Jin Ho Hwang

Urinary N-acetyl-β-D glucosaminidase as a surrogate marker for renal function in autosomal dominant polycystic kidney disease: 1 year prospective cohort study

BackgroundRenal failure is one of the most serious complications associated with autosomal dominant polycystic kidney disease (ADPKD). To date, early markers have failed to predict renal function deterioration at the early stages. This 1-year prospective study evaluated N-acetyl-β-D-glucosaminidase (NAG) as a new surrogate marker for renal function in ADPKD.MethodsA total of 270 patients were enrolled in the study, and we measured urinary NAG, β2-microglobulin, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) prospectively for 1 year to compare their predictive values for renal function.ResultsBaseline urinary NAG/Cr was negatively correlated with estimated glomerular filtration rate (GFR) (r2 = 0.153, P < 0.001) and positively correlated with total kidney volume (TKV) (r2 = 0.113, P < 0.001). Among other biomarkers, urinary NAG/Cr better discriminated patients with decreased renal function from those with conserved renal function, showing the largest area under the curve (AUC 0.794). Immunohistochemical study revealed strong staining along the cyst-lining epithelial cells as well as the nearby compressed tubular epithelial cells. However, both single and repeated measurements of urinary NAG/Cr failed to predict renal function decline in 1 year.ConclusionsUrinary NAG/Cr may be a useful surrogate marker for renal function in ADPKD patients.

Serum Bilirubin Affects Graft Outcomes through UDP-Glucuronosyltransferase Sequence Variation in Kidney Transplantation

Background Oxidative stress is a major mediator of adverse outcome after kidney transplantation. Bilirubin is produced by heme oxygenase-1 (HO-1), catalyzed by UDP-glucuronosyltransferase (UGT1A1), and has potential as an antioxidant. In this study, we investigated the effects of HO-1 and UGT1A1 sequence variations on kidney allograft outcomes. Methods Clinical data were collected from 429 Korean recipients who underwent kidney transplantation from 1990–2008. Genotyping for UGT1A1*28 and HO-1 (A−413T) was performed. Acute rejection and graft survival were monitored as end-points. Results Serum levels of total bilirubin were significantly increased after transplantation (0.41±0.19 mg/dL to 0.80±0.33 mg/dL, P<0.001). Post-transplant 1-year bilirubin level was higher in 6/7 or 7/7 carriers compared with 6/6 homozygotes in terms of the UGT1A1*28 polymorphism (6/6 vs. 6/7 vs. 7/7: 0.71±0.27 vs. 1.06±0.36 vs. 1.10±0.45 mg/dL, P<0.001). According to an additive model of genotype analysis, the 7-allele genotype had a protective effect on the development of acute rejection compared with the 6-allele (odds ratio 0.43, 95% CI 0.25–0.73, P for trend = 0.006). Multivariate Cox regression analysis revealed that individuals carrying the 7-allele had a decreased risk of graft loss, by a factor of 0.36 (95% CI 0.15–0.85, P = 0.019). The HO-1 (A−413T) polymorphism had no effect on serum bilirubin levels or graft outcomes. Conclusions The UGT1A1*28 polymorphism is associated with changes in serum bilirubin and with graft outcome after kidney transplantation.

Outcome of kidney allograft in patients with adulthood-onset focal segmental glomerulosclerosis: comparison with childhood-onset FSGS

