Oguz Soylemezoglu

DGKE Variants Cause a Glomerular Microangiopathy That Mimics Membranoproliferative GN

Renal microangiopathies and membranoproliferative GN (MPGN) can manifest similar clinical presentations and histology, suggesting the possibility of a common underlying mechanism in some cases. Here, we performed homozygosity mapping and whole exome sequencing in a Turkish consanguineous family and identified DGKE gene variants as the cause of a membranoproliferative-like glomerular microangiopathy. Furthermore, we identified two additional DGKE variants in a cohort of 142 unrelated patients diagnosed with membranoproliferative GN. This gene encodes the diacylglycerol kinase DGKε, which is an intracellular lipid kinase that phosphorylates diacylglycerol to phosphatidic acid. Immunofluorescence confocal microscopy demonstrated that mouse and rat Dgkε colocalizes with the podocyte marker WT1 but not with the endothelial marker CD31. Patch-clamp experiments in human embryonic kidney (HEK293) cells showed that DGKε variants affect the intracellular concentration of diacylglycerol. Taken together, these results not only identify a genetic cause of a glomerular microangiopathy but also suggest that the phosphatidylinositol cycle, which requires DGKE, is critical to the normal function of podocytes.

Genetic screening in adolescents with steroid-resistant nephrotic syndrome

Genetic screening paradigms for congenital and infantile nephrotic syndrome are well established; however, screening in adolescents has received only minor attention. To help rectify this, we analyzed an unselected adolescent cohort of the international PodoNet registry to develop a rational screening approach based on 227 patients with nonsyndromic steroid-resistant nephrotic syndrome aged 10-20 years. Of these, 21% had a positive family history. Autosomal dominant cases were screened for WT1, TRPC6, ACTN4, and INF2 mutations. All other patients had the NPHS2 gene screened, and WT1 was tested in sporadic cases. In addition, 40 sporadic cases had the entire coding region of INF2 tested. Of the autosomal recessive and the sporadic cases, 13 and 6%, respectively, were found to have podocin-associated nephrotic syndrome, and 56% of them were compound heterozygous for the nonneutral p.R229Q polymorphism. Four percent of the sporadic and 10% of the autosomal dominant cases had a mutation in WT1. Pathogenic INF2 mutations were found in 20% of the dominant but none of the sporadic cases. In a large cohort of adolescents including both familial and sporadic disease, NPHS2 mutations explained about 7% and WT1 4% of cases, whereas INF2 proved relevant only in autosomal dominant familial disease. Thus, screening of the entire coding sequence of NPHS2 and exons 8-9 of WT1 appears to be the most rational and cost-effective screening approach in sporadic juvenile steroid-resistant nephrotic syndrome.

Polymorphisms in the Vitamin D Receptor Gene and the Risk of Calcium Nephrolithiasis in Children

OBJECTIVE Polymorphism in the Vitamin D Receptor (VDR) gene has recently been reported to be associated with calcium metabolism disorders. This study was conducted to investigate the association of VDR gene polymorphism with the risk of calcium nephrolithiasis. METHODS We investigated the VDR ApaI, BsmI and TaqI polymorphisms, in relation to serum calcium, phosphate, intact parathyroid hormone and 1.25(OH)(2)D(3) in 64 hypercalciuric stone-forming children and 90 healthy children. DNA was isolated from peripheral blood, and genotyping was performed with PCR-based methods. RESULTS The frequency of ApaI AA genotype was significantly higher in the children with calcium nephrolithiasis than the controls (chi(2)=9.5; p=0.008). The distribution of BsmI and TaqI genotypes in stone-forming patients was similar to those in the control group. There was a significant association between TaqI TT genotype and the strength of the family history. The patients with TT genotype were observed to have a 8 times more risk than patients with Tt/tt genotype for recurrent stone episodes (OR 8, 95%CI 1.61-39.6). CONCLUSION VDR genotype determination may provide a tool to identify individuals who are at a risk for calcium nephrolithiasis.

