ACE gene polymorphism and IgA nephropathy: an ethnically homogeneous study and a meta-analysis

The Influence of ACE Insertion/Deletion Gene Polymorphism on the Risk of IgA Nephropathy: A Debatable Topic

Background

The connection between angiotensin-converting enzyme insertion/deletion (ACE I/D) gene polymorphisms and IgA nephropathy (IgAN) was conflicting. This pooled analysis was performed to explore this issue.

Methods

All eligible investigations were identified from various electronic databases, and the pooled analysis was evaluated using Stata software.

Results

27 studies with 2538 IgAN cases and 3592 controls were included. In overall subjects, ACE D allele, DD, and II genotype were associated with IgAN susceptibility (D vs. I: OR = 1.21, 95% CI: 1.10–1.32, P < 0.001; DD vs. ID + II: OR = 1.38, 95% CI: 1.20–1.60, P < 0.001; and II vs. DD + ID: OR = 0.83, 95% CI: 0.73–0.95, P=0.007). In Asian and Chinese patients, ACE I/D gene polymorphism was also correlated with IgAN vulnerability. Moreover, ACE D allele, DD, and II genotype were correlated with the progression of IgAN (D vs. I: OR = 1.37, 95% CI: 1.09–1.73, P=0.008; DD vs. ID + II: OR = 1.57, 95% CI: 1.06–2.31, P=0.024; and II vs. DD + ID: OR = 0.69, 95% CI: 0.49–0.99, P=0.045). Conversely, in Caucasian subjects, there was no link between ACE I/D gene polymorphism and the risk of IgAN.

Conclusion

ACE I/D gene polymorphism was correlated with the vulnerability and progression of IgAN in Asian and Chinese patients, and ACE D allele and DD homozygote genotype could be adverse factors for IgAN, while the II homozygote genotype could be an advantage factor. But, no significant association was found between ACE I/D gene polymorphism and IgAN in Caucasians.

A New Vision of IgA Nephropathy: The Missing Link

IgA Nephropathy (IgAN) is a primary glomerulonephritis problem worldwide that develops mainly in the 2nd and 3rd decade of life and reaches end-stage kidney disease after 20 years from the biopsy-proven diagnosis, implying a great socio-economic burden. IgAN may occur in a sporadic or familial form. Studies on familial IgAN have shown that 66% of asymptomatic relatives carry immunological defects such as high IgA serum levels, abnormal spontaneous in vitro production of IgA from peripheral blood mononuclear cells (PBMCs), high serum levels of aberrantly glycosylated IgA1, and an altered PBMC cytokine production profile. Recent findings led us to focus our attention on a new perspective to study the pathogenesis of this disease, and new studies showed the involvement of factors driven by environment, lifestyle or diet that could affect the disease. In this review, we describe the results of studies carried out in IgAN patients derived from genomic and epigenomic studies. Moreover, we discuss the role of the microbiome in the disease. Finally, we suggest a new vision to consider IgA Nephropathy as a disease that is not disconnected from the environment in which we live but influenced, in addition to the genetic background, also by other environmental and behavioral factors that could be useful for developing precision nephrology and personalized therapy.

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.

Dietary zinc is a key environmental modifier in the progression of IgA nephropathy

IgA nephropathy (IgAN) shows diverse epidemiological characteristics, resulting from both genetic and acquired (e.g., environmental) causes. Environmental factors, such as diet or exposure to exogenous antigens, may prescribe the progression or prognosis of IgAN. It remains unclear as to how diet and infection influence susceptibility to IgAN. A relationship, such as Toll-like receptors (TLRs), especially TLR9 and TLR4, was demonstrated between IgAN and pathogen-recognition molecules. Recently, zinc (Zn) was discovered to be involved in various immune-related diseases, affecting B, T, and dendritic cells (DCs). This study investigates the relationship between dietary Zn and IgAN development in IgAN-prone mice. Seven-week-old IgAN-prone mice were divided into low, normal, and high Zn diet groups. To assess exogenous pathogen-mediated immune responses, lipopolysaccharide (LPS) was nasally administered. The activity of IgAN was biochemically and pathologically evaluated during the disease course. We also examined in vitro IgA production in spleen cells or in combinations of cocultured B, T, and DCs under various Zn conditions with or without LPS. Dietary conditioning with Zn affected serum immunoglobulins and urinary albumin levels, and mesangial deposition of IgA and IgG. Zn deficiency is associated with IgAN progression through the activation of the TLR4/TIR-domain-containing adapter-inducing interferon-β (TRIF), but not the TLR9, in DCs. Zn supplementation prevented disease aggravation. Our findings indicate that immune conditioning with dietary Zn alters nephritogenic IgA production after mucosal infection.

Development of a model of early-onset IgA nephropathy

ddY mice spontaneously develop IgA nephropathy (IgAN) with a variable age of disease onset. Establishing a model with early-onset IgAN could aid the investigation of mechanisms that underlie the pathogenesis of this disease. On the basis of histologic grading in serial biopsies, we previously classified ddY mice into early-onset, late-onset, and quiescent groups. Here, we selectively mated mice with the early-onset phenotype for >20 generations and established "grouped ddY" mice that develop IgAN within 8 weeks of age. Similar to human IgAN, the prognosis was worse for male mice than females. These mice homogeneously retained genotypes of four marker loci previously associated with the early-onset phenotype, confirming a close association of these loci with early-onset IgAN in ddY mice. Grouped ddY mice comprised two sublines, however, which had distinct genotypes at a susceptibility locus for high serum IgA levels, which maps within the Ig heavy-chain gene complex. The subline bearing the Igh-2(a) IgA allotype had a more rapid course of fatal disease and lower oligosaccharide content, suggesting that aberrant IgA glycosylation may promote the progression of murine IgAN. Taken together, these data indicate that grouped ddY mice may be a useful model for the identification of susceptibility genes and the underlying molecular mechanisms involved in the pathogenesis of human IgAN.

The association between angiotensin-converting enzyme insertion/deletion gene variant and risk of focal segmental glomerulosclerosis: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The association of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) gene polymorphism with the risk of focal segmental glomerulosclerosis (FSGS) is still controversial. A meta-analysis was performed to evaluate the association between ACE I/D gene polymorphism and FSGS susceptibility.

