Disease Progression In IgA Nephropathy Research Articles

Glomerular IgG deposition predicts kidney disease progression in IgA nephropathy

ObjectiveWe aimed to explore the relationship between the presence and intensity of glomerular IgG deposition and the occurrence of kidney progression events in IgA nephropathy (IgAN). MethodsThis retrospective study encompassed a total of 1207 patients with IgAN spanning the period from 2010 to 2022, and complete follow-up data were accessible for 736 patients. The IgG intensity was categorized as follows: low-level, defined as IgG (±) and IgG (+), and high-level, defined as IgG (++) and IgG (+++). ResultsWe found that the IgG-positive deposited group (N = 113, 9.36%) had significantly higher levels of ESR, TC, LDL, uric acid, proteinuria, and blood glucose, and lower serum albumin level compared to the IgG-negative deposited group (N = 1094, 90.64%). In terms of pathology, the IgG-positive deposited group had a significantly higher percentage of T2 score compared to the IgG-negative deposited group (p = 0.002). At the end of the follow-up period, the IgG-positive deposited group had a higher eGFR decline (−5.7 ± 4.37 ml/year) compared to the IgG-negative deposited group (−4 ± 2.52 ml/year), however, there was not a statistically significant difference between the two groups (p = 0.096). We observed that the high-IgG group had significantly higher level of TG compared to the low-IgG group (p = 0.042). Further analysis revealed that the group of patients with high level of IgG deposition in the kidney experienced a higher incidence of composite kidney outcomes compared to the group with low level of IgG deposition (p = 0.009). Logistic regression analyses showed that high level IgG deposition was an independent risk factor for kidney progression of IgAN (HR 13.419; 95% CI 2.690–66.943, P = 0.029). Further analyses for a solid conclusion using Cox regression that we found high level IgG deposition (HR 115.277; 95% CI 2.299–5.779E3, P = 0.017), eGFR (HR 0.932; 95% CI 0.870–0.999, P = 0.047), and urine protein excretion (HR 1.001; 95% CI 1.000–1.002, P = 0.015) were independent risk factor for kidney progression of IgAN. ConclusionsThe intensity of IgG deposition has been found to be associated with the progression of IgAN. Future prospective studies should provide more robust evidence on the impact of IgG deposition on kidney outcomes in patients with IgAN.

Association between urinary C4d levels and disease progression in IgA nephropathy.

C4d mesangial deposition, a hallmark of lectin pathway activation in IgA nephropathy (IgAN), has been shown to be associated with risk of kidney failure. To date, the relationship between urinary C4d and renal outcome remain unelucidated. A total of 508 patients with biopsy-proven IgAN were enrolled in this study, whose baseline urine samples at the time of biopsy were collected and the levels of urinary C4d were quantified by enzyme-linked immunosorbent assay. The time-averaged C4d (TA-C4d) and the change in proteinuria were measured in sequential urine samples obtained from IgAN patients. The kidney progression event was defined as a 50% estimated glomerular filtration rate (eGFR) decline or end-stage kidney disease (ESKD) or death. After a median follow-up of 36 months, 70 (13.8%) of the participants reached the kidney progression event. Higher levels of urinary C4d/creatinine were found to be associated with decreased eGFR, massive proteinuria, lower serum albumin levels, hypertension, and severe Oxford E and T scores. Upon adjusting for traditional risk factors (including demographics, eGFR, proteinuria, hypertension, Oxford pathologic score, and immunosuppressive therapy), elevated levels of urinary C4d/creatinine were independently associated with an increased risk of CKD progression (adjusted HR per standard deviation increment of log-transformed C4d/creatinine: 1.46; 95% CI: 1.04 to 2.06; P=0.030). In reference to the low C4d group, the risk of poor renal outcome increased for the high C4d group (adjusted HR: 1.93; 95% CI: 1.05 to 3.54; P=0.033). Additionally, a low baseline C4d level was independently assosicated with a favorable proteinuria response to immunosuppressive therapy at three months (adjusted relative risk: 2.20; 95% CI: 1.04-4.63, P=0.038). The urinary C4d, serving as a non-invasive biomarker, is associated with the progression of IgAN and holds the potential to predict proteinuria response in this disease.

Serum Phosphorus Might Be a Predictor of Kidney Disease Progression in IgA Nephropathy.

