Reassuring pregnancy outcomes in women with mild COL4A3-5-related disease (Alport syndrome) and genetic type of disease can aid personalized counseling

Individualized pre-pregnancy counseling and antenatal care for women with chronic kidney disease (CKD) require disease-specific data. Here, we investigated pregnancy outcomes and long-term kidney function in women with COL4A3-5 related disease (Alport Syndrome, (AS)) in a large multicenter cohort. The ALPART-network (mAternaL and fetal PregnAncy outcomes of women with AlpoRT syndrome), an international collaboration of 17 centers, retrospectively investigated COL4A3-5 related disease pregnancies after the 20th week. Outcomes were stratified per inheritance pattern (X-Linked AS (XLAS)), Autosomal Dominant AS (ADAS), or Autosomal Recessive AS (ARAS)). The influence of pregnancy on estimated glomerular filtration rate (eGFR)-slope was assessed in 192 pregnancies encompassing 116 women (121 with XLAS, 47 with ADAS, and 12 with ARAS). Median eGFR pre-pregnancy was over 90ml/min/1.73m2. Neonatal outcomes were favorable: 100% live births, median gestational age 39.0 weeks and mean birth weight 3135 grams. Gestational hypertension occurred during 23% of pregnancies (reference: 'general' CKD G1-G2 pregnancies incidence is 4-20%) and preeclampsia in 20%. The mean eGFR declined after pregnancy but remained within normal range (over 90ml/min/1.73m2). Pregnancy did not significantly affect eGFR-slope (pre-pregnancy β=-1.030, post-pregnancy β=-1.349). ARAS-pregnancies demonstrated less favorable outcomes (early preterm birth incidence 3/11 (27%)). ARAS was a significant independent predictor for lower birth weight and shorter duration of pregnancy, next to the classic predictors (pre-pregnancy kidney function, proteinuria, and chronic hypertension) though missing proteinuria values and the small ARAS-sample hindered analysis. This is the largest study to date on AS and pregnancy with reassuring results for mild AS, though inheritance patterns could be considered in counseling next to classic risk factors. Thus, our findings support personalized reproductive care and highlight the importance of investigating kidney disease-specific pregnancy outcomes.

Throwing off the keratin chains: a potential therapy for hereditary podocytopathy

In the current issue, Kuzmuk et al. offer a therapeutic option for patients with NPHS2 R138Q-associated nephrotic syndrome. For the first time in hereditary podocytopathies, this is offered by restoring the membrane targeting of a pathogenic protein. The idea that it is enough to liberate podocin from the trap of keratin 8, a key member of endoplasmic-reticulum-associated protein degradation complex, was brilliantly recognized based on former results obtained in cystic fibrosis.

Examination of Subbasal Nerve Plexus and Central Corneal Stromal Microstructure in Subjects With Congenital Aniridia, Using in Vivo Confocal Laser Scanning Microscopy

PURPOSE

During life up to 70% of aniridia subjects develop aniridia-associated keratopathy (AAK). AAK is characterized by limbal stem cell insufficiency, impaired corneal epithelial cell differentiation and abnormal cell adhesion, which leads to centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. Our aim was to examine the subbasal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy CLSM.

METHODS

31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 46 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph-III. At the subbasal nerve plexus, corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were analyzed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually.

RESULTS

The CNFD (2.02 ± 4.08 vs 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects than in controls (0.03 ± 0.004 vs 0.02 ± 0.003 mm/mm2) (p = 0.003). Keratocyte density was significantly lower in all stromal layers of aniridia subjects than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in aniridia.

CONCLUSIONS

Decrease in CNFD, CNFL, and CTBD, as well as increase in CNFW well refer to the congenital aniridia-associated neuropathy. The decreased keratocyte density and the stromal alterations may be related to an increased cell death in congenital aniridia, nevertheless, stromal changes in different stages of AAK have to be further analyzed in detail.

Multicenter Long-Term Real World Data on Treatment With Lumasiran in Patients With Primary Hyperoxaluria Type 1

Introduction

The RNA interference (RNAi) medication lumasiran reduces hepatic oxalate production in primary hyperoxaluria type 1 (PH1). Data outside clinical trials are scarce.

Methods

We report on retrospectively and observationally obtained data in 33 patients with PH1 (20 with preserved kidney function, 13 on dialysis) treated with lumasiran for a median of 18 months.

Results

Among those with preserved kidney function, mean urine oxalate (Uox) decreased from 1.88 (baseline) to 0.73 mmol/1.73 m2 per 24h after 3 months, to 0.72 at 12 months, and to 0.65 at 18 months, but differed according to vitamin B6 (VB6) medication. The highest response was at month 4 (0.55, -70.8%). Plasma oxalate (Pox) remained stable over time. Glomerular filtration rate increased significantly by 10.5% at month 18. Nephrolithiasis continued active in 6 patients, nephrocalcinosis ameliorated or progressed in 1 patient each. At last follow-up, Uox remained above 1.5 upper limit of normal (>0.75 mmol/1.73 m2 per 24h) in 6 patients. Urinary glycolate (Uglyc) and plasma glycolate (Pglyc) significantly increased in all, urine citrate decreased, and alkali medication needed adaptation. Among those on dialysis, mean Pox and Pglyc significantly decreased and increased, respectively after monthly dosing (Pox: 78-37.2, Pglyc: 216.4-337.4 μmol/l). At quarterly dosing, neither Pox nor Pglyc were significantly different from baseline levels. An acid state was buffered by an increased dialysis regimen. Systemic oxalosis remained unchanged.

Conclusion

Lumasiran treatment is safe and efficient. Dosage (interval) adjustment necessities need clarification. In dialysis, lack of Pox reduction may relate to dissolving systemic oxalate deposits. Pglyc increment may be a considerable acid load requiring careful consideration, which definitively needs further investigation.

The dominant findings of a recessive man: from Mendel's kid pea to kidney

The research of Mendel, born two centuries ago, still has many direct implications for our everyday clinical work. He introduced the terms "dominant" and "recessive" characters and determined their 3:1 ratio in the offspring of heterozygous "hybrid" plants. This distribution allowed calculation of the number of the phenotype-determining "elements," i.e., the alleles, and has been used ever since to prove the monogenic origin of a disorder. The Mendelian inheritance of monogenic kidney disorders is still of great help in distinguishing them from those with multifactorial origin in clinical practice. Inheritance of most monogenic kidney disorders fits to Mendel's observations: the equal contribution of the two parents and the complete penetrance or the direct correlation between the frequency of the recessive character and the degree of inbreeding. Nevertheless, beyond the truth of these basic concepts, several observations have expanded their genetic characteristics. The extreme genetic heterogeneity, the pleiotropy of the causal genes and the role of modifiers in ciliopathies, the digenic inheritance and parental imprinting in some tubulopathies, and the incomplete penetrance and eventual interallelic interactions in podocytopathies, reflect this expansion. For all these reasons, the transmission pattern in a natural setting may depend not only on the "character" but also on the causal gene and the variant. Mendel's passion for research combined with his modest personality and meticulous approach can still serve as an example in the work required to understand the non-Mendelian universe of genetics.

[Congenital aniridia patients' experience on their visual impairment in Hungary.]

INTRODUCTION

Aniridia is a rare congenital panocular disease associated with varying degrees of visual acuity impairment.

OBJECTIVE

To assess the experiences of congenital aniridia patients in Hungary, with visual impairment using a questionnaire developed by the ANIRIDIA-NET.

PATIENTS AND METHOD

Patients completed the Hungarian version of the 20-item ANIRIDIA-NET questionnaire with our assistance. The questionnaire covered demographic data, the most common complaints caused by the disease, the difficulties caused by low vision in different life situations and the frequency of low vision aids used in daily life.

RESULTS

33 subjects (17 female [51.51%] and 16 male [48.48%]), 16 (48.5%) children and 17 (51.5%) adults completed the questionnaire, with an age of 25.69 ± 17.49 years (5-59 years). Daily photosensitivity was reported by 27 (81.8%), dry eyes by 5 (15.2%), tearing by 4 (12.1%), fluctuating vision by 3 (9.1%), and eye pain by 2 (6.1%) subjects. The majority of respondents said that personal communication with schoolmates (16 [48.5%]) or colleagues at work (11 [33.3%]) never caused difficulties because of their visual impairment. 29 people (87.9%) never needed help with daily routines at home, 24 (72.7%) with getting to school/work and 17 (51.5%) with various activities. 29 people (87.8%) never used low vision aids for communication, 23 (69.7%) for travelling, 20 (60.6%) for participating in social activities, 18 (54.5%) for studying/work.

CONCLUSION

Although aniridia is associated with reduced visual acuity, the majority of people with congenital aniridia, especially in childhood, manage to cope with personal communication and various life situations without difficulty, despite their eye complaints. Low vision aids can be an important aid for them as they grow into adulthood and as they age. Orv Hetil. 2023; 164(34): 1342-1349.

