Race/ethnicity and disease severity in IgA nephropathy

Association of Obesity With Kidney and Cardiac Outcomes Among Patients With Glomerular Disease: Findings From the Cure Glomerulonephropathy Network

RATIONALE & OBJECTIVE

The influence of obesity on cardiorenal outcomes in individuals with glomerular disease is incompletely known. This study examined the association between obesity and kidney and cardiovascular outcomes in children and adults with glomerular kidney disease.

STUDY DESIGN

Prospective, multicenter, observational study.

SETTING & PARTICIPANTS

Participants in the Cure Glomerulonephropathy Network (CureGN) who were≥5 years of age at enrollment.

EXPOSURE

Adult body mass index (BMI) groups: 20-24 (healthy) versus 25-34 (overweight/class 1 obesity) versus≥35 (class 2-3 obesity); and pediatric BMI percentiles: 5th-84th (healthy) versus 85th-94th (overweight) versus≥95th (obese).

OUTCOME

A composite kidney outcome (40% estimated glomerular filtration rate [eGFR] decline or kidney failure) and a composite cardiovascular outcome (myocardial infarction, stroke, heart failure, or death).

ANALYTICAL APPROACH

Time to composite primary outcomes by BMI strata were estimated using Kaplan-Meier analysis. The adjusted associations between BMI and outcomes were estimated using Cox proportional hazards analysis.

RESULTS

The study included 2,301 participants (1,548 adults and 753 children). The incidence of the primary kidney end point was 90.8 per 1,000 person-years in adults with class 2-3 obesity, compared with 58.0 in normal weight comparators. In the univariable analysis, class 2-3 obesity was associated with the primary kidney outcome only in adults (HR, 1.6 [95% CI, 1.1-2.2], P=0.006) compared with the healthy weight groups. In the multivariable adjusted analysis, class 2-3 obesity did not remain significant among adults when controlling for baseline eGFR and proteinuria. Adults with class 2-3 obesity had an incidence of 19.7 cardiovascular events per 1,000 person-years and greater cardiovascular risk (HR, 3.9 [95% CI, 1.4-10.7], P=0.009) in the fully adjusted model.

LIMITATIONS

BMI is an imperfect indicator of adiposity. Residual confounding may exist from socioeconomic factors.

CONCLUSIONS

Among adult patients in CureGN, class 2-3 obesity is associated with cardiovascular but not kidney outcomes when adjusted for potential confounding factors.

PLAIN-LANGUAGE SUMMARY

Obesity is a risk factor for adverse heart and kidney outcomes in patients with chronic kidney disease, but whether it is associated with these outcomes in patients with glomerulonephropathy is not known. This study used existing data from a large sample of adults and children with glomerular diseases to address this question. The findings suggest that obesity increases the risk of cardiovascular but not kidney disease events in adult patients with glomerular disease.

Uromodulin and progression of IgA nephropathy

Background

This study investigates the link between genetic variants associated with kidney function and immunoglobulin A (IgA) nephropathy (IgAN) progression.

Methods

We recruited 961 biopsy-proven IgAN patients and 651 non-IgAN end-stage renal disease (ESRD) patients from Ruijin Hospital. Clinical and renal pathological data were collected. The primary outcome was the time to ESRD. A healthy population was defined as estimated glomerular filtration rate >60 mL/min/1.73 m2 without albuminuria or hematuria. Fifteen single-nucleotide polymorphisms (SNPs) were selected from a genome-wide association study of kidney function and genotyped by the SNaPshot. Immunohistochemistry in renal tissue and ELISA in urine samples were performed to explore the potential functions of genetic variations.

Results

The rs77924615-G was independently associated with an increased risk for ESRD in IgAN patients after adjustments for clinical and pathologic indices, and treatment (adjusted hazard ratio 2.10; 95% confidence interval 1.14-3.88). No significant differences in ESRD-free survival time were found among different genotypes in non-IgAN ESRD patients (log-rank, P = .480). Moreover, rs77924615 exhibited allele-specific enhancer activity by dual-luciferase reporter assay. Accordingly, the urinary uromodulin-creatinine ratio (uUCR) was significantly higher in healthy individuals with rs77924615 AG or GG than in individuals with AA. Furthermore, uromodulin expression in tubular epithelial cells was higher in patients with rs77924615 AG or GG. Finally, we confirmed that an increased uUCR (P = .009) was associated with faster IgAN progression.

Conclusion

The SNP rs77924615, which modulates the enhancer activity of the UMOD gene, is associated with renal function deterioration in IgAN patients by increasing uromodulin levels in both the renal tubular epithelium and urine.

A Rare Presentation of IgA Nephropathy in a 62-Year-Old Hispanic Female

A case of immunoglobulin A (IgA) nephropathy is presented here that demonstrates an unusual clinical presentation in multiple ways and is vitally important for clinicians to consider. The patient is a Hispanic female in her 7th decade of life that presented with nephrotic-range proteinuria without hematuria ultimately leading to a diagnosis of IgA nephropathy. After diagnosis, her clinical course was complicated by continued poorly controlled type II diabetes mellitus and hypertension, and ultimately her kidney disease progressed to chronic kidney disease IV and then end-stage renal disease requiring hemodialysis. Though IgA nephropathy predominantly presents as nephritic syndrome, it can also present as nephrotic range proteinuria and even rapidly progressive glomerulonephritis which should be considered even when the patient's ethnicity and age group carry a smaller risk.

