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

A Review of Specific Biomarkers of Chronic Renal Injury and Their Potential Application in Nonclinical Safety Assessment Studies

A host of novel renal biomarkers have been developed over the past few decades which have enhanced monitoring of renal disease and drug-induced kidney injury in both preclinical studies and in humans. Since chronic kidney disease (CKD) and acute kidney injury (AKI) share similar underlying mechanisms and the tubulointerstitial compartment has a functional role in the progression of CKD, urinary biomarkers of AKI may provide predictive information in chronic renal disease. Numerous studies have explored whether the recent AKI biomarkers could improve upon the standard clinical biomarkers, estimated glomerular filtration rate (eGFR), and urinary albumin to creatinine ratio, for predicting outcomes in CKD patients. This review is an introduction to alternative assays that can be utilized in chronic (>3 months duration) nonclinical safety studies to provide information on renal dysfunction and to demonstrate specific situations where these assays could be utilized in nonclinical drug development. Novel biomarkers such as symmetrical dimethyl arginine, dickkopf homolog 3, and cystatin C predict chronic renal injury in animals, act as surrogates for GFR, and may predict changes in GFR in patients over time, ultimately providing a bridge from preclinical to clinical renal monitoring.

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 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 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.

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.

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.

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.

Structural equation modeling identifies markers of damage and function in the aging male Fischer 344 rat

The male Fischer 344 rat is an established model to study progressive renal dysfunction that is similar, but not identical, to chronic kidney disease (CKD) in humans. These studies were designed to assess age-dependent alterations in renal structure and function at late-life timepoints, 16-24 months. Elevations in BUN and plasma creatinine were not significant until 24 months, however, elevations in the more sensitive markers of function, plasma cystatin C and proteinuria, were detectable at 16 and 18 months, respectively. Interestingly, cystatin C levels were not corrected by caloric restriction. Urinary Kim-1, a marker of CKD, was elevated as early as 16 months. Klotho gene expression was significantly decreased at 24 months, but not at earlier timepoints. Alterations in renal structure, glomerulosclerosis and tubulointerstitial fibrosis, were noted at 16 months, with little change from 18 to 24 months. Tubulointerstitial inflammation was increased at 16 months, and remained similar from 18 to 24 months. A SEM (structural equation modeling) model of age-related renal dysfunction suggests that proteinuria is a marker of renal damage, while urinary Kim-1 is a marker of both damage and function. Taken together, these results demonstrate that age-dependent nephropathy begins as early as 16 months and progresses rapidly over the next 8 months.