High serum phosphorus level has been reported to be a risk factor for disease progression in patients with chronic kidney disease, whereas, its role in IgA nephropathy (IgAN) still remains uncertain. This study aimed to investigate the association between serum phosphorus and progression of IgAN. A total of 247 patients diagnosed with IgAN from 2016.11 to 2019.12 at the First Affiliated Hospital of Xi'an Jiaotong University were retrospectively enrolled in this study. The association between serum phosphorus and kidney disease progression events, defined as 30% estimated glomerular filtration rate (eGFR) decline or kidney failure, was evaluated using Cox models. Serum phosphorus was an independent risk factor for poor renal outcome after adjusting for age, gender, urine protein, MAP, eGFR, hemoglobin, Oxford S and T scores (HR, 2.586; 95% CI, 1.238-5.400, p = 0.011). The addition of serum phosphorus to the reference model containing clinical and pathological variables significantly improved the risk prediction of IgAN progression (C statistic, 0.836; 95% CI, 0.783-0.889) as compared with the reference model (C statistic, 0.821; 95% CI, 0.756-0.886). The ability of serum phosphorus level to predict progression was much stronger in IgAN patients without use of immunosuppression (HR 5.173; 95% CI, 1.791-14.944; p = 0.002). Higher serum phosphorus levels were independently associated with kidney disease progression in patients with IgAN, especially in those without immunosuppression. The addition of serum phosphorus to clinical and pathological data at the time of biopsy significantly improved risk prediction of IgAN progression.

Genome-Wide Association Analysis of Protein-Coding Variants in IgA Nephropathy.

Genome-wide association studies have identified nearly 20 IgA nephropathy susceptibility loci. However, most nonsynonymous coding variants, particularly ones that occur rarely or at a low frequency, have not been well investigated. The authors performed a chip-based association study of IgA nephropathy in 8529 patients with the disorder and 23,224 controls. They identified a rare variant in the gene encoding vascular endothelial growth factor A (VEGFA) that was significantly associated with a two-fold increased risk of IgA nephropathy, which was further confirmed by sequencing analysis. They also identified a novel common variant in PKD1L3 that was significantly associated with lower haptoglobin protein levels. This study, which was well-powered to detect low-frequency variants with moderate to large effect sizes, helps expand our understanding of the genetic basis of IgA nephropathy susceptibility. Genome-wide association studies have identified nearly 20 susceptibility loci for IgA nephropathy. However, most nonsynonymous coding variants, particularly those occurring rarely or at a low frequency, have not been well investigated. We performed a three-stage exome chip-based association study of coding variants in 8529 patients with IgA nephropathy and 23,224 controls, all of Han Chinese ancestry. Sequencing analysis was conducted to investigate rare coding variants that were not covered by the exome chip. We used molecular dynamic simulation to characterize the effects of mutations of VEGFA on the protein's structure and function. We also explored the relationship between the identified variants and the risk of disease progression. We discovered a novel rare nonsynonymous risk variant in VEGFA (odds ratio, 1.97; 95% confidence interval [95% CI], 1.61 to 2.41; P = 3.61×10 -11 ). Further sequencing of VEGFA revealed twice as many carriers of other rare variants in 2148 cases compared with 2732 controls. We also identified a common nonsynonymous risk variant in PKD1L3 (odds ratio, 1.16; 95% CI, 1.11 to 1.21; P = 1.43×10 -11 ), which was associated with lower haptoglobin protein levels. The rare VEGFA mutation could cause a conformational change and increase the binding affinity of VEGFA to its receptors. Furthermore, this variant was associated with the increased risk of kidney disease progression in IgA nephropathy (hazard ratio, 2.99; 95% CI, 1.09 to 8.21; P = 0.03). Our study identified two novel risk variants for IgA nephropathy in VEGFA and PKD1L3 and helps expand our understanding of the genetic basis of IgA nephropathy susceptibility.

Mesangial C3 Deposition, Complement-Associated Variant, and Disease Progression in IgA Nephropathy.