Identifying Genetic Variants and Metabolites Associated with Rapid Estimated Glomerular Filtration Rate Decline in Korea Based on Genome-Metabolomic Integrative Analysis

Identifying the predisposing factors to chronic or end-stage kidney disease is essential to preventing or slowing kidney function decline. Therefore, here, we investigated the genetic variants related to a rapid decline in the estimated glomerular filtration rate (eGFR) (i.e., a loss of >5 mL/min/1.73 m2 per year) and verified the relationships between variant-related diseases and metabolic pathway signaling in patients with chronic kidney disease. We conducted a genome-wide association study that included participants with diabetes, hypertension, and rapid eGFR decline from two Korean data sources (N = 115 and 69 for the discovery and the validation cohorts, respectively). We identified a novel susceptibility locus: 4q32.3 (rs10009742 in the MARCHF1 gene, beta = −3.540, P = 4.11 × 10−8). Fine-mapping revealed 19 credible, causal single-nucleotide polymorphisms, including rs10009742. The pimelylcarnitine and octadecenoyl carnitine serum concentrations were associated with rs10009742 (beta = 0.030, P = 7.10 × 10−5, false discovery rate (FDR) = 0.01; beta = 0.167, P = 8.11 × 10−4, FDR = 0.08). Our results suggest that MARCHF1 is associated with a rapid eGFR decline in patients with hypertension and diabetes. Furthermore, MARCHF1 affects the pimelylcarnitine metabolite concentration, which may mediate chronic kidney disease progression by inducing oxidative stress in the endoplasmic reticulum.

IgA Nephropathy: A Chinese Perspective

Background

IgA nephropathy (IgAN) is the most common primary glomerular disease worldwide and remains a leading cause of chronic kidney disease and end-stage renal disease. The disease prevalence, clinical and pathological phenotypes, the underlying pathogenic molecular mechanisms, and the response to treatments are highly heterogeneous in different ethnic populations, which raise the concern that IgAN may differ across different parts of the world.

Summary

From a Chinese perspective, we stated the disease burden of IgAN, summarized genome-wide association studies and research into pathological molecules, and compared them with findings based on other populations. The emerging biomarkers, indigenous clinical trials, and major challenges for Chinese researchers and nephrologists in studying IgAN are also discussed.

Key Messages

In this review, we described a higher risk of major susceptible loci in mucosal immunity, IgA production, and complement activation pathways in Chinese patients with IgAN. With our understanding of the pathogenesis of IgAN, novel biomarkers are emerging. Although there are challenges for conducting high-quality clinical trials in China, it is still feasible to conduct innovative and well-designed studies of IgAN. In the future, international collaborations on research infrastructure would be helpful to advance clinical and basic research in China.

Is IgA nephropathy the same disease in different parts of the world?

Since it was first described in 1968, immunoglobulin A nephropathy (IgAN) is understood to be the most common form of glomerulonephritis worldwide. The diagnosis of IgAN depends on the presence of dominant mesangial IgA1 deposition by renal biopsy. To date, a wide spectrum of clinical and pathologic features of IgAN have been observed, implying that IgAN might not be the same disease across the world. Here, we review the characteristics of IgAN from perspectives of epidemiology, clinical-pathological patterns, disease pathogenesis, and treatment response across different ethnic populations. Overall, IgAN is most prevalent in Asians, followed by Caucasians, and relatively rare in Africans. More severe clinical presentation and higher risk of disease progression have been reported in Asians than Europeans. Moreover, active lesions, such as endocapillary hypercellularity and crescents, are more commonly reported in Asians than Europeans. Response to corticosteroid/immunosuppression therapy is variably reported, with greater apparent efficacy reported in Asian than European studies. Although a multi-hit hypothesis has been suggested for IgAN, the relative importance of each "hit" may vary in different ethnic populations and this variation underlies the differences in presentation of IgAN. In the future, a better understanding of pathogenic pathways operating in different ethnic populations may help provide better biomarkers of disease and more precise targeting of treatment strategies for IgAN.

New therapeutic perspectives for IgA nephropathy in children

Childhood IgA nephropathy (cIgAN) differs from the adult by having an abrupt clinical onset, often presenting as an acute attack that can progress to a chronic phase. No treatment guidelines have been established for the treatment of cIgAN. Given the severity of acute attack in children, and the number of life-years at stake, pediatricians prescribe immunosuppression in addition to renin-angiotensin system blockade. Non-specific immunosuppressors, such as corticosteroids, have systemic toxic effects, and given recent therapeutic advances in adult glomerulonephritis, new tailored strategies should be expected for children. The mucosal immune system has been highlighted as a key player in IgAN pathogenesis, and several biomarkers have been identified with a direct role in pathogenesis. In this review, we discuss current studies of conventional and novel therapeutic approaches for cIgAN.

Integration of genetic and histopathology data in interpretation of kidney disease

For many years renal biopsy has been the gold standard for diagnosis in many forms of kidney disease. It provides rapid, accurate and clinically useful information in most individuals with kidney disease. However, in recent years, other diagnostic modalities have become available that may provide more detailed and specific diagnostic information in addition to, or instead of, renal biopsy. Genomics is one of these modalities. Previously prohibitively expensive and time consuming, it is now increasingly available and practical in a clinical setting for the diagnosis of inherited kidney disease. Inherited kidney disease is a significant cause of kidney disease, in both the adult and paediatric populations. While individual inherited kidney diseases are rare, together they represent a significant burden of disease. Because of the heterogenicity of inherited kidney disease, diagnosis and management can be a challenge and often multiple diagnostic modalities are needed to arrive at a diagnosis. We present updates in genomic medicine for renal disease, how genetic testing integrates with our knowledge of renal histopathology and how the two modalities may interact to enhance patient care.

ST6GAL1 polymorphisms influence susceptibility and progression of IgA nephropathy in a Chinese Han population

BACKGROUND

ST6GAL1 has been identified as a novel susceptibility gene for IgA nephropathy (IgAN) in a previous genome-wide association study. The present study is aimed at exploring whether the genetic polymorphisms of ST6GAL1 gene correlate with IgAN susceptibility, clinical phenotypes and progression in a Chinese Han population.

METHODS

Twenty-six single nucleotide polymorphisms (SNPs) of ST6GAL1 were genotyped in 1000 biopsy-proven IgAN patients and 1000 control subjects of Chinese Han population using Sequenom MassARRAY iPLEX. A logistic regression analysis with age and sex as covariates was performed to evaluate the effects of ST6GAL1 gene polymorphisms on IgAN susceptibility. Kaplan-Meier method and Cox proportional hazard models were applied to analyze the associations between genetic variants and renal survival.