BACKGROUND Idiopathic focal segmental glomerulosclerosis (FSGS) occurring at young age is known to predispose to poor graft outcome, but the outcome of adulthood-onset FSGS (A-FSGS) has not been thoroughly investigated. Here, we compared the graft outcomes between kidney recipients with A-FSGS and childhood-onset FSGS (C-FSGS). METHODS We enrolled 47 A-FSGS recipients and 60 C-FSGS recipients with an onset age of ≤ 15, from four of the largest transplant centers in Korea. RESULTS The baseline characteristics were similar between two groups. The 1- and 3-year cumulative recurrence rates were 20.0 and 22.1%, respectively. FSGS was recurrent in 19 C-FSGS patients [median duration, 2 months (interquartile range, IQR, 1-35)], and 11 patients had recurrent disease in A-FSGS [5 months (IQR, 3-37)]. The recurrence rate was similar between two groups (P = 0.126). The 5- and 10-year graft survival rates were 90.0 and 78.5%, respectively. The overall graft survival rates were not different between two groups. After adjusting baseline characteristics, the development of major outcomes was similar between two groups except acute rejection that was more frequent in A-FSGS. The age of disease onset did not affect recurrence in both groups. While grafts with recurrence had poorer graft survival in the A-FSGS group (P = 0.005), the recurrence was not associated with graft loss in the C-FSGS group (P = 0.558). CONCLUSIONS The onset age did not affect the graft outcome in patients with FSGS, and the recurrence significantly affected graft survival in A-FSGS. Therefore, the main focus should aim for the management of recurrence.

Urinary Periostin Excretion Predicts Renal Outcome in IgA Nephropathy

Background: Periostin is a matricellular protein and plays a vital role in tissue regeneration, fibrosis and wound healing. However, data about its significance in nephrology are limited. We investigated the correlation between urinary periostin excretion and its clinical significance including renal histologic findings and prognosis in IgA nephropathy (IgAN). Methods: Of 399 patients from a glomerulonephritis cohort recruited between January 2009 and December 2014, 314 were enrolled. Serum and urine periostin (uPOSTN) were measured using enzyme-linked immunosorbent assay. We divided the patients into 3 groups by uPOSTN/creatinine (uPOSTN/Cr): group 1 (undetectable), group 2 (lower than the median) and group 3 (higher than the median). Results: The uPOSTN level was correlated with pathologic classifications and both initial and final IDMS-MDRD estimated glomerular filtration rates (eGFRs; p < 0.001). Histologically, group 3 patients were correlated with severe interstitial fibrosis/tubular atrophy (p = 0.004), interstitial inflammation (p = 0.007), hyaline arteriolosclerosis (p = 0.001) and glomerular sclerosis (p < 0.001). A higher initial uPOSTN/Cr level was associated with a greater decline in eGFR during follow-up (p = 0.043 when initial eGFR ≥60; p = 0.025 when eGFR <60 ml/min/1.73 m2), and the renal outcomes with end-stage renal disease (ESRD; p = 0.003), ESRD and/or eGFR decrease of >30% (p = 0.033) and ESRD and/or eGFR decrease of >50% (p = 0.046) occurred significantly more in group 3. In multivariate analysis, uPOSTN group 3 (hazards ratio 2.839, 95% CI 1.013-7.957; p = 0.047) was independently associated with ESRD in IgAN patients. Conclusion: uPOSTN/Cr value at initial diagnosis correlated with renal fibrosis and predicted the renal outcomes in patients with IgAN. It could be a promising urinary biomarker for renal fibrosis.

Change in Body Compositions of Asian Recipients after Kidney Transplantation

Kidney transplantation and accompanying medical conditions may result in changes in body composition. Such changes have been evaluated in Caucasian recipients, but not in Asian recipients. Herein, we conducted a study on Asian recipients because Asians have a different body composition from Caucasians. A total of 50 Asian recipients was enrolled as a prospective cohort. Using bioelectrical impedance analysis, body composition (muscle and fat mass) was assessed after 2 weeks (baseline), and at 1, 3, 6, 9, and 12 months following kidney transplantation. To find predictors related to changes, the data were analyzed by multivariate analysis using forward selection. All of the patients had good graft function during the study period. Patients gained approximately 3 kg within 1 yr of kidney transplantation. The proportion of muscle mass significantly decreased (Ptrend = 0.001) and the proportion of fat mass significantly increased over time (Ptrend = 0.002). The multivariate results revealed that male recipients, deceased donor type, and low protein intake were associated with an increase in fat mass and a decrease in muscle mass. The results from this study may help to investigate differences in body composition changes between races, as well as the factors related to these changes.

