High urinary excretion of kidney injury molecule-1 is an independent predictor of end-stage renal disease in patients with IgA nephropathy

The ratio of high aspartate aminotransferase to alanine aminotransferase: an independent risk factor associated with poor prognosis in IgA nephropathy

OBJECTIVE

To investigate the relationship between the aspartate aminotransferase to alanine aminotransferase ratio (AAR) and the prognosis of IgA nephropathy (IgAN).

METHODS

Clinical, pathological and follow-up data of 271 patients with IgAN from January 1, 2013, to July 31, 2023, were collected. A 50% decrease in estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD) was used as renal composite end point events. A receiver operating characteristic (ROC) curve was plotted to predict the composite end point events by AAR. The optimal cutoff value of 1.24 was determined, and patients were allocated to high AAR and low AAR groups. Kaplan‒Meier (K‒M) curves and Cox proportional hazard models were used to evaluate the predictive effect of AAR on renal composite end point events.

RESULTS

After a mean follow-up of 29 months, 39 patients achieved renal composite end point events. Among them, 9 and 30 patients in the low and high AAR groups achieved renal composite end point events, respectively, with a significant difference (P < 0.001). After adjustment for confounding factors, AAR was found to be an independent prognostic factor for renal composite end point events (HR = 3.283, 95% CI: 1.489-7.238, P = 0.003). Kaplan‒Meier analysis showed that high AAR was associated with achieving renal composite end point events in patients with IgAN. Moreover, the clinical features in the high AAR group were more severe. Further subgroup analysis showed that high AAR had a better predictive effect in patients with more severe clinicopathological manifestations.

CONCLUSION

AAR is an independent prognostic factor in patients with IgAN.

Development and application of an amplified luminescent proximity homogeneous assay-linked immunosorbent assay for the accurate quantification of kidney injury molecule-1

Background: Kidney injury molecule-1 (Kim-1), a specific marker of kidney injury, is usually not expressed in normal kidneys or at very low levels but is highly expressed in injured renal tubular epithelial cells until the damaged cells recover completely. Therefore, we aimed to develop an efficient and highly sensitive assay to accurately quantify Kim-1 levels in human serum and urine. Methods: In this study, a novel immunoassay was developed and named amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA). Anti-Kim-1 antibodies can be directly coupled to carboxyl-modified donor and acceptor beads for the rapid detection of Kim-1 by double-antibody sandwich method. Serum and urine samples for Kim-1 measurements were obtained from 129 patients with nephropathy and 17 healthy individuals. Results: The linear range of Kim-1 detected by AlphaLISA was 3.83-5000 pg/mL, the coefficients of variation of intra-assay and inter-assay batches were 3.36%-4.71% and 5.61%-11.84%, respectively, and the recovery rate was 92.31%-99.58%. No cross reactions with neutrophil gelatinase-associated lipocalin, liver-type fatty acid binding protein, and matrix metalloproteinase-3 were observed. A good correlation (R 2 = 0.9086) was found between the findings of Kim-1-TRFIA and Kim-AlphaLISA for the same set of samples. In clinical trials, both serum and urine Kim-1 levels were significantly higher in patients with nephropathy than in healthy individuals, especially in patients with acute kidney injury. Furthermore, serum Kim-1 was superior to urinary Kim-1 in distinguishing between patients with nephropathy and healthy individuals. Conclusion: The developed Kim-1-AlphaLISA is highly efficient, precise, and sensitive, and it is suitable for the rapid detection of patients with acute kidney injury.

Urinary C5b-9 as a Prognostic Marker in IgA Nephropathy

C5b-9 plays an important role in the pathogenesis of immunoglobin A nephropathy (IgAN). We evaluated C5b-9 as a prognostic marker for IgAN. We prospectively enrolled 33 patients with biopsy-proven IgAN. We analyzed the correlation between baseline urinary C5b-9 levels, posttreatment changes in their levels, and clinical outcomes, including changes in proteinuria, estimated glomerular filtration rate (eGFR), and treatment response. Baseline urinary C5b-9 levels were positively correlated with proteinuria (r = 0.548, p = 0.001) at the time of diagnosis. Changes in urinary C5b-9 levels were positively correlated with changes in proteinuria (r = 0.644, p < 0.001) and inversely correlated with changes in eGFR (r = −0.410, p = 0.018) at 6 months after treatment. Changes in urinary C5b-9 levels were positively correlated with time-averaged proteinuria during the follow-up period (r= 0.461, p = 0.007) but were not correlated with the mean annual rate of eGFR decline (r = −0.282, p = 0.112). Baseline urinary C5b-9 levels were not a significant independent factor that could predict the treatment response in logistic regression analyses (odds ratio 0.997; 95% confidence interval, 0.993 to 1.000; p = 0.078). Currently, urinary C5b-9 is not a promising prognostic biomarker for IgAN, and further studies are needed.

Kidney injury molecule-1 levels are associated with therapeutic outcomes and renal tubulointerstitial injury severity in idiopathic membranous nephropathy

Kidney injury molecule-1 (KIM-1) has an important role in chronic kidney disease development. The present study aimed to retrospectively analyze patients with idiopathic membranous nephrology (IMN) with different therapeutic outcomes to investigate the association between KIM-1 levels and therapeutic outcomes. A total of 51 patients with IMN and 20 healthy controls were included. Patients were classified into three groups: Spontaneous remission, remission with immunosuppressive therapy (IST) and nonremission with IST. Clinical and biochemical variables were collected. Urinary KIM-1 levels were measured by ELISA and renal KIM-1 expression was evaluated by immunohistochemistry. Patients with IMN were characterized as having elevated urinary and renal KIM-1 levels compared with those in the controls. Significantly increased urinary and renal KIM-1 levels were observed in the nonremission with IST group compared with those in the spontaneous remission group, and the same trend was observed for the plasma anti-podocyte antigen phospholipase A2 receptor antibody levels. Patients with more severe tubular injury (T2 index) presented with significantly higher urinary and renal KIM-1 levels than those with the T0 index. Urinary and renal KIM-1 levels were positively correlated with blood urea nitrogen, serum creatinine, serum cystatin-C, urinary albumin/creatinine ratio, urinary β2-microglobulin and the renal interstitial fibrosis index, and they were negatively correlated with serum albumin. Furthermore, urinary KIM-1 levels were positively correlated with the renal KIM-1 levels. In conclusion, the measurement of urinary and renal KIM-1 levels may be helpful in guiding medication selection and predicting therapeutic outcomes for patients with IMN.

The molecular mechanisms of inflammation and scarring in the kidneys of immunoglobulin A nephropathy : Gene involvement in the mechanisms of inflammation and scarring in kidney biopsy of IgAN patients

Kidney biopsy is the cornerstone for the diagnosis of immunoglobulin A nephropathy (IgAN). The immunofluorescence technique evidences the IgA deposits in the glomeruli; the routine histology shows degree of active and chronic renal lesions. The spectrum of renal lesions is highly variable, ranging from minor or no detectable lesions to diffuse proliferative or crescentic lesions. Over the past three decades, renal transcriptomic studies have been performed on fresh or frozen renal tissue, and formalin-fixed paraffin-embedded kidney tissue specimens obtained from archival histological repositories. This paper aims to describe (1) the transcriptomic profiles of the kidney biopsy and (2) the potential urinary biomarkers that can be used to monitor the follow-up of IgAN patients. The use of quantitative Real-Time Polymerase Chain Reaction (qRT-PCR), microarrays and RNA-sequencing (RNA-seq) techniques on renal tissue and separated compartments of the nephron such as glomeruli and tubule-interstitium has clarified many aspects of the renal damage in IgAN. Recently, the introduction of the single-cell RNA-seq techniques has overcome the limitations of the previous methods, making that it is possible to study the whole renal tissue without the dissection of the nephron segments; it also allows better analysis of the cell-specific gene expression involved in cell differentiation. These gene products could represent effective candidates for urinary biomarkers for clinical decision making. Finally, some of these molecules may be the targets of old drugs, such as corticosteroids, renin-angiotensin-aldosterone blockers, and new drugs such as monoclonal antibodies. In the era of personalized medicine and precision therapy, high-throughput technologies may better characterize different renal patterns of IgAN and deliver targeted treatments to individual patients.

Immunoglobulin A nephropathy in paediatrics: An up-to-date

Immunoglobulin A nephropathy is the main cause of glomerulonephritis globally and an important aetiology of end-stage renal disease in children. It has been considered an autoimmune disease that can lead to the production of autoantibodies against abnormal IgA1 and formation of immune complexes. These autoantibodies and immune complexes deposit in the glomeruli, resulting in renal injury. At the beginning of IgA nephropathy course, most patients are asymptomatic and the first clinical manifestations in children are macroscopic hematuria and proteinuria. The diagnosis is defined by the detection of IgA mesangial deposits in kidney biopsy using immunofluorescence techniques. The Oxford MEST-C score is the most used classification to associate histological findings and clinical outcomes, being validated for application in children. Recommended treatment options are antihypertensive and antiproteinuric therapy, corticosteroids, immunosuppressive agents, and other non-pharmacological approaches. There is no ideal prognosis indicator but new perspectives are in science's scope to find possible biomarkers of the disease through OMICS's research. This review aims to summarize and to up-to-date the scientific literature on paediatric IgA nephropathy, focusing on pathophysiology, clinical findings, histopathology, current treatment, prognosis, and future perspectives.