RESULTS

We found that rs7634389 (OR = 1.24, 95 % CI = 1.02-1.50, p_dominant = 0.034) and rs6784233 (OR = 1.23, 95 % CI = 1.05-1.45, p_additive = 0.013; OR = 1.28, 95 % CI = 1.05-1.55, p_dominant = 0.014) were associated with susceptibility of IgAN. In addition, rs7634389 was correlated with hyperuricemia (OR = 1.27, p =  0.012) and segmental glomerulosclerosis (OR = 1.21, p = 0.047) in IgAN patients. Furthermore, rs7634389 was independently associated with renal survival after adjustments for multiple confounders (hazard ratio [HR] = 0.51, 95 % CI = 0.33-0.78, p =  0.002). Haplotype analysis for ST6GAL1 polymorphisms confirmed their associations with the susceptibility to IgAN.

CONCLUSIONS

Our research suggested that ST6GAL1 gene polymorphisms were implicated in IgAN susceptibility and clinical outcome in a Chinese Han population.

The potential effects of anabolic-androgenic steroids and growth hormone as commonly used sport supplements on the kidney: a systematic review

BACKGROUND

Anabolic-androgenic steroids and growth hormone are among the most commonly used supplements by sportsmen and sportswomen. The aim of this systematic review is to collect and report available data about renal safety of anabolic-androgenic steroids and growth hormone (GH).

METHODS

The search strategy was in accordance with the PRISMA guideline. Seven databases such as Scopus, Medline, Embase, and ISI Web of Knowledge were searched using keywords, such as "growth hormone", "anabolic-androgenic steroids", and "kidney injury". Articles published from 1950 to December 2017 were considered. Randomized clinical trials, prospective or retrospective human studies, case series as well as case reports, and experimental (in vivo) studies were included. Twenty one clinical and experimental articles were selected (12 for anabolic-androgenic steroids and 9 for GH).

RESULTS

Anabolic-androgenic steroids can affect the kidney in different aspects. They can induce or aggravate acute kidney injury, chronic kidney disease, and glomerular toxicity. These adverse effects are mediated through pathways such as stimulating renin-angiotensin-aldosterone system, enhancing the production of endothelin, producing reactive oxygen species, over-expression of pro-fibrotic and pro-apoptotic mediators (e.g., TGF-β1), as well as inflammatory cytokines (e.g., TNF-α, IL-1b, and IL-6). Although GH may affect the kidney in different aspects, such as size, glomerular filtration rate, and tubule functions, either directly or indirectly, there is no conclusive clinical evidence about its detrimental effects on the kidney in athletes and body builders.

CONCLUSION

Evidence regarding effects of anabolic-androgenic steroids exists; However, GH's exact effect on the kidney at doses used by athletes and body builders has not yet been clarified. Cohort clinical studies with long-term follow-up are warranted in this regard.

Is immunoglobulin A nephropathy different in different ethnic populations?

Immunoglobulin A nephropathy (IgAN) is one of the commonest global patterns of primary glomerulonephritis and remains a leading cause of chronic kidney disease and end-stage renal disease. The sole diagnostic criterion of IgAN remains the presence of dominant mesangial immunoglobulin A deposits on kidney biopsy. Beyond this defining feature, there is significant heterogeneity in the epidemiology, clinical presentation, renal progression and long-term outcomes of IgAN in different ethnic populations. Mirroring this heterogeneity in clinical phenotypes, there is also marked ethnic variation in the extent of histopathological lesions observed on kidney biopsy, which may partly explain the well-documented differences in response to immunomodulatory agents reported in different regions of the world. In parallel, disparities have been identified in genetic association studies and key pathogenic pathways in different ethnic populations. Understanding the basis for these differences in IgAN has important implications for both clinical care and future research. In this review, we will examine the impact of ethnicity on the epidemiology, clinical presentation and outcomes, pathogenesis and genetic associations in IgAN.

Genetic Determinants of IgA Nephropathy: Western Perspective

IgA nephropathy (IgAN) represents a genetically complex multifactorial trait. Its prevalence and clinical features vary geographically, and the disease has a range of clinical presentations that suggest multiple subtypes. Although familial aggregation of IgAN has been reported and prior linkage studies have highlighted significant locus heterogeneity, specific genetic variants underlying familial IgAN have not yet been defined. Population-based genome-wide association studies (GWAS) have discovered nearly 20 IgAN risk loci, providing novel insights into disease epidemiology and molecular mechanisms, shifting old paradigms of the disease pathogenesis. Follow-up fine-mapping studies have identified specific causal variants, and genotype-phenotype correlation studies have begun to delineate clinical consequences of GWAS risk alleles. The association between IgAN and galactose-deficient IgA1 (Gd-IgA1), a validated serum biomarker of IgAN, presented another avenue for genetic discovery because elevated serum levels of Gd-IgA1 are highly heritable. Recent GWAS for serum Gd-IgA1 levels provided novel insights into genetic regulation of this trait, but the genetic link between Gd-IgA1 and IgAN has not yet been established. In this review, we discuss these developments in the broader context of modern genetic approaches to complex traits, and provide our perspective on the critical challenges that need to be addressed to advance the field.

Complement factor H gene polymorphism rs6677604 and the risk, severity and progression of IgA nephropathy: A systematic review and meta-analysis

AIM

Studies reporting the association between complement factor H gene rs6677604 polymorphism and susceptibility to IgA nephropathy (IgAN) had yielded inconsistent results. We performed a systematic review and meta-analysis to clarify the association between rs6677604 and IgAN susceptibility, disease severity and chronic progression.

METHODS

A comprehensive database search was performed to identify eligible studies. Meta-analyses were performed for rs6677604 allele frequency, genotypes and the association with IgAN susceptibility.