[Staging of aniridia-associated keratopathy]

INTRODUCTION

Congenital aniridia is a rare panocular disease that affects almost all eye structures leading in most patients to reduced visual acuity. Ophthalmological signs include aniridia-associated keratopathy, secondary glaucoma, cataract, macular and optic nerve head hypoplasia, nystagmus. Although the term aniridia-associated keratopathy has long been used in the literature, various staging proposals have been described.

OBJECTIVE

To analyze aniridia-associated keratopathy stages, using available literature classifications, in patients with aniridia in Hungary.

PATIENTS AND METHODS

We examined 65 eyes of 33 patients with congenital aniridia (age: 25.69 ± 17.49 [5-59] years, 17 females [51.51%]). We recorded the corneal status by slit-lamp examination and classified the corneal abnormalities according to the Mackman, Mayer, López-García and Lagali staging.

RESULTS

According to Mackman's classification, 8 eyes (12.3%) were in stage 0, 0 eye in stage 1A, 38 eyes (58.46%) in stage 1B and 19 eyes (29.23%) in stage 2. According to Mayer, stage I included 8 eyes (12.3%), stage II 38 eyes (58.46%), stage III 5 eyes (7.7%), stage IV 7 eyes (10.77%) and stage V 7 eyes (10.77%). In López-García's classification, 8 eyes (12.3%) could not be grouped, 20 eyes (30.77%) were in stage 1, 18 eyes (27.7%) in stage 2 and 19 eyes (29.3%) in stage 3. Lagali's classification included 8 eyes (12.3%) in stage 0, 20 eyes (30.77%) in stage 1, 18 eyes (27.7%) in stage 2, 5 eyes (7.7%) in stage 3 and 14 eyes (21.54%) in stage 4.

CONCLUSION

We recommend using Lagali's staging scheme for aniridia-associated keratoptahy due to its ease of use, detailed progression assessment, and treatment planning. In stage 1 according to Lagali, blood vessels cross the limbus by up to 1 mm, in stage 2 the central 2-3 mm of the corneal area is spared of blood vessels. When the blood vessels reach the center of the cornea, it is stage 3, followed by opaque, uneven corneal pannus in stage 4. Orv Hetil. 2023; 164(27): 1063-1069.

The importance of pseudouridylation: human disorders related to the fifth nucleoside

Pseudouridylation is one of the most abundant RNA modifications in eukaryotes, making pseudouridine known as the "fifth nucleoside." This highly conserved alteration affects all non-coding and coding RNA types. Its role and importance have been increasingly widely researched, especially considering that its absence or damage leads to serious hereditary diseases. Here, we summarize the human genetic disorders described to date that are related to the participants of the pseudouridylation process.

[Congenital aniridia - Hungarian data of a spectrum disease]

INTRODUCTION

Congenital aniridia is a rare disease, characterised by the complete or partial absence of the iris, but lesions may be present in all structures of the eye.

OBJECTIVE

To determine the prevalence of ocular diseases in congenital aniridia by analyzing patients from a Hungarian centre.

PATIENTS AND METHODS

Patients at the Department of Ophthalmology of Semmelweis University, examined between October 2005 and May 2022, have been included. After taking the patients' medical history, a detailed ophthalmological examination has been performed.

RESULTS

Of the 82 patients in the database, 33 (age 25.69 ± 17.49 [5-59] years, 17 females [51.51%]) presented for examination and 65 eyes were examined. Nystagmus was found in 45 eyes of 23 patients (69.23%), and the patients' uncorrected distance visual acuity was 0.14 ± 0.128 (0.9 logMAR; 0.63-0.005). The aniridia-associated keratopathy was Grade 0 in 8 eyes (12.3%), Grade 1 in 10 eyes (15.38%), Grade 2 in 16 eyes (24.62%), Grade 3 in 4 eyes (6.15%) and Grade 4 in 25 eyes (38.46%). 30 eyes (46.15%) of 15 patients had secondary glaucoma, 6 eyes (9.2%) of 3 patients were glaucoma suspect. 8 eyes (12.3%) had a clear lens, 44 eyes (67.69%) had cataract, of which 22 (33.84%) were anterior cortical polar cataracts. 13 eyes (20%) were pseudophakic (PCL) and 7 eyes (10.77%) had lens dislocation or zonular insufficiency. Macular hypoplasia was found in 6 eyes of 3 patients (4.6%) and optic nerve head malformation in 2 eyes of 1 patient (3.03%).

CONCLUSION

The ocular signs of congenital aniridia are aniridia-associated keratopathy, secondary glaucoma, cataract, macular and optic nerve head hypoplasia. Systematic collaboration of different ophthalmological specialties is required for the management and care of all these ocular abnormalities. Orv Hetil. 2023; 164(4): 148-155.

FC015: High Salt Environment Disrupts the Regulatory Effect of Podocin on the Nephrin-Nephrin Distance

BACKGROUND AND AIMS

The podocin encoding NPHS2 is the most frequently mutated gene in steroid-resistant nephrotic syndrome. Podocin homooligomerizes through C-terminal helical regions [1] and binds nephrin in the glomerular slit diaphragm [2]. We formerly showed that podocin regulates the distance between two neighbouring nephrin molecules in cis, i.e. the shortest dimension of the glomerular pore (3.5-4nm) [3, 4].

High sodium diet has been shown to promote glomerular injury and proteinuria [5]. We aimed to assess the effect of high salt environment on the nephrin-nephrin distance in the presence and absence of podocin.

METHODS

To generate extracellularly tagged nephrin constructs, cDNA sequences encoding YPet or mCherry were inserted in the human wild type nephrin cDNA (YPet-N1 plasmid) replacing the c.3136-3162 nucleotides. Thus, the p.Glu1046-Pro1054 residues of the fibronectin domain, located in the juxtamembraneous extracellular part of nephrin was replaced with either YPet or mCherry. HEK-293 cells were co-transfected with both nephrin constructs with or without wild type HA-tagged podocin construct (pLEX-MCS plasmid). To measure the effect of salt overload, DMEM was supplemented with either 25 mM NaCl or 50 mM mannitol as osmotic control 24-h prior to the FRET measurements. The fluorescence decay curves measured by time-correlated single photon counting (TCSPC) (Chronos BH, ISS Inc.) were decomposed into lifetime components and the longest lifetime population—most suitable for long-range FRET—was used for further calculations. Nonparametric tests were used for statistical analysis.

RESULTS

High salt environment did not influence the nephrin-nephrin distance in the absence of podocin. In accordance with our previous results, podocin decreased the nephrin-nephrin distance in physiological salt environment, as reflected by an increased FRET efficiency between the extracellular YPet and mCherry tags. High salt environment (+25 mM) completely disrupted this effect. Mannitol of similar osmotic concentration did not modify the effect of podocin (Figure 1).

CONCLUSION

High salt environment increases the distance between the nephrin molecules in cis by disrupting the organizing effect of podocin. The deleterious effect of high salt is not explained by an increased osmotic pressure.

MO044: Cellular mechanism of the exceptional dominant transmission in NPHS2-associated glomerulopathy

BACKGROUND AND AIMS

Mutations of NPHS2 cause autosomal recessive steroid-resistant nephrotic syndrome (SRNS). The encoded podocin, a key component of the slit diaphragm, homo-oligomerizes through two C-terminal oligomerization sites. We formerly found that specific podocin variants may exert a dominant negative effect against R229Q podocin variant secondary to an altered oligomerization [1, 2]. Recently, two families with autosomal dominant focal segmental glomerulosclerosis were found to carry a de novo heterozygous NPHS2 last-exon frameshift mutations affecting the second oligomerization site (either c.989_992delTGTC, p.L330Pfs*17 or c.988_989delCT, p.L330Vfs*15) [3]. We hypothesized that these podocin variants exert a dominant negative effect against wild type (WT) podocin.

METHODS

We coexpressed eGFP-tagged WT podocin with either hemagglutinin-tagged (HA) WT, p.L330Pfs*17 or p.L330Vfs*15 podocin variants in cultured podocytes. Plasma membrane was stained with CF405M-conjugated wheat germ agglutinin (WGA), and immunohistochemical staining was performed with primary anti-HA and secondary AlexaFluor568-conjugated antibodies. All analysis was done in a blinded fashion. The membrane-targeting of podocin was assessed by the ratio of the WGA-labeled perimembranous area that colocalized with podocin (Mander's overlap coefficients, MOC) and the colocalization of the coexpressed variants were estimated as Pearson correlation coefficients (PCC) by FiJi software on confocal microscopic images. MOC and PCC were compared by Holmes–Bonferroni adjusted Wilcoxon signed-rank test.