METHOD

We performed a predefined literature search and selection of eligible relevant studies to collect data from electronic databases.

RESULTS

In total, 12 articles were identified for the analysis of the association between ACE I/D gene polymorphism and FSGS risk. One report included an investigation in Arab and Jewish populations separately. Thus, there were seven reports in Asians, two in Caucasians, one in Africans, two in Arabs and one in Jews. In Asians, there was a markedly positive association between the D allele or DD genotype and FSGS susceptibility (p = 0.008; p = 0.002), and the II genotype may play a protective role against FSGS onset (p = 0.002). However, a link between ACE I/D gene polymorphism and FSGS risk was not found in Caucasians, Africans, Arabs or Jews (Caucasians: D: p = 0.11, DD: p = 0.19, II: p = 0.70; Africans: D: p = 0.40, DD: p = 0.49, II: p = 0.61; Arabs: D: p = 0.34, DD: p = 0.10, II: p = 0.42; Jews: D: p = 0.90, DD: p = 0.97, II: p = 0.83).

CONCLUSION

The D allele or DD homozygosity may become a significant genetic molecular marker for the onset of FSGS in Asians, but not for Caucasians, Africans, Arabs or Jews.

IgA nephropathy in India: what we do know

BACKGROUND

Even though IgA nephropathy (IgAN) is not the most common primary glomerulonephritis (GN) in India, the outcome of patients with IgAN in India is poor when compared with other parts of the world, which is a burden in itself.

METHODS

Basic and clinical research work in India on primary IgAN was systematically reviewed. Comparisons between data from India and those from other countries were made.

RESULTS

IgAN constitutes between 7% and 16% of most biopsy samples from India, bearing in mind these figures may represent only the tip of the iceberg. Nephrotic syndrome and renal failure seem to be common presenting features. The renal survival rates appear to be dismally low. DD genotype of angiotensin-1 converting enzyme (ACE) gene may predispose the individual to IgAN in Indian population. As might be expected, IgAN can recur posttransplant though the posttransplant course is indolent. There are no data on the treatment aspects of IgAN.

CONCLUSION

Low incidence but marked severity characterizes IgAN in India. It is apparent that IgAN seems to have a poor outcome in India. What we are unsure of is the reason behind it. In-depth basic studies and multicenter clinical trials are needed to address this bizarre pattern.

ACE I/D gene polymorphism can't predict the steroid responsiveness in Asian children with idiopathic nephrotic syndrome: a meta-analysis

Background

The results from the published studies on the association between angiotensin-converting enzyme (ACE) insertion/deletion (I/D) gene polymorphism and the treatment response to steroid in Asian children with idiopathic nephrotic syndrome (INS) is still conflicting. This meta-analysis was performed to evaluate the relation between ACE I/D gene polymorphism and treatment response to steroid in Asian children and to explore whether ACE D allele or DD genotype could become a predictive marker for steroid responsiveness.

Methodology/Principal Findings

Association studies were identified from the databases of PubMed, Embase, Cochrane Library and CBM-disc (China Biological Medicine Database) as of September 1, 2010, and eligible investigations were synthesized using meta-analysis method. Five investigations were identified for the analysis of association between ACE I/D gene polymorphism and steroid-resistant nephrotic syndrome (SRNS) risk in Asian children and seven studies were included to explore the relationship between ACE I/D gene polymorphism and steroid-sensitive nephrotic syndrome (SSNS) susceptibility. Five investigations were recruited to explore the difference of ACE I/D gene distribution between SRNS and SSNS. There was no a markedly association between D allele or DD genotype and SRNS susceptibility or SSNS risk, and the gene distribution differences of ACE between SRNS and SSNS were not statistically significant. II genotype might play a positive role against SRNS onset but not for SSNS (OR = 0.51, P = 0.02; OR = 0.95, P = 0.85; respectively), however, the result for the association of II genotype with SRNS risk was not stable.

Conclusions/Significance

Our results indicate that D allele or DD homozygous can't become a significant genetic molecular marker to predict the treatment response to steroid in Asian children with INS.

Relationship between Angiotensin-Converting Enzyme Insertion/Deletion Gene Polymorphism and Susceptibility of Minimal Change Nephrotic Syndrome: A Meta-Analysis

Aim. This meta-analysis was performed to evaluate the association between ACE I/D gene polymorphism and MCNS susceptibility. Method. A predefined literature search and selection of eligible relevant studies were performed to collect the data from electronic databases. Results. Six articles were identified for the analysis of association between ACE I/D gene polymorphism and MCNS risk, including 4 for Asians, one in Caucasian population and one for Africans. There was a markedly positive association between D allele or DD genotype and MCNS susceptibility in Asians (D: P = .01, DD: P = .02), but not for Caucasians and Africans (Caucasians: D: P = .16, DD: P = .98; Africans: D: P = .81, DD: P = .49). Furthermore, the II genotype seemed not to play a protective role against MCNS risk for Asians, Caucasians and Africans (P = .12, P = .09, P = .76, resp.). Interestingly, there was also significant association between ACE I/D gene polymorphism and MCNS susceptibility in overall populations (D: P = .007, DD: P = .04, II: P = .03). Conclusion. D allele or DD genotype might be a significant genetic molecular marker for MCNS susceptibility in Asians and overall populations, but not for Caucasians and Africans. More larger and rigorous genetic epidemiological investigations are required to further explore this association.

Association between ACE polymorphism and risk of IgA nephropathy: a meta-analysis

BACKGROUND

and objective: The effect of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism on risk or progression of immunoglobulin A nephropathy (IgAN) is still debated.Therefore, a meta-analysis was performed to evaluate the association of ACE gene polymorphism with IgAN in different ethnic groups.

METHOD

A predefined search strategy was performed to collect data from electronic databases.