IgA nephropathy is the most common primary GN worldwide, with dominant deposition of IgA and co-deposits of complement component 3 (C3). Phenotypes and progression of IgA nephropathy varies among different ethnic populations, while patients with IgA nephropathy from Asia showed more severe clinical phenotypes, active kidney lesions, and rapid progression. Our previous genome-wide association study identified complement factor H ( CFH ) variant rs6677604, tightly linked with the deletion of CFH -related protein 3 and CFH -related protein 1 genes ( ΔCFHR3-1 ), as IgA nephropathy susceptible variant, and additionally revealed its effect on complement regulation in IgA nephropathy. To further explore the effect of rs6677604 on IgA nephropathy progression, here we enrolled a Chinese IgA nephropathy cohort of 1781 patients with regular follow-up for analysis. The rs6677604 genotype was measured, and the genotype-phenotype correlation was analyzed using the t test, the chi-squared test, or the nonparametric test, and the association between rs6677604 genotype or mesangial C3 deposition and IgA nephropathy prognosis was analyzed using Kaplan-Meier analysis and Cox regression. We found that patients with rs6677604-GG genotype had a stronger intensity of mesangial C3 deposition than those with the rs6677604-AA/AG genotype. Patients with IgA nephropathy who had stronger intensity of C3 deposition manifested with more severe clinical and pathological manifestations, including lower eGFR and higher Oxford-M/S/T/C (mesangial hypercellularity, endocapillary cellularity, segmental sclerosis, interstitial fibrosis/tubular atrophy, and crescent) scores. In the survival analysis, stronger intensity of mesangial C3 deposition, but not rs6677604-GG genotypes, was associated with poor long-term kidney outcome in IgA nephropathy. We found that in Chinese patients with IgA nephropathy, variant rs6677604 was associated with mesangial C3 deposition, and mesangial C3 deposition, but not rs6677604, was associated with IgA nephropathy severity and progression.

Proteinuria as a Surrogate Endpoint for Disease Progression in IgA Nephropathy: Predicting Long-Term Treatment Effects of Sparsentan

IgA nephropathy (IgAN) is a rare, life-limiting disease for which there is significant unmet need. Until recently, drug development for IgAN had been impeded by the requirement for large-scale, long-term clinical trials to measure clinical outcomes. However, the recent establishment of ‘reduction in proteinuria’ as a surrogate endpoint to predict clinical outcomes in IgAN, as a basis for accelerated drug approval, has transformed the field. At the 60th European Renal Association (ERA) Congress in June 2023, two oral poster presentations focused on the use of early reduction in proteinuria as an endpoint for clinical studies in IgAN. Alex Mercer, Consultant in Clinical Drug Development at JAMCO Pharma Consulting in Stockholm, Sweden, presented data estimating the long-term clinical outcome of reductions in proteinuria (clinically meaningful extensions in time to kidney failure or death), which could help predict the future protective effect of any new intervention on kidney function. Following this, Jonathan Barratt, Mayer Professor of Renal Medicine at the University of Leicester, and Honorary Consultant Nephrologist at Leicester General Hospital, UK, described findings from the prespecified interim analysis of the Phase III PROTECT study of sparsentan (a novel dual endothelin angiotensin receptor antagonist) in IgAN, which included reduction in proteinuria as a primary endpoint. In patients with IgAN at high risk of disease progression, sparsentan produced a rapid and significant reduction in proteinuria of a level that, according to the study data presented by Mercer, would correspond to a substantially lowered risk of kidney failure or death. Long-term data to confirm this predicted clinical outcome on disease progression are anticipated.

Visit-to-visit variability in blood pressure and kidney disease progression in IgA nephropathy.

The visit-to-visit variability (VVV) in blood pressure (BP) is an important risk factor for stroke and coronary heart disease and may also be associated with kidney damage and the development of chronic kidney disease (CKD). Data on the association between VVV in BP and the risk of CKD progression among patients with immunoglobulin A nephropathy (IgAN) are limited. We aimed to evaluate the relationships of VVV in BP with the progression of IgAN. We assessed 1376 patients with IgAN at Peking University First Hospital. The main VVV in BP was expressed as the standard deviation (SD), coefficient of variation (CV) and average real variability (ARV). The associations of variability in BP with composite kidney disease progression events, defined as a 50% decline in estimated glomerular filtration rate (eGFR) and kidney failure, were examined using Cox models. During a median follow-up of 44.1months (interquartile range 23.0-76.7), 247 (18.0%) patients experienced composite kidney disease progression events. With a higher SD in systolic BP (SBP) values, the risk of kidney disease progression events increased {hazard ratio [HR] 1.07 [95% confidence interval (CI) 1.03-1.11]; P<.001} after maximal adjustment, including baseline SBP and mean SBP during the first 12-month period. Using the first quartile of SD SBP values as the reference, the risk of composite kidney disease progression events was higher among patients with higher SD SBP values; the HR was 2.12 (95% CI 1.31-3.44) in the highest quartile (P for trend<.001). A similar trend could be observed when analysing the SD of diastolic BP, but the risk was not significantly increased. The associations were similar when analysed with the CV and ARV. SBP variability was significantly associated with kidney disease progression in IgAN.