RESULTS

The frameshift podocin variants were not membranous in monoexpression [MOC: HA-p.L330Pfs*17 (n = 26): 0.08 (0.03–0.22) median (interquartile ranges); HA-p.L330Vfs*15 (n = 24): 0.07 (0.02–0.16)]. The GFP-tagged WT podocin strongly colocalized with the HA-tagged WT or frameshift podocin variants [PCC: WT-eGFP + HA-WT (n = 19): 0.64 (0.49–0.71); WT-eGFP + HA-L330Pfs*17 (n = 17): 0.54 (0.35–0.58); WT-eGFP + HA-L330Vfs*15 (n = 17): 0.44 (0.29–0.66)]. The GFP-WT podocin was retained in intracellular compartments in the presence of any of the two frameshift podocin variants [MOCWT(WT) = 0.58 (0.46–0.69)], MOCWT(L330Pfs*17) = 0.01 (0.002–0.029), P = 2x10-6 versus WT(WT); MOCWT(L330Vfs*15) = 0.003 (0.001–0.013), P = 2 x 10−6 versus WT(WT)].

CONCLUSIONS

The dominant podocin variants retain WT podocin in intracellular compartments explaining the exceptional dominant transmission of NPHS2-associated glomerulopathy. This is in accordance with our former results showing the primary role of C-terminal hetero-oligomerization in exerting interallelic interactions of NPHS2 alleles.

FUNDING

MTA-SE Lendulet Research Grant (LP2015-11/2015), OTKA KH125566 and K135798, and ÚNKP-20–3-I-SE-29 from the source of the National Research, Development and Innovation Fund.

Arthrogryposis–renal dysfunction–cholestasis syndrome

Összefoglaló. Az arthrogryposis-renalis diszfunkció-cholestasis (ARC) szindróma igen rossz prognózisú autoszomális recesszív kórkép. A három vezető tünethez társulhat központi idegrendszeri érintettség, siketség, cardiovascularis anomália (pitvari és kamrai sövényhiány), thrombocytafunkció-zavar, rekurrens szepszisek, ichthyosis, valamint súlyfejlődésben való elmaradás. A háromnapos újszülöttet neuromuscularis betegség gyanúja miatt vettük át a szülészeti intézményből. Fizikális vizsgálat során pes equinovarust és hypotrophiás küllemet tapasztaltunk. Kéthetes korában súlyos tubulopathia, valamint cholestasis igazolódott normális gamma-glutamil-transzferáz-szint mellett. A perifériás vérkenet vizsgálata során abnormális morfológiájú thrombocyták ábrázolódtak. Súlygyarapodást komplex felépített enteralis és parenteralis táplálás segítségével sem sikerült elérni. Három hónapos korára a gyermek súlya 15%-kal a születési súlya alatt volt. A kórkép szövődményeként ismétlődő bakteriális véráramfertőzés súlyosbította az állapotát. Az újszülött klinikai képe az ARC-szindrómának felelt meg. A kóroki gének szekvenálása során a VPS33B-génben homozigóta c.498+1G>T variáns igazolódott, mely igazolja a betegség fennállását. Orv Hetil. 2022; 163(2): 74-78. Summary. Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is an autosomal recessive multisystem disorder that typically presents with arthrogryposis, renal tubular leak and neonatal cholestatic jaundice. It can be accompanied by nervous system abnormalities, deafness, structural cardiac defects, abnormal platelet morphology, recurrent sepsis, ichthyosis and failure to thrive. The three-day-old neonate was admitted for a suspected neuromuscular disorder. On examination, clubfoot, jaundice and hypotonia were found. Laboratory evaluation revealed tubulopathy and cholestasis with normal gamma-glutamyl transferase level. Peripheral blood smear evaluation revealed abnormally giant platelets. Despite the combined enteral and parenteral nutrition, the infant experienced severe failure to thrive. The phenotype of the presented neonate is consistent with ARC syndrome. Sequencing of the causal genes revealed a homozygous consensus splice site VPS33B mutation (c.498+1G>T), confirming the clinical diagnosis. Orv Hetil. 2022; 163(2): 74-78.

Identification of incompletely penetrant variants and interallelic interactions in autosomal recessive disorders by a population-genetic approach

We aimed to identify incompletely penetrant (IP) variants and interallelic interactions in autosomal recessive disorders by a population-genetic approach. Genotype and clinical data were collected from 9038 patients of European origin with ASL, ATP7B, CAPN3, CFTR, CTNS, DHCR7, GAA, GALNS, GALT, IDUA, MUT, NPHS1, NPHS2, PAH, PKHD1, PMM2, or SLC26A4-related disorders. We calculated the relative allele frequency of each pathogenic variant (n = 1936) to the loss-of-function (LOF) variants of the corresponding gene in the patient ( A C p t V / A C p t L O F ) and the general population ( AC gnomAD V / AC gnomAD LOF ) and estimated the penetrance of each variant by calculating their ratio: ( A C p t V / A C p t L O F ) ( A C g n o m A D V / A C g n o m A D L O F ) (V/LOF ratio). We classified all variants as null or hypomorphic based on the associated clinical phenotype. We found 25 variants, 29% of the frequent 85 variants, to be underrepresented in the patient population (V/LOF ratio <30% with p < 7.22 × 10^-5 ), including 22 novel ones in the ASL, CAPN3, CFTR, GAA, GALNS, PAH, and PKHD1 genes. In contrast to the completely penetrant variants (CP), the majority of the IP variants were hypomorphic (IP: 16/18, 88%; CP: 177/933, 19.0%; p = 5.12 × 10^-10 ). Among them, only the NPHS2 R229Q variant was subject to interallelic interactions. The proposed algorithm identifies frequent IP variants and estimates their penetrance and interallelic interactions in large patient cohorts.

Diagnosis and treatment of paediatric multisystem inflammatory syndrome

Összefoglaló. A SARS-CoV-2-fertőzés ritka gyermekkori szövődménye a sokszervi gyulladás, angol terminológiával paediatric inflammatory multisystem syndrome (PIMS). Két vagy több szerv érintettségével járó, súlyos tünetekkel induló betegségről van szó, amelynek tünetei átfedést mutatnak a Kawasaki-betegséggel, a toxikus sokk szindrómával és a makrofágaktivációs szindrómával. A PIMS-betegek intenzív terápiás osztályon vagy intenzív terápiás háttérrel rendelkező intézményben kezelendők, ahol biztosítottak a kardiológiai ellátás feltételei is. A szükséges immunterápia a klinikai prezentációtól függ. A jelen közleményben a szerzők a releváns nemzetközi irodalom áttekintését követően ajánlást tesznek a PIMS diagnosztikai és terápiás algoritmusára. Orv Hetil. 2021; 162(17): 652-667. Summary. Pediatric inflammatory multisystem syndrome (PIMS) is a rare complication of SARS-CoV-2 infection in children. PIMS is a severe condition, involving two or more organ systems. The symptoms overlap with Kawasaki disease, toxic shock syndrome and macrophage activation syndrome. PIMS patients should be treated in an intensive care unit or in an institution with an intensive care background, where cardiological care is also provided. The required specific immunotherapy depends on the clinical presentation. In this paper, after reviewing the relevant international literature, the authors make a recommendation for the diagnostic and therapeutic algorithm for PIMS. Orv Hetil. 2021; 162(17): 652-667.

Clinical and genetic findings in Hungarian pediatric patients carrying chromosome 16p copy number variants and a review of the literature

The short arm of chromosome 16 (16p) is enriched for segmental duplications, making it susceptible to recurrent, reciprocal rearrangements implicated in the etiology of several phenotypes, including intellectual disability, speech disorders, developmental coordination disorder, autism spectrum disorders, attention deficit hyperactivity disorders, obesity and congenital skeletal disorders. In our clinical study 73 patients were analyzed by chromosomal microarray, and results were confirmed by fluorescence in situ hybridization or polymerase chain reaction. All patients underwent detailed clinical evaluation, with special emphasis on behavioral symptoms. 16p rearrangements were identified in 10 individuals. We found six pathogenic deletions and duplications of the recurrent regions within 16p11.2: one patient had a deletion of the distal 16p11.2 region associated with obesity, while four individuals had duplications, and one patient a deletion of the proximal 16p11.2 region. The other four patients carried 16p variations as second-site genomic alterations, acting as possible modifying genetic factors. We present the phenotypic and genotypic results of our patients and discuss our findings in relation to the available literature.

An international cohort study of autosomal dominant tubulointerstitial kidney disease due to REN mutations identifies distinct clinical subtypes

There have been few clinical or scientific reports of autosomal dominant tubulointerstitial kidney disease due to REN mutations (ADTKD-REN), limiting characterization. To further study this, we formed an international cohort characterizing 111 individuals from 30 families with both clinical and laboratory findings. Sixty-nine individuals had a REN mutation in the signal peptide region (signal group), 27 in the prosegment (prosegment group), and 15 in the mature renin peptide (mature group). Signal group patients were most severely affected, presenting at a mean age of 19.7 years, with the prosegment group presenting at 22.4 years, and the mature group at 37 years. Anemia was present in childhood in 91% in the signal group, 69% prosegment, and none of the mature group. REN signal peptide mutations reduced hydrophobicity of the signal peptide, which is necessary for recognition and translocation across the endoplasmic reticulum, leading to aberrant delivery of preprorenin into the cytoplasm. REN mutations in the prosegment led to deposition of prorenin and renin in the endoplasmic reticulum-Golgi intermediate compartment and decreased prorenin secretion. Mutations in mature renin led to deposition of the mutant prorenin in the endoplasmic reticulum, similar to patients with ADTKD-UMOD, with a rate of progression to end stage kidney disease (63.6 years) that was significantly slower vs. the signal (53.1 years) and prosegment groups (50.8 years) (significant hazard ratio 0.367). Thus, clinical and laboratory studies revealed subtypes of ADTKD-REN that are pathophysiologically, diagnostically, and clinically distinct.