Unresponsiveness to Colchicine Therapy in Patients with Familial Mediterranean Fever Homozygous for the M694V Mutation

Objective. More than 50 disease-associated mutations of the Mediterranean fever gene (MEFV) have been identified in familial Mediterranean fever (FMF), some of which were shown to have different clinical, diagnostic, prognostic, and therapeutic implications. The aim of our study was to define the frequency of mutation type, genotype-phenotype correlation, and response to colchicine treatment in patients with FMF. Methods. This study included 222 pediatric FMF patients. All patients were investigated for 6 MEFV mutations. Then patients were divided into 3 groups according to the presence of M694V mutation on both of the alleles (homozygotes), on only 1 allele (heterozygotes), and on none of the alleles, and compared according to their phenotypic characteristics and response to treatment. M694V/M694V was denoted Group A, M694V/Other Group B, and Other/Other, Group C. Results. Complete colchicine response was significantly lower while the rate of unresponsiveness was significantly higher in Group A compared to Groups B and C (p = 0.031, p < 0.001 and p = 0.005, p = 0.029, respectively). No differences except proteinuria were found between the phenotypic features of 3 groups. Group C had the lowest rate of proteinuria development (p = 0.024). All the amyloidosis patients were in Group A. Conclusion. Our results indicate that the M694V/M694V mutation is associated with lower response to colchicine treatment. Therefore, patients homozygous for M694V/M694V may be carrying an increased risk for development of amyloidosis.

Henoch-Schönlein nephritis: a nationwide study.

Background/Aim: The aim of this retrospective study was to evaluate the presentation, clinical and pathological manifestations and outcome of the Henoch-Schönlein purpura (HSP) nephritis in children. Methods: Clinical and laboratory data of 443 children with HSP nephritis aged between 3 and 16 years from 16 pediatric nephrology reference centers were analyzed retrospectively. The biopsy findings were graded according to the classification developed by the International Study of Kidney Disease in Children (ISKDC). Results: Renal biopsy was performed in 179 of the patients with HSP nephritis. The most common presenting clinical finding in patients who were biopsied was nephrotic range proteinuria (25%) which was followed by nephritic-nephrotic syndrome (23.5%). The biopsy findings according to the ISKDC were as follows: class I: 8.3%; II: 44.1%; III: 36.3%; IV: 6.7%; V: 3.3%; VI: 1.1%. All of the patients who developed end-stage renal disease had nephritic-nephrotic syndrome at presentation. Of 443 patients, 87.2% had a favorable outcome and 12.8% had an unfavorable outcome. The overall percentage of children who developed end-stage renal disease at follow-up was 1.1%. Logistic regression analysis did not show any association of initial symptoms and histology with outcome. Conclusion: In the presented cohort, the presence of crescents in the first biopsy or presenting clinical findings did not seem to predict the outcome of HSP nephritis in children. We conclude that children with HSP nephritis even with isolated microscopic hematuria and/or mild proteinuria should be followed closely.

Renin-angiotensin system gene polymorphisms: association with susceptibility to Henoch-Schonlein purpura and renal involvement.

The clinical course of Henoch–Schönlein Purpura (HSP) in children is variable, with some patients having a much more rapidly progressing course than others. We investigated whether polymorphisms of the renin–angiotensin system (RAS) genes are involved in HSP. Three RAS genotypes were examined in 114 children with HSP and in 164 healthy children: the angiotensin I converting enzyme (ACE) insertion/deletion polymorphism, the M235T mutation in the angiotensinogen gene (Agt), and the A1166C in the angiotensin II type I receptor (AT1R) gene. Significant differences were observed between HSP patients and control group in the frequency of ACE and Agt genotypes (p=0.004 and p=0.003, respectively). The TT genotype of Agt gene was associated with a 3.5-fold increased risk for Henoch–Schönlein nephritis (HSN) compared with the MM/MT genotype (odds ratio, 3.5; 95% confidence interval, 1.2–10.4). There was a trend to a higher prevalence of the TT genotype of the Agt gene among patients with nephrotic range proteinuria when compared to the patients with mild proteinuria, although the difference did not reach a statistical significance. The results of this study suggest that polymorphisms of ACE gene and Agt gene likely influence the risk of developing HSP. However, among the three genes of the RAS studies, only Agt gene was associated with the susceptibility to HSN. RAS gene polymorphisms studied are not associated with the presence of nephrotic range proteinuria. Additional studies are warranted to verify the correlation between RAS gene polymorphisms and susceptibility to HSP.

