Effects of Genetic Polymorphisms of the Renin-Angiotensin System in Children with Nephrotic Syndrome

Biomarkers in Primary Focal Segmental Glomerulosclerosis in Optimal Diagnostic-Therapeutic Strategy

Focal segmental glomerulosclerosis (FSGS) involves podocyte injury. In patients with nephrotic syndrome, progression to end-stage renal disease often occurs over the course of 5 to 10 years. The diagnosis is based on a renal biopsy. It is presumed that primary FSGS is caused by an unknown plasma factor that might be responsible for the recurrence of FSGS after kidney transplantation. The nature of circulating permeability factors is not explained and particular biological molecules responsible for inducing FSGS are still unknown. Several substances have been proposed as potential circulating factors such as soluble urokinase-type plasminogen activator receptor (suPAR) and cardiolipin-like-cytokine 1 (CLC-1). Many studies have also attempted to establish which molecules are related to podocyte injury in the pathogenesis of FSGS such as plasminogen activator inhibitor type-1 (PAI-1), angiotensin II type 1 receptors (AT1R), dystroglycan(DG), microRNAs, metalloproteinases (MMPs), forkheadbox P3 (FOXP3), and poly-ADP-ribose polymerase-1 (PARP1). Some biomarkers have also been studied in the context of kidney tissue damage progression: transforming growth factor-beta (TGF-β), human neutrophil gelatinase-associated lipocalin (NGAL), malondialdehyde (MDA), and others. This paper describes molecules that could potentially be considered as circulating factors causing primary FSGS.

Effect of angiotensin converting enzyme gene I/D polymorphism in South Indian children with nephrotic syndrome

Nephrotic syndrome is one of the most common childhood kidney diseases. It is mostly found in the age group of 2 to 8 years. Around 10%–15% of nephrotic syndrome cases are non-responders of steroid treatment (SRNS). Angiotensin converting enzyme (ACE) (I/D) gene association studies are important for detecting kidney disease and herein we assessed the association of ACE (I/D) polymorphism with nephrotic syndrome in South Indian children. We recruited 260 nephrotic syndrome (162 boys and 98 girls) and 218 (140 boys and 78 girls) control subjects. ACE I/D polymorphism was analyzed by PCR using genotype allele specific primers. In ACE (I/D), we did not find significant association for the ungrouped data of nephrotic syndrome children and the control subjects. Kidney biopsies were done in 86 nephrotic syndrome cases (minimal change disease, n=51; focal segmental glomerulosclerosis, n=27; diffuse mesangial proliferation, n=8). We segregated them into the minimal change disease / focal segmental glomerulosclerosis groups and observed that the ACE ‘D’ allele was identified with borderline significance in cases of focal segmental glomerulosclerosis and the ‘I’ allele was assessed as having very weak association in cases of minimal change disease. ‘II’ genotype was weakly associated with minimal change disease. Gender specific analysis revealed weak association of ‘ID’ genotype with female nephrotic syndrome in females. Dominant expression of DD genotype was observed in males with nephrotic syndrome. Our finding indicated that ACE (I/D) has moderate association with focal segmental glomerulosclerosis. However, due to the limited number of biopsy proven focal segmental glomerulosclerosis subjects enrolled, further studies are required to confirm these results.

Angiotensin-Converting Enzyme Gene Polymorphism in Children with Idiopathic Nephrotic Syndrome, Effect on Biopsy Findings

OBJECTIVE

Angiotensin converting enzyme (ACE) converts angiotensin I into angiotensin II. The ACE gene shows an I/D polymorphism, which correlates with ACE concentrations. The aim of this study is to evaluate the distribution of the ACE I/D genotype in children with idiopathic nephrotic syndrome (INS) and healthy controls and study the effect of this polymorphism on clinical and pathologic findings.

METHODS

ACE gene I/D polymorphism of 104 patients with INS and 119 controls were determined.

RESULTS

The DD, ID, and II genotypes were found in 58.7%, 22.1%, and 19.2% of the patients, and in 79.8%, 2.5%, and 17.6% of controls, respectively (p > 0.05). The ID genotype was seen more frequently in patients resistant to treatment.

CONCLUSION

The observed differences with previous reports suggest the influence of the genetic background on disease course. The ACE I/D gene polymorphism's role seems to be more important in renal disease progression than susceptibility.

Angiotensin-converting enzyme genotype is not a significant genetic risk factor for idiopathic nephrotic syndrome in Croatian children

AIM

The association of the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism with idiopathic nephrotic syndrome (INS) is controversial. Only scarce information on European populations is available. The aim of the study was to investigate the distribution of the ACE gene I/D polymorphism and its impact on INS in children from Croatia.

