damage, histopathology, and clinical outcomes that can be associated with the landscape of the nephritogenic immune response. Beyond impaired immune responses and genetic factors, recent evidence indicates that microbiota can be contributed to the pathogenesis of GN and patients' outcomes by impacting many aspects of the innate and adaptive immune systems. It is still unknown whether dysbiosis induces GN or it is a secondary effect of the disease. Several factors such as drugs and nutritional problems can lead to dysbiosis in GN patients. It has been postulated that gut dysbiosis activates immune responses, promotes a state of systemic inflammation, and produces uremic toxins contributing to kidney tissue inflammation, apoptosis, and subsequent proteinuric nephropathy. In this review, the impact of gastrointestinal tract (GI) microbiota on the pathogenesis of the primary GN will be highlighted. The application of therapeutic interventions based on the manipulation of gut microbiota with special diets and probiotic supplementation can be effective in GN.

Clinical Efficacy of Persian Medicine Diet Combined with Western Medicine-Based Diet on Proteinuria in Pediatric Nephrotic Syndrome: A Randomized Controlled Clinical Trial

Introduction

Nephrotic syndrome (NS) is a common chronic kidney disorder during childhood. The most important characteristic of this disease is proteinuria. The Persian medicine (PM) has important dietary recommendations for strengthening the kidney function and treatment of this disease. The aim of this study was to investigate the effect of a diet including PM recommendations and general principles of Western medicine.

Materials and Methods

Twenty children with nephrotic syndrome were randomly divided into intervention and control groups and monitored for one month. The control group received a diet based on the general principles of Western medicine. In the intervention group, in addition to the Western medicine diet, dietary recommendations of PM were also prescribed including the pomegranate (Cydonia oblonga mill.), quince (Cydonia oblonga mill.), and whole grains (wheat and barley). A 24-hour dietary questionnaire was applied and anthropometric and biochemical indices including spot urine protein (proteinuria), albumin (Alb), urea, creatinine (Cr), total cholesterol (TC), and triglyceride (TG) were measured before and after the study.

Results

The amount of protein intake reduced significantly in the diet of both groups but the differences between the two groups were not significant. Proteinuria reduced significantly in both the Western and PM groups; however, proteinuria was significantly lower in the Persian medicine group compared to the control group. TC and Cr levels reduced significantly in the intervention group, although the changes were not significant compared to the control group.

Conclusion

The results of this study showed that adding dietary recommendations of the Persian medicine to the general rules of the Western medicine diet reduced proteinuria and improved the combat against nephrotic syndrome.

Immunological Impact of a Gluten-Free Dairy-Free Diet in Children With Kidney Disease: A Feasibility Study

Kidney disease affects 10% of the world population and is associated with increased mortality. Steroid-resistant nephrotic syndrome (SRNS) is a leading cause of end-stage kidney disease in children, often failing standard immunosuppression. Here, we report the results of a prospective study to investigate the immunological impact and safety of a gluten-free and dairy-free (GF/DF) diet in children with SRNS. The study was organized as a four-week summer camp implementing a strict GF/DF diet with prospective collection of blood, urine and stool in addition to whole exome sequencing WES of DNA of participants. Using flow cytometry, proteomic assays and microbiome metagenomics, we show that GF/DF diet had a major anti-inflammatory effect in all participants both at the protein and cellular level with 4-fold increase in T regulatory/T helper 17 cells ratio and the promotion of a favorable regulatory gut microbiota. Overall, GF/DF can have a significant anti-inflammatory effect in children with SRNS and further trials are warranted to investigate this potential dietary intervention in children with SRNS.

Effect of a gluten-free diet on albuminuria in children with newly diagnosed celiac disease

Background and objectives

Altered gastrointestinal permeability in celiac disease (CD) is mediated by zonulin. The receptor for zonulin is expressed on podocytes. Therefore, we tested the effect of a gluten-free diet (GFD) on albuminuria in pediatric patients with newly diagnosed CD.

Methods

We performed a cohort study comparing urinary albumin (μg):creatinine (mg) ratio (ACR) in CD patients vs controls and in response to a GFD.

Results

Children with CD (n=46) had higher ACR compared to controls (n=21), 20.2±5.6 versus 8.4±1.1 μg/mg, P=0.16 and exceeded 30 μg/mg (microalbuminuria cut-off) in 7/46 cases. 17 patients had a follow-up assessment (interval 6.1±0.7 months) on a GFD. Baseline ACR was 20.7±5.2 that fell to 10.4±1.5 μg/mg, P=0.035.