Correlation analysis between expression of histone deacetylase 6 and clinical parameters in IgA nephropathy patients

Background

It has been demonstrated that histone deacetylase 6 (HDAC6) is involved in various kidney diseases in experimental study. However, correlation between HDAC6 and clinical parameters in IgA nephropathy (IgAN) patients is still unknown.

Methods

A total of 46 human kidney biopsy specimens with IgAN were selected as observation group, specimens of normal renal cortex tissue that was not affected by the tumor from patients with renal carcinoma (n = 7) served as control. We investigated the relationship between HDAC6 and clinical parameters in IgAN.

Results

HDAC6 was highly expressed in human kidney biopsy specimens with IgAN compared with control group, while the number of acetyl histone H3 positive cells were significantly decreased. There was a statistical difference in the indexes of albumin, estimated glomerular filtration rate (eGFR), serum urea, serum creatinine, serum uric acid, β2-microglobulin, cystatin C, cholesterol, high-density lipoprotein, low-density lipoprotein, and HDAC6 positive area among the different Oxford Classification (p < 0.05). The expression of HDAC6 was different in various eGFR levels, the expression of HDAC6 increased with the decreasing of eGFR level, the expression of acetyl histone H3 decreased with the decreasing of eGFR level. In addition, the expression of HDAC6 positively correlated with Masson trichrome positive area, serum urea, serum creatinine, β2 macroglobulin, and cystatin C, while negatively correlated with eGFR and acetyl histone H3. Multivariate linear regression analysis demonstrated that eGFR and cystatin C were independently associated with HDAC6, respectively (p < 0.05).

Conclusions

These results suggested that high level of HDAC6 expression in IgAN is correlated with renal dysfunction.

The Network of Inflammatory Mechanisms in Lupus Nephritis

Several signaling pathways are involved in the progression of kidney disease in humans and in animal models, and kidney disease is usually due to the sustained activation of these pathways. Some of the best understood pathways are specific proinflammatory cytokine and protein kinase pathways (e.g., protein kinase C and mitogen-activated kinase pathways, which cause cell proliferation and fibrosis and are associated with angiotensin II) and transforming growth factor-beta (TGF-β) signaling pathways (e.g., the TGF-β signaling pathway, which leads to increased fibrosis and kidney scarring. It is thus necessary to continue to advance our knowledge of the pathogenesis and molecular biology of kidney disease and to develop new treatments. This review provides an update of important findings about kidney diseases (including diabetic nephropathy, lupus nephritis, and vasculitis, i.e., vasculitis with antineutrophilic cytoplasmic antibodies). New disease targets, potential pathological pathways, and promising therapeutic approaches from basic science to clinical practice are presented, and the blocking of JAK/STAT and TIM-1/TIM-4 signaling pathways as potential novel therapeutic agents in lupus nephritis is discussed.

Monitoring Immune Responses in IgA Nephropathy: Biomarkers to Guide Management

IgA nephropathy (IgAN) is the commonest biopsy-reported primary glomerulonephritis worldwide. It has an incidence which peaks among young adults, and 30 to 40% of patients' progress to end stage kidney disease within twenty years of diagnosis. Ten-year kidney survival rates have been reported to be as low as 35% in some parts of the world. The successful management of IgAN is limited by an incomplete understanding of the pathophysiology of IgAN and a poor understanding of how pathophysiology may vary both from patient to patient and between patient groups, particularly across races. This is compounded by a lack of rigorously designed and delivered clinical trials in IgAN. This is slowly changing, with a number of Phase 2 and 3 clinical trials of novel therapies targeting a number of different putative pathogenic pathways in IgAN due to report in the next 5 years. From our current, albeit limited, understanding of the pathophysiology of IgAN it is unlikely a single therapy will be effective in all patients with IgAN. The successful management of IgAN in the future is, therefore, likely to be reliant on targeted therapies, carefully selected based on an individualized understanding of a patient's risk of progression and underlying pathophysiology. The potential role of biomarkers to facilitate personalization of prognostication and treatment of IgAN is immense. Here we review the progress made over the past decade in identifying and validating new biomarkers, with a particular focus on those that reflect immunological responses in IgAN.

Urinary cMet as a prognostic marker in immunoglobulin A nephropathy

The prediction of prognosis in patients with immunoglobulin A nephropathy (IgAN) is challenging. We investigated the correlation between urinary cMet (ucMet) levels and clinical parameters and examined the effects of cMet agonistic antibody (cMet Ab) in an in vitro IgAN model. Patients diagnosed with IgAN (n = 194) were divided into three groups representing undetectable (Group 1), below‐median (Group 2) and above‐median (Group 3) levels of ucMet/creatinine (ucMet/Cr). Stained kidney biopsy samples were graded according to cMet intensity. Primary‐cultured human mesangial cells were stimulated with recombinant tumour necrosis factor (TNF)‐α and treated with cMet Ab. Our results showed that ucMet/Cr levels positively correlated with proteinuria (P < .001). During the follow‐up, patients in Group 3 showed a significantly lower probability of complete remission (CR; uPCr < 300 mg/g) than those in groups 1 and 2, after adjusting for blood pressure, estimated glomerular filtration rate, and proteinuria, which influence clinical prognosis (HR 0.60, P = .038); moreover, ucMet/Cr levels were also associated with glomerular cMet expression. After TNF‐α treatment, the proliferation of mesangial cells and increased interleukin‐8 and intercellular adhesion molecule‐1 expression were markedly reduced by cMet Ab in vitro. In conclusion, ucMet/Cr levels significantly correlated with proteinuria, glomerular cMet expression, and the probability of CR. Further, cMet Ab treatment alleviated the inflammation and proliferation of mesangial cells. Hence, ucMet could serve as a clinically significant marker for treating IgAN.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

The Many Faces of Matrix Metalloproteinase-7 in Kidney Diseases

Matrix metalloproteinase-7 (MMP-7) is a secreted zinc-dependent endopeptidase that is implicated in regulating kidney homeostasis and diseases. MMP-7 is produced as an inactive zymogen, and proteolytic cleavage is required for its activation. MMP-7 is barely expressed in normal adult kidney but upregulated in acute kidney injury (AKI) and chronic kidney disease (CKD). The expression of MMP-7 is transcriptionally regulated by Wnt/β-catenin and other cues. As a secreted protein, MMP-7 is present and increased in the urine of patients, and its levels serve as a noninvasive biomarker for predicting AKI prognosis and monitoring CKD progression. Apart from degrading components of the extracellular matrix, MMP-7 also cleaves a wide range of substrates, such as E-cadherin, Fas ligand, and nephrin. As such, it plays an essential role in regulating many cellular processes, such as cell proliferation, apoptosis, epithelial-mesenchymal transition, and podocyte injury. The function of MMP-7 in kidney diseases is complex and context-dependent. It protects against AKI by priming tubular cells for survival and regeneration but promotes kidney fibrosis and CKD progression. MMP-7 also impairs podocyte integrity and induces proteinuria. In this review, we summarized recent advances in our understanding of the regulation, role, and mechanisms of MMP-7 in the pathogenesis of kidney diseases. We also discussed the potential of MMP-7 as a biomarker and therapeutic target in a clinical setting.

Urinary Matrix Metalloproteinase 7 and Prediction of IgA Nephropathy Progression

RATIONALE & OBJECTIVE

A major challenge in the management of immunoglobulin A nephropathy (IgAN) is the inability to identify patients at high risk for disease progression at an early stage. Our objective was to determine whether urinary matrix metalloproteinase 7 (MMP-7) is a promising predictor for IgAN progression and whether its addition to clinical data at the time of biopsy improves risk prediction.

STUDY DESIGN

Prospective observational cohort study in China.

SETTING & PARTICIPANTS

946 Chinese patients with IgAN followed up for a median of 40 months in 1 clinical center serving as the training set (n=554) and for 28 months in a second clinical center serving as the validation set (n = 392).

PREDICTORS

Urinary MMP-7 and 7 previously reported biomarkers measured at the time of kidney biopsy and a score of histologically defined disease severity (MEST-C).

OUTCOMES

IgAN progression was defined as a composite of >40% loss of estimated glomerular filtration rate, kidney failure, or death.

ANALYTICAL APPROACH

Cox proportional hazard models adjusted for clinical characteristics, kidney function, relevant medications, and MEST-C score. Risk classification statistics were calculated for IgAN progression at 3 years, including C statistic, net reclassification index, and integrated discrimination index.