RESULTS

10 studies were included in the systematic review. Among them, four studies containing 10 distinct datasets (15,617 cases and 31,957 controls) were included in the meta-analysis. The pooled frequency of the minor allele (A) was significantly higher in Europeans than in Asians across both IgAN cases and controls, and the frequency of the minor allele (A) in IgAN cases was also significantly lower than that in controls across both European and Asian subgroups. Significant associations were detected between rs6677604 and risk of developing IgAN, when comparing allele A vs. G, genotype AA vs. GG, genotype AA vs. AG and genotype AG vs. GG. In analysis stratified by ethnicity, significant association was only observed in Europeans but not in Asians when comparing AA vs. GG or AA vs. AG.

CONCLUSION

Our pooled analysis showed a significant association between rs6677604-(A) allele and IgAN susceptibility, supporting the importance of complement activation in the pathogenesis of IgAN. The presence of rs6677604-(A) allele may be associated with a decreased the risk of IgAN in Europeans, but the association was not confirmed in Asians.

Protocol and rationale for the first South Asian 5-year prospective longitudinal observational cohort study and biomarker evaluation investigating the clinical course and risk profile of IgA nephropathy: GRACE IgANI cohort

Background: IgA nephropathy (IgAN) is the most common primary glomerulonephritis and an important cause of end-stage kidney disease. Unlike the slowly progressive course seen among Caucasian and East Asian subjects (actuarial survival 80-85% over 10 years), in India about 30-40% of patients have nephrotic syndrome and renal dysfunction at presentation and a 10-year renal survival of 35%, as reported from a retrospective registry. These observations cannot be entirely attributed to a lack of uniform screening protocols or late referral and attest to the probability that IgAN may not be the same disease in different parts of the world. Methods: We will prospectively recruit 200 patients with IgAN (the GRACE IgANI- Glomerular Research And Clinical Experiments- Ig A Nephropathy in Indians-cohort) and stratify them into low and high risk of progression based on published absolute renal risk scores. We will test the validity of this risk score in an unselected Indian IgAN population over a 5-year follow-up period. In parallel, we will undertake extensive exploratory serum, urine, renal and microbiome biomarker studies, firstly, to determine if the underlying pathogenic pathways are the same in Indian IgAN compared to those reported in Caucasian and East Asian IgAN. Secondly, we will systematically assess the value of measuring selected biomarkers and adding this data to traditional measures of risk in IgAN to predict kidney failure. We ultimately hope to generate a composite IgAN risk score specific for the Indian population. Ethics and data dissemination: Approval was obtained from the Institutional Review Board (Silver, Research and Ethics Committee) of the Christian Medical College, Vellore, India (Ref. No. IRB Min. No. 8962 [Other] dated 23.07.2014 and IRB Min. No. 9481 [Other] dated 24.06.2015). It is anticipated that results of this study will be presented at national and international meetings, with reports being published from late 2018.

IgA Nephropathy in Salvador, Brazil. Clinical and laboratory presentation at diagnosis

Introduction:

IgA nephropathy (IgAN) is the most prevalent primary glomerulopathy in the world, but great variation is reported in different countries. In Brazil, the reported prevalence is high in the Southeastern States and low in Salvador, Bahia State, Brazil.

Objectives:

This study investigated the clinical and histological patterns of patients with IgAN in Salvador, Brazil.

Methods:

This is a descriptive study that included all patients with a diagnosis of IgAN performed in native kidney biopsies collected from referral nephrology services of public hospitals in Salvador between 2010 and 2015. Results: Thirty-two cases of IgAN were identified, corresponding to 6% of primary glomerulopathies. There was a slight male predominance (56%) and the median age was 30 [22-40] years. Hematuria was present in 79%, non-nephrotic proteinuria was present in 61%, and hypertension was present in 69% of patients. Segmental sclerosis (S1 lesions) was present in 81% of cases, and chronic tubulo-interstitial lesions (T1 and T2 lesions) were present in 44% of cases. Patients with M1 and T2 MEST-C scores exhibited higher serum urea and creatinine than other patients.

Conclusion:

The prevalence of IgAN was lower in Salvador than other regions of Brazil. Chronic histological lesions and laboratory markers of severe disease were frequent. M1 and T2 MEST-C scores were correlated with markers of renal dysfunction.

The Association of rs1047763 and rs1008898 of C1GALT1 with IgA Nephropathy Risk: A Global Meta-Analysis

IgA nephropathy (IgAN) is a globally common primary glomerulonephritis characterized by an elevated level of serum IgA and immune complex deposition in the mesangial area. In the serum of patients with IgAN, the hinge region of IgA1 immunoglobulin contains aberrantly glycosylated O-glycans deficient in galactose, which is normally added to the core 1 O-glycan structure by core 1 synthase, glycoprotein-N-acetylgalactosamine 3-beta-galactosyltransferase 1 (C1GALT1), the key enzyme in the process of glycosylation. It is unknown if single-nucleotide polymorphisms rs1047763 and rs1008898 of C1GALT1 increase the risk of IgAN. We enrolled 5 subjects in this meta-analysis, including a total of 1693 IgAN patients and 1864 control subjects. We performed meta-analysis on associations between rs1047763, rs1008898, and IgAN using the allele model, dominant model, recessive model, and additive model. We found that there was no relationship between rs1047763 and rs1008898 in C1GALT1 and susceptibility to IgAN.

Predicting Post-Transplant Recurrence of IgA Nephropathy: The Importance of Crescents

BACKGROUND

Most studies that have assessed the predictors of recurrent IgA nephropathy (IgAN) in the renal allograft have focused on post-transplant features. Identifying high-risk pre-transplant features of IgAN is useful for counseling patients and may help in tailoring post-transplant immunosuppression.

METHODS

We investigated the pre-transplant clinical and biopsy features of 62 patients with IgAN who received transplants at Columbia University Medical Center from 2001 to 2012 and compared the characteristics and outcomes of patients with IgAN recurrence to those without recurrence. The primary outcome was time to recurrent IgAN. Secondary outcomes were a composite of doubling of creatinine or allograft failure, and recurrent IgAN as a cause of allograft dysfunction.