Nitric oxide in Henoch-Schönlein purpura.

Objective : To assess the value of nitric oxide (NO) production on the disease activity in children with Henoch-Schönlein purpura (HSP) by measuring serum nitrate levels and urinary nitrate excretion as an indicator for NO production. Methods : The study group consisted of 25 patients and 20 healthy children. We measured serum nitrate, urinary excretion of nitrate, and CRP levels in the acute phase and after remission. Results : Serum nitrate levels in the acute phase of the disease were found to be increased compared to the remission phase (28.67 - 10.3 mmol/l, 14.16 - 2.02 mmol/l) (p<0.001) and the control group (13.15 - 2.28 mmol/l) (p<0.001). Urinary nitrate excretion in the acute phase of the patients (15.32 - 9 mmol/mg) was increased compared to that in the remission phase (8.26 - 4.3 mmol/mg) (p=0.016) and in the control group (7.24 - 4.9 mmol/mg) (p<0.01). Conclusion : Serum NO and urinary nitrate excretion were found to be elevated in patients with HSP and this increase was associated with activation of the disease rather than its severity. These findings suggest a role for NO in the pathogenesis of HSP, but nitric oxide in HSP should be further studied in order to elucidate the pathophysiology of the disease

Desmopressin versus indomethacin treatment in primary nocturnal enuresis and the role of prostaglandins

OBJECTIVES To compare the efficacy of desmopressin and indomethacin and also determine the prostaglandin E2 (PGE2) concentrations in the patient and control groups. METHODS Eighty-five children with primary nocturnal enuresis were followed up for a baseline period of 4 weeks, during which they recorded wet and dry nights. After this period, the patients were divided into three groups that used desmopressin, indomethacin, or placebo for 4 weeks. The dosage of desmopressin (group A, n = 31 ) was 20 microg/day and the dosage of indomethacin (group B, n = 29) was 100 mg/day. The placebo group (group C) consisted of 25 patients. We determined the serum PGE2 and urine PGE2 concentrations before and after treatment in the three groups and in a control group. RESULTS Treatment with desmopressin and indomethacin resulted in significantly more dry nights during the 4 weeks of observation than did placebo (P <0.005). The number of dry nights was also significantly different in the desmopressin group than in the indomethacin group (P <0.01). In the total patient group, the mean serum and urine PGE2 concentrations were significantly different from the control groups serum and urine PGE2 concentrations (P <0.001). There was a significant decrease in the serum and urine PGE2 concentrations in group A and group B after the treatment period (P <0.01). CONCLUSIONS Desmopressin and indomethacin were found to be more effective than placebo. We conclude that prostaglandins have an important role in the pathophysiology of primary nocturnal enuresis.