MATERIALS AND METHODS

Ninety-five children with INS were investigated: 30 with minimal change disease (MCD), 35 with mesangial proliferative glomerulonephritis (MesPGN) and 30 with focal segmental glomerulosclerosis (FSGS). The control group consisted of 73 healthy adults. ACE gene was analyzed using the PCR method. The results were correlated with clinical features, renal morphology and response to immunosuppresive therapy.

RESULTS

There was no correlation of ACE genotype with gender, age of the disease onset, level of proteinuria, presence of hematuria or hypertension, and GFR at onset of the disease. No statistically significant differences in ACE genotype or allele frequencies between the controls and whole group of patients, MCD group, MesPGN group, FSGS group, steroid sensitive (SS) patients, steroid resistant (SR) patients, as well as each other, were found, although DD genotype tended to be more frequent in FSGS patients, SR patients, and frequent relapsers. Among 11 children treated with cyclophosphamide the D allele was significantly higher among non-responders (p = 0.003).

CONCLUSION

DD genotype is not a genetic risk factor for acquiring INS nor significant phenotype modifier regarding to clinical and pathohistological picture and response to steroids in Croatian children. The potential application of ACE genotyping in predicting cyclophosphamide response deserves further investigation.

The role of genetic polymorphisms of the Renin-Angiotensin System in renal diseases: A meta-analysis

Renal failure has a complex phenotype resulting from an underlying kidney disease as well as environmental and genetic factors. In the present study we performed a systematic review and meta-analyses to evaluate the association of the A1166C polymorphism of Angiotensin II type 1 Receptor gene (AGTR1) with Chronic Kidney Disease (CKD), End Stage Renal Disease (ESRD), IgA Nephropathy (IgAN) and Vesicoureteral Reflux (VUR) as well as the association of A1332G polymorphism of Angiotensin II type 2 Receptor (AGTR2) gene with Vesicoureteral Reflux (VUR). We found that neither AGTR1 Α1166C, nor AGTR2 A1332G polymorphisms were significantly associated with any of the aforementioned renal diseases, suggesting that they cannot be used as predictive markers in either general or subgroup ethnic populations.

Impact of interaction of cigarette smoking with angiotensin-converting enzyme polymorphisms on end-stage renal disease risk in a Han Chinese population

BACKGROUND

Several polymorphisms in the angiotensin-converting enzyme (ACE) and ACE2 genes are associated with the development of end-stage renal disease (ESRD). Certain genetic polymorphisms may modify the deleterious effects of environmental factors such as cigarette smoking and may also modify the inherited risk. We investigated the association of six ACE and ACE2 polymorphisms with ESRD to determine whether a relationship exists between gene-smoking interactions and ESRD.

MATERIALS AND METHODS

We performed a case-control association study and genotyped 683 ESRD patients and 653 healthy controls. All subjects were genotyped for ACE (I/D, G2350A and A-240T) and ACE2 (G8790A, A1075G and G16854C) gene polymorphisms by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

Significant associations were observed between ACE I/D and G2350A polymorphisms and ESRD. There was no difference in ACE2 genotype distribution between ESRD patients and healthy controls. Haplotype analysis showed that DAA and DAT haplotypes were risk factors for ESRD. Moreover, a gene-environment interaction was observed between ACE I/D polymorphism and cigarette smoking.

CONCLUSION

ACE I/D and ACE G2350A polymorphisms were associated with the development of ESRD. The interaction between ACE I/D polymorphism and smoking is also associated with an enhanced risk of ESRD.

Polymorphisms of the MDR1 and MIF genes in children with nephrotic syndrome

Oral steroid treatment is the first line of therapy for childhood nephrotic syndrome (NS). Nonetheless, some patients are resistant to this treatment. Many efforts have been made to explain the differences in the response to steroid treatment in patients with NS based on the genetic background. We have investigated single nucleotide polymorphisms of the MDR1 [C1236T (rs1128503), G2677T/A (rs2032582), and C3435T (rs1045642)] and MIF (G-173C, rs755622) genes in 170 children with NS. Of these children, 69 (40.6%) were initial steroid non-responders, and 23 (13.5% of total) developed chronic kidney disease. Renal biopsy findings, which were available for 101 patients, showed that 35 patients had minimal change lesion and 66 had focal segmental glomerulosclerosis. The frequencies of the MDR1 1236 CC (18.8 vs 7.2%) or TC (53.5 vs 43.5%) genotype and C allele (45.5 vs 29.0%) were significantly higher in the initial steroid responders than in the non-responders. Analysis of MDR1 three-marker haplotypes revealed that the frequency of the TGC haplotype was significantly lower in the initial steroid responders than in the non-responders (15.8 vs 29.0%). There was no association between the MIF G-173C polymorphism and clinical parameters, renal histological findings, and steroid responsiveness. These data suggest that the initial steroid response in children with NS may be influenced by genetic variations in the MDR1 gene.