RESULTS

Of the 62 patients, 14 had recurrent IgAN in the allograft. Mean time to recurrence was 2.75 years. Those with recurrent disease were younger at the time of native kidney biopsy (29 vs. 41 years, p < 0.0009). Black race and Hispanic ethnicity composed a higher proportion of the recurrent disease group. On multivariable analysis, significant predictors of recurrent IgAN included age at diagnosis (hazards ratio (HR) 0.911, 95% CI 0.85-0.98), burden of crescents on native biopsy (HR 1.21 per 10% increase in crescents, 95% CI 1.00-1.47) and allograft rejection (HR 3.59, 95% CI 1.10-11.7).

CONCLUSIONS

Features of native IgAN can help predict the risk of recurrent disease in the renal allograft. In particular, immunologically active disease represented by earlier age of onset and greater burden of crescents on native biopsy is more likely to recur after transplant.

IgA1 Glycosylation Is Heritable in Healthy Twins

IgA nephropathy (IgAN) is the most common form of primary GN and an important cause of kidney failure. Characteristically, patients with IgAN have increased serum levels of undergalactosylated IgA1 (gd-IgA1). To assess the degree to which serum gd-IgA1 levels are genetically determined in healthy individuals, we determined serum IgA and gd-IgA1 levels by ELISA in a sample of 148 healthy female twins, including 27 monozygotic and 47 dizygotic pairs. Using the classic twin model, we found the heritability of serum gd-IgA1 and IgA levels to be 80% (95% confidence interval, 66% to 89%) and 46% (95% confidence interval, 15% to 69%), respectively. These data indicate that serum gd-IgA1 levels are highly heritable. Elucidating the genetic basis of this heritability will be important in understanding the pathogenesis of IgAN.

Recent advances in the understanding and management of IgA nephropathy

Since its first description in 1968, IgA nephropathy has remained the most common form of primary glomerulonephritis leading to chronic kidney disease in developed countries. The clinical progression varies, and consequent end-stage renal disease occurs in 30% to 40% of patients 20 to 30 years after the first clinical presentation. Current data implicate overproduction of aberrantly glycosylated IgA1 as being pivotal in the induction of renal injury. Effective and specific treatment is still lacking, and new therapeutic approaches will be developed after better understanding the disease pathogenesis.

The long-term efficacy and safety of immunosuppressive therapy on the progression of IgA nephropathy: a meta-analysis of controlled clinical trials with more than 5-year follow-up

OBJECTIVE

To evaluate the long-term efficacy of immunosuppressive therapy on Immunoglobulin A nephropathy (IgAN).

METHODS

Trials with at least 5-year follow-up investigating immunosuppressive therapy were selected.

MAIN OUTCOME MEASURES

Primary outcome was end-stage renal disease (ESRD). Secondary outcome was deterioration in renal function defined as doubled serum creatinine or 50% reduction of eGFR.

RESULTS

Seven studies were enrolled. Immunosuppression lowered the risk for ESRD risk ratio (RR = 0.30, 95% CI 0.19 - 0.48, p < 0.00001) and deterioration in renal function (RR = 0.19, 95% CI 0.07 - 0.54, p = 0.002). As for pooled RRs of ESRD, there were four studies with < 7-year follow-up, three followed for > 7 years, four adopted corticosteroids, two used corticosteroids plus other immunosuppressive agents, four were from Asia, and three from Europe. Pooled RRs were 0.32 (95% CI, 0.18 - 0.58, p = 0.0001), 0.28 (95% CI, 0.13 - 0.59, p = 0.0009), 0.34 (95% CI, 0.17 - 0.67, p = 0.002), 0.29 (95% CI, 0.15 - 0.58, p = 0.0005), 0.37 (95% CI, 0.20 - 0.68, p = 0.001) and 0.23 (95% CI, 0.11 - 0.47, p < 0.0001), respectively. Immunosuppression was associated with an increased risk for adverse events (RR = 2.13, 95% CI 1.17 - 3.86, p = 0.01).

CONCLUSIONS

Immunosuppressive therapy for IgAN might reduce long-term risk of ESRD and deterioration in renal function but increase risk of adverse events, and the efficacy on patients from Europe and Asia might be similar. Addition of other immunosuppressive agents did not provide additional benefit.

UMOD polymorphism rs12917707 is not associated with severe or stable IgA nephropathy in a large Caucasian cohort

Background

Genetic factors are suspected in the pathogenesis of IgA nephropathy, as well as in the course of IgA nephropathy progression towards end stage renal failure. UMOD polymorphism rs12917707 is known to associate with end stage renal failure of mixed aetiologies.

Methods

We tested a large cohort of Caucasian patients for association of rs12917707 with IgA nephropathy showing a benign, stable course and with IgA nephropathy that progressed toward end stage renal failure.

Results

No association was observed between either groups, and a non-significant trend was observed for more severe IgA nephropathy with the allele reported to protect against end stage renal failure of mixed aetiologies.

Conclusion

We conclude that UMOD is unlikely to play a role in IgA nephropathy pathogenesis nor progression to end stage renal failure, and suggest that UMOD effects are restricted to some causes of renal disease, e.g. diabetes or hypertension.

The genetics and immunobiology of IgA nephropathy

IgA nephropathy (IgAN) represents the leading cause of kidney failure among East Asian populations and the most frequent form of primary glomerulonephritis among Europeans. Patients with IgAN develop characteristic IgA1-containing immune complexes that deposit in the glomerular mesangium, producing progressive kidney injury. Recent studies define IgAN as an autoimmune trait of complex architecture with a strong genetic determination. This Review summarizes new insights into the role of the O-glycosylation pathway, anti-glycan immune response, mucosal immunity, antigen processing and presentation, and the alternative complement pathway in the pathogenesis of IgAN.