P0072GENERATION OF A C. ELEGANS MODEL TO STUDY THE INTERALLELIC INTERACTIONS OF PODOCIN

Background and Aims

NPHS2 is the most frequently mutated gene in steroid-resistant nephrotic syndrome. NPHS2 encodes podocin, a key component of the glomerular filtration barrier. Podocin is a 42 kDa integral membrane protein, which accumulates in lipid raft microdomains at the podocyte slit diaphragm and is known to form oligomers.

The c.686G&gt;A, p.R229Q is the most common non-silent variant of NPHS2. We formerly described that R229Q is pathogenic only when trans-associated to specific 3’ missense mutations on the other parental allele. These C-terminal podocin mutants exert a dominant negative effect on R229Q podocin and retain it in intracellular compartments. As such, R229Q is the first variant in human genetics with a mutation-dependent pathogenicity. Based on FRET analysis and structural modeling, we formerly showed that the dominant negative effect is mediated by an altered oligomerization. However, the pathogenicity of several [mutation];[R229Q] associations is still in question and the identification of other rare NPHS2 variants with a mutation-dependent pathogenicity require an in vivo model. We therefore aimed to generate a Caenorhabditis elegans model, deficient for the homologous gene of NPHS2 (mec-2) and coexpressing differently (GFP- and mCherry-) tagged human podocin pairs. MEC-2 shares 45% identity and 83% similarity over 275aa (72%) of podocin (383aa). Expressed in six neurons, it is responsible for gentle-touch mechanosensation. The mec-2 mutants are insensitive to gentle touch in the center part of the body.

Method

Vectors encoding C-terminal GFP- or mCherry-tagged MEC-2 or human podocin with C. elegans codon optimization under mec-2 promoter and a selection marker (unc-119) were generated. Double (mec-2 and unc-119) mutant strains were established. Mutant strains were transformed by microparticle bombardment. The gentle-touch mechanosensation was examined by cat’s whiskers in a blinded experiment.

Results

The expression pattern of GFP and mCherry under mec-2 promoter corresponded to the six neurons responsible for gentle-touch sensation, indicating the proper functioning of the promoter. Strains with extrachromosomal MEC-2 or podocin coding vectors were successfully established (GFP-tagged MEC-2: n= 55 strains, GFP-tagged podocin: n= 81, mCherry-tagged podocin: n= 18). However, we found no rescue of the gentle touch sensation in any of them in blinded experiments. We hypothesized that either the fluorescent tag or the lack of chromosomal integration prevents the rescue effect of MEC-2. We therefore aimed to achieve self-cleaving of MEC-2 and the fluorescent tag, and inserted a T2A self-cleaving peptide-encoding sequence between them. To achieve chromosomal integration, we are implementing the MosSCI (Mos1-mediated Single Copy Insertion) technique.

Conclusion

Once the rescue with MEC-2 is achieved, the rescue effect of wild type and next different human podocin variant(s) will be aimed to analyze. The generation of the first animal model to study human interallelic interactions is challenging.

MO032PODOCIN REGULATES THE SIZE OF THE GLOMERULAR PORE

Background and Aims

Podocin is a major component of the glomerular slit diaphragm. It is encoded by NPHS2, the most frequently mutated gene in steroid-resistant nephrotic syndrome. We previously showed that podocin oligomerization occurs exclusively through the C-terminal helical region and is responsible for mediating interallelic interactions of NPHS2. Podocin anchors the main slit diaphragm component nephrin to the podocyte cell membrane. The shortest dimension of the glomerular pore (3,5-4nm) is determined by the distance between two neighboring nephrin molecules in cis position and – according to our structural model – corresponds perfectly to the distance between the nephrin binding domains of two podocin molecules in an oligomer. We therefore hypothesized that podocin regulates the distance between nephrin molecules, thus affecting the size of the glomerular pore. Here we aimed to explore the effects of podocin variants on the distance between neighboring nephrin molecules.

Method

Wild type nephrin was tagged with C-terminal YPet or mRuby3 fluorescent proteins and the two constructs were transiently coexpressed in HEK293 cells, together with podocin variants of different oligomer-forming capacity. We verified the plasmamembrane localization of the fluorescently labelled nephrin molecules by confocal microscopy. Förster resonance energy transfer (FRET) was measured between the fluorescently labelled nephrin molecules in living cells. In a second set of experiments the fluorescent tags (Ypet and mCherry) were inserted in the extracellular part of nephrin at a distance of ten amino acids from the N-terminal end of the transmembrane domain. The fluorescence decay curves measured by time-correlated single photon counting (TCSPC) (Chronos BH, ISS Inc.) were decomposed into lifetime components, and the longest lifetime population – most suitable for long-range FRET – was used for further calculations. Nonparametric tests were used to analyze the data.

Results

Similar results were obtained with the extracellular and the intracellular tags. FRET efficiency was increased in the presence of the wild type podocin (p&lt;0.0005 with both extracellular and intracellular tags), but remained unaltered in the presence of the monomer-forming R286Tfs*17 podocin. Similar to R286Tfs*17, the other pathogenic podocin variants (R138Q, A284V and F344Lfs*4) did not alter the FRET efficiency, irrespective of the different effect of these mutations on podocin oligomerization and localization. On the other hand, the coexpression of the R229Q podocin variant, which is benign in the homozygous state, resulted in a similarly high FRET efficiency as the wild type podocin. The FRET efficiency measured between extracellularly labelled nephrin molecules in the presence of the V290M podocin variant correlated with its clinically hypomorphic effect: it fell between that of the wild type and the R286Tfs*17 podocin, being statistically different from both.

Conclusion

Wild type podocin significantly reduces the distance between the nephrin molecules in cis: the shortest dimension of the glomerular pore. Several pathogenic podocin variants do not. The FRET efficiency between the nephrin molecules correlates with the clinical effect of the podocin variants. We thus suggest that a major function of podocin is the regulation of the critical dimension of the glomerular pore.

A molecular mechanism explaining albuminuria in kidney disease

Mammalian kidneys constantly filter large amounts of liquid, with almost complete retention of albumin and other macromolecules in the plasma. Breakdown of the three-layered renal filtration barrier results in loss of albumin into urine (albuminuria) across the wall of small renal capillaries, and is a leading cause of chronic kidney disease. However, exactly how the renal filter works and why its permeability is altered in kidney diseases is poorly understood. Here we show that the permeability of the renal filter is modulated through compression of the capillary wall. We collect morphometric data prior to and after onset of albuminuria in a mouse model equivalent to a human genetic disease affecting the renal filtration barrier. Combining quantitative analyses with mathematical modelling, we demonstrate that morphological alterations of the glomerular filtration barrier lead to reduced compressive forces that counteract filtration pressure, thereby resulting in capillary dilatation, and ultimately albuminuria. Our results reveal distinct functions of the different layers of the filtration barrier and expand the molecular understanding of defective renal filtration in chronic kidney disease.

[Trisomy 9p and clinical heterogeneity: case report of an unusual presentation]

Whole or partial trisomy of the short arm of chromosome 9 (9p) is considered to be one of the more frequent chromosome abnormalities compatible with life. The duplication may affect various organs, however the most common symptoms are certain specific facial dysmorphisms and abnormalities of the fingers, toes and nails. A one month old boy presented with failure to thrive, jaundice, ventricular septal defect (VSD) and dysmorphic face. He displayed symptoms of heart failure. The cardiologic examination revealed a significant VSD, hypoplasia of the aortic arch, pulmonary hypertension, decompensated circulatory failure and moderate left ventricle dysfunction. Routine cytogenetic analysis revealed a supernumerary marker chromosome. Fluorescence in situ hybridization (FISH) identified this as the short arm of chromosome 9. The child's karyotype was determined as 47,XY,+der(9)dup(9)(p10p24)dn. Due to his worsening condition and the high risk of the operation, it was decided to forego the procedure. After a short palliative care the child passed away. The child's clinical presentation and the uncharacteristic severity of his condition show that chromosome abnormalities involving duplicated genetic material are extremely heterogeneous. Thus treatment of each child should be individualized and may also involve difficult ethical considerations. Orv Hetil. 2018; 159(47): 1994-2000.