Conclusion

Children and adolescents with newly diagnosed CD have low-grade albuminuria that is numerically higher than controls and that declined after implementation of a GFD. CD may be associated with reversible defects in the glomerular barrier.

Pediatric Nephrotic Syndrome: Pharmacologic and Nutrition Management

Nephrotic syndrome is a common kidney disease during childhood that is characterized by alterations in glomerular filtration and leads to protein, fluid, and nutrient loss in the urine. Most patients experience peripheral, gravity-dependent edema; however, serious cases exhibit anasarca and ascites. Many long-term complications of the disease exist due to the underlying pathology and the therapies used for treatment, including metabolic bone disease, micronutrient deficiencies, and hyperlipidemia. Pharmacologic and nutrition interventions are key to appropriate management. Fluid and sodium restriction in combination with corticosteroids, albumin, and diuretics are used to manage edema. Steroid-sparing therapies like alkylating agents and calcineurin inhibitors and dietary modification to eliminate dairy and gluten may be warranted in patients with frequent relapses or steroid-refractory disease. Nutrition clinicians should familiarize themselves with the nuances of treating this disease to optimize care for children with nephrotic syndrome.

Advances in the role and mechanism of zonulin pathway in kidney diseases

The intestinal barrier is the first line of defense against foreign antigens. Tight junctions play an important role in maintaining the function of the intestinal wall. Zonulin is the only physiological protein discovered in recent years that can reversibly regulate tight junctions in human body. It changes the permeability of intestinal epithelial cells by regulating the state of tight junctions. Increased intestinal permeability can lead to abnormal activation of intestinal mucosal immune and bacterial translocation, then inducing systemic inflammation. It has already been reported that zonulin plays an important pathogenic role in a variety of diseases by regulating tight junctions leading to an abnormal increase of intestinal permeability. However, the research on the pathogenic role and mechanism of zonulin pathway in kidney disease is still in its infancy. Therefore, we reviewed the progress on pathophysiological characteristics of zonulin as well as the pathogenesis of zonulin in kidney disease in this paper.

Plasma Zonulin Levels in Childhood Nephrotic Syndrome

Objective: We conducted this study to test the hypothesis that plasma zonulin levels are elevated in pediatric patients with nephrotic syndrome compared to healthy controls. Study Design: Plasma zonulin levels were measured by ELISA in 114 children enrolled in the NEPTUNE study. Clinical and laboratory data were retrieved from the NEPTUNE database. Results: The median age of the patients was 10 (IQR = 5 to 14) years, 59 were male, 64 had minimal change disease, 47 focal segmental glomerulosclerosis, median eGFR was 96 (IQR = 80 to 114) ml/min/1.73 m², and median urine protein:creatinine ratio was 0.5 (IQR = 0.1 to 3.4) (g:g). The plasma zonulin level was 14.2 ± 5.0 vs. 10.2 ± 2.5 ng/ml in healthy adults in a report using the same assay kit, P = 0.0025. These findings were confirmed in an independent cohort of children with nephrotic syndrome compared to healthy age-matched controls, P = 0.01. Zonulin concentrations did not differ in children with minimal change disease vs. focal segmental glomerulosclerosis, frequently relapsing vs. steroid-dependent vs. steroid-resistant clinical course, and were not influenced by the immunosuppressive treatment regimen. There was no relationship between plasma zonulin levels and the absolute or percentage change in proteinuria from enrollment until the time of the zonulin assay. Conclusion: Plasma zonulin levels are elevated in childhood nephrotic syndrome regardless of level of proteinuria or specific treatment. The cause of the high plasma zonulin levels and whether zonulin contributes to glomerular injury requires further study.

Difficult-to-treat idiopathic nephrotic syndrome: established drugs, open questions and future options

The idiopathic nephrotic syndrome in childhood can be classified according to the International Study of Kidney Disease in Children (ISKDC) based on the response to steroids. Typically, steroid-sensitive nephrotic syndrome (SSNS) is characterised by minimal changes in disease (MCD) histology, whereas in steroid-resistant nephrotic syndrome (SRNS) focal segmental glomerulosclerosis (FSGS) is the most prevalent lesion. Patients with SSNS may develop frequent relapses and/or steroid dependency, which can be difficult to treat. New studies confirm the value of calcineurin inhibitors (CNIs) and mycophenolic acid in preventing relapses of SSNS. Rituximab also plays an important role, but many questions regarding initial dosing, repetitions of courses, and long-term side effects remain unclear. SRNS, especially when unresponsive to treatment, can lead to chronic kidney disease. In particular, treatment with CNIs has improved the prognosis and recent data indicate that treatment can even be discontinued in many patients with full remission. In CNI-unresponsive SRNS, rituximab is less effective than in SSNS and the role of other biologicals (such as ofatumumab, abatacept, and others) remains unclear. A significant proportion of children with FSGS have genetic causes and most patients do not respond to immunosuppression, although individual patients with partial and even complete response have been documented. Future studies should evaluate treatments leading to long-term remission without maintenance immunosuppression in SSNS; in both genetic and immune-mediated SRNS, novel options to decrease the number of treatment-unresponsive patients seem mandatory, as they are at a high risk of developing end-stage renal disease.