The level of urinary C4d is associated with disease progression in IgA nephropathy with glomerular crescentic lesions: a cohort study.

Positive glomerular C4d staining, representative of lectin pathway activation, has been proven to be associated with unfavorable outcomes in immunoglobulin A nephropathy (IgAN). Our previous study suggested that urinary C4d correlated positively with an increase in crescents while the relationship between urinary C4d and disease severity and progression remains unelucidated. In this study we enrolled 168 patients diagnosed with IgAN with varying proportions of crescent formation at the time of biopsy. An independent cohort of 107 IgAN patients was enrolled for validation. Kidney biopsy specimens were stained using immunohistochemistry. Urinary C4d levels at renal biopsy were measured by enzyme-linked immunosorbent assay. The primary endpoint was end-stage kidney disease (ESKD). Higher urinary C4d/creatinine levels were associated with a lower estimated glomerular filtration rate (eGFR); massive proteinuria; hypertension and severe Oxford M, E, T and C scores. After a median follow-up of 19 months (interquartile range 9-27), 53 (31.5%) participants reached ESKD. High urinary C4d/creatinine levels were independently and significantly associated with a risk of developing ESKD [hazard ratio per standard deviation increment of log-transformed C4d/creatinine 7.623 (95% confidence interval 4.117-14.113)]. The urinary C4d/creatinine level is a potential useful biomarker that was associated with disease severity and progression in patients with IgAN and crescents.

Urine β2-Microglobulin and Retinol-Binding Protein and Renal Disease Progression in IgA Nephropathy.

Background: Tubulointerstitial involvement has been reported to have a decisive influence on the progression of IgA nephropathy (IgAN). High levels of urine β2-microglobulin (β2-MG) and retinol-binding protein (RBP) were observed in patients with IgAN with tubulointerstitial lesions. However, their roles in disease progression remain unclear. This study aimed to evaluate the associations of urine β2-MG and RBP with the progression of IgAN.Methods: We retrospectively investigated a cohort of 2,153 patients with IgAN. Clinical and pathological features, outcomes, and urine β2-MG, and RBP at the time of biopsy were collected. The associations, of urine β2-MG and RBP with the composite renal outcome, defined as a decline in estimated glomerular filtration rate (eGFR) of ≥50% from baseline or end-stage renal disease (ESRD), were examined using restricted cubic splines and the Cox proportional hazards models.Results: During a median follow-up of 20.40 months, 140 (6.50%) patients reached the composite renal outcomes. Restricted cubic splines showed that patients with higher urinary β2-MG and RBP levels had worse renal outcomes. The Cox regression analysis revealed that urine β2-MG and RBP were associated with a risk of the composite renal outcome in the multivariate adjusted model [+1 SD for log β2-MG, hazard ratio (HR) = 1.462, 95% CI: 1.136–1.882, p = 0.003; +1 SD for log RBP, HR = 1.972, 95% CI: 1.486–2.617, p = 0.001]. The associations were detectable within patients with baseline eGFR <90 ml/min/1.73 m2 (+1 SD for log β2-MG, HR = 1.657, 95% CI: 1.260–2.180, p < 0.001; +1 SD for log RBP, HR = 1.618, 95% CI: 1.199–2.183, p = 0.002), but not among patients with eGFR ≥90 ml/min/1.73 m2.Conclusion: Higher levels of urine β2-MG and RBP were independent risk factors for renal disease progression in IgAN.