The mutation-dependent pathogenicity of NPHS2 p.R229Q: A guide for clinical assessment

NPHS2, encoding podocin, is the major gene implicated in steroid-resistant nephrotic syndrome. Its c.686G>A, p.R229Q variant is the first human variant with a mutation-dependent pathogenicity; it is only pathogenic when trans-associated to specific mutations. Secondary to its high allele frequency in the European, South Asian, African, and Latino populations, its benign trans-associations can be accidentally identified in affected patients. Distinguishing pathogenic and benign p.R229Q associations can be challenging. In this paper, we present the currently known pathogenic and benign associations, and show that a rare p.R229Q association can be considered pathogenic if the variant in trans meets the following criteria; it affects the 270-351 residues and alters but does not disrupt the oligomerization, its p.R229Q association is found in a family with slowly progressing focal segmental glomerulosclerosis, but is expected to be rare in the general population (<1:10⁶ ). We show that >15% of the p.R229Q associations identified so far in patients are benign.

Comprehensive genetic testing in children with a clinical diagnosis of ARPKD identifies phenocopies

BACKGROUND

Autosomal recessive polycystic kidney disease (ARPKD) is genetically one of the least heterogeneous ciliopathies, resulting primarily from mutations of PKHD1. Nevertheless, 13-20% of patients diagnosed with ARPKD are found not to carry PKHD1 mutations by sequencing. Here, we assess whether PKHD1 copy number variations or second locus mutations explain these cases.

METHODS

Thirty-six unrelated patients with the clinical diagnosis of ARPKD were screened for PKHD1 point mutations and copy number variations. Patients without biallelic mutations were re-evaluated and screened for second locus mutations targeted by the phenotype, followed, if negative, by clinical exome sequencing.

RESULTS

Twenty-eight patients (78%) carried PKHD1 point mutations, three of whom on only one allele. Two of the three patients harbored in trans either a duplication of exons 33-35 or a large deletion involving exons 1-55. All eight patients without PKHD1 mutations (22%) harbored mutations in other genes (PKD1 (n = 2), HNF1B (n = 3), NPHP1, TMEM67, PKD1/TSC2). Perinatal respiratory failure, a kidney length > +4SD and early-onset hypertension increase the likelihood of PKHD1-associated ARPKD. A patient compound heterozygous for a second and a last exon truncating PKHD1 mutation (p.Gly4013Alafs*25) presented with a moderate phenotype, indicating that fibrocystin is partially functional in the absence of its C-terminal 62 amino acids.

CONCLUSIONS

We found all ARPKD cases without PKHD1 point mutations to be phenocopies, and none to be explained by biallelic PKHD1 copy number variations. Screening for copy number variations is recommended in patients with a heterozygous point mutation.

C-terminal oligomerization of podocin mediates interallelic interactions

Interallelic interactions of membrane proteins are not taken into account while evaluating the pathogenicity of sequence variants in autosomal recessive disorders. Podocin, a membrane-anchored component of the slit diaphragm, is encoded by NPHS2, the major gene mutated in hereditary podocytopathies. We formerly showed that its R229Q variant is only pathogenic when trans-associated to specific 3' mutations and suggested the causal role of an abnormal C-terminal dimerization. Here we show by FRET analysis and size exclusion chromatography that podocin oligomerization occurs exclusively through the C-terminal tail (residues 283-382): principally through the first C-terminal helical region (H1, 283-313), which forms a coiled coil as shown by circular dichroism spectroscopy, and through the 332-348 region. We show the principal role of the oligomerization sites in mediating interallelic interactions: while the monomer-forming R286Tfs*17 podocin remains membranous irrespective of the coexpressed podocin variant identity, podocin variants with an intact H1 significantly influence each other's localization (r² = 0.68, P = 9.2 × 10^-32). The dominant negative effect resulting in intracellular retention of the pathogenic F344Lfs*4-R229Q heterooligomer occurs in parallel with a reduction in the FRET efficiency, suggesting the causal role of a conformational rearrangement. On the other hand, oligomerization can also promote the membrane localization: it can prevent the endocytosis of F344Lfs*4 or F344* podocin mutants induced by C-terminal truncation. In conclusion, C-terminal oligomerization of podocin can mediate both a dominant negative effect and interallelic complementation. Interallelic interactions of NPHS2 are not restricted to the R229Q variant and have to be considered in compound heterozygous individuals.

QMPSF is sensitive and specific in the detection of NPHP1 heterozygous deletions

Background:

Nephronophthisis, an autosomal recessive nephropathy, is responsible for 10% of childhood chronic renal failure. The deletion of its major gene, NPHP1, with a minor allele frequency of 0.24% in the general population, is the most common mutation leading to a monogenic form of childhood chronic renal failure. It is challenging to detect it in the heterozygous state. We aimed to evaluate the sensitivity and the specificity of the quantitative multiplex PCR of short fluorescent fragments (QMPSF) in its detection.

Methods:

After setting up the protocol of QMPSF, we validated it on 39 individuals diagnosed by multiplex ligation-dependent probe amplification (MLPA) with normal NPHP1 copy number (n=17), with heterozygous deletion (n=13, seven parents and six patients), or with homozygous deletion (n=9). To assess the rate of the deletions that arise from independent events, deleted alleles were haplotyped.

Results:

The results of QMPSF and MLPA correlated perfectly in the identification of 76 heterozygously deleted and 56 homozygously deleted exons. The inter-experimental variability of the dosage quotient obtained by QMPSF was low: control, 1.05 (median; range, 0.86−1.33, n = 102 exons); heterozygous deletion, 0.51 (0.42−0.67, n = 76 exons); homozygous deletion, 0 (0−0, n = 56 exons). All patients harboring a heterozygous deletion were found to carry a hemizygous mutation. At least 15 out of 18 deletions appeared on different haplotypes and one deletion appeared de novo.

Conclusions:

The cost- and time-effective QMPSF has a 100% sensitivity and specificity in the detection of NPHP1 deletion. The potential de novo appearance of NPHP1 deletions makes its segregation analysis highly recommended in clinical practice.

Selective measurement of α smooth muscle actin: why β-actin can not be used as a housekeeping gene when tissue fibrosis occurs

Background

Prevalence of fibroproliferative diseases, including chronic kidney disease is rapidly increasing and has become a major public health problem worldwide. Fibroproliferative diseases are characterized by increased expression of α smooth muscle actin (α-SMA) that belongs to the family of the six conserved actin isoforms showing high degree homology. The aim of the present study was to develop real-time PCRs that clearly discriminate α-SMA and ß-actin from other actin isoforms.

Results

Real-time PCRs using self-designed mouse, human and rat specific α-SMA or ß-actin primer pairs resulted in the specific amplification of the artificial DNA templates corresponding to mouse, human or rat α-SMA or ß-actin, however ß-actin showed cross-reaction with the housekeeping γ-cyto-actin. We have shown that the use of improperly designed literary primer pairs significantly affects the results of PCRs measuring mRNA expression of α-SMA or ß-actin in the kidney of mice underwent UUO.

Conclusion

We developed a set of carefully designed primer pairs and PCR conditions to selectively determine the expression of mouse, human or rat α-SMA and ß-actin isoforms. We demonstrated the importance of primer specificity in experiments where the results are normalized to the expression of ß-actin especially when fibrosis and thus increased expression of α-SMA is occur.

Activating HSP72 in rodent skeletal muscle increases mitochondrial number and oxidative capacity and decreases insulin resistance

Induction of heat shock protein (HSP)72 protects against obesity-induced insulin resistance, but the underlying mechanisms are unknown. Here, we show that HSP72 plays a pivotal role in increasing skeletal muscle mitochondrial number and oxidative metabolism. Mice overexpressing HSP72 in skeletal muscle (HSP72Tg) and control wild-type (WT) mice were fed either a chow or high-fat diet (HFD). Despite a similar energy intake when HSP72Tg mice were compared with WT mice, the HFD increased body weight, intramuscular lipid accumulation (triacylglycerol and diacylglycerol but not ceramide), and severe glucose intolerance in WT mice alone. Whole-body VO2, fatty acid oxidation, and endurance running capacity were markedly increased in HSP72Tg mice. Moreover, HSP72Tg mice exhibited an increase in mitochondrial number. In addition, the HSP72 coinducer BGP-15, currently in human clinical trials for type 2 diabetes, also increased mitochondrial number and insulin sensitivity in a rat model of type 2 diabetes. Together, these data identify a novel role for activation of HSP72 in skeletal muscle. Thus, the increased oxidative metabolism associated with activation of HSP72 has potential clinical implications not only for type 2 diabetes but also for other disorders where mitochondrial function is compromised.

Improvement of insulin sensitivity by a novel drug candidate, BGP-15, in different animal studies

BACKGROUND

Insulin resistance has been recognized as the most significant predictor of further development of type 2 diabetes mellitus (T2DM). Here we investigated the effect of a heat shock protein (HSP) co-inducer, BGP-15, on insulin sensitivity in different insulin-resistant animal models and compared its effect with insulin secretagogues and insulin sensitizers.

METHODS

Insulin sensitivity was assessed by the hyperinsulinemic euglycemic glucose clamp technique in normal and cholesterol-fed rabbits and in healthy Wistar and Goto-Kakizaki (GK) rats in dose-ranging studies. We also examined the effect of BGP-15 on streptozotocin-induced changes in the vasorelaxation of the aorta in Sprague-Dawley rats.