RESULTS

High levels (>3.9μg/g of creatinine) of urinary MMP-7 were associated with a 2.7-fold higher risk for IgAN progression in adjusted analyses. Urinary MMP-7 level outperformed (C statistic, 0.78) levels of urinary angiotensinogen (C statistic, 0.75), epidermal growth factor (C statistic, 0.75), kidney injury molecule 1 (C statistic, 0.68), and serum galactose-deficient IgA1 (C statistic, 0.59) for predicting IgAN progression. The addition of urinary MMP-7 level to a model with clinical data from the time of biopsy (estimated glomerular filtration rate, mean arterial blood pressure, and proteinuria) and MEST-C score significantly improved the C statistic from 0.79 to 0.85, improved the 3-year risk prediction of IgAN progression (from 0.84 to C statistic of 0.90), and improved risk reclassification (category-free net reclassification improvement, 0.60). The predictive performance of urinary MMP-7 level, alone or combined with clinical data, was consistent in the external validation set.

LIMITATIONS

Lack of validation in other ethnic populations.

CONCLUSIONS

In this study cohort, urinary MMP-7 level is an independent predictor of IgAN progression. The addition of urinary MMP-7 level to MEST-C score and clinical data at the time of biopsy significantly improved risk prediction of IgAN progression.

Plasma Galactose-Deficient IgA1 and C3 and CKD Progression in IgA Nephropathy

BACKGROUND AND OBJECTIVES

Increased circulating galactose-deficient IgA1 and subsequently complement activation both play important roles in the pathophysiology of IgA nephropathy. However, their relationship to disease severity and progression remains unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We assessed 1210 participants in a cohort study of biopsy-proven IgA nephropathy at Peking University First Hospital. Plasma concentrations of galactose-deficient IgA1 and complement component C3 were measured at the time of biopsy. We tested associations of galactose-deficient IgA1 and galactose-deficient IgA1/C3 ratio with CKD progression event, defined as ESKD or 50% decline in eGFR, using Cox proportional hazards models and restricted cubic splines.

RESULTS

After a median follow-up of 43 months (interquartile range, 24-76 months), 172 (14%) participants reached the CKD progression event. The association of galactose-deficient IgA1 levels and CKD progression event showed a nonlinear relationship. The risk of CKD progression events was greater with higher plasma galactose-deficient IgA1 levels but reached a plateau when galactose-deficient IgA1>325 U/ml, whereas the risk of CKD progression events monotonically increased with higher galactose-deficient IgA1/C3 ratio. After adjustment for traditional risk factors (demographics, eGFR, proteinuria, hypertension, Oxford pathologic score, and corticosteroids/immunosuppressive therapy), higher levels of galactose-deficient IgA1/C3 ratio were independently associated with CKD progression event (per natural log-transformed [galactose-deficient IgA1/C3], hazard ratio, 2.03; 95% confidence interval [95% CI], 1.25 to 3.29; P=0.004). In reference to the first quartile of the galactose-deficient IgA1/C3 ratio, hazard ratios were 1.71 (95% CI, 1.01 to 2.89) for the second quartile, 1.55 (95% CI, 0.91 to 2.63) for the third quartile, and 2.17 (95% CI, 1.33 to 3.56) for the fourth quartile.

CONCLUSIONS

In IgA nephropathy, plasma galactose-deficient IgA1/C3 ratio was associated with CKD progression event independent of clinical and biopsy characteristics.

Serum levels of miR-126 and miR-223 and outcomes in chronic kidney disease patients

Several microRNAs (miRNAs) have been linked to chronic kidney disease (CKD) mortality, cardiovascular (CV) complications and kidney disease progression. However, their association with clinical outcomes remains poorly evaluated. We used real-time qPCR to measure serum levels of miR-126 and miR-223 in a large cohort of 601 CKD patients (CKD stage G1 to G5 patients or on renal replacement therapy – CKD G5D) from Ghent University Hospital and 31 healthy controls. All-cause mortality and cardiovascular and renal events were registered as endpoints over a 6 year follow-up period. miR-126 levels were significantly lower from CKD stage G2 on, compared to controls. The serum levels of miR-223 were significantly lower from CKD stage G3B on. When considering overall mortality, patients with levels of either miR-126 or miR-223 below the median had a lower survival rate. Similar results were observed for CV and renal events. The observed link between the two miRNAs’ seric levels and mortality, cardiovascular events or renal events in CKD appears to depend on eGFR. However, this does not preclude their potential role in the pathophysiology of CKD. In conclusion, CKD is associated with a decrease in circulating miR-223 and miR-126 levels.

Urine markers of renal tubular injury in idiopathic membranous nephropathy: A cross sectional study

INTRODUCTION

Idiopathic membranous nephropathy (IMN) is a primary glomerular disease and a major cause of adult nephrotic syndrome. Presently, little is known about the capabilities of the urine markers to reflect the severity of IMN. We aimed at establishing whether urinary N-acetyl-β-glucosaminidase (NAG), Retinol binding protein (RBP), Kidney injury molecule-1 (KIM-1) and Neutrophil gelatianse-associated lipocalin (NGAL) are related with renal parameters and the histological grades tubular injury.

METHODS

The levels of urinary NAG, RBP, KIM-1 and NGAL were determined in 165 biopsy-proven patients and 64 healthy controls. Their levels were then compared between patients and healthy subjects, and between patients with and without nephrotic syndrome. Their linearity with renal parameters and associations with histological grades of renal tubular injury were also assessed.

RESULTS

All biomarkers were significantly increased in patients (p < .001). However, no significant increase was observed between patients exhibiting moderate and severe grades tubular injury and those exhibiting mild histological grade. With exception of RBP, all biomarkers were higher in patients with nephrotic syndrome (p < .001) and significantly correlated with majority of renal parameters including proteinuria.

CONCLUSION

Our findings suggest that although urine markers of tubular injury are increased in IMN, they may not offer a reflection of histological grades.

Blockade of ERK1/2 by U0126 alleviates uric acid-induced EMT and tubular cell injury in rats with hyperuricemic nephropathy

Extracellular signal-regulated kinases 1 and 2 (ERK1/2) are serine/threonine kinases and function as regulators of cellular proliferation and differentiation. Recently, we demonstrated that inhibition of ERK1/2 alleviates the development and progression of hyperuricemia nephropathy (HN). However, its potential roles in uric acid-induced tubular epithelial-mesenchymal transition (EMT) and tubular epithelial cell injury are unknown. In this study, we showed that hyperuricemic injury induced EMT as characterized by downregulation of E-cadherin and upregulation of vimentin and Snail1 in a rat model of HN. This was coincident with epithelial cells arrested at the G₂/M phase of cell cycle, activation of Notch1/Jagged-1 and Wnt/β-catenin signaling pathways, and upregulation of matrix metalloproteinase-2 (MMP-2) and MMP-9. Administration of U0126, a selective inhibitor of ERK1/2, blocked all these responses. U0126 was also effective in inhibiting renal tubular cell injury, as shown by decreased expression of lipocalin-2 and kidney injury molecule-1 and active forms of caspase-3. U0126 or ERK1/2 siRNA can inhibit tubular cell EMT and cell apoptosis as characterized with decreased expression of cleaved caspase-3. Moreover, ERK1/2 inhibition suppressed hyperuricemic injury-induced oxidative stress as indicated by decreased malondialdehyde and increased superoxide dismutase. Collectively, ERK1/2 inhibition-elicited renal protection is associated with inhibition of EMT through inactivation of multiple signaling pathways and matrix metalloproteinases, as well as attenuation of renal tubule injury by enhancing cellular resistance to oxidative stress.

Urinary kidney injury molecule-1 in renal disease

Kidney injury molecule-1 (KIM-1), a type l transmembrane glycoprotein, is recognized as a potential biomarker for detection of tubular injury in the main renal diseases. Urinary KIM-1 increases rapidly upon the tubular injury, and its levels are associated with the degree of tubular injury, interstitial fibrosis, and inflammation in the injured kidney. Currently, the investigation of kidney diseases is usually performed through the assessment of serum creatinine and urinary albumin. However, these biomarkers are limited for the early detection of changes in renal function. Besides, the tubular injury appears to precede glomerular damage in the pathophysiology of renal diseases. For these reasons, the search for sensitive, specific and non-invasive biomarkers is of interest. Therefore, the purpose of this article is to review the physiological mechanisms of KIM-1, as well to present clinical evidence about the association between elevated urinary KIM-1 levels and the main renal diseases such as chronic kidney disease, diabetic kidney disease, acute kidney injury, and IgA nephropathy.

Urinary Tubular Injury Biomarkers Are Associated With ESRD and Death in the REGARDS Study

Introduction

Urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary kidney injury molecule-1 (uKIM-1) are established markers of subclinical acute kidney injury. In persons with reduced estimated glomerular filtration rate (eGFR) and albuminuria who are at high risk for end-stage renal disease (ESRD) and death, the associations of these urinary markers with incident ESRD or death is an area of active investigation.