Association of angiotensin converting enzyme insertion/deletion gene polymorphism with idiopathic nephrotic syndrome susceptibility in children: a meta-analysis

Background and objective: Angiotensin converting enzyme (ACE) gene contains either an insertion (I) allele or a deletion (D) allele forming three potential genotypes: II, ID and DD. The D allele or DD genotype has been reported to be associated with higher plasma ACE level. An assessment of the association between ACE I/D gene polymorphism and idiopathic nephrotic syndrome (INS) susceptibility in children is still controversial. This meta-analysis was performed to evaluate the association between ACE I/D gene polymorphism and the onset of INS.

Method: A predefined literature search and selection of eligible relevant studies were performed to collect data from electronic databases, and eligible investigations were synthesized using the meta-analysis method.

Results: Nine investigations were identified for the analysis of association between ACE I/D gene polymorphism and INS risk in children, including six in Asians, one study for Caucasians and two for Africans. There was positive association between D allele or DD genotype and INS susceptibility in Asians (OR = 1.75, p = 0.01; OR = 2.01, p = 0.02), but not for Caucasian children and Africans (for Caucasians, D: OR=1.35, p = 0.27, DD: OR = 0.95, p = 0.91; for Africans, D: OR = 1.70, p = 0.56, DD: OR = 1.60, p = 0.73). Furthermore, II homozygous seemed to play a positive role against INS onset for Asians (OR = 0.59, p = 0.02), but the link between II genotype and INS risk was not observed in Caucasian children and Africans (Caucasians: OR = 0.31, p = 0.06; Africans: OR = 0.50, p = 0.59).

Conclusions: D allele and DD homozygous might become significant genetic molecular markers for INS susceptibility in Asian children, but the association was not observed in Caucasians or Africans. However, the conclusion from our study cannot be sustained and more investigations on larger sample in different populations are required to further clarify the role of D allele or DD homozygous in the onset of INS in difference races.

Angiotensin-converting enzyme (ACE), angiotensinogen (AGT), and angiotensin II type 1 receptor (AT1R) gene polymorphisms in generalized aggressive periodontitis

AIM

Host response to periodontopathic microorganisms can be modulated by genetic factors. Accumulated evidence highlighted the role of renin-angiotensin system (RAS) in inflammatory response thus potential implication of this molecular system in the pathogenesis of periodontitis can be suggested. The present study investigated common genetic variants of molecules within the RAS family namely angiotensin-converting enzyme (ACE), angiotensinogen (AGT) and angiotensin II type 1 receptor (AT1R) in relation to generalized aggressive periodontitis (G-AgP).

METHODS

DNA was obtained from peripheral blood of 103 G-AgP patients and 100 periodontally healthy subjects. ACE I/D, AGT M235T and AT1R A1166C polymorphisms were genotyped by polymerase chain reaction and restriction fragment length polymorphism method. Chi-square, ANOVA and logistic regression were used in statistical analyses.

RESULTS

Both ACE I/D and AT1R polymorphisms were similar in G-AgP and healthy groups (p>0.05). G-AgP subjects exhibited decreased AGT TT genotype and T allele frequency as compared to healthy subjects (p<0.05). The same trend was also observed in the nonsmoker subgroup regarding investigated RAS polymorphisms.

CONCLUSIONS

Present findings suggest that AGT M235T TT genotype and T allele might be associated with decreased risk for G-AgP in Turkish population.

Angiotensin II type 1 receptor polymorphisms and susceptibility to hypertension: a HuGE review

The angiotensin II type 1 receptor (AGTR1) plays an integral role in blood pressure control, and is implicated in the pathogenesis of hypertension. Polymorphisms within this gene have been extensively studied in association with hypertension; however, findings are conflicting. To clarify these data, we conducted a systematic review of association studies of AGTR1 polymorphisms and hypertension, and performed a meta-analysis of the rs5186 variant. Results show that the currently available literature is too heterogeneous to draw meaningful conclusions. The definition of hypertension and gender composition of individual studies helps to explain this heterogeneity. Although the structure and splicing pattern of AGTR1 would suggest a likely effect of polymorphisms within the promoter region on gene function, few studies have been conducted thus far. In conclusion, there is insufficient evidence that polymorphisms in the AGTR1 gene are risk factors for hypertension. However, most studies are inadequately powered, and larger well-designed studies of haplotypes are warranted.