RESULTS

BGP-15 doses of 10 and 30 mg/kg increased insulin sensitivity by 50% and 70%, respectively, in cholesterol-fed but not in normal rabbits. After 5 days of treatment with BGP-15, the glucose infusion rate was increased in a dose-dependent manner in genetically insulin-resistant GK rats. The most effective dose was 20 mg/kg, which showed a 71% increase in insulin sensitivity compared to control group. Administration of BGP-15 protected against streptozotocin-induced changes in vasorelaxation, which was similar to the effect of rosiglitazone.

CONCLUSION

Our results indicate that the insulin-sensitizing effect of BGP-15 is comparable to conventional insulin sensitizers. This might be of clinical utility in the treatment of T2DM.

Defects in the IFT-B component IFT172 cause Jeune and Mainzer-Saldino syndromes in humans

Intraflagellar transport (IFT) depends on two evolutionarily conserved modules, subcomplexes A (IFT-A) and B (IFT-B), to drive ciliary assembly and maintenance. All six IFT-A components and their motor protein, DYNC2H1, have been linked to human skeletal ciliopathies, including asphyxiating thoracic dystrophy (ATD; also known as Jeune syndrome), Sensenbrenner syndrome, and Mainzer-Saldino syndrome (MZSDS). Conversely, the 14 subunits in the IFT-B module, with the exception of IFT80, have unknown roles in human disease. To identify additional IFT-B components defective in ciliopathies, we independently performed different mutation analyses: candidate-based sequencing of all IFT-B-encoding genes in 1,467 individuals with a nephronophthisis-related ciliopathy or whole-exome resequencing in 63 individuals with ATD. We thereby detected biallelic mutations in the IFT-B-encoding gene IFT172 in 12 families. All affected individuals displayed abnormalities of the thorax and/or long bones, as well as renal, hepatic, or retinal involvement, consistent with the diagnosis of ATD or MZSDS. Additionally, cerebellar aplasia or hypoplasia characteristic of Joubert syndrome was present in 2 out of 12 families. Fibroblasts from affected individuals showed disturbed ciliary composition, suggesting alteration of ciliary transport and signaling. Knockdown of ift172 in zebrafish recapitulated the human phenotype and demonstrated a genetic interaction between ift172 and ift80. In summary, we have identified defects in IFT172 as a cause of complex ATD and MZSDS. Our findings link the group of skeletal ciliopathies to an additional IFT-B component, IFT172, similar to what has been shown for IFT-A.

Cardiovascular risk assessment in children with chronic kidney disease

Chronic kidney disease (CKD) is a major factor contributing to cardiovascular (CV) morbidity and mortality with the highest risk in patients on dialysis. An estimation of CV risk is important not only to identify potential modifiable risk factors but also to evaluate the effect of treatments aimed to reduce the risk. Non-invasive methods of measuring vascular changes and circulating biomarkers are available to assess the presence and severity of cardiovascular damage. These include measures of structural (carotid intima-media thickness and coronary artery calcification score) and functional (aortic pulse wave velocity, 24-h ambulatory blood pressure monitoring, ambulatory arterial stiffness index, heart rate variability and flow-mediated dilatation) changes in the vessel wall. In addition, a number of circulating biomarkers of vascular damage and its progression have been studied. Many of these tests are well validated as surrogate markers of future cardiovascular events and death in adult CKD patients, but need technical adaptation, standardization and validation for use in children. With our current state of knowledge, these are best reserved for research studies and scarce clinical resources may be better utilized for preventative strategies to reduce the modifiable risk factors for calcification from early CKD stages.

Synergic insulin sensitizing effect of rimonabant and BGP-15 in Zucker-obese rats

Abdominal obesity is referred for as a common pathogenic root of multiple risk factors, which include insulin resistance, dyslipidemia, hypertension, and a pro-atherogenic and pro-inflammatory state. Irrespective of its psychiatric side effects, rimonabant through blocking cannabinoid-1 receptor (CB1R) induces an increase in whole body insulin sensitivity. The aim of this work was to study the effect of selected doses of another insulin sensitizer compound BGP-15, and rimonabant on insulin resistance in Zucker obese rats with a promise of inducing insulin sensitization together at lower doses than would have been expected by rimonabant alone. We found that BGP-15 potentiates the insulin sensitizing effect of rimonabant. The combination at doses, which do not induce insulin sensitization by themselves, improved insulin signaling. Furthermore our results suggest that capsaicin-induced signal may play a role in insulin sensitizing effect of both molecules. Our data might indicate that a lower dose of rimonabant in the treatment of insulin resistance and type 2 diabetes is sufficient to administer, thus a lower incidence of the unfavorable psychiatric side effects of rimonabant are to be expected.

Cardiovascular risk assessment in children following kidney transplantation

CV diseases are the leading cause of death among patients with ESRD. RTX decreases the CV risk; however, it still remains definitely higher than that of the general population. Large multicenter and longitudinal studies are difficult to perform and hard end-points of CV events are usually missing among pediatric population. Thus, appropriate estimation of CV risk is of crucial importance to define the potential hazards and to evaluate the effect of treatments aimed to reduce the risk. A number of validated non-invasive methods are available to assess the extent of CV damage in adults, such as calcification scores, cIMT, aPWV, 24-h ABPM, AASI, and HRV; however, they need adaptation, standardization, and validation in pediatric studies. cIMT and PWV are the most promising methods, as pediatric normative values are already present. The up-to-date treatment of ESRD aims not only to save life, but to offer the patient a life expectancy approaching that of the healthy population and to ensure a reasonable quality of life.

The HSP co-inducer BGP-15 can prevent the metabolic side effects of the atypical antipsychotics

Weight gain and dysfunction of glucose and lipid metabolism are well-known side effects of atypical antipsychotic drugs (AAPD). Here, we address the question whether a heat-shock protein (HSP) co-inducer, insulin sensitizer drug candidate, BGP-15, can prevent AAPD-induced glucose, lipid, and weight changes. We also examined how an AAPD alters HSP expression and whether BGP-15 alters that expression. Four different experiments are reported on the AAPD BGP-15 interventions in a human trial of healthy men, a rodent animal model, and an in vitro adipocyte cell culture system. Olanzapine caused rapid insulin resistance in healthy volunteers and was associated with decreased level of HSP72 in peripheral mononuclear blood cells. Both changes were restored by the administration of BGP-15. In Wistar rats, weight gain and insulin resistance induced by clozapine were abolished by BGP-15. In 3T3L1 adipocytes, clozapine increased intracellular fat accumulation, and BGP-15 inhibited this process. Taken together, our results indicate that BGP-15 inhibits multiple metabolic side effects of atypical antipsychotics, and this effect is likely to be related to its HSP co-inducing ability.

Beneficial effect of the insulin sensitizer (HSP inducer) BGP-15 on olanzapine-induced metabolic disorders

Olanzapine is a widely used atypical antipsychotic, with well known metabolic side effects such as weight gain, insulin resistance and blood glucose abnormalities. It has been previously shown in a phase II clinical trial that BGP-15, an amidoxim derivative has insulin-sensitizing effects. The aim of this study was to investigate the efficacy of BGP-15 for the treatment of olanzapine-induced metabolic side effects, in healthy volunteers. Thirty-seven (37) subjects (ages 18-55 years) with normal glucose metabolism were randomly assigned to 17 days of once-daily treatment with 400mg of BGP-15 or placebo and 5mg of olanzapine for 3 days followed by 10mg for 14 days. Total body and muscle tissue glucose utilization was determined by hyperinsulinemic-euglycemic clamp technique. As expected the 17-day olanzapine treatment provoked insulin resistance and body weight gain (p<0.05) in both groups. Administration of BGP-15 significantly reduced olanzapine-induced insulin resistance. The protective effect of BGP-15 on insulin stimulated glucose utilization had the highest magnitude in the values calculated for the muscle tissue (p=0.002). In healthy individuals BGP-15 was safe and well tolerated during the whole study period. It is suggested that BGP-15 can be a successful insulin sensitizer agent to prevent side effects of olanzapine treatment.

Hypomorphic mutations in meckelin (MKS3/TMEM67) cause nephronophthisis with liver fibrosis (NPHP11)

BACKGROUND

Nephronophthisis (NPHP), a rare recessive cystic kidney disease, is the most frequent genetic cause of chronic renal failure in children and young adults. Mutations in nine genes (NPHP1-9) have been identified. NPHP can be associated with retinal degeneration (Senior-Løken syndrome), brainstem and cerebellar anomalies (Joubert syndrome), or liver fibrosis.

METHODS

To identify a causative gene for the subset of patients with associated liver fibrosis, the authors performed a genome wide linkage search in a consanguineous family with three affected patients using 50K SNP microarrays and homozygosity mapping.

