LG3 fragment of endorepellin is a possible biomarker of severity in IgA nephropathy.

IgA nephropathy (IgAN), the most common primary glomerulonephritis, is characterized by deposition of IgA in the glomerular mesangium. The diagnosis of IgAN still requires a kidney biopsy that cannot easily be repeated in the same patient during follow-up. Therefore, identification of noninvasive urinary biomarkers would be very useful for monitoring patients with IgAN. We first used bidimensional electrophoresis (2DE) coupled to MALDI-TOF-TOF and Western blot to identify some urinary biomarkers associated with IgAN. Urine of IgAN patients showed an increase of albumin fragments, α-1-antitrypsin and α-1-ß-glycoprotein, along with a decrease of a single spot that was identified as the laminin G-like 3 (LG3) fragment of endorepellin. The urinary proteomes of 43 IgAN patients were compared to those of 30 healthy individuals by ELISA. Quantification of LG3 confirmed a significant decrease in the urine of IgAN patients compared to healthy controls, except in ten patients in whom LG3 was increased. These ten patients had a more severe disease with lower glomerular filtration rate values. We found a significant inverse correlation between LG3 levels and glomerular filtration rate in the 43 patients with IgAN, which was not observed in 65 patients with other glomerular diseases including membranous nephropathy (23), lupus nephropathy (13), focal segmental glomerulosclerosis (15), diabetic nephropathy (14), and six patients with nonglomerular diseases. Therefore, we suggest that the LG3 fragment of endorepellin could be associated with IgAN severity and might be related to pathogenesis of IgAN.

Urinary protein expression patterns in children with sleep-disordered breathing: preliminary findings.

BACKGROUND: Obstructive sleep apnea (OSA) is the most common form of sleep-disordered breathing, with almost 15 million Americans affected and many more at risk. Current diagnostic approach to OSA requires polysomnography, which is laborious, onerous, and time-consuming. There is ample evidence that inflammatory responses to the perturbations associated with OSA trigger a variety of genes and signaling cascades that ultimately lead to end-organ injury and changes in kidney function and protein expression. The aim of this study was therefore to analyze proteins in human urine and assess whether differential expression of particular proteins is associated with the presence of OSA. METHODS: Eleven OSA and 11 control children between the ages of three and 14 (males=17; females=5) underwent overnight sleep studies followed by a first-morning urine sample. Proteomic analysis of urine samples yielded a unique map of proteins, of which, five spots were selected for further analysis due to their significant intensity differences between OSA and control groups. RESULTS: Mass spectrometry followed by peptide mass fingerprinting conclusively identified four of the five spots as gelsolin, perlecan (a heparan sulfate proteoglycan), albumin, and immunoglobulin (P<0.05 and protein scores>67). CONCLUSIONS: Overall, increased expression of gelsolin and perlecan in the urinary proteome of children with OSA suggests that the episodic hypoxia associated with OSA may lead to changes in protein permeability or alternatively to increased catabolism of these proteins and their excretion in urine.

Markers of diabetic nephropathy.

It is well established that the detection of microalbuminuria in a patient with diabetes mellitus indicates the presence of glomerular involvement in early renal damage. Recent studies have demonstrated that there is also a tubular component to renal complications of diabetes, as shown by the detection of renal tubular proteins and enzymes in the urine. In fact, tubular involvement may precede glomerular involvement, as several of these tubular proteins and enzymes are detectable even before the appearance of microalbuminuria. This review looks at the studies reported so far on serum and urinary markers of diabetic nephropathy, both glomerular and tubular, and their roles in the early detection of renal damage. The advantages and disadvantages of some of these markers are also discussed. The markers reviewed include (1) glomerular--transferrin, fibronectin, and other components of glomerular extracellular matrix, and (2) tubular--low molecular weight proteins (beta 2 microglobulin, retinol binding protein, alpha 1 microglobulin, urine protein 1), other proteins such as Tamm-Horsfall protein, beta 2 glycoprotein-1, urinary enzymes (N-acetyl-beta-D-glucosaminidase, cholinesterase, gamma glutamyltranspeptidase, alanine aminopeptidase), and tubular brush-border antigen.

The identification of three novel biomarkers of major adverse kidney events.

AIM: To describe the prognostic value of three novel biomarkers for acute adverse kidney events compared with routine biological markers. MATERIAL & METHODS: We used high-end MS to quantify biomarkers predictive of acute kidney injury (AKI) and major adverse kidney events (MAKE) in 100 adult patients after open heart surgery (n = 100). RESULTS: Early postoperatively measured LG3 (a C-terminal fragment of perlecan), LTBP2 (latent transforming growth factor binding protein-2), Cathepsin L as well as two other renal biomarkers (NGAL, Cystatin C) had greater predictive value for AKI (n = 23) and MAKE (n = 24) compared with creatinine, urea and urine output. CONCLUSIONS: LG3, LTBP2 and Cathepsin L deserve further exploration as biomarkers for the early identification of patients at risk of MAKE.

Association of urinary laminin G-like 3 and free K light chains with disease activity and histological injury in IgA nephropathy.

BACKGROUND AND OBJECTIVES: IgA nephropathy has variable clinical presentation and progression. Its definitive diagnosis and prognosis require renal biopsy. The identification of new biomarkers allowing noninvasive diagnosis and monitoring of disease activity would be advantageous. This study analyzed the urine proteome of IgA nephropathy patients at an early stage of disease. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Urine from 49 IgA nephropathy patients, 42 CKD patients, and 40 healthy individuals was analyzed by surface-enhanced laser desorption/ionization time of flight/mass spectrometry. Differentially excreted proteins were identified by matrix-enhanced laser desorption/ionization time of flight/mass spectrometry, confirmed by immunologic methods, and validated in an independent set of patients (14 IgA nephropathy and 24 CKD). All patients were recruited at the Division of Nephrology of the University of Foggia from January of 2005 to March of 2007. RESULTS: Two proteins, with 21,598 and 23,458 m/z, were significantly decreased in IgA nephropathy and identified as Perlecan laminin G-like 3 peptide and Ig κ light chains, respectively. Western blot analysis confirmed the lower urinary excretion of laminin G-like 3 in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunonephelometry analysis confirmed the lower urinary excretion of free κ light chains in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunohistochemistry analysis justified the urinary excretion profile of such proteins in IgA nephropathy. Finally, urinary free κ light chains and laminin G-like 3 concentration inversely correlated with severity of clinical and histologic features of our IgA nephropathy cohort. CONCLUSIONS: Laminin G-like 3 and free κ light chains can contribute to the noninvasive assessment of IgA nephropathy disease activity.