Methods

Among 1472 black and white participants from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study with eGFR ≤60 ml/min per 1.73 m² (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] cystatin, 2012) and albumin-to-creatinine ratio (ACR) ≥30 mg/g, we evaluated the associations of baseline uNGAL and uKIM-1 with progression to ESRD and all-cause death. Cox models were sequentially adjusted for urinary creatinine, traditional risk factors, C-reactive protein, ACR, and eGFR.

Results

There were 257 ESRD events and 819 deaths over a median follow-up of 5.7 and 6.5 years, respectively. In demographic adjusted models, higher levels of uNGAL were associated with increased risk of ESRD and death, but these associations were attenuated in fully adjusted models including baseline eGFR for both ESRD (hazard ratio [HR] = 1.06 per doubling, 95% confidence interval [CI] 0.98-1.14) and death (HR = 1.04, 95% CI = 1.00-1.08). Higher levels of uKIM-1 were associated with increased risk of ESRD and death in demographic-adjusted models, and although attenuated in fully adjusted models, remained statistically significant for both ESRD (HR = 1.24 per doubling, 95% CI = 1.08-1.42) and death (HR = 1.10, 95% CI =1.03-1.19).

Conclusion

In this cohort of high-risk patients with baseline eGFR ≤60 ml/min per 1.73 m² and albuminuria, renal tubular injury is associated with higher mortality and progression to ESRD. Further studies are necessary to investigate the mechanism underlying this increased risk.

Urinary Biomarkers of Aminoglycoside-Induced Nephrotoxicity in Cystic Fibrosis: Kidney Injury Molecule-1 and Neutrophil Gelatinase-Associated Lipocalin

Aminoglycosides are commonly used for the treatment of pulmonary exacerbations in patients with cystic fibrosis (CF). However, they are potentially nephrotoxic. This prospective observational cohort study aimed to investigate the potential validity of two urinary renal biomarkers, Kidney Injury Molecule-1 (KIM-1) and Neutrophil Gelatinase-associated Lipocalin (NGAL), in identifying aminoglycoside-induced nephrotoxicity in children with CF. Children and young adults up to 20 years of age with a confirmed diagnosis of CF were recruited from ten United Kingdom hospitals. Participants provided urine samples for measurement of KIM-1 and NGAL concentrations, at baseline, at regular outpatient appointments, and before, during and after exposure to clinically-indicated treatment with the aminoglycoside tobramycin. 37/158 patients recruited (23.4%) received at least one course of IV tobramycin during the study. The median peak fold-change during tobramycin exposure for KIM-1 was 2.28 (IQR 2.69) and 4.02 (IQR 7.29) for NGAL, in the absence of serum creatinine changes. Baseline KIM-1 was positively associated with cumulative courses of IV aminoglycosides (R² = 0.11; β = 0.03; p < 0.0001). KIM-1, in particular, may be a useful, non-invasive, biomarker of acute and chronic proximal tubular injury associated with exposure to aminoglycosides in patients with CF, but its clinical utility needs to be further evaluated in prospective studies.

Protective effects of hydrogen sulfide on chronic kidney disease by reducing oxidative stress, inflammation and apoptosis

The current study aimed to examine the renoprotective effects of long-term treatment with sodium hydrosulfide (NaHS), a prominent hydrogen sulfide donor, in 5/6 nephrectomy animal model. Twenty-four rats were randomly divided into 3 groups including sham-operated group (Sham), 5/6-nephrectomized group (5/6 Nx), and NaHS-treated group (5/6Nx+NaHS). NaHS (30 micromol/l) was added twice daily into the drinking water and renal failure was induced by 5/6 nephrectomy. Twelve weeks after surgical procedure, blood pressure, creatinine clearance (CCr), urine concentration of neutrophil gelatinase associated lipocalin (NGAL) and tissue concentration of malondialdehyde (MDA), superoxide dismutase (SOD), as well as renal morphological changes, apoptosis (cleaved caspase-3) and inflammation (p-NF-κB) were measured. Five-sixth nephrectomy induced severe renal damage as indicated by renal dysfunction, hypertension and significant histopathological injury which were associated with increased NGAL and MDA levels, oxidant/antioxidant imbalance, decreased SOD activity and CCr and also overexpression of p-NF-κB and cleaved caspase-3 proteins. Instead, NaHS treatment attenuated renal dysfunction through reduction of NGAL concentration, hypertension, CCr, oxidant/antioxidant imbalance, inflammation and apoptosis. These findings suggest that long term NaHS treatment can be useful in preventing the progression of CKD by improving oxidant/antioxidant balance and reducing inflammation and apoptosis in the kidney.

Clinical Significance of Urinary Biomarkers in Patients With Primary Focal Segmental Glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is often accompanied with tubulointerstitial lesion. This study aimed to assess the role of urinary biomarkers in predicting tubulointerstitial lesion and treatment response in FSGS patients.

METHODS

Urinary neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), N-acetyl-β-d-glucosaminidase (NAG) and retinol-binding protein (RBP) were measured in 32 FSGS patients and 22 patients with minimal change nephrotic syndrome. Patients with FSGS were followed up to investigate the value of these markers in predicting treatment response.

RESULTS

FSGS patients had higher urinary NGAL, NAG and RBP than patients with minimal change nephrotic syndrome with comparable proteinuria. A cutoff value of 15.87ng/mL NGAL demonstrated 87.1% sensitivity and 59.1% specificity for the diagnosis of FSGS, with an area under the receiver operator characteristic curve of 0.801. In FSGS, these markers correlated significantly with the degree of acute tubulointerstitial damage but not with chronic tubulointerstitial lesion. Response to immunosuppressive therapy was significantly different in patients with KIM-1, NAG and RBP levels below and above the cutoff values.

CONCLUSIONS

Urinary NGAL, KIM-1, NAG and RBP are reliable biomarkers of tubulointerstitial lesion in FSGS patients. The measurements of these markers may be useful in diagnosing FSGS, detecting acute tubulointerstitial lesion and predicting treatment response.

Kidney Injury Molecule-1 Level is Associated with the Severity of Renal Interstitial Injury and Prognosis in Adult Henoch-Schönlein Purpura Nephritis

BACKGROUND AND AIMS

Kidney injury molecule-1 (KIM-1) was identified the most highly upregulated protein in chronic kidney diseases and prolonged KIM-1 expression may be maladaptive. The present study was aimed to investigate urinary, renal and plasma KIM-1 levels and to analyze association between KIM-1 levels with clinical and pathological indexes in adult Henoch-Schönlein purpura (HSP) patients.

METHODS

Twenty healthy individuals, 20 HSP patients without nephritis and 35 HSP patients with nephritis were recruited. Urinary and plasma KIM-1 levels were determined by ELISA and Luminex, respectively. Renal KIM-1 expression was evaluated by immunohistochemistry.

RESULTS

HSP patients with nephritis were characterized as elevated levels of urinary, renal and plasma KIM-1. Those with more severe tubular injury of renal biopsy tissues presented significantly higher urinary and renal KIM-1 levels compared to control and patients without nephritis. Urinary and renal levels of KIM-1 were positively correlated with blood urea nitrogen and proteinuria, while they were negatively correlated with eGFR at both baseline and after two years follow-up. Moreover, plasma KIM-1 levels were associated with blood urea nitrogen and proteinuria as well. Further univariate correlation analysis indicated urinary and renal KIM-1 levels were positively correlated with interstitial inflammation index and tubulointerstitial chronicity index. Only urinary KIM-1 levels were associated with interstitial inflammation index, tubulointerstitial chronicity index and extracapillary glomerular activity index, after logistic regression analysis. The area under the curve (AUC) for urinary KIM-1/Cr predicting progression of renal damage was significantly greater than the AUC for proteinuria.

CONCLUSIONS

This finding suggests that measurement of urinary and renal KIM-1 level may be helpful to evaluate severity of renal pathological damage and prognosis in adult HSP patients with nephritis.

Performance of urinary kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, and N-acetyl-β-D-glucosaminidase to predict chronic kidney disease progression and adverse outcomes

Urinary biomarkers can predict the progression of chronic kidney disease (CKD). In this study, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and N-acetyl-β-D-glucosaminidase (NAG) were correlated with the stages of CKD, and the association of these biomarkers with CKD progression and adverse outcomes was determined. A total of 250 patients, including 111 on hemodialysis, were studied. Urinary KIM-1, NGAL, and NAG were measured at baseline. Patients not on dialysis at baseline who progressed to a worse CKD stage were compared with those who did not progress. The association of each biomarker and selected covariates with progression to more advanced stages of CKD, end-stage kidney disease, or death was evaluated by Poisson regression. NGAL was moderately correlated (r^s=0.467, P<0.001) with the five stages of CKD; KIM-1 and NAG were also correlated, but weakly. Sixty-four patients (46%) progressed to a more advanced stage of CKD. Compared to non-progressors, those patients exhibited a trend to higher levels of KIM-1 (P=0.064) and NGAL (P=0.065). In patients not on dialysis at baseline, NGAL was independently associated with progression of CKD, ESKD, or death (RR=1.022 for 300 ng/mL intervals; CI=1.007-1.037, P=0.004). In patients on dialysis, for each 300-ng/mL increase in urinary NGAL, there was a 1.3% increase in the risk of death (P=0.039). In conclusion, urinary NGAL was associated with adverse renal outcomes and increased risk of death in this cohort. If baseline urinary KIM-1 and NGAL predict progression to worse stages of CKD is something yet to be explored.