RESULTS

Twenty articles were identified for the analysis of the relationship between ACE polymorphism and IgAN risk, including 11 in Asians and nine in Caucasians. There was a markedly positive association between the D allele or DD genotype and IgAN risk in Asians (OR = 1.27, p = 0.006; OR = 1.83, p < 0.0001). However, a link between D allele or DD genotype and IgAN risk was not found in Caucasians (OR = 1.04, p = 0.46; OR = 1.13, p = 0.12). Ten investigations were included for analysis of the association of ACE polymorphism with IgAN progression, including six in Asians and four in Caucasians. These data did not support a link between the ACE D allele or DD genotype and IgAN progression in Asians and Caucasians (Asians: D: OR = 1.03, p = 0.80; DD: OR = 1.43, p = 0.16; Caucasians: D: OR = 1.29, p = 0.22; DD: OR = 1.31, p = 0.17).

CONCLUSIONS

The D allele or DD genotype is associated with IgAN risk in Asian, but not in Caucasian populations; there was no significant association between the D allele or DD gene and IgAN progression for Asians and Caucasians.

Association of the genetic polymorphisms of the ACE gene and the eNOS gene with lupus nephropathy in northern Chinese population

BACKGROUND

It has been reported that some single nucleotide polymorphisms (SNPs) of the angiotensin converting enzyme (ACE) gene and the endothelial nitric oxide synthase (eNOS) gene are associated with the development of systemic lupus erythematosus (SLE) and the progression of nephropathy. The aim of this study was to evaluate the possible association between six SNPs (A-5466C, T-3892C, A-240T, C1237T, G2215A and A2350G) of the ACE gene and two SNPs (T-786C and G894T) of the eNOS gene with lupus nephropathy in a northern Chinese population.

METHODS

In this study, 225 patients with lupus nephropathy were compared to 232 healthy controls, matched by gender, age and ethnicity. Following the extraction of genomic DNA from the leukocytes in the peripheral blood, the genotypes of the eight selected SNPs were determined by the method of PCR-RFLP; the haplotypes were inferred using PHASE 2.1. The associations between the SNPs and the risk of lupus nephropathy were analyzed using Chi-square test and Logistic regression with SPSS13.0 software.

RESULTS

Statistically significant differences of the allele frequency distribution of three SNPs (A-5466C, A2350G and G894T) were observed between cases and controls (P<0.05). Among the 53 haplotypes identified, the frequencies of five haplotypes (CTTCGA, ACTTAA, ACATGG, ACACGG and ATTCGA) were significantly different between cases and controls (P<0.05).

CONCLUSIONS

Our study indicated an association between the risk of lupus nephropathy and the sequence variations of both the ACE gene and the eNOS gene, which may play an important role in the pathogenesis of lupus nephropathy in the northern Chinese population. Further studies are warranted to validate our findings.

Unravelling the genetic basis of renal diseases; from single gene to multifactorial disorders

Chronic kidney disease is common with up to 5% of the adult population reported to have an estimated glomerular filtration rate of < 60 ml/min/1.73 m(2). A large number of pathogenic mutations have been identified that are responsible for 'single gene' renal disorders, such as autosomal dominant polycystic kidney disease and X-linked Alport syndrome. These single gene disorders account for < 15% of the burden of end-stage renal disease that requires dialysis or kidney transplantation. It has proved more difficult to identify the genetic susceptibility underlying common, complex, multifactorial kidney conditions, such as diabetic nephropathy and hypertensive nephrosclerosis. This review describes success to date and explores strategies currently employed in defining the genetic basis for a number of renal disorders. The complementary use of linkage studies, candidate gene and genome-wide association analyses are described and a collation of renal genetic resources highlighted.

Genetical, histological, and clinical characteristics of IgA-negative mesangioproliferative glomerulopathy

BACKGROUND

Mesangioproliferative glomerulopathy (MesPGN) is a well-defined pathohistological entity. However, the clinical characteristics and prognosis have not been fully established in patients without immunoglobulin (Ig)A (N-IgAN) in contrast to patients with IgA nephropathy (IgAN).

METHODS

A total of 837 consecutive patients underwent renal biopsies. Among them, 465 patients were diagnosed with MesPGN by light microscopy. With immunofluorescent study and electron microscopy (EM), 344 were diagnosed as having IgAN. Among the rest, 84 patients who had no immunofluorescence evidence of IgA and no deposits in EM were defined as N-IgAN. We compared the clinical characteristics, histological findings, and genotypes of the angiotensin-converting enzyme (ACE) gene and plasminogen activator inhibitor-1 gene between IgAN and N-IgAN patients.

RESULTS

Urinary protein excretion and the degree of hematuria were significantly lower in N-IgAN than IgAN patients (0.50 vs. 0.82 g/day; P = 0.01), (1.33 vs. 2.50; P < 0.001, respectively). Creatinine clearance was higher in N-IgAN than IgAN patients (89.4 vs. 74.4 ml/min; P < 0.001). Histopathologically, N-IgAN patients had significantly less advanced glomerular and tubulointerstitial lesions than IgAN patients. Pathological grades in patients with untreated IgAN were more advanced in a time-dependent manner, whereas there was no relationship between histological grades and time of illness in N-IgAN patients. Frequency of the DD genotype of the ACE gene was significantly lower in N-IgAN (DD/ID+II = 8/76) than IgAN (24/90) patients.

CONCLUSIONS

IgA-negative MesPGN is a distinct type of glomerulopathy with a benign renal prognosis. Insertion/deletion polymorphisms of the ACE gene may play some role in the genesis and progression of MesPGN.

A scoring system to predict renal outcome in IgA nephropathy: a nationwide 10-year prospective cohort study

Background. Immunoglobulin A nephropathy (IgAN) is the most common form of glomerulonephritis, and a substantial number of patients succumb to end-stage renal disease (ESRD). However, prediction of the renal outcome in individual patients remains difficult. We have already published a scoring system using the data in a prospective cohort of IgAN patients followed up from 1995 to 2002.

Methods. The cohort was further followed up until 2005 in 97 clinical units in Japan. The data from 2283 patients were analysed by Cox regression to determine the predictors of ESRD in IgAN, and their β-coefficients were converted into scores to estimate ESRD risk within 10 years.