Pathology of IgA nephropathy

IgA nephropathy is defined by the presence of IgA-dominant or co-dominant immune deposits within glomeruli. Biopsy specimens meeting these diagnostic criteria have a range of histological changes that are reflected in the variable clinical course of IgA nephropathy. The impact of histology on outcomes in IgA nephropathy has been clarified in a number of large retrospective clinicopathological studies. These studies have consistently demonstrated that the stage of disease at presentation, as indicated by the extent of interstitial fibrosis and tubular atrophy in the biopsy, is the strongest histological predictor of renal survival. The effect of active proliferative lesions on the disease course is less clear cut, owing in part to considerable treatment bias in most published retrospective studies. There is evidence that endocapillary hypercellularity and cellular crescents are responsive to immunosuppressive therapy, but this observation requires confirmation in prospective randomized controlled trials. Future challenges include improving the reproducibility of histological scoring, particularly for the presence and extent of endocapillary lesions, and to improve prognostic modelling by combining histological data with clinical variables and biomarker data.

Role of testosterone in the pathogenesis, progression, prognosis and comorbidity of men with chronic kidney disease

Testosterone deficiency and hypogonadism are common conditions in men with chronic kidney disease (CKD). A disturbed hypothalamic-pituitary-gonadal axis due to CKD is thought to contribute to androgen deficiency. Data from experimental studies support the hypothesis that exogenous administration of testosterone may induce the activation of the renin-angiotensin system (RAS), the production of endothelin and the regulation of anti- or/and proinflammatory cytokines involved in the pathogenesis of hypertension and kidney damage. On the other hand, low testosterone levels in male patients with CKD are paradoxically associated with a higher risk of morbidity and mortality, possibly explained by anemia, osteoporosis and cardiovascular disease. In this article, we present an overview of clinical and experimental studies of the impact of testosterone on the progression and prognosis of male patients with CKD; even today, this remains a controversial issue.

The coincidence of IgA nephropathy and Fabry disease

Background

IgA nephropathy (IgAN) is the most common glomerulonephritis, which may also coexist with other diseases. We present two patients with an unusual coincidence of IgAN and Fabry disease (FD).

Case presentation

A 26 year-old man underwent a renal biopsy in February 2001. Histopathology showed very advanced IgAN and vascular changes as a result of hypertension. Because of his progressive renal insufficiency the patient began hemodialysis in August 2001. By means of the blood spot test screening method the diagnosis of FD was suspected. Low activity of alpha-galactosidase A in the patient’s plasma and leukocytes and DNA analysis confirmed the diagnosis of FD. Enzyme replacement therapy started in July 2004. Then the patient underwent kidney transplantation in November 2005. Currently, his actual serum creatinine level is 250 μmol/l. Other organ damages included hypertrophic cardiomyopathy, neuropathic pain and febrile crisis. After enzyme replacement therapy, myocardial hypertrophy has stabilized and other symptoms have disappeared. No further progression of the disease has been noted.

The other patient, a 30 year-old woman, suffered from long-term hematuria with a good renal function. Recently, proteinuria (2.6 g/day) appeared and a renal biopsy was performed. Histopathology showed IgAN with remarkably enlarged podocytes. A combination of IgAN and a high suspicion of FD was diagnosed. Electron microscopy revealed dense deposits in paramesangial areas typical for IgAN and podocytes with inclusive zebra bodies and myelin figures characteristic of FD. FD was confirmed by the decreased alpha-galactosidase A activity in plasma and leukocytes and by DNA and RNA analysis. Enzyme replacement therapy and family screening were initiated.

Conclusions

Our results emphasize the role of complexity in the process of diagnostic evaluation of kidney biopsy samples. Electron microscopy represents an integral part of histopathology, and genetic analysis plays a more and more important role in the final diagnosis, which is followed by causal treatment.

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.

Genetic studies of IgA nephropathy: past, present, and future

Immunoglobulin A nephropathy (IgAN) is the most common form of primary glomerulonephritis worldwide and an important cause of kidney disease in young adults. Highly variable clinical presentation and outcome of IgAN suggest that this diagnosis may encompass multiple subsets of disease that are not distinguishable by currently available clinical tools. Marked differences in disease prevalence between individuals of European, Asian, and African ancestry suggest the existence of susceptibility genes that are present at variable frequencies in these populations. Familial forms of IgAN have also been reported throughout the world but are probably underrecognized because associated urinary abnormalities are often intermittent in affected family members. Of the many pathogenic mechanisms reported, defects in IgA1 glycosylation that lead to formation of immune complexes have been consistently demonstrated. Recent data indicates that these IgA1 glycosylation defects are inherited and constitute a heritable risk factor for IgAN. Because of the complex genetic architecture of IgAN, the efforts to map disease susceptibility genes have been difficult, and no causative mutations have yet been identified. Linkage-based approaches have been hindered by disease heterogeneity and lack of a reliable noninvasive diagnostic test for screening family members at risk of IgAN. Many candidate-gene association studies have been published, but most suffer from small sample size and methodological problems, and none of the results have been convincingly validated. New genomic approaches, including genome-wide association studies currently under way, offer promising tools for elucidating the genetic basis of IgAN.

Genetic contribution and associated pathophysiology in end-stage renal disease

End-stage renal disease (ESRD) or chronic kidney disease (CKD) is the terminal state of the kidney when its function has been permanently and irreversibly damaged. A wide variety of etiologies and pathological processes culminate in ESRD, and both environmental and genetic factors contribute to its development and progression. Various reports suggest that susceptibility to develop ESRD has a significant genetic component. These studies include familial aggregation studies, comparisons of incidence rates between different racial or ethnic populations, and segregation analysis. Genetic approaches have been used to identify genes that contribute to genetic susceptibility. Many studies have now been carried out assessing the contribution of specific “candidate genes”, which correlate with different functions that are involved in the renal pathogenesis. Independent studies for specific associated genes have frequently provided contradictory results. This may be due, in part, to the modest contribution to genetic susceptibility which these genes impart. With the availability of different genomewide association studies, chromosomal regions harboring novel, previously unrecognized, genes that may contribute to renal diseases have been recently reported. We have focused on different genetic studies conducted on ESRD and have discussed the strength and weaknesses of these studies. The nonmuscle myosin heavy chain 9 gene (MYH9) and renin–angiotensin system (RAS) have been discussed in detail.

