Gut Microbiota Dysbiosis in Children with Relapsing Idiopathic Nephrotic Syndrome.

BACKGROUND: While the etiology of idiopathic nephrotic syndrome (idiopathic nephrotic syndrome [INS]; characterized by repeated relapses and comorbid allergic conditions) remains unknown, recent evidence suggests that dysfunction in regulatory T cells (Tregs) plays an important role in the development of INS as well as allergic diseases. We hypothesized that dysbiosis involving decreased butyric acid-producing gut microbiota leads to defective induction and differentiation of peripherally induced Tregs, resulting in INS relapse. METHODS: Study subjects were 12 children with INS, 8 classified as relapsing (R group; median age: 3.0 years) and 4 as non-relapsing (NR group; median age: 4.3 years), and 11 healthy children (HC group; median age: 5.1 years) serving as normal controls. Measurement of microbiota was performed using 16S ribosomal RNA metagenomic analysis, and fecal butyric acid was measured using high performance liquid chromatography. Flow-cytometric analysis of Tregs and CD4-positive (CD4+) cells in peripheral blood was also performed. RESULTS: Metagenomic analysis of gut microbiota using feces showed that the proportion of butyric acid-producing bacteria was significantly lower in R (median 6.36%) than HC (median 18.84%; p = 0.0013), but no different between NR (median 16.71%) and HC (p = 0.29). Fecal organic acid analysis revealed significantly lower butyric acid quantities in R than HC (medians: 0.48 vs. 0.99 mg/g, p = 0.042). Circulating Tregs as a proportion of CD4+ cells were decreased in 75% of R and NR. CONCLUSION: Pediatric relapsing INS patients show gut microbiota dysbiosis, characterized by a decreased proportion of butyric acid-producing bacteria and lower fecal butyric acid quantities, concomitant with reduced circulatory Tregs.

Antiproteinuric effect of an endothelin-1 receptor antagonist in puromycin aminonucleoside-induced nephrosis in rat.

BackgroundThe pathogenesis of idiopathic nephrotic syndrome (INS) remains unclear, although recent studies suggest endothelin 1 (ET-1) and CD80 of podocytes are involved. We investigated the potential of antagonist to ET-1 receptor type A (ETRA) as therapeutic agent through the suppression of CD80 in a rat model of INS.MethodsPuromycin aminonucleoside (PAN) was injected to Wister rats to induce proteinuria: some were treated with ETRA antagonist and others were treated with 0.5% methylcellulose. Blood and tissue samples were collected. Quantitative PCR was used to determine the expression of Toll-like receptor-3 (TLR-3), nuclear factor-κB (NF-κB), CD80, talin, ETRA, and ET-1 in the kidney. To confirm the level of CD80 protein expression, immunofluorescence staining and western blot analysis of the renal tissue were performed.ResultsAmount of proteinuria in the treatment group was significantly lower than the other groups. The same-day body weight, serum creatinine values, and blood pressure were not significantly different. ETRA antagonist restores podocyte foot process effacement as well as the aberrant expression of TLR-3, nuclear factor-κB (NF-κB), and CD80 in PAN-injured kidneys.ConclusionsThe ETRA antagonist may be promising drug for INS as it showed an antiproteinuric effect. Its action was considered to be through suppression of CD80 expression on podocytes.

Urinary C-megalin for screening of renal scarring in children after febrile urinary tract infection.

BackgroundFebrile urinary tract infection (fUTI) in children may cause renal scarring. This study aimed to investigate the usefulness of urinary biomarkers for diagnosing renal scarring after fUTI.MethodsThirty-seven children (median age: 1.36 years, range: 0.52-12.17 years, 25 boys) with a history of fUTI, who underwent renal scintigraphy for 4 months or longer after the last episode of fUTI, were analyzed. A spot urine sample was obtained on the day of renal scintigraphy to measure levels of total protein, N-acetyl-ß-D-glucosaminidase (NAG), ß2-microglobulin (BMG), neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid binding protein (L-FABP), and C-megalin (full-length megalin). Results were corrected for urinary creatinine (Cr) and compared between the group with renal scarring (n=23) and that without scarring (n=14). Urinary levels of C-megalin were also measured in healthy control subjects.ResultsNo significant differences in total protein, NGAL, L-FABP, NAG, and BMG levels were found between the groups. However, C-megalin levels were significantly higher in the renal scarring group than in the non-renal scarring group and healthy controls (P<0.001). A cutoff value of 6.5 pmol/nmol of urinary C-megalin/Cr yielded 73.9% of specificity and 92.9% of sensitivity.ConclusionUrinary C-megalin is useful for diagnosing renal scarring caused by fUTI.

Regulatory T cells and CTLA-4 in idiopathic nephrotic syndrome.