RESULTS

The authors obtained a significant maximum parametric LOD (logarithm of odds) score of Z(max) = 3.72 on chromosome 8q22 and identified a homozygous missense mutation in the gene MKS3/TMEM67. When examining a worldwide cohort of 62 independent patients with NPHP and associated liver fibrosis we identified altogether four novel mutations (p.W290L, p.C615R, p.G821S, and p.G821R) in five of them. Mutations of MKS3/TMEM67, found recently in Meckel-Gruber syndrome (MKS) type 3 and Joubert syndrome (JBTS) type 6, are predominantly truncating mutations. In contrast, the mutations detected here in patients with NPHP and associated liver fibrosis are exclusively missense mutations. This suggests that they may represent hypomorphic alleles, leading to a milder phenotype compared with the more severe MKS or JBTS phenotype. Additionally, mutation analysis for MKS3/TMEM67 in 120 patients with JBTS yielded seven different (four novel) mutations in five patients, four of whom also presented with congenital liver fibrosis.

CONCLUSIONS

Hypomorphic MKS3/TMEM67 mutations cause NPHP with liver fibrosis (NPHP11). This is the first report of MKS3 mutations in patients with no vermian agenesis and without neurological signs. Thus NPHP, JBTS, and MKS represent allelic disorders.

Improvement of insulin sensitivity by a novel drug, BGP-15, in insulin-resistant patients: a proof of concept randomized double-blind clinical trial

The efficacy and safety of the new drug, BGP-15, were compared with placebo in insulin-resistant patients in a 28-day dose-ranging study. Forty-seven nondiabetic patients with impaired glucose tolerance were randomly assigned to 4 weeks of treatment with 200 or 400 mg of BGP-15 or placebo. Insulin resistance was determined by hyperinsulinemic euglycemic clamp technique and homeostasis model assessment method, and beta-cell function was measured by intravenous glucose tolerance test. Each BGP-15 dose significantly increased whole body insulin sensitivity (M-1, p=0.032), total body glucose utilization (M-2, p=0.035), muscle tissue glucose utilization (M-3, p=0.040), and fat-free body mass glucose utilization (M-4, p=0.038) compared to baseline and placebo. No adverse drug effects were observed during treatment. BGP-15 at 200 or 400 mg significantly improved insulin sensitivity in insulin-resistant, nondiabetic patients during treatment compared to placebo and was safe and well-tolerated. This was the first clinical study demonstrating the insulin-sensitizing effect of a molecule, which is considered as a co-inducer of heat shock proteins.

Mutations of NPHP2 and NPHP3 in infantile nephronophthisis

Nephronophthisis is an autosomal recessive chronic tubulointerstitial disease that progresses to end-stage renal disease (ESRD) in about 10% of cases during infancy. Mutations in the INVS (NPHP2) gene were found in a few patients with infantile nephronophthisis. Mutations of NPHP3, known to be associated with adolescent nephronophthisis, were found in two patients with early-onset ESRD. Here we screened 43 families with infantile nephronophthisis (ESRD less than 5 years of age) for NPHP2 and NPHP3 mutations and determined genotype-phenotype correlations. In this cohort there were 16 families with NPHP2 mutations and NPHP3 mutations in seven. Three patients carried only one heterozygous mutation in NPHP3. ESRD arose during the first 2 years of life in 16 of 18 patients with mutations in NPHP2, but in only two patients with mutations in NPHP3. Renal morphology, characterized by hyper-echogenic kidneys on ultrasound and tubular lesions with interstitial fibrosis on histology, was similar in the two patient groups. The kidney sizes were highly diverse and ultrasound-visualized cysts were present in a minority of cases. Extra-renal anomalies were found in 80% of the entire cohort including hepatic involvement (50%), cardiac valve or septal defects (20%) and recurrent bronchial infections (18%). We show that NPHP3 mutations in both infantile and adolescent nephronophthisis point to a common pathophysiological mechanism despite their different clinical presentations.

High NPHP1 and NPHP6 mutation rate in patients with Joubert syndrome and nephronophthisis: potential epistatic effect of NPHP6 and AHI1 mutations in patients with NPHP1 mutations

Joubert syndrome (JS) is an autosomal recessive disorder that is described in patients with cerebellar ataxia, mental retardation, hypotonia, and neonatal respiratory dysregulation. Kidney involvement (nephronophthisis or cystic renal dysplasia) is associated with JS in one fourth of known cases. Mutations in three genes--AHI1, NPHP1, and NPHP6--have been identified in patients with JS. However, because NPHP1 mutations usually cause isolated nephronophthisis, the factors that predispose to the development of neurologic involvement are poorly understood. In an attempt to identify such genetic determinants, a cohort of 28 families with nephronophthisis and at least one JS-related neurologic symptom were screened for mutations in AHI1, NPHP1, and NPHP6 genes. NPHP1 and NPHP6 homozygous or compound heterozygous mutations were found in 13 (46%) and six (21%) unrelated patients, respectively. Two of the 13 patients with NPHP1 mutations carried either a heterozygous truncating mutation in NPHP6 or a heterozygous missense mutation in AHI1. Furthermore, five patients with NPHP1 mutations carried the AHI1 variant R830W, which was predicted to be "possibly damaging" and was found with significantly higher frequency than in healthy control subjects and in patients with NPHP1 mutations without neurologic symptoms (five of 26 versus four of 276 and three of 152 alleles; P < 0.001 and P < 0.002, respectively). In contrast to the variable neurologic and milder retinal phenotype of patients with NPHP1 mutations, patients with NPHP6 mutations presented with a more severe neurologic and retinal phenotype. In conclusion, NPHP1 and NPHP6 are major genes of nephronophthisis associated with JS. Epistatic effects that are provided by heterozygous NPHP6 and AHI1 mutations and variants may contribute to the appearance of extrarenal symptoms in patients with NPHP1 mutations.

Effect of propranolol on heart rate variability in patients with end-stage renal disease: a double-blind, placebo-controlled, randomized crossover pilot trial

BACKGROUND

Low heart rate variability (HRV) is an independent risk factor of cardiac mortality in patients with end-stage renal disease (ESRD). It has been explained by uremic parasympathetic neuropathy. Sympathetic overactivity can also reduce HRV. Our aim was to determine whether there is vagal activity in ESRD patients that is masked by sympathetic activity.

METHODS

The effect of propranolol on HRV was examined in 13 patients with ESRD, aged 20.1 +/- 7.6 years without diabetes. All patients were given intravenous propranolol (0.05 mg/kg) once and placebo once in a randomized, double-blind way, with an interval of 6.6 days (mean, range: 2-9). Propranolol was administered before hemodialysis treatment, after 40 minutes supine resting period. HRV was registered for 10 minutes, during supine, before and after the injection. Patients' HRV data were compared to that of 29 age-matched healthy controls.

RESULTS

Initially, both high-(HFV) and low-frequency (LFV) bands of heart rate variability were lower in ESRD patients compared to controls (p < 0.001 for both). Propranolol resulted in a significant increase of HFV (propranolol: AlgHFV = 0.182 (0.027 - 0.337), placebo: deltalgHFV = -0.029 (-0.128 - +0.070); p = 0.032). Elevation of LFV was not significant. Six patients had an elevated plasma norepinephrine and/or epinephrine level. Plasma dopamine level was elevated in all but 1 patient (mean: 432 pmol/l, 95% CI: 320-543) and showed an inverse relationship with the increase of IgHFV secondary to propranolol (r = -0.66, p = 0.014).

CONCLUSIONS

Low HFV of ESRD patients can be improved by beta-adrenergic blockade. It demonstrates that there is some vagal activity in ESRD that is masked by sympathetic activity. Therefore, altered sympathovagal balance of ESRD patients should be taken into consideration in the assessment of vagal uremic neuropathy.

Autonomic dysfunction in uremia assessed by heart rate variability

Decreased heart rate variability is an independent risk factor for cardiac mortality in hemodialysis patients. Our aim was to determine whether it is already present in uremic children and young adults on hemodialysis and following renal transplantation. Twenty-two hemodialysis patients [age 17.2 years (median, quartiles 13.0-22.6)], 22 transplant patients [18.4 years (14.4-21.2)], and 29 healthy controls [16.4 years (15.7-21.1)] were examined. Heart rate and its high (HF) and low (LF) frequency variability were measured in the supine position for 10 min. High and low frequency variability was significantly reduced, whereas heart rate and LF/HF ratio was significantly elevated in both patient groups compared with controls. There was a clear-cut difference between the dialyzed and the transplanted groups based on the HF variability, with the lowest values in the dialysis group ( P<0.01). LF and LF/HF data did not allow us to distinguish between the patient groups. In conclusion, heart rate variability in the HF range is a sensitive tool for detecting cardiovascular autonomic dysfunction that is already present in children and adolescents with impaired kidney function.