Results. During the follow-up (median, 87 months), 252 patients developed ESRD. Male sex, age less than 30 years, family histories of chronic renal failure and chronic glomerulonephritis, hypertension, proteinuria, mild haematuria, hypoalbuminaemia, low glomerular filtration rate and a high histological grade at initial renal biopsy were associated with the risk of ESRD in the multivariable analysis. A scoring system was framed to estimate the 10-year ESRD risk using eight variables significant in both univariable and multivariable models. This prognostic score accurately classified patients by risk: patients with estimates of 0–4.9, 5.0–19.9, 20.0–49.9 and 50.0–100% had an observed incidence of 1.7, 8.3, 36.7 and 85.5%, respectively. The corresponding area under the receiver-operating characteristic curve was 0.942 (95% confidence interval, 0.925–0.958).

Conclusion. This validated scoring system to quantitatively estimate ESRD risk during the 10-year follow-up of IgAN patients will serve as a useful prognostic tool in clinical practice.

A candidate gene approach to genetic prognostic factors of IgA nephropathy--a result of Polymorphism REsearch to DIstinguish genetic factors Contributing To progression of IgA Nephropathy (PREDICT-IgAN)

BACKGROUND

Renal prognosis of IgA nephropathy (IgAN) is affected by environmental and genetic factors. Other studies demonstrated that some atherosclerotic disease-related genes were significantly associated with renal prognosis.

METHODS

The Polymorphism REsearch to DIstinguish genetic factors Contributing To progression of IgAN (PREDICT-IgAN) was a multicentre retrospective observational study to investigate associations between progression of IgAN (a 50% increase of serum creatinine level and slope of eGFR) and a hundred atherosclerotic disease-related gene polymorphisms, mainly single nucleotide polymorphisms (SNPs) in 320 IgAN patients who had more than a normal range of urinary protein (> or =0.25 g/day) at diagnosis.

RESULTS

During 8.3 +/- 4.2 years of a follow-up period, 83 patients (25.9%) developed progression. In log-rank tests, glycoprotein Ia GPIa C807T and G873A and intercellular adhesion molecule-1 ICAM-1 A1548G (K469E) were found to be significantly associated with progression even after adjustment for multiple comparisons by the method of Bonferroni (adjusted P = 0.0174, 0.0176 and 0.0430, respectively). In a multivariate Cox proportional-hazards model, GPIa 807TT (873CC) [versus 807TT, adjusted hazard ratio 2.05 (95% confidence interval 1.13-3.71)] and ICAM-1 1548GG [versus 1548AA, 2.55 (1.40-4.65)] were identified as independent genetic predictors of progression, along with conventional clinical prognostic factors such as eGFR, urinary protein and use of antihypertensives at diagnosis.

CONCLUSIONS

PREDICT-IgAN distinguished GPIa C807T/ G873A and ICAM-1 A1548G from multiple athero- sclerotic disease-related gene polymorphisms by their predictive indicator for progression of IgAN.

Association of angiotensin I-converting enzyme gene insertion/deletion polymorphism and IgA nephropathy: a meta-analysis

BACKGROUND/AIMS

The angiotensin I-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism has been extensively examined for the association with immunoglobulin A (IgA) nephropathy (IgAN), however, conflicting results have occurred. We performed a meta-analysis to evaluate the association of ACE I/D polymorphism with IgAN in different ethnic groups.

METHODS

11 studies testing the association between ACE I/D polymorphism and IgAN susceptibility, and 9 studies testing the association of ACE I/D with IgAN progression were used in this analysis. The overall odds ratio (OR) was estimated by a fixed or random effect model.

RESULTS

The overall OR for the risk of susceptibility and progression of IgAN in Asians for the DD genotype is 2.37 (95% CI 1.04-5.41) and 1.75 (95% CI 1.24-2.56). The overall OR for the D allele in Asians also showed a similar magnitude, though without statistical significance (p = 0.09, p = 0.13, respectively). In Caucasians, both the DD genotype and D allele were associated with IgAN progression (OR 1.90, 1.61, respectively), but not IgAN susceptibility (p = 0.30, p = 0.41, respectively).

CONCLUSION

Our findings support the notion that ACE I/D polymorphism is associated with IgAN. Meanwhile, the role of ACE I/D polymorphism in Asians is different from that of Caucasians.

CC-chemokine receptor five gene polymorphism in primary IgA nephropathy: the 32 bp deletion allele is associated with late progression to end-stage renal failure with dialysis

The chemokine (CK) receptor 5 (CCR5) is necessary for two adjacent cysteines (CC)-CKs such as Regulated upon Activation Normal T cell Expressed and Secreted, a/o Macrophage Inflammatory Protein 1alpha/beta to mediate their inflammatory properties. The CCR5 gene polymorphism with 32-basepair deletion (d32) leads to receptor inactivation/dysfunction in homo/heterozygous individuals. We have evaluated its role in both initiation and/or progression of primary immunoglobulin A (IgA) nephropathy (IGAN) in a case-control study involving a prospective cohort of 318 IGAN patients and a matched group of 294 controls. Genotyping was performed by a two-specific primers single polymerase chain reaction technique: normal allele (nl) vs d32 allele. The d32 allele frequency was not different in patients (11.0%) vs controls (8.3%), indicating no significant influence on IGAN initiation. Genotype to clinical phenotype correlation demonstrated that progression to renal/patient death was associated with the d32 allele: 18.2% (12 out of 66 with d32) vs 8.3% (21 out of 252); chi(2)=6.73; P=0.017. The Kaplan-Meier survival without renal/patient death was worse in d32-positive patients (log-rank test; P=0.002). The Cox regression analyses confirmed that the nl/nl genotype was a significant and independent protective factor for progression to end-stage renal failure (ESRF)/dialysis: beta/standard error (s.e.)=-3.1; chi(2)=9.5; relative risk=0.31 (95% confidence interval 0.15-0.65); P=0.002. The d32-CCR5 polymorphism played a significant role in the progression of primary IGAN, with the nl/nl genotype being an independent protective factor for late progression towards ESRF/dialysis. These data raise question about the usefulness of systematic CCR5 genotyping in IGAN patients.