P0350THE DURATION OF PROTEINURIA REMISSION AND CLINICAL OUTCOMES IN IGA NEPHROPATHY

Abstract Background and Aims A relative reduction in proteinuria has been proposed as a surrogate outcome for therapeutic trials in IgA nephropathy. It is currently unknown how long a reduction in proteinuria needs to be maintained in order to mitigate the long-term risk of disease progression. To address this knowledge gap we sought to quantify the association between duration of proteinuria remission and the risk of disease progression in IgA nephropathy. Method In this retrospective multi-ethnic international cohort of adult patients with biopsy-proven IgA nephropathy, we defined proteinuria remission based on three criteria: (i) peak proteinuria on/after biopsy ≥1g/day; (ii) an absolute reduction in proteinuria to &amp;lt;1g/day; (iii) a ≥25% reduction in proteinuria from the peak value. The exposure of interest was the total duration of first remission, treated as a time-varying covariate using longitudinal proteinuria measurements. The primary outcome was the occurrence of end-stage kidney disease or a sustained 50% reduction in estimated glomerular filtration rate (eGFR). The association between duration of remission and the primary outcome was visualized using restricted cubic splines, and quantified using extended Cox proportional hazards regression models. Results A total of 1864 patients met criteria for remission, which occurred a median of 8.3 months after biopsy (IQR 3.6-22). They had a median age of 36.8 (IQR 29.4-46.6) years and a median eGFR of 78 (IQR 55-104) mL/min/1.73m2. Median proteinuria was 1.54 (IQR 1.09-2.4) g/day at the time of biopsy and 0.55 (IQR 0.33-0.76) g/day at the time of entering remission. During a median follow-up of 3.9 years, 274 patients (14.7%) experienced the primary outcome. The relationship between duration of proteinuria remission and the primary outcome was non-linear (Figure). Each 3 months in sustained remission up to 51 months was associated with an additional 9% reduction in the risk of disease progression (hazard ratio 0.91, 95% confidence interval 0.89-0.93). In contrast, each additional 3 months in remission beyond 51 months was associated with a smaller non-significant risk reduction (hazard ratio 0.99, 95% confidence interval 0.96-1.03). These finding were robust to multivariable adjustment and were consistent across subgroups based on the MEST histology score, and whether or not the remission occurred while on renin-angiotensin-aldosterone-system blockade or after immunosuppression treatment. Results were similar when relapse was defined as either a 50% or 100% increase in proteinuria from the nadir value after remission to an absolute value of ≥1g/day. Conclusion We observed a strong non-linear dose-response relationship between the duration of proteinuria remission and the risk of disease progression in patients with IgA nephropathy. The ability to quantitate the renal survival benefit related to the duration of remission is an important advance for patients and their physicians. Rather than there being a minimum duration of proteinuria remission in IgA nephropathy, our results demonstrate that even short durations in remission, or small increases in remission duration, are both associated with significant reductions in the risk of disease progression. For future therapeutic trials in IgA nephropathy using proteinuria as a surrogate outcome, our findings illustrate the need to consider the duration of proteinuria reduction, in addition to the magnitude of proteinuria reduction, when evaluating the anticipated treatment effect on long-term clinical endpoints.

SUN-376 Contribution of Genetic Factors in Disease Progression of IgA nephropathy

SUN-376 Contribution of Genetic Factors in Disease Progression of IgA nephropathy

Evaluating a New International Risk-Prediction Tool in IgA Nephropathy

Although IgA nephropathy (IgAN) is the most common glomerulonephritis in the world, there is no validated tool to predict disease progression. This limits patient-specific risk stratification and treatment decisions, clinical trial recruitment, and biomarker validation. To derive and externally validate a prediction model for disease progression in IgAN that can be applied at the time of kidney biopsy in multiple ethnic groups worldwide. We derived and externally validated a prediction model using clinical and histologic risk factors that are readily available in clinical practice. Large, multi-ethnic cohorts of adults with biopsy-proven IgAN were included from Europe, North America, China, and Japan. Cox proportional hazards models were used to analyze the risk of a 50% decline in estimated glomerular filtration rate (eGFR) or end-stage kidney disease, and were evaluated using the R2D measure, Akaike information criterion (AIC), C statistic, continuous net reclassification improvement (NRI), integrated discrimination improvement (IDI), and calibration plots. The study included 3927 patients; mean age, 35.4 (interquartile range, 28.0-45.4) years; and 2173 (55.3%) were men. The following prediction models were created in a derivation cohort of 2781 patients: a clinical model that included eGFR, blood pressure, and proteinuria at biopsy; and 2 full models that also contained the MEST histologic score, age, medication use, and either racial/ethnic characteristics (white, Japanese, or Chinese) or no racial/ethnic characteristics, to allow application in other ethnic groups. Compared with the clinical model, the full models with and without race/ethnicity had better R2D (26.3% and 25.3%, respectively, vs 20.3%) and AIC (6338 and 6379, respectively, vs 6485), significant increases in C statistic from 0.78 to 0.82 and 0.81, respectively (ΔC, 0.04; 95% CI, 0.03-0.04 and ΔC, 0.03; 95% CI, 0.02-0.03, respectively), and significant improvement in reclassification as assessed by the NRI (0.18; 95% CI, 0.07-0.29 and 0.51; 95% CI, 0.39-0.62, respectively) and IDI (0.07; 95% CI, 0.06-0.08 and 0.06; 95% CI, 0.05-0.06, respectively). External validation was performed in a cohort of 1146 patients. For both full models, the C statistics (0.82; 95% CI, 0.81-0.83 with race/ethnicity; 0.81; 95% CI, 0.80-0.82 without race/ethnicity) and R2D (both 35.3%) were similar or better than in the validation cohort, with excellent calibration. In this study, the 2 full prediction models were shown to be accurate and validated methods for predicting disease progression and patient risk stratification in IgAN in multi-ethnic cohorts, with additional applications to clinical trial design and biomarker research.

