Sevim Gönen

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.

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.

CTLA-4 +49 A/G genotype and HLA-DRB1 polymorphisms in Turkish patients with Henoch–Schönlein purpura

The pathogenesis of Henoch–Schönlein purpura (HSP) remains unknown; however, it is generally considered to be an immune complex-mediated disease. Cytotoxic T lymphocyte-associated protein 4 (CTLA-4) is expressed on activated T cells, and, thus, it is critically involved in the immune response. We aimed to investigate the possible influence of CTLA-4 polymorphisms for susceptibility to HSP and determine if there were associations with human leukocyte antigen (HLA)-DRB1 genotypes. Using polymerase chain reaction-based DNA genotyping, we investigated the polymorphisms located in the genes encoding CTLA-4 in 100 patients with HSP and 156 ethnically matched healthy controls. When CTLA-4 +49 A/G polymorphism of HSP patients and control group was compared, no associations with joint, gastrointestinal or renal manifestations, or susceptibility to HSP, were observed. However, patients with nephrotic proteinuria had higher HLA-DRB1*13 positivity [odds ratio (OR) = 3.76, 95% confidence interval (95%CI) = 1.25–11.23, P = 0.025]. When the patients were stratified according to CTLA-4 polymorphism, a significant association between nephrotic proteinuria patients and carriage of the AG genotype was also found (OR = 15.42, 95%CI = 1.59–148.82, P = 0.008). These results suggested that CTLA-4 +49 A/G polymorphism does not contribute to susceptibility to HSP; however, the presence of CTLA-4 AG genotype and HLA-DRB1*13 could be a risk factor for developing nephrotic-range proteinuria in these patients.

Vitamin D receptor gene polymorphism in hypercalciuric children

Idiopathic hypercalciuria is a complex disease resulting from an interaction between environmental and genetic factors. Recently, the relationship between vitamin D receptor (VDR) alleles and calcium homeostasis has been investigated. This study was conducted to explore the association of VDR gene polymorphism with the risk of absorptive hypercalciuria (AH). We investigated the VDR gene polymorphisms, ApaI, BsmI, and TaqI, in relation to intact parathormone (PTH), osteocalcin, and 25-hydroxyvitamin D in 80 children (42 males, 38 girls) with AH and in 86 healthy children without hypercalciuria. A significant difference in the ApaI genotype was observed between the AH group and the control group (χ2=7.21, P=0.027). The AA genotype was associated with a 3.5-fold increased risk for idiopathic hypercalciuria compared with the Aa/aa genotype (odds ratio 3.5, 95% confidence interval 1.1–11). The BsmI and TaqI polymorphisms did not show any significant association with AH. Serum osteocalcin levels were significantly higher in the group with the AA genotype compared with those with the Aa or aa genotype (P=0.02, P=0.05, respectively). The results indicate that the ApaI AA genotype of the VDR gene is not only associated with AH but is also related to differences in serum osteocalcin.

Angiotensinogen and plasminogen activator inhibitor-1 gene polymorphism in relation to chronic allograft dysfunction

Abstract:  Chronic allograft dysfunction (CAD) is the most common cause of allograft failure in the long‐term, and current immunologic strategies have little effect on this condition. The renin‐angiotensin system (RAS) plays important roles progression of chronic renal disease. It is thought that plasminogen activator inhibitor‐1 (PAI‐1) functions in the RAS, in addition to involvement in thrombotic risk and fibrosis. This study investigated possible links between angiotensinogen (AGT) genotypes (M235T/MM, MT, TT) and PAI‐1 genotypes (4G4G, 4G5G, 5G5G) and CAD assessments of both types of polymorphism were performed in 82 renal allograft recipients. One hundred healthy subjects were also investigated for AGT polymorphism, and 80 healthy subjects for PAI‐1 polymorphism. Genotypes were determined using polymerase chain reaction (PCR) sequence‐specific primers, and PCR followed by restriction fragment length polymorphism analysis. Kidney recipients with CAD had significantly lower frequencies of the MM genotype and the M allele than the recipients without CAD (p < 0.05 and <0.001). The transplant recipients with CAD also had significantly lower frequencies of the 5G5G genotype and the 5G allele than those without CAD (p < 0.001 and <0.05). Determination of AGT M235T and PAI‐1 genotypes prior to transplantation may help identify patients who at risk for chronic renal transplant dysfunction.

Osteoprotegerin and RANKL Serum Levels and Their Relationship with Serum Ghrelin in Children with Chronic Renal Failure and on Dialysis

Background: Osteoprotegerin (OPG) and receptor activator of the nuclear factor ĸB ligand (RANKL) constitute a complex system of mediators involved in the regulation of bone resorption process. Ghrelin, a growth hormone secretagogue, has been shown to modulate proliferation and differentiation of osteoblasts. The present study was carried out to evaluate the serum concentrations of OPG and sRANKL in children with chronic renal impairment (CRI) and on dialysis, and to establish a possible relationship between their serum levels and that of ghrelin. Methods: 33 patients including 10 patients with CRI, 12 peritoneal dialysis (PD) and 11 hemodialysis (HD) patients and 22 healthy controls were enrolled into the study. OPG, sRANKL and ghrelin levels were studied with radioimmunoassay. Results: Serum OPG levels in CRI, PD and HD groups were significantly higher than the healthy controls (p = 0.002, p < 0.001, p < 0.001, respectively) whereas sRANKL levels were significantly lower than the healthy controls (p = 0.03, p = 0.01, p = 0.001, respectively). Ghrelin levels were significantly higher in CRI, PD and HD groups compared to healthy controls (p = 0.001, p < 0.001, p < 0.001, respectively). We observed a negative correlation between the sRANKL and OPG levels (r = –0.27, p = 0.04) as well as between sRANKL and ghrelin levels (r = –0.31, p = 0.02). OPG levels showed a positive correlation with ghrelin levels (r = 0.63, p < 0.001). Conclusion: We found a lower RANKL bioactivity index in children with CRI and on dialysis. The mechanism and the role of elevated OPG and low sRANKL in uremia are unclear, but they might partly represent a compensatory mechanism to the negative balance of bone remodeling in renal bone disease in children. Additionally, we demonstrated for the first time that ghrelin and the RANKL/OPG system have a close relationship in CRF. Therefore, ghrelin may be of importance in mediating the effects of the RANKL/OPG system in renal bone disease.