The pathogenesis of idiopathic nephrotic syndrome (INS) remains unknown. Recently, it was postulated that suppression of regulatory T cells (Treg) leads to massive proteinuria in INS, although there is some controversy. Considering the important role of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) in Treg-mediated immune suppression, the aim of this study was therefore to clarify the involvement of Treg and CTLA-4 in the pathogenesis of INS. Fifteen patients with INS were enrolled. Their blood was sampled twice, once at onset and once at remission induced by glucocorticoid. Although median Treg number was significantly lower at onset than in healthy children, it increased at remission. Similarly, serum CTLA-4 concentration significantly increased at remission compared with onset. Furthermore, a positive significant correlation was observed between Treg number and serum CTLA-4 level. This suggests that Treg and CTLA-4 are involved in the induction of remission in INS.

Urinary Biomarkers for Screening for Renal Scarring in Children with Febrile Urinary Tract Infection: Pilot Study.

PURPOSE: Recurrent febrile urinary tract infections during infancy cause renal scarring, which is characterized by progressive focal interstitial fibrosis and may lead to renal failure. Renal scarring can be diagnosed through scintigraphy, although it seems impractical to perform renal scintigraphy for all infants with febrile urinary tract infections. Therefore, it is important to search for a biomarker to identify the presence of renal scarring. We hypothesized that urinary biomarkers of nephropathy may increase in infants with renal scarring following febrile urinary tract infections. MATERIALS AND METHODS: A total of 49 infants who underwent renal scintigraphy for febrile urinary tract infections were enrolled in the study. Several measurements were performed using urine samples, including total proteins, beta2-microglobulins, N-acetyl-ß-D-glucosaminidase, neutrophil gelatinase associated lipocalin, liver-type fatty acid binding protein and angiotensinogen. Values were corrected by creatinine and compared between patients with and without renal scarring. RESULTS: Among urinary biomarkers only angiotensinogen in patients with scarring (median 14.6 µg/gm creatinine) demonstrated significantly higher levels than in patients without scarring (3.6 µg/gm creatinine, p <0.001). CONCLUSIONS: Urinary angiotensinogen may be useful for diagnosing the presence of renal scarring.

Pathogenesis of childhood idiopathic nephrotic syndrome: a paradigm shift from T-cells to podocytes.

BACKGROUND: Nephrotic syndrome is the most common cause of kidney disease in children, but its pathogenesis remains unclear. This article reviews the novel aspects of the mechanisms underlying massive proteinuria in minimal-change disease, which is the most common form of childhood nephrotic syndrome. DATA SOURCES: This article integrates the findings of a PubMed database search for English language articles published in the past 40 years (from September 1974 to February 2014) using the key words "pathogenesis", "minimal change nephrotic syndrome" or "idiopathic nephrotic syndrome". RESULTS: Unknown humoral factors associated with T-cell dysfunction have been thought to play an important role in the pathogenesis of minimal-change disease. However, recent findings are changing this paradigm, i.e., visceral glomerular epithelial cells (podocytes) may be involved via expression of molecules such as CD80 and angiopoietin-like 4. CONCLUSIONS: Recent evidence suggests that minimal-change disease results from interactions between humoral factors and dysfunctional podocytes. In addition to immunosuppressant drugs that target lymphocytes, a biological agent such as an antibody against the abnormal molecule(s) expressed by podocytes may provide novel drug treatment for minimal-change disease.

Novel use of rituximab for steroid-dependent nephrotic syndrome in children.

BACKGROUND: Though rituximab (RTX) is effective for childhood steroid-dependent nephrotic syndrome (SDNS), an established regimen does not exist. The relapses tend to occur when the peripheral blood B-cell count re-arises at 3 months upon single RTX infusion. This study was conducted to clarify whether the long-term remission of SDNS can be obtained by repeated RTX administrations. METHODS: RTX was administered 4 times at 3-month intervals at 375 mg/m(2)/time to 5 children with SDNS. The changes in the clinical indicators were analyzed. RESULTS: The median (range) observation period was 6.3 (0.9-8.4) years before RTX and 3.2 (1.9-3.8) years following the commencement of RTX. The changes in the clinical indicators were as follows (median and range): (1) annual number of relapses: before administration 1.4 (1.1-3.5) times/year, after administration 0.0 (0.0-0.0) times/year, and (2) median steroid dosage: before administration 0.80 (0.23-0.96) mg/kg/day, after administration 0.00 (0.00-0.00) mg/kg/day. All changes were significant at p < 0.05. Relapse occurred 3 times following the start of RTX (the period to relapse was 2.2, 1.9, and 2.3 years, respectively). No serious side effects were seen. CONCLUSIONS: Repeated RTX against SDNS in children may be a useful therapeutic option.

Voiding cystourethrography is mandatory in infants with febrile urinary tract infection.