Effect of Combined Gluten-Free, Dairy-Free Diet in Children With Steroid-Resistant Nephrotic Syndrome: An Open Pilot Trial

Introduction

Steroid-resistant nephrotic syndrome (SRNS) affects both children and adults and has a high rate of progression to end-stage renal disease. Although a subset of patients have well-characterized genetic mutation(s), in the majority of cases, the etiology is unknown. Over the past 50 years, a number of case reports have suggested the potential impact of dietary changes in controlling primary nephrotic syndrome, especially gluten and dairy restrictions.

Methods

We have designed a prospective, open-label, nonrandomized, pilot clinical trial, to study the effect of a gluten-free and dairy-free (GF/DF) diet in children with SRNS. The study will be organized as a 4-week summer camp to implement a GF/DF diet in a tightly controlled and monitored setting. Blood, urine, and stool samples will be collected at different time points during the study.

Results

The primary end point is a reduction of more than 50% in the urine protein:creatinine ratio. The secondary end points include changes in urine protein, kidney function, and serum albumin, as well as effects in immune activation, kidney injury biomarkers, and gut microbiome composition and function (metagenomic/metatranscriptomic).

Conclusion

This study will advance the field by testing the effect of dietary changes in patients with SRNS in a highly controlled camp environment. In addition, we hope the results will help to identify a responder profile that may guide the design of a larger trial for further investigation.

HLA-DQA1 and APOL1 as Risk Loci for Childhood-Onset Steroid-Sensitive and Steroid-Resistant Nephrotic Syndrome

BACKGROUND

Few data exist for the genetic variants underlying the risk for steroid-sensitive nephrotic syndrome (SSNS) in children. The objectives of this study were to evaluate HLA-DQA1 and APOL1 variants as risk factors for SSNS in African American children and use classic HLA antigen types and amino acid inference to refine the HLA-DQA1 association.

STUDY DESIGN

Case-control study.

SETTING & PARTICIPANTS

African American children with SSNS or steroid-resistant nephrotic syndrome (SRNS) were enrolled from Duke University and centers participating in the Midwest Pediatric Nephrology Consortium.

FACTOR

Genetic variants in HLA-DQA1 (C34Y [rs1129740]; F41S [rs1071630]) and APOL1 high-risk alleles.

OUTCOMES

SSNS and SRNS.

MEASUREMENTS

Direct sequencing for the HLA-DQA1 and APOL1 variants in 115 African American children (65 with SSNS and 50 with SRNS). Imputation of classic HLA alleles and amino acids was done in 363 South Asian children.

RESULTS

The 2 HLA-DQA1 variants were significantly associated with SSNS in African American children (C34Y: P=5.7 × 10^-11; OR, 3.53; 95% CI, 2.33-5.42; F41S: P=1.2 × 10^-13; OR, 4.08; 95% CI, 2.70-6.28), but not with SRNS (C34Y: P=0.6; F41S: P=0.2). APOL1 high-risk variants were not associated with SSNS (P=0.5) but showed significant associations with SRNS (P=1.04 × 10^-7; OR, 4.17; 95% CI, 2.23-7.64). HLA-DQA1*0201, HLA-DQB1*0201, and HLA-DRB1*0701 were the classic HLA alleles with the most significant associations with SSNS risk. The most significantly associated amino acid positions were HLA-DQα1 56 and 76 (both P=2.8 × 10^-7). Conditional analysis revealed that these variants most likely account for the observed association.

LIMITATIONS

Modest sample size and limited statistical power to detect small to moderate effect sizes. Children studied may not be representative of all African American children in the United States.

CONCLUSIONS

HLA-DQA1 is a risk locus for SSNS, but not SRNS, in African American children, consistent with its role in SSNS risk in children of European, Asian, and African ancestries. There is little evidence of a significant role for the APOL1 high-risk alleles in childhood SSNS in African American children. Refinement of the HLA-DQA1 association identified the critical classic HLA antigen types and amino acids of the HLA-DQ α1 molecule.