Immunogenicity of hepatitis A vaccine in children with celiac disease.

Objectives: The response to hepatitis A vaccine has not been studied in children with celiac disease (CD). The aim of the present study was to evaluate the immunogenicity of an inactivated hepatitis A virus (HAV) vaccine and the effect of the human leukocyte antigen (HLA) type on immunogenicity in children with CD. Patients and Methods: Thirty-three patients with CD and 62 healthy controls were enrolled in the study. Inactivated HAV vaccine (Havrix; GlaxoSmithKline Biologicals, Rixensart, Belgium) containing 720 enzyme-linked immunosorbent assay units of alum-adsorbed hepatitis A antigen was administered intramuscularly in a 2-dose schedule at 0 and 6 months. Seroconversion rates and antibody titers of HAV were measured at 1 and 7 months. Results: At 1 month, seroconversion rates were 78.8% and 77.4% and geometric mean titers were 50.7 and 49.9 mIU/mL in the CD and control groups, respectively (P > 0.05). At 7 months, seroconversion rates were 97% and 98.4% and geometric mean titers were 138.5 and 133 mIU/mL in the CD and control groups, respectively (P > 0.05). The most frequent HLA types were HLA-DQ2, -DR3, and -DR7 alleles in patients with CD and HLA-DQ3, -DQ6, -DR11, and -DR14 in the controls. There was no association between HLA alleles and antibody titers of hepatitis A vaccine. Conclusion: Children with CD have a good immune response to hepatitis A vaccine, similar to healthy controls.

Angiotensinogen and Plasminogen Activator Inhibitor-1 Gene Polymorphism in Relation to Renovascular Disease

The present study was designed to evaluate angiotensinogen (AGT) M235T and plasminogen activator inhibitor-1 (PAI-1) (4G/5G) polymorphisims in relation to the occurrence of atherosclerotic renal artery stenosis (ARAS) and recurrent stenosis. In this study, 30 patients were enrolled after angiographic demonstration of ARAS; 100 healthy subjects for AGT polymorphism and 80 healthy subjects for PAI-1 polymorphism were considered the control group. The patients were followed for a mean 46.1 ± 9.2 months. The patients had significantly higher frequencies of the MT genotype and the T allele than control group (χ2 = 18.2, p < 0.001 and χ2 = 11.5 p < 0.001). There were no significant differences in the PAI-1 genotype and allele findings when the data for all patients were compared with that for the controls (χ2= 2.45, p = 0.29 and χ2 = 0.019, p = 0.89). There were no significant differences in the genotype and allele findings for the patients with and without restenosis (p > 0.05). The C-reactive protein (CRP) level was higher in the patients with restenosis than in the patients without restenosis (7.694 ± 0.39 mg/L and 1.56 ± 1.08 mg/L) (p = 0.001). Our results suggest that the M235T MT genotype and T allele might be associated with increased risk of atherosclerotic renal artery stenosis. The CRP level might be an independent predictor for recurrent stenosis.

The association of cytokine gene polymorphism with reflux nephropathy

OBJECTIVE To identify genetic risk factors for the progression of vesicoureteral reflux (VUR) to reflux nephropathy, we examined polymorphisms of multiple cytokine genes among VUR patients with or without renal scarring. METHODS A total of 238 VUR patients aged between 1 and 18 years with (n = 113) or without renal scarring (n = 125) were included. The presence of renal scarring was demonstrated by renal parenchymal examination using Technetium-99m dimercaptosuccinate scintigraphy. Sera of the patients were examined for tumor necrosis factor-alpha (TNF-α, -308), transforming growth factor-beta1 (TGF-β1, +869, +915), interleukin-6 (IL-6, -174), interleukin-10 (IL-10, -1082, -819, -592) and interferon-gamma (IFN-γ, +874) gene polymorphisms using the polymerase chain reaction sequence-specific primer method. RESULTS Among patients with renal scarring, frequencies for the T/T G/C and C/C G/C genotypes of TGF-β1 gene (p = 0.003), GCC/GCC genotype of IL-10 gene (p = 0.015), GC phenotype of IL-6 gene (p = 0.001) and T/T genotype of IFN-γ gene (p = 0.001) were higher compared to patients without renal scarring. Regarding the TNF-α gene, among patients with low grade VUR only, the G/G genotype was associated with an increased risk. CONCLUSIONS Certain genotypes of cytokine gene polymorphisms seem to be associated with an increased or decreased susceptibility to reflux nephropathy, which may explain why only a proportion of VUR patients progress to reflux nephropathy. This information may aid in prediction of prognosis and implementing more aggressive management strategies at earlier stages. Further immunogenetic studies may identify novel targets for the management and prevention of the condition.