Diagnostic Value of Urine Tissue Inhibitor of Metalloproteinase-2 and Insulin-Like Growth Factor-Binding Protein 7 for Acute Kidney Injury: A Meta-Analysis

Background

Tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein-7 (IGFBP7) are both involved in renal tubular epithelial cell cycle arrest in acute kidney injury (AKI). Several recent studies showed that urine TIMP-2 times IGFBP7 ([TIMP-2]*[IGFBP7]) is a promising biomarker to predict AKI.

Methods

The aim of this meta-analysis was to assess the diagnostic value of urine [TIMP-2]*[IGFBP7] for early diagnosis of AKI. Relevant studies were retrieved from the PubMed, EMBASE, and Cochrane Library databases. The sensitivity and specificity were determined, and summary receiver operating characteristic (SROC) curves were constructed.

Results

Ten full-text prospective studies were included in this meta-analysis. The estimated sensitivity of urine [TIMP-2]*[IGFBP7] for the early diagnosis of AKI was 0.84 (95% CI = 0.80–0.88) and the specificity was 0.57 (95%CI = 0.55–0.60). The SROC analysis showed an area under the curve of 0.8813.

Limitation

The limited number of included studies, small sample size, unpublished negative results and language limitation might have affected the evaluation.

Conclusion

Urine [TIMP-2]*[IGFBP7] is a promising candidate for early detection of AKI, especially in ruling-out AKI. However, the potential of this biomarker should be validated in larger studies with a broader spectrum of clinical settings.

The Associations of Blood Kidney Injury Molecule-1 and Neutrophil Gelatinase-Associated Lipocalin with Progression from CKD to ESRD

BACKGROUND AND OBJECTIVES

Elevated levels of urinary kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin are associated with negative outcomes in CKD. Our study aimed to explore the prognostic accuracy of blood levels of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin for progression to ESRD, major adverse cardiovascular events, and death in a large cohort of adult patients with all-cause nondialysis-dependent CKD stages 3-5. We considered whether these factors improve prediction in relation to traditional biomarkers and clinical parameters.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin were measured on baseline plasma samples from 1982 patients who were recruited to the Chronic Renal Insufficiency Standards Implementation Study between the start of June of 2002 and the start of June of 2013. Associations with study end points were assessed using Cox regression models, receiver operator characteristic curve analyses, and reclassification statistics.

RESULTS

Over a median follow-up of 29.5 months (interquartile range, 14.9-53.5), 21.6% of patients progressed to ESRD, 27% died, and 6.6% suffered a major adverse cardiovascular event. Higher blood levels of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin were independently associated with a greater risk for ESRD (hazard ratio, 1.25; 95% confidence interval, 1.10 to 1.43; P<0.001 and hazard ratio, 1.35; 95% confidence interval, 1.14 to 1.59; P≤0.001, respectively, per 1 SD higher biomarker concentration). There was no association with risk for cardiovascular events or death. The addition of biomarkers to our baseline risk model of traditional clinical characteristics and laboratory parameters did not significantly improve model discrimination or risk reclassification.

CONCLUSIONS

In patients with moderate to severe CKD, kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin blood levels are independent risk factors for progression to ESRD. Additional studies are needed to establish the utility and cost-effectiveness of these novel biomarkers in the clinical setting.

Kidney injury molecule-1 in kidney disease

Kidney injury molecule-1(KIM-1) is a type I membrane protein, comprising an extracellular portion and a cytoplasmic portion, which is expressed at very low levels in the normal kidney. The extracellular portion can cleave and rapidly enter tubule lumens after kidney injury, and can then be detected in the urine. It has been confirmed that the urine KIM-1 level is closely related to tissue KIM-1 level and correlated with kidney tissue damage. Not only is KIM-1 proven to be an early biomarker of acute kidney injury but it also has a potential role in predicting long-term renal outcome. This review summarizes the relationships between KIM-1 and kidney injury, especially in chronic kidney disease.

Elevated serum immunoglobulin E level as a marker for progression of immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin E (IgE) has traditionally been associated with anaphylaxis and atopic disease. Previous studies reported that serum IgE levels are elevated in nephrotic syndrome and suggested IgE levels as a prognostic indicator in glomerular diseases. The aim of this study was to explore the association between serum IgE levels and renal outcome in patients with immunoglobulin A nephropathy (IgAN).

METHODS

We included 117 patients with biopsy-proven IgAN. Renal progression was defined if a patient meets one of these criteria: (1) a negative value of delta estimated glomerular filtration rate (mL/min/1.73 m(2)/mo) or (2) a rise in serum creatinine to an absolute level of ≥ 1.3 mg/dL (male) or 1.2 mg/dL (female). We defined delta changes in serum creatinine, estimated glomerular filtration rate, and proteinuria as a difference of values during the follow-up period.

RESULTS

A total of 117 patients with IgAN were included. The serum IgE level was significantly high in the renal progressive group compared with the nonprogressive group. Sex and history of gross hematuria were significantly different between the high-IgE group and the low-IgE group. Regression analysis showed that a male sex, initial proteinuria, and change of proteinuria were significantly associated with serum IgE levels.

CONCLUSION

The serum IgE level is potentially associated with disease progression and pathogenesis of IgAN.

[IgA nephropathy]

IgA nephropathy is the most common form of primary glomerulonephritis worldwide and an important cause of chronic kidney disease and end-stage kidney failure. Its pathophysiology remains in part unsolved but it is recognized as an immune complex disease. Recent years have brought progress in the field through the discovery of several genetic susceptibility loci and the formulation of the multi-hit pathogenesis model. Presentation, clinical course and histology can be extremely variable, making any histological classification still difficult. Indeed, most therapeutic studies until now include patients based only on the severity of clinical criteria but the new classification of Oxford should change that. Only the management of patients with nephropathy with minimal change glomerular lesions and nephrotic syndrome, or extra-capillary glomerulonephritis and rapidly progressive renal failure, is consensual: Corticosteroids alone for the first and associated with immunosuppressive drugs for the latter. The recent Kidney Disease Improving Global Outcomes (KDIGO) consensus treatment guideline is still controversial, especially in light of the last clinical studies. Corticosteroid therapy can be discussed in patients with proteinuria greater than 1 g/day without renal failure. All IgA nephropathy patients should benefit from the global management of chronic glomerular disease, including a renin-angiotensin system blocker in the presence of hypertension or proteinuria.

Markers for the progression of IgA nephropathy

We have summarized the latest findings on markers for progression of immunoglobulin A (IgA) nephropathy (IgAN), the most common primary glomerulonephritis with a high prevalence among end-stage renal disease (ESRD) patients. The clinical predictors of renal outcome in IgAN nephropathy, such as proteinuria, hypertension, and decreased estimated glomerular filtration rate (eGFR) at the time of the diagnosis, are well known. The Oxford classification of IgAN identified four types of histological lesions (known as the MEST score) associated with the development of ESRD and/or a 50 % reduction in eGFR. In addition, the role of genetic risk factors associated with IgAN is being elucidated by genome-wide association studies, with multiple risk alleles described. Recently, biomarkers in serum (galactose-deficient IgA1, IgA/IgG autoantibodies against galactose-deficient IgA1, and soluble CD 89-IgA complexes) and urine (soluble transferrin receptor, interleukin-6/epidermal growth factor ratio, fractalkine, laminin G-like 3 peptide, κ light chains, and mannan-binding lectin) have been identified. Some of these biomarkers may represent candidates for the development of noninvasive diagnostic tests, that would be useful for detection of subclinical disease activity, monitoring disease progression, assessment of treatment, and at the same time circumventing the complications associated with renal biopsies. These advances, along with future disease-specific therapy, will be helpful in improving the treatment effectiveness, prognosis, and the quality of life in connection with IgAN.

The Application of Kidney Injury Molecule-1 to Determine the Duration Between Shockwave Lithotripsy Sessions

PURPOSE

We aimed to evaluate the role of kidney injury molecule-1 (KIM-1) in determining the intervals between shockwave lithotripsy (SWL) sessions.

PATIENTS AND METHODS

This was a prospective, controlled study. It included 40 patients with unilateral kidney stones and 40 healthy persons of a similar age group as controls. The patients' midflow urine samples were collected before SWL and 1 hour, 1 day, 1 week, and 1 month after the procedure.