Vesicoureteral reflux (VUR) is common condition in infants with febrile urinary tract infections (UTIs). Both VUR and febrile UTIs are risk factors for renal scars, characterized by glomerular hypertrophy with global or segmental sclerosis as cardinal features in pathology. Because renal scars may cause hypertension or chronic kidney diseases in later life, voiding cystourethrography (VCUG) has been mandatory for infants following their first febrile UTIs to identify VUR. However, increasing evidence suggests that the presence of VUR may not represent a direct risk factor for renal scars, which has led to an increase in the use of a stratified approach, in which VCUG is not performed for all patients. This study was conducted to verify whether the stratified approach is justified to identify infants at risk for renal scarring. The medical records of 306 infants with first febrile UTIs (median age, 4 months; 0-72 months) were reviewed. VUR was detected in 40.4% (67/166) of patients by the non-stratified approach, in which VCUG was performed in all patients. In contrast, VUR was identified in only 27.1% (38/140) of patients by the stratified approach, in which VCUG was performed only in the patients with high risk of developing renal scars. This difference in the discovery rate was significant (p = 0.02). Renal bladder ultrasonography had the sensitivities of as low as 45.7% and 52.9% in detecting VUR and in predicting renal scarring assessed by renal scintigraphy, respectively. In conclusion, VCUG should be performed in all infants after their first febrile UTIs.

Close association between proteinuria and regulatory T cells in patients with idiopathic nephrotic syndrome.

BACKGROUND: Idiopathic nephrotic syndrome (INS) has been considered to be a T cell disorder. Supporting this hypothesis is the reported occurrence of remission following measles infection, which suppresses T cell function. In contrast, there has been no case report suggesting an association between influenza B virus infection and the remission of INS. CASE-DIAGNOSIS/TREATMENT: We report the case of a 5-year-old boy with INS who achieved remission without steroid treatment in response to influenza B virus infection. Although he relapsed soon after remission, he was successfully treated with prednisolone. Both the induction of remission and the response to prednisolone were associated with an increase in the number of circulating regulatory T cells (Tregs), assessed as CD4(+)CD25(+)Foxp3(+) cells. These results suggest that both influenza B virus infection and steroid administration increased the number of circulating Tregs, thus leading to the remission of INS. CONCLUSIONS: In summary, our case indicates an important role for Tregs in the development of the proteinuria associated with INS and sheds light on its pathogenesis. Further studies are warranted.

Genetic analysis of PRRT2 for benign infantile epilepsy, infantile convulsions with choreoathetosis syndrome, and benign convulsions with mild gastroenteritis.

PURPOSE: PRRT2 mutations were recently identified in benign familial infantile epilepsy (BFIE) and infantile convulsions with paroxysmal choreoathetosis (ICCA) but no abnormalities have so far been identified in their phenotypically similar seizure disorder of benign convulsions with mild gastroenteritis (CwG), while mutations in KCNQ2 and KCNQ3 have been recognized in benign familial neonatal epilepsy (BFNE). The aim of this study was to identify PRRT2 mutations in infantile convulsions in Asian families with BFIE and ICCA, CwG and BFNE. METHODS: We recruited 26 unrelated Japanese affected with either BFIE or non-familial benign infantile seizures and their families, including three families with ICCA. A total of 17 Japanese and Taiwanese with CwG, 50 Japanese with BFNE and 96 healthy volunteers were also recruited. Mutations of PRRT2 were sought using direct sequencing. RESULTS: Heterozygous truncation mutation (c.649dupC) was identified in 15 of 26 individuals with benign infantile epilepsy (52.1%). All three families of ICCA harbored the same mutation (100%). Another novel mutation (c.1012+2dupT) was found in the proband of a family with BFIE. However, no PRRT2 mutation was found in either CwG or BFNE. CONCLUSIONS: The results confirm that c.649dupC, a truncating mutation of PRRT2, is a hotspot mutation resulting in BFIE or ICCA regardless of the ethnic background. In contrast, PRRT2 mutations do not seem to be associated with CwG or BFNE. Screening for PRRT2 mutation might be useful in early-stage differentiation of BFIE from CwG.

Intravenous immunoglobulin counteracts oxidative stress in Kawasaki disease.

Oxidative stress (OS) appears to play a pivotal role in many medical conditions. This study aimed to investigate whether OS is associated with Kawasaki disease (KD) or not, and if so, then to determine whether the mechanism of intravenous immunoglobulin therapy (IVIG) is associated with scavenging reactive oxygen species. Results show a significant difference between patients with KD and those with febrile illnesses (p = 0.018) in terms of OS, as assessed by the d-ROMs/BAP ratio, an arbitrary index comprising derivatives of reactive oxygen metabolites (d-ROMs) relative to a biologic antioxidant potential (BAP). Furthermore, children with KD had a significantly decreased d-ROMs/BAP ratio after IVIG (p = 0.011). Interestingly, the d-ROMs/BAP ratio decreased in 12 of 14 patients with KD who defervesced after IVIG, whereas all but one patient who did not defervesce showed an increase in this ratio. In conclusion, OS plays an important role in the pathogenesis of acute KD. Because IVIG therapy relieves OS by augmenting BAP, an assessment of OS in the acute phase of KD may be useful for early recognition of the necessity to perform additional IVIG treatment. Further study to elucidate this point would be worthwhile.