Association of Uteroglobin G38A Polymorphism With IgA Nephropathy: A Meta-Analysis

Both uteroglobin knockout and antisense transgenic mice develop pathological and clinical features similar to immunoglobulin A (IgA) nephropathy. However, several association studies of uteroglobin G38A polymorphism and IgA nephropathy showed controversial findings. We used meta-analysis to assess the impact of the uteroglobin G38A polymorphism on susceptibility to and progression of IgA nephropathy. Six studies involving uteroglobin G38A genotyping of 930 patients with IgA nephropathy and 768 healthy controls were included. No significant publication bias was found (Egger's linear regression, P = 0.763; 95% confidence interval [CI], -0.610 to 0.476). All control samples were in Hardy-Weinberg proportion. No association between the AA genotype and risk for IgA nephropathy relative to both other genotypes (odds ratio [OR], 1.05; 95% CI, 0.71 to 1.54) or A allele and risk for IgA nephropathy (OR, 0.96; 95% CI, 0.84 to 1.11) were shown in the total meta-analysis. In both Asian and European subgroups, the overall effect of the AA genotype and A allele also showed no significant difference. There also was no significant association between uteroglobin AA genotype or A allele and IgA nephropathy progression (OR, 3.62; 95% CI, 0.59 to 22.34; OR, 2.19, 95% CI, 0.37 to 13.14, respectively). We suggest that uteroglobin G38A polymorphism is not related to the development and progression of IgA nephropathy.

Impact of violations and deviations in Hardy-Weinberg equilibrium on postulated gene-disease associations

The authors evaluated whether statistically significant violations of Hardy-Weinberg equilibrium (HWE) or the magnitude of deviations from HWE may contribute to the problem of replicating postulated gene-disease associations across different studies. Forty-two gene-disease associations assessed in meta-analyses of 591 studies were examined. Studies with disease-free controls in which HWE was violated gave significantly different results from HWE-conforming studies in five instances. Exclusion of the former studies resulted in loss of statistical significance of the overall meta-analysis in three instances and more than a 10% change in the summary odds ratio in six. Exclusion of HWE-violating studies changed the formal significance of the estimated between-study heterogeneity in three instances. After adjustment for the magnitude of the deviation from HWE for the controls, formal significance was lost in another three instances. Studies adjusted for the magnitude of deviation from HWE tended to become more heterogeneous among themselves, and, for seven gene-disease associations, between-study heterogeneity became significant, while it was not so in the unadjusted analyses. Gene-disease association studies and meta-analyses thereof should routinely scrutinize the potential impact of HWE violations as well as nonsignificant deviations from the exact frequencies expected under HWE. Postulated genetic associations with modest-sized odds ratios and borderline statistical significance may not be robust in such sensitivity analyses.

The familial clustering of renal disease and related phenotypes

This article reviews the familial aggregation of chronic kidney diseases including end-stage renal disease and albuminuria, along with variation in glomerular filtration rate. In addition to environmental influences on the progression of nephropathy, epidemiologic evidence in support of the existence of renal failure susceptibility genes is presented.

Genetics of common progressive renal disease

Familial aggregation of common chronic kidney diseases provides a unique opportunity to investigate the susceptibility genetic and environmental factors. In the past decade, a wealth of new data has become available concerning the genetic susceptibility leading to numerous nephropathies. Knowledge of the genetic components allows better understanding of initiation and progression of these chronic kidney diseases. In addition, one can envision that identification of genetically susceptible individuals might lead to earlier diagnosis and potential reversal of the current epidemic of end-stage renal disease. The goal of the current discussion is to review various issues pertaining to the role of genetic factors in common chronic kidney diseases, as exemplified by two leading causes of end-stage renal diseases worldwide, nephropathy of type 2 diabetes and IgA nephropathy. The genetic and environmental interplay leading to the nephropathies is highlighted.

Genome-wide scan in a novel IgA nephropathy model identifies a susceptibility locus on murine chromosome 10, in a region syntenic to human IGAN1 on chromosome 6q22-23

Genetic factors are considered to be involved in the initiation and progression of IgA nephropathy (IgAN) on the basis of racial differences in the prevalence and familial aggregation. The ddY mouse is a spontaneous animal model of human IgAN, with a highly variable incidence and extent of glomerular injury as a result of the heterogeneous background, resembling the human situation. It was hypothesized that susceptibility genes for IgAN can be detected by a genome-wide scan using this model. First, serial renal biopsies were performed at 20, 40, and 60 wk of age in 361 ddY mice. The ddY mice were classified into three groups on the basis of the onset of glomerular injury: Early onset at 20 wk (31.9%), late onset at 40 wk (37.9%), and quiescent even at 60 wk (30.2%). The severity of glomerular lesions in both onset groups correlated with the intensity of glomerular IgA deposition but not with serum IgA level. The genome-wide scan with 270 microsatellite markers identified three chromosomal regions on chromosomes 1, 9, and 10, which were significantly associated with the glomerular injuries. Surprisingly, the peak marker D10MIT86 on chromosome 10 is located on the region syntenic to human 6q22-23 with IGAN1, which is the responsible candidate of familial IgAN. In addition, D1MIT16 on chromosome 1 was very closely located at the locus of selectin gene, which is a known candidate of human IgAN. In conclusion, the three-group ddY mouse model can be a useful tool for identifying the susceptibility genes and also to examine their roles in the pathogenesis of IgAN.

Angiotensin-converting-enzyme inhibitors slow renal decline in IgA nephropathy, independent of tubulointerstitial fibrosis at presentation

BACKGROUND

Tubulointerstitial fibrosis (TIF) is a marker of progression of diabetic and non-diabetic nephropathy, correlating with creatinine clearance (CCr), and functional outcome. Angiotensin-converting-enzyme inhibitors (ACEIs) slow the rate of decline of renal function in proteinuric patients.

AIM

To examine whether ACEIs affect TIF, directly or indirectly.

DESIGN

Prospective 3-year follow-up study.