Serum miR-192 Is Related to Tubulointerstitial Lesion and Short-Term Disease Progression in IgA Nephropathy

Background/Aims: Clinical manifestation and renal histology serve as the current “gold standard” for evaluation of renal lesions in IgA nephropathy. MiR-192 is regarded as a potential noninvasive biomarker for kidney disease. We sought to elucidate a relationship between intrarenal, serum, and urinary exosomal miR-192 with renal lesions and disease progression in IgA nephropathy. Methods: Serum and urinary exosomal miR-192 were detected and correlated with clinical and pathological parameters from consecutive IgA nephropathy patients (n = 50) and healthy control patients (n = 25). Patients then received a follow-up of 24 months after biopsy. Disease progression was defined as a 40% reduction in estimated glomerular filtration rate. Expression of miR-192 was quantified by Taqman RT-PCR. Intrarenal ­miR-192 was detected in 8 IgA nephropathy patients and 4 matched patients receiving kidney nephrectomy as controls via in situ hybridization. TGF-β1 and E-cadherin expression in renal tissue was evaluated using immunohistochemistry. Results: Intrarenal miR-192 was correlated with serum miR-192 (r = 0.690, p = 0.013). Both intrarenal and serum miR-192 decreased in IgA nephropathy patients and were correlated with estimated glomerular filtration ratio. Patients with lower intrarenal and serum miR-192 levels had a higher interstitial fibrosis and tubular atrophy score, more severe lesions in tubular atrophy, and interstitial inflammation. Renal E-cadherin expression was correlated (r = 0.484, p = 0.004) and TGF-β1 was inversely correlated (r = –0.527, p < 0.001) with serum miR-192 in IgA. Patients with higher serum miR-192 had a lower disease progression rate over the course of 2 years (0 vs. 16%, p = 0.028). No correlation was found in urinary exosomal miR-192 with the clinical and pathological parameters mentioned earlier. Conclusions: Lower serum miR-192 in IgA nephropathy patients indicates lower intrarenal miR-192 expression, more severe tubular atrophy, interstitial inflammation, and fibrotic tendency (with higher TGF-β and E-cadherin in renal miR-192). IgA nephropathy patients with higher serum miR-192 are less likely to have renal function decline over the course of 2 years.

Circulating CD89-IgA complex does not predict deterioration of kidney function in Korean patients with IgA nephropathy.