Galactose-deficient IgA1 in African Americans with IgA nephropathy: serum levels and heritability

BACKGROUND AND OBJECTIVES

Serum levels of galactose-deficient IgA1 (Gd-IgA1) are elevated and heritable in Caucasian and Asian patients with IgA nephropathy (IgAN), but have not been characterized in African Americans (AA). Our objective was to determine whether serum Gd-IgA1 levels are increased in AA patients with IgAN and whether this is a heritable trait in this group.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Blood and urine samples were obtained from 18 adult and 11 pediatric AA patients with biopsy-proven IgAN and from 34 of their first-degree relatives. Healthy controls included 150 Caucasian adults, 65 AA adults, 45 Caucasian children, and 49 AA children. Serum total IgA and Gd-IgA1 levels were measured in patients and controls. Significant differences between patient and control groups for serum total IgA, Gd-IgA1, and ratio of Gd-IgA1/total IgA were determined by the Mann-Whitney U test. Heritability was calculated using SOLAR.

RESULTS

After stratifying by age, 7 of 11 pediatric and 9 of 18 adult AA patients with IgAN had serum Gd-IgA1 levels above the 95th percentile for age-appropriate AA controls. For first-degree relatives, the serum Gd-IgA1 level was >95th percentile for 1 of 8 when the patient's level was <95th percentile and 12 of 26 when the patient's level was >95th percentile (P = 0.116, Fisher exact test). Heritability was 0.74 (P = 0.007).

CONCLUSIONS

Serum levels of Gd-IgA1 are often elevated in AA patients with IgAN and their first-degree relatives. Thus, aberrant IgA1 glycosylation is a heritable risk factor for IgAN in African Americans.

Polymorphisms of theCOL1A2,CYP1A1andHS1,2 Ig enhancergenes in the Tuaregs from Libya

BACKGROUND

Restriction fragment length polymorphisms (RFLPs) of the COL1A2 and CYP1A1 and short tandem repeats of HS1,2 Ig enhancer genes are proving to be useful markers for describing human populations and thus are of interest for anthropogenetic research. Moreover, they can provide useful information in identifying alleles and haplotypes associated with particular forms of common diseases or for pharmacogenomics studies.

AIM

The objective of this study was to define the genetic structure of Libyan Tuaregs and to establish the degree of genetic homogeneity amongst the El Awaynat and Tahala groups.

SUBJECTS AND METHODS

Tuareg individuals from El Awaynat (n = 99) and Tahala (n = 18), in Libyan Sahara, were analysed for the RFLPs of COL1A2 and CYP1A1 and short tandem repeats of HS1,2 Ig enhancer genes. In order to provide a clearer picture of COL1A2, CYP1A1 and HS1,2 Ig enhancer allele and haplotype frequency distributions in various human groups distributed over a wide geographic area, comparisons with other African, European and Asian populations were carried out by analysis of molecular variance (AMOVA) and genetic distance analysis.

RESULTS

No significant level of differentiation was evident between the two Libyan Tuareg groups according to AMOVA. For the CYP1A1 gene, a possible new haplotype was observed, even though at a very low frequency. Linkage disequilibrium was assessed only for COL1A2, since CYP1A1 turned out to be poorly polymorphic for m2 and m3.

CONCLUSIONS

Statistical analyses showed that Tuaregs from Libya are located in a intermediate position between south Saharan populations on one side and the Europeans and the Asians on the other.

IgA nephropathy: a twenty year retrospective single center experience

IgA nephropathy (IgAN) is a common glomerular disease whose etiology is unknown. Previous studies have described the clinical and laboratory features but none have specifically compared patients during different time periods. This 20 year retrospective study was performed to assess trends in the severity of IgAN from 1989-2008. We reviewed 57 patient charts that contained a confirmed biopsy diagnosis of IgAN and recorded data at the time of diagnosis and the final follow-up appointment. Clinical data included physical examination, urine, and blood tests. Patients were separated into two cohorts, Cohort 1 1989-1998 and Cohort 2 1999-2008. An increase in severity was noted in Cohort 2 based on a significantly higher Up/c and lower serum albumin level. Other prognostic indicators including GFRe, hematocrit, and glomerular injury score also demonstrated a trend towards more severe disease over the past 20 years. The patients in both Cohorts received similar treatments and had comparable renal function at the last follow-up visit. Based on our findings, we suggest that although a kidney biopsy is required to diagnose IgAN, the procedure may not be necessary in patients clinically suspected of having the disease but who have normal kidney function and minimal urine abnormalities.

Continental variations in IgA nephropathy among Asians

BACKGROUND/AIMS

Local variations in patient demographics and medical practice can contribute to differences in renal outcomes in patients with IgA nephropathy. We report the experiences of two groups of Asians with IgA nephropathy across continents.

MATERIALS AND METHODS

We retrospectively examined two cohorts of Asian patients with IgA nephropathy from The King Chulalongkorn Memorial Hospital registry, Thailand (1994 - 2005), and The Metropolitan Toronto Glomerulonephritis registry, Canada (1975 - 2006), and compared their baseline characteristics. Slope of estimated glomerular filtration rate (eGFR) in each group was approximated using separate repeated measures regression models for each country.

RESULTS

There were 152 Canadian and 76 Thai patients. At the time of first presentation, Thai patients were more likely to be female (63.2 vs. 44.1%, p = 0.01), have less baseline proteinuria (1.2 vs. 1.7 g/d, p = 0.08) and more likely to receive angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB) (64.0 vs. 15.2%, p < 0.01), or prednisone (41.3 vs. 4.6%, p < 0.01). The annual change in estimated glomerular filtration rate (eGFR) for the Thai and Canadian groups were -0.82 ml/min/1.73 m2/year and -3.35 ml/min/1.73 m2/year, respectively, after adjustment for age, sex, mean arterial pressure (MAP), proteinuria, body mass index, Haas histological grade, chronicity scores and baseline medications.