METHODS

We enrolled 49 patients with IgA nephropathy (IgAN), treating some with ACE inhibitors (n = 26, 1-2 mg/day temocapril or trandolapril) and some with calcium-channel blockers (CCB, n = 23, 2.5-5 mg/day amlodipine). Blood pressure, serum creatinine, and urinalysis were measured monthly, and 24-h endogenous creatinine clearance (CCr) at least once a year.

RESULTS

In the CCB group, TIF was positively correlated with the rate of decline in CCr (dCCr), consistent with previous observations. In the ACEI group, dCCr was lower (0.02 +/- 0.02 vs. 0.06 +/- 0.03), and the TIF-dCCr correlation was absent.

DISCUSSION

In the absence of post-treatment histological data, it is not possible to say whether ACEIs have an effect on TIF. However, ACEIs appear to slow the progression of renal failure in IgAN, regardless of the degree of TIF at presentation.

Pediatric IgA nephropathies: clinical aspects and therapeutic approaches

The pediatric IgA nephropathies are IgA nephrothapy (Berger's Disease) and Henoch-Schönlein purpura nephritis. Both conditions are reviewed in detail with respect to epidemiology, clinical features, outcome, prognostic markers, and therapeutic approaches. For both conditions variable disease severity and outcome along with the lack of conclusive evidence for efficacy of treatment based on randomized clinical trials makes it difficult to make strong recommendations regarding therapy.

Natural history of idiopathic IgA nephropathy and factors predictive of disease outcome

Among the numerous studies published in the last 20 years that have calculated the actuarial renal survival and tried to individuate the prognostic role of the clinical and histologic features present at the onset of the disease or the time of biopsy, we chose to critically analyze the results of the most valid (23 studies). Actuarial renal survival at 10 years in adults was between 80% and 85% in most of the European, Asian, and Australian studies, but was lower than this in studies from the United States and exceeded 90% in the few studies on children. Concordance existed in this selected literature on the fact that impairment of renal function, severe proteinuria, and arterial hypertension are the strongest and more reliable clinical predictors of an unfavorable outcome. Extent of proteinuria during follow up was an even stronger predictor. In adult patients, a high score of the glomerular and tubulointerstitial lesions predicted a more rapid progression. When the single lesions were analyzed separately, glomerular sclerosis and interstitial fibrosis appeared to be the strongest, most reliable predictors of unfavorable prognosis. More controversial was the role of crescents and capsular adhesions.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers for IgA nephropathy

The lengthy course of IgA nephropathy and the possibility of good outcomes without therapy suggest nontoxic therapies such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs.) Among patients with IgA nephropathy, both ACE inhibitors and ARBs reduce the transglomerular passage of large, but not small, molecules, reducing proteinuria. The antiproteinuric effects of ACE inhibitors and ARBs are probably equivalent. Dual ACE inhibitor-ARB therapy reduces proteinuria by 54% to 73% and is more effective than either agent alone. To determine whether ACE inhibitors or ARBs preserve renal function long-term, one must rely on trials studying nondiabetic, proteinuric renal diseases rather than on trials specific to IgA nephropathy. Among this group of patients, several randomized, controlled trials, including the AIPRI trial, the REIN trial, and a metaanalysis of 11 randomized, controlled trials, have established clearly that the ACE inhibitors preserve renal function. There is no reason to believe that this information is not applicable to IgA nephropathy. The COOPERATE trial, in which 50% of the subjects had IgA nephropathy, established that ACE inhibitors and ARBs preserve renal function equally, and that dual ACE inhibitor-ARB therapy preserves renal function more effectively than either therapy alone. These data suggest that most individuals with proteinuric renal diseases, including IgA nephropathy, should be treated with ACE inhibitors and ARBs, ideally in combination. Polymorphisms of the angiotensinogen gene, the ACE gene, and the angiotensin II type I receptor gene have, so far, failed to predict either susceptibility to or progression of IgA nephropathy. However, the D allele of the ID polymorphism, particularly the DD genotype, could predict a favorable response to renin-angiotensin blockade.

Pathogenesis of IgA nephropathy

In IgA nephropathy (IgAN), there is dysregulation of the IgA response to a wide range of antigens. The dysregulation promotes synthesis of polymeric IgA1 (pIgA1) with physicochemical characteristics that favor mesangial deposition, including altered O-glycosylation of the hinge region. This may be the synthesis of IgA in the systemic compartment, which has the phenotype of mucosal IgA. There is not a change in IgA1 structure to an entirely abnormal form; rather, there is a shift that results in a proportional increase in forms of IgA1 also found in healthy individuals. Altered O-glycosylation could favor pIgA1 deposition by promoting formation of macromolecular IgA and immune complexes. Mesangial injury follows through interactions of pIgA1 with the cells and extracellular matrix proteins of the mesangium and the activation of complement. The final clinical expression of IgAN also depends on generic factors, including hypertension and proteinuria, and a fibrotic renal response. No single "IgAN gene" has been identified, and it is likely that multiple interacting genes will eventually prove to underlie susceptibility to IgAN and the risk of progressive renal disease. These new pathogenic insights have not yet led to new therapeutic opportunities.

Interaction between gene polymorphisms of nitric oxide synthase and renin-angiotensin system in the progression of membranous glomerulonephritis

BACKGROUND

The renin-angiotensin system (RAS) and nitric oxide synthase (NOS) play a key role in the progression of primary glomerulonephritis (GN). Although previous studies have examined genetic risk associated with single gene variations, experiments assessing risk conferred by multiple gene variations are still scanty.

METHODS

The effect of combination of variant alleles of four genes encoding for three components of the RAS [angiotensin converting enzyme insertion/deletion (ACE I/D), angiotensin II receptor 1 (AT1R 1166A/C), angiotensinogen (AGT M235T)] and for NOS (ecNOS4b/a) on the development and progression of membranous GN (MGN) were evaluated in a longitudinal study comparing 117 patients with serum creatinine (s-Cr) <1.5 mg/dl at renal biopsy and follow-up > or = 5 years (Kaplan-Meier and Cox multivariate analysis). The control group consisted of DNA from 171 organ donors.