BGP-15, a hydroximic acid derivative, protects against cisplatin- or taxol-induced peripheral neuropathy in rats

The neuroprotective effect of BGP-15 against peripheral sensory neuropathy was studied in rats that were exposed to short-term cisplatin or taxol administration. The changes of nerve conduction velocity were determined in situ after treating the Wistar rats with BGP-15 (50, 100, and 200 mg/kg po daily doses throughout the experiment), cisplatin (1.5 mg/kg ip daily dose for 5 days), or taxol (5.0 mg/kg ip daily dose every other day in a 10-day interval) alone or giving the test compound in combination with cisplatin or taxol. Electrophysiological recordings were carried out in vivo by stimulating the sciatic nerve at both sciatic notch and ankle site. Neither motor nor sensory nerve conduction velocity was altered by any dose level of BGP-15 tested. Both anticancer drugs decreased the sensory nerve conduction velocity (SNCV). BGP-15 treatment prevented the impairment of SNCV either in part or totally in the cisplatin- or taxol-treated groups. This neuroprotective potential of BGP-15 could be well correlated with its recently described poly(ADP-ribose) polymerase- inhibitory effect and its ability to protect against the damages induced by the increased level of reactive oxygen species in response to anticancer treatment.

Evaluation of the tyrosine kinase domain of the Met proto-oncogene in sporadic ovarian carcinomas*

Most of the ovarian cancers originate from the ovarian surface epithelium derived from the coelomic mesothelium. The Met proto-oncogene encodes a transmembrane tyrosine kinase receptor (Met) that has the capacity to regulate cell proliferation and differentation and it is activated by hepatocyte growth factor. Trisomy of chromosome 7 and Met protein overexpression have been were observed in ovarian carcinomas, the papillary renal cancers and other solid tumors. Frequent mutations of Met proto-oncogene have been found in hereditary papillary renal cancer (HPRC) and most of the mutations are located in the tyrosine kinase domain. The aim of this study to perform a mutation analysis of exons 17 19 of Met proto-oncogene in epithelial ovarian tumors (EOTs). We have examined 24 tumor samples from patients, operated with EOTs. Mutation was detected in exon 18 in only one sample of 24 EOTs. Our results indicate that mutations located in the Met proto-oncogene is not a common event in EOT. It is not clear whether the mutation plays a role in the tumorigenesis or progression of EOT or not.

Clinical relevance of immunohistochemical expression of p53-targeted gene products mdm-2, p21 and bcl-2 in breast carcinoma

The present study was designed to investigate the clinical/prognostic relevance of immunohistochemical expression of p53-targeted genes mdm-2, p21WAF1 and bcl-2 alone and in combination with p53 for the indirect assessment of p53 gene status in breast cancer. 141 archival breast carcinomas were immunostained, and the putative mutational status of the p53 gene was defined in 21 of them, as a control for immunohistochemistry, using the polymerase chain reaction single-strand conformational polymorphism (PCR-SSCP) analysis. Genetic changes of p53 correlated significantly with p53 protein overexpression (p = 0.01) but did not do so with any of the related molecules. Immunohistochemical p53 status was directly correlated with mdm-2 (p = 0.0001), p21 (p = 0.0004) and inversely with bcl-2 (p = 0.005) expression. bcl-2 proved to be an independent marker of prognosis, p53 only in the group of node-positive carcinomas, whereas bcl-2-/p53+ tumours revealed the worst prognosis. Mdm-2 and p21 expression was of prognostic significance neither alone nor in combination. We conclude that the detection of down-stream regulators of p53 does not increase the efficacy of immunohistochemistry in assessing the functional status of p53 in breast cancer; however, their combined analysis may help to select subgroups of patients at the extremes of risk for recurrence, or those with greater chances for survival.

Signs of autonomic neuropathy in childhood uremia

To evaluate the presence of autonomic neuropathy in childhood uremia, cardiovascular autonomic reflexes were examined in children with chronic renal failure. Cardiovascular autonomic reflexes of 10 uremic patients on chronic dialysis and 10 transplanted patients were compared to assess the effect of transplantation on autonomic neuropathy. Resting heart rate, heart rate changes induced by deep breathing, by Valsalva maneuver, and following standing up, and blood pressure change induced by handgrip test were examined. Of the 10 uremic children, 4 showed early involvement and 2 had definite involvement of autonomic neuropathy. Only 1 of the 10 transplanted patients showed early signs of autonomic neuropathy. Autonomic tests demonstrated predominantly parasympathetic dysfunction. In conclusion, cardiovascular autonomic neuropathy is not rare in children and adolescents and young adults with chronic renal failure. In contrast, the prevalence is very low in transplanted patients with similar uremic precedents. Efforts should be made to prevent or delay this uremia-related complication.

Monitoring cardiovascular changes during hemodialysis in children

Hemodialysis (HD) causes rapid volume shifts and circulatory changes. In chronic renal failure (CRF) Na+/K+ATP-ase is depressed, whereas endogenous digoxin-like factor (EDLF) is elevated. Our aim was to characterize HD-induced cardiovascular adaptation and its possible links to Na+/K+ATP-ase and EDLF. Eleven children with CRF on HD (aged 14.7 +/- 3.7 years) and 11 healthy children were investigated for basic circulatory parameters. Thoracic impedance (Zo) and circulatory parameters were monitored by impedance cardiography (ICG) during HD. Erythrocyte Na+/K+ATP-ase and EDLF were measured before and after HD. Up to the loss of 6% of total body weight, Zo rose linearly with fluid removal, above this no further increase occurred. Heart rate and mean arterial pressure (MAP) were inversely related (r = -0.97); MAP rose in the first and decreased in the second part of HD. Systemic vascular resistance paralleled MAP, whereas stroke volume rapidly decreased, but stabilized in the second part of HD. The ratio of preejection period/ventricular ejection time (PEP/VET) correlated positively with HD duration (r = 0.92), suggesting diminished cardiac filling. Cardiac index (CI) remained stable. EDLF was high in uremia accompanied by depressed Na+/K+ATP-ase (P < 0.05 and P < 0.01, respectively). Following HD Na+/K+ATP-ase normalized. Correlation between Na+/K+ATP-ase activity and MAP was linear (r = 0.85). In conclusion, ICG during HD provides detailed information concerning circulatory adaptation resulting in stable CI, suggesting that the dialysis-induced hypovolemia is compensated by the centralization of the blood volume. Changes of Na+/K+ATP-ase indicate that dialyzable blood pressure-regulating substance(s) inhibit(s) the pump. However, lack of further correlation between Na+/K+ATP-ase, EDLF, and cardiovascular parameters indicates the complexity of the regulatory processes.

Analysis of p53 mutation and cyclin D1 expression in breast tumors

P53 and cyclin D1 are interacting regulatory genes and both are frequently altered in breast cancer. We analysed p53 mutation by SSCP and sequencing methods as well as p53 protein accumulation immunohistochemically in 34 consecutively operated breast tumors. None of 4 fibroadenomas revealed p53 mutation or p53 protein accumulation. Mutation of p53 was present in 7 carcinomas. Immunohistochemistry revealed accumulation of p53 protein in 6 carcinomas and there was a significant correlation between p53 mutation and protein accumulation. Overexpression of cyclin D1 protein was observed in 11 carcinomas by immunohistochemistry and no correlation was observed between cyclin D1 overexpression and p53 mutation or accumulation. Our data support the concept that the p53-cyclin D1 signal pathway and the cyclin D1 cascade are disregulated in breast cancer.

Diagnostic relevance of chromosomal in-situ hybridization in Merkel cell carcinoma: targeted interphase cytogenetic tumour analyses

AIMS

To resolve the conflicting diagnoses of five pathologists (which included well-differentiated neuroendocrine carcinoma, malignant carcinoid, undifferentiated small-cell carcinoma, primitive neuroectodermal tumour, metastases of small-cell lung carcinoma (SCLC) and Merkel cell carcinoma (MCC)), and tumour-free lungs after necropsy, we investigated an alarmingly metastasizing MCC in a 32-year-old Caucasian man using chromosomal in-situ hybridization (CISH). Differences in incidence and course in males and females also prompted targeted analyses for chromosomes X and Y. The lesion was also analysed for p53 gene mutations.

METHODS AND RESULTS

Paraffin sections of the thorax, buccal lymph nodes and scalp tumours were stained with haematoxylin and eosin. Immunohistochemistry was performed with antibodies against pancytokeratin, keratin 20, neuron-specific enolase (NSE), chromogranin, neurofilaments and vimentin, among others. Sections (5-6 microm) of the tumours were analysed with alpha-satellite probes for chromosomes 1, 6, 7, 11, 12, 17, 18, X and Y using CrSH; and exons 5-9 of the p53 gene were examined by polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP) methods. Although positive for pancytokeratin, keratin 20, chromogranin, NSE, synaptophysin and vimentin, the similarity in antigen profiles expressed by SCLC and MCC prevented a definitive tumour diagnosis. Chromosomal in-situ hybridization, however, revealed trisomies 1 and 11, two frequent aberrations in MCC, and trisomy 18. Moreover, 71% of the tumour cells had two to three copies of X, whereas 98% of the cell nuclei in the hair follicles and normal epidermis (purported Merkel cell origins) displayed one X chromosome. No mutations were detected in the five exons of the p53 gene examined.

CONCLUSIONS

Had CISH been performed earlier, treatment may have been tailored specifically to suit MCC, since MCC and SCLC have different therapeutic strategies. Finally, chromosome X may be of prognostic relevance in MCC, which apparently predominates in females and yet shows poorer prognosis in males, and hence be worthy of further investigation.