Experimental Inhibition of Periostin Attenuates Kidney Fibrosis

Background: Periostin is responsible for tissue regeneration, fibrosis, and wound healing via its interaction with integrin. Recently, the role of periostin has been shown to contribute to fibrosis in chronic kidney disease. We investigated the role of periostin and the effect of periostin blockade in renal fibrogenesis. Methods: We investigated the function of periostin in vivo in wild-type and periostin-null mice (Postn-KO) in a unilateral ureteral obstruction (UUO) model. For the in vitro experiments, primary cultured inner medullary collecting duct cells from the wild-type and Postn-KO mice were used. Results: Periostin expression was strongly induced by UUO in the wild-type mice. UUO induced renal fibrosis and morphological changes in the obstructed kidney of wild-type mice, whereas global knockout of periostin reduced fibrosis induced by UUO and improved kidney structure. Fibrosis- and inflammation-related mRNA were significantly induced in the wild-type mice and were decreased in the Postn-KO mice. Additionally, α-smooth muscle actin expression was increased following the administration of recombinant periostin in vitro. The effect of periostin blockade was examined using 2 methods. The integrin blockade peptide decreased fibrosis-related gene expression in in vitro experiments. Anti-periostin polyclonal antibody attenuated renal fibrosis induced by UUO through changes in transforming growth factor-β signaling and the inflammatory and apoptotic pathways. Conclusion: Periostin is a marker of renal fibrosis and may augment the progression of fibrogenesis as an extracellular matrix protein. Periostin blockade effectively attenuated renal fibrogenesis. Thus, periostin inhibition may be a therapeutic strategy for the amelioration of renal disease progression.

Outcomes of kidney allograft in recipients with kidney disease of unknown etiology

The etiology of renal disease is important because the primary renal pathology may affect the outcomes of kidney allograft with respect to recurrence, rejection, and survival. However, for a significant number of patients who undergo kidney transplantation, the disease etiology is unknown. Here, allograft outcomes for patients with kidney disease of unknown etiology (UEK) at three affiliated Korean hospitals were identified. The incidence of biopsy‐proven acute rejection (BPAR) for UEK was 22.9%, which was similar to the rates for diabetic nephropathy (DN, 24.4%) and IgA nephropathy (IgAN, 20.0%; p = 0.345). The cumulative incidence of post‐transplant glomerulonephritis (PTGN) among patients with UEK was significantly lower than that among patients with IgAN (p < 0.001). Overall graft survival of the UEK group was superior to that of the DN group (hazards ratio 0.39, 95% confidence interval 0.17–0.92, p = 0.030). Preemptive transplantation for UEK significantly reduced the incidence of BPAR (preemptive vs. non‐preemptive 9.6% vs. 30.3%, p = 0.001), but graft survival and recurrence were not affected by preemptive transplantation. The outcomes of kidney transplantation for patients with UEK were not inferior to those for patients with IgAN or DN. Preemptive kidney transplantation may be encouraged for UEK patients.

Elevated bilirubin levels are associated with a better renal prognosis and ameliorate kidney fibrosis.

Background Bilirubin has been reported to protect against kidney injury. However, further studies highlighting the beneficial effects of bilirubin on renal fibrosis and chronic renal function decline are necessary. Methods We assessed a prospective cohort with a reference range of total bilirubin levels. The primary outcome was a 30% reduction in the estimated glomerular filtration rate (eGFR) from baseline, and the secondary outcome was a doubling of the serum creatinine levels, halving of the eGFR and the initiation of dialysis. In addition, experiments with tubular epithelial cells and C57BL/6 mice were performed to investigate the protective effects of bilirubin on kidney fibrosis. Results As a result, 1,080 patients were included in the study cohort. The study group with relative hyperbilirubinemia (total bilirubin 0.8–1.2 mg/dL) showed a better prognosis in terms of the primary outcome (adjusted hazard ratio (HR) 0.33, 95% confidence interval (CI) 0.19–0.59, P < 0.001) and the secondary outcome (adjusted HR 0.20, 95% CI 0.05 to 0.71, P = 0.01) than that of the control group. Moreover, the bilirubin-treated mice showed less fibrosis in the unilateral ureteral obstruction (UUO) model (P < 0.05). In addition, bilirubin treatment decreased fibronectin expression in tubular epithelial cells in a dose-dependent manner (P < 0.05). Conclusions Mildly elevated serum bilirubin levels were associated with better renal prognosis, and bilirubin treatment induced a beneficial effect on renal fibrosis. Therefore, bilirubin could be a potential therapeutic target to delay fibrosis-related kidney disease progression.