RESULTS

We found no relationship between single or combined variations of the four gene polymorphisms and development of MGN. Among single gene variations, there were no independent genetic risk factors for the progression of renal disease, after adjustment for age, sex, hypertension, proteinuria, s-Cr, chronicity and activity index. However, double variation coincidences such as the combination of the allele a of ecNOS4b/a and both the allele D of ACE I/D (chi(2) =4.80, P = 0.028; HR = 1.97, 95% CI 0.98-3.96) and the allele T of AGT (M235T) (chi(2) = 5.09, P = 0.024; HR = 2.84, 95% CI 1.39-5.82) exerted an additional effect that was higher than that of the single gene variations.

CONCLUSION

This study is the first to demonstrate a role for an interaction between simultaneous variations of genes encoding for NOS and components of RAS in the progression of MGN. Interactions between various polymorphisms may explain conflicting results obtained in previous studies that examined single gene variations, since the effect of a single locus variation may be influenced by the simultaneous presence of other variant alleles in polygenic diseases such as primary GN. However, the small sample sizes and possible multiple interactions limited the interpretation of the current findings, which may represent true biological interaction or simply statistical interactions or spurious results due to the small sample sizes.

Influence of genetic polymorphisms of the renin-angiotensin system on IgA nephropathy

BACKGROUND

We evaluated the impact of the three major genetic polymorphisms of the renin-angiotensin system [angiotensinogen (AGT) gene M235T, angiotensin-converting enzyme (ACE) gene-I/D and angiotensin II-type 1 receptor (AT1R) gene A1166C polymorphisms] as risk factors in IgA nephropathy.

METHODS

The clinical course of 107 patients with biopsy proven IgA nephropathy followed up for 6.6 +/- 5.8 years was examined. The genetic polymorphisms were determined by PCR amplification.

RESULTS

The allele frequencies of the polymorphisms studied were similar in patients and control subjects. AGT-M235T genotype was associated with the presence of nephrotic syndrome (p < 0.05), correlated to the number of antihypertensive drugs agents taken (p < 0.01) and influenced the rate of deterioration of renal function (p < 0.05). Combined analysis of AGT-M235T and ACE-I/D polymorphisms detected an interaction on affecting progression (p < 0.05). ACE-inhibition had a more pronounced effect in certain AGT-M235T and ACE-I/D genotypes (p < 0.05) and their combined analysis showed a synergistic effect (p < 0.01). No association between AT(1)R-A1166C polymorphism and any of the parameters studied was observed.

CONCLUSIONS

Our results suggest that angiotensinogen-M235T polymorphism is an important marker of progression in IgA nephropathy in Caucasian patients, especially when analyzed in combination with ACE-I/D polymorphism.

Exploring the pathways leading from disadvantage to end-stage renal disease for Indigenous Australians

Indigenous Australians are disadvantaged, relative to other Australians, over a range of socio-economic and health measures. The age- and sex-adjusted incidence of end-stage renal disease (ESRD)--the irreversible preterminal phase of chronic renal failure--is almost nine times higher amongst Indigenous than it is amongst non-indigenous Australians. A striking gradient exists from urban to remote regions, where the standardised ESRD incidence is from 20 to more than 30 times the national incidence. We discuss the profound impact of renal disease on Indigenous Australians and their communities. We explore the linkages between disadvantage, often accompanied by geographic isolation, and both the initiation of renal disease, and its progression to ESRD. Purported explanations for the excess burden of renal disease in indigenous populations can be categorised as: primary renal disease explanations;genetic explanations;early development explanations; and socio-economic explanations. We discuss the strengths and weaknesses of these explanations and suggest a new hypothesis which integrates the existing evidence. We use this hypothesis to illuminate the pathways between disadvantage and the human biological processes which culminate in ESRD, and to propose prevention strategies across the life-course of Indigenous Australians to reduce their ESRD risk. Our hypothesis is likely to be relevant to an understanding of patterns of renal disease in other high-risk populations, particularly indigenous people in the developed world and people in developing countries. Furthermore, analogous pathways might be relevant to other chronic diseases, such as diabetes and cardiovascular disease. If we are able to confirm the various pathways from disadvantage to human biology, we will be better placed to advocate evidence-based interventions, both within and beyond the scope of the health-care system, to address the excess burden of renal and other chronic diseases among affected populations.

Angiotensin-converting enzyme gene insertion/deletion polymorphism in children with Henoch-Schonlein purpua nephritis

This study investigated the relationship between angiotensin-converting enzyme (ACE) gene insertion/deletion polymorphism and the occurrence, severity, prognosis of HSPN. The polymorphism of ACE gene in 103 HSPN cases and 100 healthy children was studied by using the polymerase chain reactions (PCR). Its relation to the clinical manifestation, pathological classification and prognosis of HSPN was analyzed accordingly. The results showed that: (1) there was a significantly higher frequency for DD genotype in HSPN children (P<0.01); (2) DD genotype was more frequently seen in HSPN children with gross hematuria and massive proteinuria (P<0.05), while DI genotype was more common in HSPN children group with renal insufficiency (P<0.05); (3) although mesangial proliferative lesion was most frequently observed in 21 biopsied HSPN children, and DD genotype frequency was still higher in children with severe pathology (Class III IV); (4) II genotype was significantly frequent in HSPN children with complete remission in the follow-up of 32 HSPN children. It was concluded that the deletion allele of ACE gene might play a role, at least to some extent, in the occurrence, deterioration and progression in juvenile HSPN.