RESULTS

The average age in the SWL and control groups was 45 ± 14 and 39 ± 15 years, respectively (P = 0.336). The average KIM-1 value before SWL was 0.74 ± 0.35 ng/mL, which was significantly higher than that of the control group (0.51 ± 0.14 ng/mL) (P < 0.001). Similarly, the average values of the urine samples after SWL were higher than those of the control group (P < 0.001). When the KIM-1 values of the patients given SWL were compared within the group, the KIM-1 values 1 hour (1.06 ± 0.51) and 1 day (0.99 ± 0.67) after the procedure were statistically clearly higher than those before the procedure (P < 0.001) and statistically clearly higher than those of the control group (P = 0.005). The KIM-1 values 1 week and 1 month after the procedure were not significantly different than the preprocedure values (P = 0.652 and P = 0.747, respectively).

CONCLUSION

KIM-1 is a noninvasive biomarker that may be used to show renal damage because of stones and early-stage renal damage linked to SWL. In addition, post-SWL KIM-1 values may be used to determine the interval between SWL sessions.

Plasma neutrophil gelatinase-associated lipocalin as a potential predictor of adverse renal outcomes in immunoglobulin A nephropathy

BACKGROUND/AIMS

Neutrophil gelatinase-associated lipocalin (NGAL) is a well-known biomarker of acute kidney injury. We evaluated the value of plasma NGAL (pNGAL) as an independent predictor of prognosis in immunoglobulin A nephropathy (IgAN).

METHODS

In total, 91 patients with biopsy-proven IgAN at a single center were evaluated. pNGAL was measured using a commercial enzyme-linked immunosorbent assay kit (R&D Systems). Adverse renal outcome was defined as chronic kidney disease (CKD) stage 3 or above at the last follow-up. Pearson correlation coefficient and Cox regression were used for analyses.

RESULTS

The mean age of all patients (male:female, 48:43) was 35 years (range, 18 to 77). pNGAL ranged between 21.68 and 446.40 ng/mL (median, 123.97) and showed a correlation with age (r = 0.332, p = 0.001), creatinine (r = 0.336, p = 0.001), estimated glomerular filtration rate (r = -0.397, p < 0.001), uric acid (r = 0.289, p = 0.006), and the protein-to-creatinine ratio (r = 0.288, p = 0.006). During a mean follow-up period of 37.6 months, 11 patients (12.1%) had CKD stage 3 or above. In a multivariate Cox regression model, hypertension (hazard ratio [HR], 8.779; 95% confidence interval [CI], 1.526 to 50.496; p = 0.015), proteinuria > 1 g/day (HR, 5.184; 95% CI, 1.124 to 23.921; p = 0.035), and pNGAL (HR, 1.012; 95% CI, 1.003 to 1.022; p = 0.013) were independent predictors associated with adverse renal outcome.

CONCLUSIONS

pNGAL showed strong correlations with other clinical prognostic factors and was also an independent predictor of adverse renal outcome. We suggest pNGAL as a potential predictor for prognosis in IgAN, while further studies are needed to confirm the clinical value.

High serum and urine neutrophil gelatinase-associated lipocalin levels are independent predictors of renal progression in patients with immunoglobulin A nephropathy

BACKGROUND/AIMS

Tubulointerstitial injury plays an important role in the progression of immunoglobulin A nephropathy (IgAN), and neutrophil gelatinase-associated lipocalin (NGAL) is among the most sensitive tubular biomarkers. We investigated whether serum or urine NGAL predicts prognosis in patients with IgAN.

METHODS

The present study enrolled patients with biopsy-proven IgAN from January 2005 to December 2010, whose serum and urine samples at the time of kidney biopsy were preserved by freezing. We retrospectively reviewed patient clinical data and followed patients until October 2012. Serum and urine NGAL levels were measured using an enzyme-linked immunosorbent assay kit. Renal progression was defined as an estimated glomerular filtration rate decline by > 50% or progression to end-stage renal disease.

RESULTS

There were 121 patients enrolled in this study. During the median follow-up period of 41.49 months, renal progression was found in nine patients (7.4%). Serum or urine NGAL alone could not predict renal progression; however, when serum and urine NGAL levels were combined, belonging to the high NGAL group independently predicted renal progression (hazard ratio [HR], 5.56; 95% confidence interval [CI], 1.42 to 21.73; p = 0.014), along with tubular damage graded according to the Oxford classification as T2 (HR, 8.79; 95% CI, 2.01 to 38.51; p = 0.004). In addition, a Kaplan-Meier curve of renal survival showed significantly higher renal progression in patients in the high NGAL group (log rank, p = 0.004).

CONCLUSIONS

In patients with IgAN, high serum and urine NGAL levels at the time of kidney biopsy predict renal progression.

Kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin as prognostic markers in idiopathic membranous nephropathy

Background

Urinary excretion of alpha-1-microglobulin and beta-2-microglobulin reflects tubular damage and predicts outcome in patients with idiopathic membranous nephropathy with reasonable accuracy. Urinary kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin are novel biomarkers of tubular damage. We investigated if these markers could improve prediction of outcome in idiopathic membranous nephropathy.

Methods

We measured kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin in urine samples from patients with idiopathic membranous nephropathy, who had nephrotic proteinuria and normal renal function. Excretion of alpha-1-microglobulin and beta-2-microglobulin had been measured previously. Progression was defined as a serum creatinine rise >30%, a rise in serum creatinine to an absolute value of ≥135  µmol/L, or a clinical decision to start immunosuppressive therapy. Remission was defined as proteinuria <3.5 g/day and >50% reduction from baseline.

Results

Sixty-nine patients were included. Median follow-up was 35 months (interquartile range 18–63 months). Progression occurred in 30 patients (44%), and spontaneous remission in 36 (52%). Kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin excretion rates were significantly correlated with each other, and with alpha-1-microglobulin and beta-2-microglobulin. The areas under the receiver operating characteristic curves for progression were 0.75 (0.62–0.87) for kidney injury molecule-1 and 0.74 (0.62–0.87) for neutrophil gelatinase-associated lipocalin. In multivariate analysis with either alpha-1-microglobulin and beta-2-microglobulin, kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin did not independently predict outcome.

Conclusion

Kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin excretion rates correlated with excretion rates of other tubular damage markers and predicted outcome in patients with idiopathic membranous nephropathy. They did not add prognostic value compared to measurement of either alpha-1-microglobulin or beta-2-microglobulin.

Biomarkers in chronic kidney disease, from kidney function to kidney damage

Chronic kidney disease (CKD) typically evolves over many years, with a long latent period when the disease is clinically silent and therefore diagnosis, evaluation and treatment is based mainly on biomarkers that assess kidney function. Glomerular filtration rate (GFR) remains the ideal marker of kidney function. Unfortunately measuring GFR is time consuming and therefore GFR is usually estimated from equations that take into account endogenous filtration markers like serum creatinine (SCr) and cystatin C (CysC). Other biomarkers such as albuminuria may precede kidney function decline and have demonstrated to have strong associations with disease progression and outcomes. New potential biomarkers have arisen with the promise of detecting kidney damage prior to the currently used markers. The aim of this review is to discuss the utility of the GFR estimating equations and biomarkers in CKD and the different clinical settings where these should be applied. The CKD-Epidemiology Collaboration equation performs better than the modification of diet in renal disease equation, especially at GFR above 60 mL/min per 1.73 m². Equations combining CysC and SCr perform better than the equations using either CysC or SCr alone and are recommended in situations where CKD needs to be confirmed. Combining creatinine, CysC and urine albumin to creatinine ratio improves risk stratification for kidney disease progression and mortality. Kidney injury molecule and neutrophil gelatinase-associated lipocalin are considered reasonable biomarkers in urine and plasma to determine severity and prognosis of CKD.

Neutrophil gelatinase-associated lipocalin (NGAL) in heart transplant recipients after conversion to everolimus therapy

BACKGROUND

Due to the lack of nephrotoxic activity, proliferation signal inhibitors (PSI) such as everolimus are recommended for immunosuppression after heart transplantation, but the assessment of renal function in patients receiving PSI has led to conflicting results. We examined renal integrity and function using neutrophil gelatinase-associated lipocalin (NGAL) and conventional markers [plasma creatinine, cystatin C, urine albumin, α1-microglobulin (α1M)] in heart transplant patients, who underwent conversion to everolimus due to allograft vasculopathy, graft rejection episodes, or renal function deterioration, and in patients maintained on calcineurin inhibitors (CNI).

METHODS

This cross-sectional study included 121 consecutive heart transplant recipients: 44 patients received CNI-free immunosuppressive therapy with everolimus and 77 patients received CNI. Renal parameters were determined in plasma and urine samples using standard enzymatic or immunochemical methods.