Soluble CD89 (sCD89)-IgA complex plays a key role in the pathogenesis of IgA nephropathy (IgAN). However, there is a lack of evidence supporting this complex as a good biomarker for disease progression. This study aimed to evaluate the usefulness of sCD89-IgA complex for risk stratification of IgAN. A total of 326 patients with biopsy-proven IgAN were included. sCD89-IgA complex was measured by sandwich-enzyme-linked immunosorbent assay. The study endpoints were a 30% decline in estimated glomerular filtration rate (eGFR). sCD89-IgA complex levels were inversely and weakly associated with eGFR at the time of biopsy (r=-0.12, p=0.03). However, the significance between the two factors was lost in the multivariate linear regression after adjustment of clinical factors (β=0.35, p=0.75). In a multivariate Cox model, the highest (hazard ratio [HR], 0.75; 95% confidence interval [CI], 0.35-1.61; p=0.45) and middle (HR, 0.93; 95% CI, 0.46-1.89; p=0.84) tertiles of sCD89-IgA complex levels were not associated with an increased risk of developing a 30% decrease in eGFR. Furthermore, the decline rates in eGFR did not differ between groups and C-statistics revealed that the sCD89-IgA complex were not superior to clinical factors in predicting disease progression. This study found no association between sCD89-IgA complex levels and disease progression in IgAN. Although sCD89 can contribute to the formation of immune complexes, our findings suggest that the sCD89-IgA level is not a good predictor of adverse outcomes and has limited clinical utility as a biomarker for risk stratification in IgAN.

Targeted steroid therapy for IgA nephropathy

Encouraging preliminary data from the NEFIGAN trial suggest that a novel oral formulation of budesonide might reduce disease progression in IgA nephropathy. This formulation releases corticosteroid in the distal small intestine and colon, so is thought to directly target the mucosal element of the pathogenesis of the disease.

Underweight Is an Independent Risk Factor for Renal Function Deterioration in Patients with IgA Nephropathy.

Studies on the relationship between body mass index (BMI) and renal progression in IgA Nephropathy (IgAN) were limited, especially for underweight patients with IgAN. To elucidate the clinical features and effect of underweight on renal function deterioration in this disease, we recruited IgAN patients with diagnostic age ≥18 years old and a baseline estimated glomerular filtration rate (eGFR) ≥15 ml/min/1.73m2 from our center between 1985 and 2014. Patients secondary to systemic diseases or follow-up less than 6 months were excluded. All patients’ clinical data at renal biopsy and during follow-up were recorded. Renal outcome was defined as end-stage kidney disease (ESRD). Baseline body mass index (BMI) was calculated by weight (kg) over squared height (m2). According to WHO Asian guideline, BMI was categorized as follows: <18.5kg/m2 (underweight), 18.5–22.99kg/m2 (normal weight), 23–27.49kg/m2 (overweight) and obese (≥27.5 kg/m2). Of 930 primary IgAN patients enrolled in this study, mean age at renal biopsy was 37.6 years and 49.2% were men. Totally, 114 (12.3%) ESRD occurred after a mean follow-up of 47.1 months. More ESRD happened in underweight patients (17.3%) compared to patients with normal weight (13.2%), overweight (11.0%) or obesity (9.5%). By multivariate Cox regression analysis, underweight was independently associated with a higher risk of ESRD after adjustment for demographic characteristics and clinical variables (HR: 3.5, 95% CI: 1.3–9.5, P = 0.01) comparing to normal weight. Underweight patients had lower hemoglobin, serum uric acid, triglycerides, cholesterol and lymphocyte counts than patients with normal weight. Furthermore, BMI was positively correlated with serum C3 (r = 0.25, p <0.001). Our research finds that underweight is an independent risk factor for kidney disease progression in IgAN, which might be associated with malnutrition status and decreased C3 levels.

Renal expression of advanced oxidative protein products predicts progression of renal fibrosis in patients with IgA nephropathy

Predicting the risk of disease progression in IgA nephropathy (IgAN) remains a challenge. This study was conducted to test the hypothesis that renal accumulation of advanced oxidized protein products (AOPPs) is an early predictor for renal progression in IgAN. This was a single-center prospective cohort study. One hundred IgAN patients with eGFR>80 ml/min/1.73 m2 were enrolled. Seventy-seven patients were followed for a mean of 4.2 years, and 30 patients received repeat renal biopsy at a mean of 42 months after diagnosis. The outcomes were the progression of renal fibrosis and rapid progression of CKD (>5 ml/min/1.73 m2/year) during follow-up. Immunoreactivity of AOPPs was detected predominantly in tubular epithelial cells and co-localized with expression of TGF-β1 and angiotensin II. Renal staining score of AOPPs at diagnosis was associated with the level of tissue cellular inflammation. Accumulation of AOPPs, particularly in interstitial-infiltrating cells, was negatively correlated with changes of eGFR during follow-up; those with expression scores greater than the median at diagnosis had significantly higher incidences of rapid decline of eGFR compared with those with the score less than or equal to the median. For patients who received repeat renal biopsy, renal AOPP levels greater than the median at diagnosis were associated with increase in renal fibrosis index at repeat biopsy. After multivariate adjustment, renal AOPP expression was an independent predictor for progression of renal fibrosis and rapid decline of eGFR. Taken together, these results demonstrate that renal AOPPs might be a predictor, detectable at the time of diagnosis, for renal progression in patients with early stage IgAN.