CONCLUSIONS

Although disease severity was similar among IgA nephropathy patients in Canada and Thailand, more Thai patients were on ACE-I/ARB or prednisone therapy at baseline. Further prospective research is needed to explore international differences in demographic and environmental factors, health resources, and disease management to determine how they may impact long-term outcomes in Asians with IgA nephropathy.

Asian leadership in chronic kidney disease

Asian Pacific countries include those with the highest incidence of renal failure in the world, the richest and poorest economies and unparalleled diversity of economy, culture and geography. From this come many challenges, but also a strong basis for the introduction of strategies to combat renal diseases. With a rapidly developing scientific community, Asia needs to accept the challenge of becoming a global leader in nephrology in the near future.

Ethnic disparity in outcomes for pediatric peritoneal dialysis patients in the ESRD Clinical Performance Measures Project

Ethnicity information was collected for all pediatric peritoneal dialysis patients from the End-Stage Renal Disease (ESRD) Clinical Performance Measures (CPM) Project for the period October 2004 through March 2005. Associations between intermediate outcomes and Hispanic ethnicity were determined. Thirty percent (207/696) of patients in the final cohort were Hispanic, 24% (165/696) non-Hispanic black, and 46% (324/696) non-Hispanic white. Hispanics were more likely to be female, older, and have a lower mean height standard deviation score (SDS). There were no significant differences among ethnic/racial groups regarding clearance parameters. More Hispanics had a mean hemoglobin > or = 11 g/dl compared with non-Hispanic blacks and non-Hispanic whites (77% vs. 55% and 70%, P < 0.0001). More Hispanics compared with non-Hispanic blacks and non-Hispanic whites had a mean serum albumin > or = 4.0/3.7 g/dl [bromcresol green/bromcresol purple laboratory method (BCG/BCP)] (50% vs. 24% and 27%, respectively, P < 0.0001). In multivariate analyses, Hispanics remained significantly more likely to achieve a mean serum albumin > or = 4.0/3.7 g/dl (BCG/BCP) compared with non-Hispanic whites (referent) and were as likely to achieve clearance and hemoglobin targets. Pediatric Hispanic peritoneal dialysis patients experience equivalent or better intermediate outcomes of dialytic care compared with non-Hispanics. Further study is needed to understand associations of Hispanic ethnicity with outcomes such as hospitalization, transplantation, and mortality.

Immunoglobulin enhancer HS1,2 polymorphism: a new powerful anthropogenetic marker

The human HS1,2 enhancer of the immunoglobulin (Ig) heavy chain 3' enhancer complex plays a central role in the regulation of Ig maturation and production. Four common alleles HS1,2-A*1, *2, *3, *4 are directly implicated with the transcription level and at least one of them, HS1, 2-A*2, seems to be related to immune disorders, such as coeliac disease, herpetiform dermatitis and Berger syndrome. Given their clinical significance it is of interest to know the distribution of HS1,2-A variants in populations from different continents, as well as to determine whether the polymorphism is associated to specific evolutionary factors. In this paper we report the distribution of the HS1,2-A polymorphism in 1098 individuals from various African, Asian and European populations. HS1,2-A*3 and HS1,2-A*4 alleles are at their highest frequencies among Africans, and HS1,2-A*2 is significantly lower in Africans in comparison with both Europeans and, to a lesser extent, Asians. Analysis of molecular variance of the allele frequencies indicates that the HS1,2-A polymorphism can be considered as a reliable anthropogenetic marker.

Testosterone supplementation in aging men and women: possible impact on cardiovascular-renal disease

Treatment of aging men and women with testosterone supplements is increasing. The supplements are given to postmenopausal women mainly to improve their libido and to aging men to improve muscle mass and bone strength, to improve libido and quality of life, to prevent and treat osteoporosis, and, with the phosphodiesterase-5 inhibitors, such as sildenafil, to treat erectile dysfunction. The increased use of testosterone supplements in aging individuals has occurred despite the fact that there have been no rigorous clinical trials examining the effects of chronic testosterone on the cardiovascular-renal disease risk. Studies in humans and animals have suggested that androgens can increase blood pressure and compromise renal function. Androgens have been shown to increase tubular sodium and water reabsorption and activate various vasoconstrictor systems in the kidney, such as the renin-angiotensin system and endothelin. There is also evidence that androgens may increase oxidative stress. Furthermore, the kidney contains the enzymes necessary to produce androgens de novo. This review presents an overview of the data from human and animal studies in which the role of androgens in promoting renal and cardiovascular diseases has been investigated.

The conundrum of increased burden of end-stage renal disease in Asians

BACKGROUND

Few cohort studies have examined the risk of end-stage renal disease (ESRD) among Asians compared with whites and blacks.

METHODS

To compare the incidence of ESRD in Asians, whites, and blacks in Northern California, we examined sociodemographic and clinical data on 299,168 adults who underwent a screening health checkup at Kaiser Permanente between 1964 and 1985. Incident cases of ESRD were ascertained by matching patient identifiers with the nationally comprehensive United States Renal Data System ESRD registry.

RESULTS

Overall, 1346 cases of ESRD occurred during 7,837,310 person-years of follow-up. The age-adjusted rate of ESRD (per 100,000 person-years) was 14.0 [95% confidence interval (CI) 10.5-18.5] among Asians, 7.9 (95% CI 6.5-9.5) among whites, and 43.4 (95% CI 36.6-51.4)] among blacks. Controlling for age, gender, educational attainment, diabetes, prior myocardial infarction, serum creatinine, systolic and diastolic blood pressure, proteinuria, hematuria, cigarette smoking, serum total cholesterol, and body mass index increased the risk of ESRD in Asians relative to whites from 1.69 to 2.08 (95% CI 1.61-2.67). By contrast, adjustment for the same covariates decreased the risk of ESRD in blacks relative to whites from 5.30 to 3.28 (95% CI 2.91-3.69).

CONCLUSION

Factors contributing to the excess ESRD risk in Asians relative to whites extend beyond usually considered sociodemographic and comorbidity disparities. Strategies aimed at examining novel risk factors for kidney disease and efforts to increase awareness of kidney disease among Asians may reduce ESRD incidence in this high-risk group.