Interaction between ACE and ADD1 gene polymorphisms in the progression of IgA nephropathy in Japanese patients

An interaction effect between the angiotensin-converting enzyme insertion/deletion (ACE I/D) and alpha-adducin (ADD1) Gly460Trp polymorphisms (G460W) on blood pressure regulation has recently been suggested, although its significance in the prognosis of renal function in IgA nephropathy (IgAN) has not been fully investigated. Therefore, we evaluated the clinical manifestations and renal prognosis in 276 Japanese patients with histologically proven IgAN with respect to their ACE I/D and ADD1 G460W polymorphisms. The prognosis of renal function was analyzed by Kaplan-Meier survival curves and multivariate Cox proportional-hazards regression models. Baseline data, including blood pressures, proteinuria, renal function, and incidence of hypertension, were similar for the different genotypes of ACE and ADD1. The individual genotypes taken alone were not associated with the progression of renal dysfunction. However, renal survival of patients with the 460WW polymorphism of ADD1 was significantly worse within the group with the II genotype of ACE (Kaplan-Meier, log rank test; chi2=6.062, P=0.0138) but not for those with other ACE genotypes. In the Cox proportional-hazards regression model with adjustment for clinical risk factors, including hypertension, proteinuria, and no administration of an angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, the 460WW variant of ADD1 was a highly significant and independent risk factor only for patients with the ACE II genotype, with a hazard ratio of 3.65 (P=0.0016), but not for those with other ACE genotypes (hazard ratio=0.65, P=0.2902). These findings suggest an interaction between ACE and ADD1 polymorphisms not only on blood pressure regulation but also on the progression of renal dysfunction in patients with IgAN.

Renin-angiotensin system polymorphisms and renal scarring

The purpose of the study was to determine whether DNA polymorphisms at the renin-angiotensin-aldosterone (RAS) genes were associated with evolution to renal scar formation and, consequently, with reflux nephropathy (RN) in patients with vesicoureteral reflux (VUR). Some authors have suggested that the DD genotype of the angiotensin-converting enzyme (ACE) gene would be an adverse renal prognosis factor. We recruited 246 patients (aged 3 months to 22 years) from four Spanish hospitals. These included 69 patients with VUR, 110 with RN (determined by absence/presence of renal scarring on dimercaptosuccinc acid scan), 27 with chronic renal failure due to RN, and 40 patients (control group) with urinary tract infection and normal findings on renal ultrasonography and voiding cystoureterogram. The ACE I/D, angiotensin II type 1 receptor AT1 A1166C, angiotensin II type 2 receptor A3123C AT2, and angiotensinogen AGT M235T polymorphisms were determined on the basis of polymerase chain reaction amplification. ACE serum levels were determined by spectrophotometric methods. We found no statistical differences in the distribution of RAS polymorphisms between the different groups. The ACE D allele was linked to higher ACE serum levels. We found no association between ACE I/D polymorphism and presence of hypertension, proteinuria, grade of VUR, or unilateral/bilateral VUR. Patients with the DD genotype had a lower incidence of febrile urinary tract infection as a first symptom of VUR/RN (P<0.05). We conclude that genetic polymorphisms of RAS components are not independent prognostic indicators of renal scarring in patients with VUR.

Increased risk of end-stage renal disease in familial IgA nephropathy

Primary IgA nephropathy (IgAN) is characterized by recurrent episodes of macroscopic hematuria accompanied by upper respiratory tract infections or persistent asymptomatic microscopic hematuria with or without proteinuria. IgAN may involve one or more members of a family. Three generations of a cohort of 110 patients with biopsy-proven IgAN, living in Southern Italy, were checked for urinalysis, and the relative risk (RR) of developing the disease was evaluated. A total of 19 unrelated familial, 37 suspected, and 54 sporadic cases of IgAN were identified. Renal survival was estimated by the Kaplan-Meier method for censored data and compared by use of the log-rank test. More than 50% of the patients with IgAN clustered in kindred with more than two probably affected relatives. In 19 unrelated IgAN families, 8 had single-generation (SG) and 11 multigenerational (MG) involvement showing a prevalent vertical transmission of the trait. The RR was 16 times higher in first-degree relatives (odds ratio [OR], 16.4; 95% confidence interval [CI], 5.7 to 47.8; P < 0.0001) and >2 times higher, even if NS, in second-degree relatives (OR, 2.4; 95 % CI, 0.7 to 7.9; P = 0.145). The clinical and histologic picture of familial and sporadic IgAN appeared to be similar. The 20-yr renal survival rate from the apparent onset of the disease was significantly poorer in patients with familial (41%) than in patients with sporadic (94%) IgAN (P = 0.003). Furthermore, 15-yr renal survival from the time of renal biopsy was significantly worse in familial IgAN (P = 0.02); end-stage renal disease was present in 64% of familial and only in 8% of patients with sporadic IgAN. Finally, renal survival was significantly worse in patients belonging to families with SG rather than with MG involvement (P = 0.03). These data show, for the first time, that familial IgAN may be considered a nonbenign disease that occurs frequently in first-degree relatives. Familial IgAN has a poorer outcome than sporadic IgAN. Therefore, an accurate family history and urinalysis in all family members is urgently recommended in clinical practice. This procedure might avoid late referral of subjects with persistent and underestimated urinary abnormalities and late diagnosis of the disease.

Dietary fish oil suppresses experimental immunoglobulin a nephropathy in mice

Dietary fish oil (FO) supplementation reportedly retards the progression of renal disease in patients with immunoglobulin (Ig)A nephropathy (IgAN), the most common glomerulonephritis worldwide. Using an experimental mouse model in which early immunopathological hallmarks of IgAN are induced by the mycotoxin vomitoxin (VT), the ameliorative effects of FO ingestion on this disease were evaluated in two studies. In Study 1, the capacity of VT to induce IgAN was evaluated in mice fed for 12 wk AIN-76A diets containing 50 g/kg corn oil (CO), 50 g/kg CO plus 9 mg/kg tert butylhydroquinone (TBHQ), or 5 g/kg CO plus 45 g/kg menhaden FO that contained 200 mg/kg TBHQ. Serum IgA, serum IgA immune complexes and kidney mesangial IgA deposition were greater in mice fed VT + CO compared with the CO control group, whereas all three variables were significantly attenuated in mice fed VT + FO. Although TBHQ also had attenuating effects, these were significantly less than those for the VT + FO group. In Study 2, the effects of feeding modified AIN 93G diets containing either 70 g/kg CO or 10 g/kg CO plus 60 g/kg FO for 20 wk on VT-induced IgAN were compared. Again, consumption of FO attenuated all three immunopathological variables. In addition, spleen cell cultures from the VT + FO group produced markedly less IgA than those cultures from mice fed VT + CO. Taken together, the results suggested that diets containing FO may impair early immunopathogenesis in VT-induced IgAN and that this was not totally dependent on the presence of the antioxidant TBHQ.