The Association of Klotho Polymorphism with Disease Progression and Mortality in IgA Nephropathy

Backgrounds: IgA nephropathy (IgAN) is the most common primary glomerulonephritis causing end stage renal disease (ESRD), and vasculopathy is known to involve disease progression. Klotho, a gene related to aging, has been reported to play a role in atherosclerosis and endothelial dysfunction. We investigated whether klotho gene polymorphism affect clinical course of IgAN. Methods: The data registered for PREMIER study which enrolled the patients with biopsy proven IgAN were analyzed. Two single nucleotide polymorphisms for klotho gene, G395A of promoter region and C1818T of exon 4, were examined, and investigated the association klotho genotypes with the progression of IgAN and patient survival. Results: Clinical data from 973 patients confirmed about survival were analyzed. The allele frequency was 0.830 and 0.170 for allele G and A, and 0.816 and 0.184 for allele C and T, which were complied with Hardy-Weinberg equilibrium (p=0.996 and 0.531 respectively). Death was observed more frequently in A-allele carriers of G395A polymorphism (0.7 vs 2.6 %, GG vs GA+AA, p=0.022). Renal survival in Kaplan-Meier survival curve was also worse in same group (p=0.04). Conclusion: Klotho gene polymorphism was associated with patient survival and disease progression of IgAN.

Aberrantly Glycosylated IgA1 as a Factor in the Pathogenesis of IgA Nephropathy

Predominant or codominant immunoglobulin (Ig) A deposition in the glomerular mesangium characterizes IgA nephropathy (IgAN). Accumulated glomerular IgA is limited to the IgA1 subclass and usually galactose-deficient. This underglycosylated IgA may play an important role in the pathogenesis of IgAN. Recently, antibodies against galactose-deficient IgA1 were found to be well associated with the development of IgAN. Several therapeutic strategies based on corticosteroids or other immunosuppressive agents have been shown to at least partially suppress the progression of IgAN. On the other hand, several case reports of kidney transplantation or acquired IgA deficiency uncovered a remarkable ability of human kidney to remove mesangial IgA deposition, resulting in the long-term stabilization of kidney function. Continuous exposure to circulating immune complexes containing aberrantly glycosylated IgA1 and sequential immune response seems to be essential in the disease progression of IgAN. Removal of mesangial IgA deposition may be a challenging, but fundamental approach in the treatment of IgAN.

A clinicopathologic study of thrombotic microangiopathy in the setting of IgA nephropathy

IgA nephropathy is the most common glomerulonephritis in the world. Thrombotic microangiopathy occurs in a number of clinical settings, including but not limited to thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, malignant hypertension, anti-phospholipid antibody syndrome and radiation nephropathy. Renovascular complications, such as thrombotic microangiopathy, in the setting of IgA nephropathy may be overlooked and their significance as a concomitant histologic finding is unclear. We conducted a clinicopathologic study to understand the possible relationship between IgA nephropathy and a concurrent thrombotic microangiopathy injury process. We identified 10 patients with an established diagnosis of IgA nephropathy and concurrent findings of thrombotic microangiopathy based on their renal biopsies. Six patients presented with malignant hypertension, while three others had severe hypertension (> or = 100 mmHg, diastolic). Five patients had nephrotic-range proteinuria. Seven patients had occasional arteriolar thrombi identified by light microscopy and prominent glomerular subendothelial space widening by electron microscopy, while three patients demonstrated only ultrastructural features of thrombotic microangiopathy. Other possible etiologic causes of thrombotic microangiopathy were not identified with the available clinical information. Our study suggests that a thrombotic microangiopathy injury, when present, is usually found in advanced stages of IgA nephropathy and can be associated with severe proteinuria. Although other possible causes of thrombotic microangiopathy, such as anti-phospholipid antibody syndrome, were excluded in only two patients, the thrombotic microangiopathy injury process may be a cause or a consequence of the severe hypertension encountered in most of the patients which, in turn, may be a consequence of the disease progression of IgA nephropathy.