RESULTS

Heart transplant recipients receiving everolimus therapy had significantly lower NGAL concentrations in plasma [median (95% CI): 128 (97-176)ng/mL vs. 252 (224-283)ng/mL, p<0.001] and urine [median (95% CI): 6.4 (4.5-7.6)ng/g vs. 15.7 (10.2-25.9)ng/g creatinine, p<0.001]. In contrast, no significant differences were observed between everolimus- and CNI-treated groups with regard to creatinine and cystatin C, as well as urine albumin and α1M levels. Significant correlations were noted between plasma NGAL and creatinine (r=0.42, p<0.001), cystatin C (r=0.44, p<0.001), N-terminal brain natriuretic propeptide (r=0.31, p<0.01) and indicators of chronic inflammation [lipoprotein-associated phospholipase A2 (Lp-PLA2), r=0.31, p<0.01] and soluble CD40 ligand (sCD40L, r=0.22, p<0.05), and between urinary NGAL and α1M (r=0.21, p<0.05). Multiple regression analysis indicated that cystatin C and Lp-PLA2 were the best predictors of plasma NGAL.

CONCLUSION

The present study documents reduced plasma and urinary NGAL levels in the absence of differences in conventional renal parameters in patients on CNI-free immunosuppressive therapy with everolimus. These results support favorable effects of everolimus on renal integrity in heart transplant recipients.

Urinary kidney injury molecule-1 is related to pathologic involvement in IgA nephropathy with normotension, normal renal function and mild proteinuria

BACKGROUND

IgA nephropathy (IgAN) may progress to renal failure for some patients without any clinical risk factors and it is not unusual to find severe pathologic damage in clinically mild IgAN. We therefore investigated whether urinary kidney injury molecule-1 (KIM-1) was related to pathologic involvement in clinically mild IgAN.

METHODS

Urinary KIM-1/creatinine of 51 IgAN patients with normotension, normal renal function and proteinuria < 1.0 g/24 h were tested. Relationships between urinary KIM-1 and pathologic features were analyzed.

RESULTS

Eighteen of the 51 patients had elevated urinary KIM-1. The tubular atrophy/interstitial fibrosis was more severe in patients with elevated urinary KIM-1 than that in patients with normal urinary KIM-1 (T0/T1/T2, 13/5/0 vs. 33/0/0, P = 0.004). Proportion of glomeruli containing cresecents was higher in patients with elevated urinary KIM-1 than that in patients with normal urinary KIM-1 (50% vs. 18%, P = 0.026). Urinary KIM-1 correlated with the proportion of total crescents (R = 0.303, p = 0.031) and fibrous crescents (R = 0.456, p = 0.001), but did not correlate with the proportion of cellular crescents or fibrocellular crescents. Although the proportion of vascular lesions was higher in patients with elevated urinary KIM-1 (44.4%) than that in patients with normal urinary KIM-1 (18.1%), the difference was not significant (p = 0.057). There was no difference of the response to treatment between patients with and without elevated urinary KIM-1 during a short-term follow-up.

CONCLUSIONS

Urinary KIM-1 is a reflection of tubularinstitial injury. For patients with clinically mild IgAN, high urinary KIM-1 is related to relatively severe pathologic involvement on renal biopsy.

Estimation of kidney injury molecule-1 (Kim-1) in patients with lupus nephritis

Objective

Biomarkers of disease activity in lupus nephritis (LN) are needed. Ideally, such biomarkers would be capable of detecting early sub-clinical disease and could be used to gauge response to therapy, thus obviating the need for serial renal biopsies. Much of the focus in the search for LN biomarkers has been on the measurement of urinary chemokines and cytokines in LN patients. However, these have yet to be widely implemented in clinical practice. Kidney injury molecule-1 (Kim-1) is expressed in damaged tubules, but whether urinary (u) and tubular (t)-Kim-1 could serve as a biomarker of active LN is unknown. To investigate the disease activity and histological findings in LN, we evaluated u-Kim-1 levels and t-Kim-1 cells in patients with systemic lupus erythematosus (SLE).

Method

We measured u-Kim-1 levels and stained t-Kim-1 expression in 57 patients with LN using an ELISA and immunohistochemistry staining. Patients were classified into two groups (active LN, n = 37; inactive LN, n = 20) based on the presence of active renal disease according to the renal SLE disease activity index. correlations of clinical, laboratory data, and histological findings with urinary and t-Kim-1 expression were assessed.

Result

The u-Kim-1 levels were significantly correlated with the expression of t-Kim-1 ( R = 0.64; P = 0.004) in the SLE patients. The active LN patients exhibited elevated u-Kim-1 levels compared to the inactive LN patients. The number of t-Kim-1 cells was also correlated with histological findings (both glomerular and interstitial inflammation). The u-Kim-1 levels were also correlated with proteinuria and tubular damage in the active LN group. The number of t-Kim-1 cells at baseline was significantly correlated with the estimated glomerular filtration rate ( R = 0.72; P = 0.005) and serum creatinine ( R = 0.53; P = 0.005) after 6–8 months of treatment.

Conclusion

These data suggest the potential use of the u-Kim-1 levels to screen for active LN and for the estimation of t-Kim-1 expression in renal biopsies to predict renal damage, ongoing glomerular nephritis and tubulointerstitial inflammation, and tubular atrophy.

Kidney injury molecule-1 expression in IgA nephropathy and its correlation with hypoxia and tubulointerstitial inflammation

Tubulointerstitial injury plays an important role in the development and progression of chronic kidney disease (CKD). Kidney injury molecule (KIM)-1 is induced in damaged proximal tubules in both acute renal injury and CKD. However, the dynamics of KIM-1 in CKD and effects of KIM-1 expression on disease progression are unknown. Here, we aimed to determine the associations between tubular KIM-1 expression levels, renal function, and inflammation in CKD. The relationships between levels of KIM-1 and clinicopathological parameters were analyzed in patients with progressive and nonprogressive IgA nephropathy. KIM-1 expression was increased in patients with IgA nephropathy, and its expression was significantly correlated with the decrease of renal function. KIM-1 was particularly evident at the site with reduced capillary density, and KIM-1-positive tubules were surrounded by infiltrates of inflammatory cells. Using in vitro cell models, we showed that cellular stressors, including hypoxia, induced KIM-1 expression. KIM-1-expressing cells produced more chemokines/cytokines when cultured under hypoxic conditions. Furthermore, we showed that tubular cells with KIM-1 expression can regulate the immune response of inflammatory cells through the secretion of chemotactic factors. These data suggest that KIM-1-expressing epithelial cells may play a role in the pathogenesis of tubulointerstitial inflammation during chronic renal injury through the secretion of chemokines/cytokines.

Biomarkers in IgA nephropathy: relationship to pathogenetic hits

INTRODUCTION

IgA nephropathy, the most prevalent glomerular disease in the world, requires a renal biopsy for diagnosis. Reliable biomarkers are needed for the non-invasive diagnosis of this disease and to more fully delineate its natural history and risk for progression.

AREAS COVERED

In this review, the authors examine serum levels of galactose-deficient IgA1 (Gd-IgA1) and glycan-specific IgG and IgA autoantibodies that are integral to pathogenesis of IgA nephropathy. They also explore biomarkers related to alternative and lectin pathways of complement activation and serum and urinary peptide biomarkers detected by mass spectrometric methods. The literature search included review of all publications having IgA nephropathy in the title that were cited in PubMed and Scopus over the past 10 years and a non-systematic review of abstracts published for the annual meetings of the American Society of Nephrology and the International Symposia on IgA Nephropathy.

EXPERT OPINION

Serum Gd-IgA1 level and glycan-specific autoantibody levels are prime candidates to become diagnostic biomarkers for IgA nephropathy because of their central role in the earliest stages of disease pathogenesis. Assays for serum levels of complement proteins C3 and factor H are readily available in clinical practice and deserve continued study, either alone or in tandem with total serum IgA or serum Gd-IgA1 levels, as prognostic biomarkers for patients with IgA nephropathy. Urinary peptidomic data are also reviewed because this approach can successfully differentiate patients with IgA nephropathy from healthy controls and from patients with other forms of renal disease.

Tissue kidney injury molecule-1 expression in the prediction of renal function for several years after kidney biopsy

Objectives. Retrospective study was designed to examine the importance of tissue kidney injury molecule-1 (KIM-1) expression in predicting kidney function in sixty patients (27 males) aged 34.15 ± 12.23 years with different kidney diseases over three years after kidney biopsy. Materials and Methods. Tissue KIM-1 expression was determined immunohistochemically and KIM-1 staining was scored semiquantitatively, as well as tubulointerstitialis (TIN), inflammation, atrophy, and fibrosis. Kidney function (MDRD formula) and proteinuria/day were evaluated at the time of biopsy (GFR0) and 6, 12, 24, and 36 months later. Results. Significantly positive correlations between tissue KIM-1 expression and age (r = 0.313), TIN inflammation (r = 0.456), fibrosis (r = 0.317), and proteinuria at 6 months (r = 0.394) as well as negative correlations with GFR0 (r = −0.572), GFR6 (r = −0.442), GFR24 (r = −0.398), and GFR36 (r = −0.412) were found. Meanwhile, TIN inflammation was the best predictor of all measured kidney functions during three years, while tissue KIM-1 expression (P = 0.016) was a predictor only at 6 months after biopsy. Conclusion. Tissue KIM-1 expression significantly predicts kidney function solely at 6 months after biopsy, when the effects of immune and nonimmune treatments are the strongest.

