Urine Proteome Analysis May Allow Noninvasive Differential Diagnosis of Diabetic Nephropathy

Abstract

OBJECTIVEChronic renal insufficiency and/or proteinuria in type 2 diabetes may stem from chronic renal diseases (CKD) other than classic diabetic nephropathy in more than one-third of patients. We interrogated urine proteomic profiles generated by surface-enhanced laser desorption/ionization-time of flight/mass spectrometry with the aim of isolating a set of biomarkers able to reliably identify biopsy-proven diabetic nephropathy and to establish a stringent correlation with the different patterns of renal injury.RESEARCH DESIGN AND METHODSTen micrograms of urine proteins from 190 subjects (20 healthy subjects, 20 normoalbuminuric, and 18 microalbuminuric diabetic patients and 132 patients with biopsy-proven nephropathy: 65 diabetic nephropathy, 10 diabetic with nondiabetic CKD [nd-CKD], and 57 nondiabetic with CKD) were run using a CM10 ProteinChip array and analyzed by supervised learning methods (Classification and Regression Tree analysis).RESULTSThe classification model correctly identified 75% of patients with normoalbuminuria, 87.5% of those with microalbuminuria, and 87.5% of those with diabetic nephropathy when applied to a blinded testing set. Most importantly, it was able to reliably differentiate diabetic nephropathy from nd-CKD in both diabetic and nondiabetic patients. Among the best predictors of the classification model, we identified and validated two proteins, ubiquitin and β2-microglobulin.CONCLUSIONSOur data suggest the presence of a specific urine proteomic signature able to reliably identify type 2 diabetic patients with diabetic glomerulosclerosis.

Diabetic Glomerulopathy

“…It remains, however, most likely that some of the patients included in the biomarker studies were unrightfully given the diagnosis of diabetic nephropathy, and it is uncertain how important this contamination of the data is for the study outcomes. Only one marker study in 2010 was found that did incorporate renal biopsy findings and interestingly, in this study, a classification model was able to reliably differentiate diabetic nephropathy from nondiabetic chronic kidney disease (Papale M 2010). Among the best predictors of this classification model were ubiquitin and b 2-microglobulin.…”

Association of Urinary Laminin G-Like 3 and Free K Light Chains with Disease Activity and Histological Injury in IgA Nephropathy

“…Urine samples were treated as described (17,21). All processed samples were stored at 280°C until use.…”

“…Only the peaks in the mass range from 3000 to 30,000 m/z with a signal-to-noise ratio greater than four were used for the data analysis. The reproducibility of SELDI analysis was assessed as previously described (17,21).…”

“…Sample Management and SELDI TOF/MS Analysis. Four-milliliter urine samples were prepared as previously reported (17) and analyzed in duplicate using CM10 protein-chip array (BIORAD, Hercules, CA). All experiments were performed according to the manufacturer's instructions.…”

“…Surface-enhanced laser desorption/ionization time of flight/mass spectrometry (SELDI-TOF-MS) analysis is gaining remarkable success as a rapid screening approach to identify new putative renal disease biomarkers (17,18). Noteworthy, it has never been applied to screen urine of IgAN patients.…”