Circulating tumour necrosis factor receptors 1 and 2 predict contrast-induced nephropathy and progressive renal dysfunction: a prospective cohort study.

Contrast‐induced nephropathy (CIN) is an important cause of hospital‐acquired acute kidney injury. An accurate understanding of the pathogenesis of CIN is crucial. The aim of this study was to evaluate the clinical role of circulating tumour necrosis factor receptors (cTNFRs) in CIN.

The prognostic significance of preoperative left ventricular diastolic dysfunction and left atrial enlargement on acute coronary syndrome in kidney transplantation

Echocardiography is commonly performed as a screening test to evaluate perioperative risks before kidney transplantation. However, only limited data are available on echocardiographic parameters of left ventricular diastolic dysfunction (LVDD) and left atrial enlargement (LAE) on acute coronary syndrome and mortality in kidney transplant recipients. We reviewed 2779 adult recipients who underwent pretransplant echocardiography from 1997 to 2012. We divided the patients into two and four groups by two categories: LVDD grades 0-1 vs. 2-3, and left atrial size quartile groups. During a mean follow-up of 4.5 years, acute coronary syndrome occurred in 89 (3.2%) patients. The recipients with LVDD grades 2-3 (P = 0.005 for non-fatal, P = 0.02 for fatal/non-fatal) and LAE (P = 0.001 for non-fatal, P = 0.03 for fatal/non-fatal) had a higher incidence of acute coronary syndrome after kidney transplantation. All-cause mortality did not differ significantly between the groups. In a multivariate analysis, LVDD of grades 2-3 (hazard ratio 2.98, 95% confidence interval 1.535-5.787; P = 0.001), and LAE (hazard ratio 1.052, 95% confidence interval 1.006-1.101; P = 0.03) were independently associated with non-fatal acute coronary syndrome. In patients who are kidney transplant candidates, pretransplant LVDD and LAE were independently associated with a higher incidence of acute coronary syndrome after kidney transplantation.Echocardiography is commonly performed as a screening test to evaluate perioperative risks before kidney transplantation. However, only limited data are available on echocardiographic parameters of left ventricular diastolic dysfunction (LVDD) and left atrial enlargement (LAE) on acute coronary syndrome and mortality in kidney transplant recipients. We reviewed 2779 adult recipients who underwent pretransplant echocardiography from 1997 to 2012. We divided the patients into two and four groups by two categories: LVDD grades 0–1 vs. 2–3, and left atrial size quartile groups. During a mean follow-up of 4.5 years, acute coronary syndrome occurred in 89 (3.2%) patients. The recipients with LVDD grades 2–3 (P = 0.005 for non-fatal, P = 0.02 for fatal/non-fatal) and LAE (P = 0.001 for non-fatal, P = 0.03 for fatal/non-fatal) had a higher incidence of acute coronary syndrome after kidney transplantation. All-cause mortality did not differ significantly between the groups. In a multivariate analysis, LVDD of grades 2–3 (hazard ratio 2.98, 95% confidence interval 1.535–5.787; P = 0.001), and LAE (hazard ratio 1.052, 95% confidence interval 1.006–1.101; P = 0.03) were independently associated with non-fatal acute coronary syndrome. In patients who are kidney transplant candidates, pretransplant LVDD and LAE were independently associated with a higher incidence of acute coronary syndrome after kidney transplantation.