Effect of treatment on urinary kidney injury molecule-1 in IgA nephropathy

Background

Kidney injury molecule-1 (KIM-1) is a biomarker useful for detecting early tubular damage and has been recently reported as a useful marker for evaluating kidney injury in IgA nephropathy (IgAN). We therefore investigated whether treatment decreases urinary KIM-1 excretion in IgAN.

Methods

We prospectively enrolled 37 patients with biopsy-proven IgAN. Urinary KIM-1 was assessed before and after treatment, which included low salt diet, blood pressure control, pharmacotherapy with angiotensin receptor blockers and/or angiotensin converting enzyme inhibitors, and immunosuppressive agents as necessary. The median treatment duration was 24 months.

Results

Urinary KIM-1/creatinine (Cr) was significantly decreased in patients with IgAN after treatment compared to baseline (P < 0.0001, 1.16 [0.51-1.83] vs 0.26 [0.12-0.65] ng/mg). There was a decrease in the amount of proteinuria after treatment, but it was not statistically significant (P = 0.052, 748.1 [405-1569.7] vs 569.2 [252.2-1114] g/d). Estimated glomerular filtration rate (eGFR) did not change with treatment (P = 0.599, 79.28 ± 30.56 vs 80.98 ± 32.37 ml/min/1.73 m²). Urinary KIM-1 was not correlated with proteinuria baseline or follow up (pre-: R = - 0.100, P = 0.577, post-: R = 0.001, P = 0.993). In patients with higher baseline urinary KIM-1, both urinary KIM-1 level and proteinuria were significantly decreased following treatment.

Conclusions

Treatment decreases urinary KIM-1/Cr in patients with IgAN. It also reduces proteinuria in patients with higher baseline urinary KIM-1. These results suggest a potential role for urinary KIM-1 as a biomarker for predicting treatment response in IgAN, however, further study is needed to verify this.

Dual involvement of growth arrest-specific gene 6 in the early phase of human IgA nephropathy

Background

Gas6 is a growth factor that causes proliferation of mesangial cells in the development of glomerulonephritis. Gas6 can bind to three kinds of receptors; Axl, Dtk, and Mer. However, their expression and functions are not entirely clear in the different glomerular cell types. Meanwhile, representative cell cycle regulatory protein p27 has been reported to be expressed in podocytes in normal glomeruli with decreased expression in proliferating glomeruli, which inversely correlated with mesangial proliferation in human IgA nephropathy (IgAN).

Methods

The aim of this study is to clarify Gas6 involvement in the progression of IgAN. Expression of Gas6/Axl/Dtk was examined in 31 biopsy proven IgAN cases. We compared the expression levels with histological severity or clinical data. Moreover, we investigated the expression of Gas6 and its receptors in cultured podocytes.

Results

In 28 of 31 cases, Gas6 was upregulated mainly in podocytes. In the other 3 cases, Gas6 expression was induced in endothelial and mesangial cells, which was similar to animal nephritis models. Among 28 podocyte type cases, the expression level of Gas6 correlated with the mesangial hypercellularity score of IgAN Oxford classification and urine protein excretion. It also inversely correlated with p27 expression in glomeruli. As for the receptors, Axl was mainly expressed in endothelial and mesangial cells, while Dtk was expressed in podocytes. In vitro, Dtk was expressed in cultured murine podocytes, and the expression of p27 was decreased by Gas6 stimulation.

Conclusions

Gas6 was uniquely upregulated in either endothelial/mesangial cells or podocytes in IgAN. The expression pattern can be used as a marker to classify IgAN. Gas6 has a possibility to be involved in not only mesangial proliferation via Axl, but also podocyte injury via Dtk in IgAN.

Advanced IgA nephropathy with impaired renal function benefits from losartan treatment in rats

BACKGROUND

Treatment with angiotensin receptor blockers (ARBs) is successful in mitigating IgA nephropathy (IgAN), independent of blood pressure changes, but the therapeutic role of ARB in advanced IgAN with impaired renal function is to be ascertained. The present study was performed to investigate the effect of losartan on advanced IgAN induced by staphylococcal enterotoxin B (SEB) combined with 5/6 nephrectomy in rats.

METHODS

Fifty-four male SD rats were randomly divided into three group: Rats in the model group were treated with SEB plus 5/6 nephrectomy, and those in the losartan group were gavaged with losartan (33.3 mg kg(-1 )d(-1)) besides the treatment with SEB plus 5/6 nephrectomy. The urine and blood biochemical changes of rats were tested. IgA, IgG, IgM and C3 depositions were studied dynamically with immunofluorescence. The renal tissue structures were observed under light microscopy. The expressions of TGF-β1, FN, alpha-SMA and FGF-1 in rat renal tissues were determined with immunohistochemical methods and real-time PCR.

RESULTS

At 12 weeks, rats with SEB treatment plus 5/6 nephrectomy showed gradually increased urinary red blood cell (URBC) with a gradual elevation of the 24 h urinary protein, serum BUN and Scr, but losartan treatment lowered the levels of 24 h urinary protein, serum BUN and Scr. A large number of IgA depositions in the mesangial area, glomerulosclerosis and tubulointerstitial fibrosis were found in the model group, and the losartan group showed relieved injury. The expressions of TGF-β1, FN, alpha-SMA and FGF-1 were significantly elevated in the model. Losartan lessened their expressions.

CONCLUSION

Losartan treatment can delay the progression of advanced IgA nephropathy with impaired renal function.

Glomerular and tubular damage markers in individuals with progressive albuminuria

BACKGROUND AND OBJECTIVES

Albuminuria is associated with risk for renal and cardiovascular disease. It is difficult to predict which persons will progress in albuminuria. This study investigated whether assessment of urinary markers associated with damage to different parts of the nephron may help identify individuals that will progress in albuminuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Individuals were selected from a prospective community-based cohort study with serial follow-up and defined as "progressors" if they belonged to the quintile of participants with the most rapid annual increase in albuminuria, and reached an albuminuria ≥150 mg/d during follow-up. Patients with known renal disease or macroalbuminuria at baseline were excluded. Each progressor was matched to two control participants, based on baseline albuminuria, age, and sex. Furthermore, damage markers were measured in a separate set of healthy individuals.

RESULTS

After a median follow-up of 8.6 years, 183 of 8394 participants met the criteria for progressive albuminuria. Baseline clinical characteristics were comparable between progressors and matched controls (n=366). Both had higher baseline albuminuria than the overall population. Urinary excretion of the glomerular damage marker IgG was significantly higher in progressors, whereas urinary excretion of proximal tubular damage markers and inflammatory markers was lower in these individuals compared with controls. Healthy individuals (n=109) had the lowest values for all urinary damage markers measured.

CONCLUSIONS

These data suggest that albuminuria associated with markers of glomerular damage is more likely to progress, whereas albuminuria associated with markers of tubulointerstitial damage is more likely to remain stable.

Prognostic value of NGAL staining in patients with IgA nephropathy

BACKGROUND

Renal tubulointerstitial injury plays an important role in disease progression of IgAN. Neutrophil gelatinase-associated lipocalin (NGAL) is a stress protein released by tubular cells. NGAL is a promising biomarker of acute kidney injury. There is a growing literature suggesting that NGAL is also a marker of chronic kidney disease and severity. Our aim was to evaluate the prognostic value of NGAL staining in patients with IgAN.

METHODS

This retrospective study included all consecutive patients who underwent a renal biopsy at our center between January 2005 and December 2009. Forty-five patients with IgA nephritis were enrolled, and renal biopsy specimens of 29 patients were evaluated. We evaluated baseline age, sex, hypertension, serum creatinine, glomerular filtration rate (GFR), urine protein, NGAL staining, glomerulosclerosis, interstitial fibrosis, and extracapillary proliferation. The primary endpoint of this study was doubling of baseline serum creatinine and/or the onset of ESRD in the course of the study. At the end of the follow-up, patients whose estimated GFR (eGFR) was ≤15 mL/min/1.73 m(2) and/or baseline serum creatinine doubled, were defined as the progressor group.

RESULTS

Nineteen patients (65.5%) were NGAL positive and 10 patients (34.5%) were NGAL negative. Female gender and hypertension were associated with NGAL-positive staining. Urinary protein excretion and serum creatinine levels were more elevated in the NGAL-positive group, but the difference was not significant. We found NGAL-positive staining in major proportion in the progressor group (88.9%) than the non-progressor group (55%) (p = 0.076).

CONCLUSION

NGAL staining can be a new histological marker in IgAN progression.