Adiponectin levels and arteriosclerotic risk factors in pediatric renal transplant recipients

Abstract:  ADPN, a recently discovered adipocytokine, has attracted great attention because of its anti‐atherogenic properties. It was suggested as a protective factor for the cardiovascular system because of its close correlation with several risk factors. Our aim was to investigate serum ADPN levels in pediatric RTR and to document possible relationships between ADPN and arteriosclerotic risk factors. Twenty‐one RTR, aged 16.3 ± 4.0 yr, and 23 healthy age and sex‐matched control subjects were enrolled in this study. Serum lipid/lipoprotein fractions, homocysteine and ADPN levels as well as intima‐media thickness of the cIMT were determined in both groups. Significantly higher serum ADPN (p < 0.001) and homocysteine (p < 0.05) levels as well as higher cIMT (p < 0.001) were found in RTR compared with the control subjects, whereas apolipoprotein B and lipoprotein (a) levels were not significantly different. HDL cholesterol was positively correlated with log ADPN (r = 0.585, p < 0.01). There were inverse correlations between log time post‐transplantation and log ADPN as well as HDL cholesterol (r = −0.438, p < 0.05 and r = −0.578, p < 0.05, respectively). There were no correlation between log ADPN, log homocysteine, log apolipoprotein B, lipoprotein (a), creatinine clearance and cumulative steroid dose. Despite reasonable lipid profiles and remarkably elevated ADPN levels, our pediatric RTR with stable graft function displayed a risk for arteriosclerosis because of increased cIMT and mild hyperhomocysteinemia. Regarding the close positive correlation between ADPN and HDL cholesterol, it could be speculated that ADPN is a novel negative surrogate marker of arteriosclerosis. To our knowledge, this is the only report investigating levels and diverse correlates of ADPN in a pediatric RTR group. Further studies in larger groups of recipients are needed to clarify the interaction between arteriosclerotic risk factors and ADPN.

High serum adiponectin levels during steroid-responsive nephrotic syndrome relapse.

Adiponectin (ADPN), exclusively expressed and secreted from adipocytes, is a recently discovered protein hormone with anti-atherogenic and anti-inflammatory properties in contrast to other well-known adipocytokines. It has independent negative associations with obesity and hyperinsulinemia/insulin resistance. Apart from chronic renal failure, nephrotic syndrome was suggested as the only renal disease condition associated with raised plasma ADPN levels in adults. We aimed to evaluate the effect of nephrotic state on serum adiponectin (ADPN) levels in pediatric patients with steroid-responsive nephrotic syndrome (SRNS) by comparing the levels in relapse and remission as well as in control subjects and documenting possible relationships between ADPN and proteinuria as well as serum protein/lipid parameters. 34 patients with SRNS and 22 healthy age, sex and BMI-matched control subjects were enrolled into the study. 15 of the 34 SRNS patients had active diseases, and these were known as the SRNS-relapse group (ten relapsed and five newly-diagnosed patients), while the remaining 19 were in complete remission (the SRNS-remission group). Serum ADPN levels, blood chemistry (protein/albumin, triglyceride (TG), cholesterol (Cho) and lipoprotein levels) and 24-hour proteinuria were studied. ADPN levels were determined by ELISA. As expectedly, there were significant alterations in serum protein-lipid parameters and 24-hour proteinuria levels in SRNS patients consistent with their disease activity. SRNS-relapse patients had substantially higher ADPN levels (36.77±15.06 (5.61–59.41, median 39.84) μg/ml), compared to those in SRNS-remission and control groups (14.17±6.02 (3.28–29.40, median 12.80) μg/ml and 11.84±7.53 (2.81–31.46, median 10.85) μg/ml, respectively, p=0.001). There were strong positive correlations between serum ADPN levels and Cho (r=0.637, p=0.000), TG (r=0.516, p=0.002), low density lipoprotein (r=0.614, p=0.000) levels and 24-hour proteinuria (r=0.828, p=0.000) levels, whereas protein (r=−0.695, p=0.000) and albumin (r=0.732, p=0.000) levels were inversely correlated with ADPN levels. Regression analysis showed a significant correlation between ADPN and proteinuria (p=0.000). In conclusion, remarkably increased serum ADPN levels were detected in SRNS-relapse compared to those in SRNS-remission. This phenomenon might be the reflection of a compensatory response to nephrotic state characterized by massive proteinuria, hypoalbuminemia and hyperlipidemia.