Urinary Collagen Fragments Are Significantly Altered in Diabetes: A Link to Pathophysiology

Abstract

BackgroundThe pathogenesis of diabetes mellitus (DM) is variable, comprising different inflammatory and immune responses. Proteome analysis holds the promise of delivering insight into the pathophysiological changes associated with diabetes. Recently, we identified and validated urinary proteomics biomarkers for diabetes. Based on these initial findings, we aimed to further validate urinary proteomics biomarkers specific for diabetes in general, and particularity associated with either type 1 (T1D) or type 2 diabetes (T2D).Methodology/Principal FindingsTherefore, the low-molecular-weight urinary proteome of 902 subjects from 10 different centers, 315 controls and 587 patients with T1D (n = 299) or T2D (n = 288), was analyzed using capillary-electrophoresis mass-spectrometry. The 261 urinary biomarkers (100 were sequenced) previously discovered in 205 subjects were validated in an additional 697 subjects to distinguish DM subjects (n = 382) from control subjects (n = 315) with 94% (95% CI: 92–95) accuracy in this study. To identify biomarkers that differentiate T1D from T2D, a subset of normoalbuminuric patients with T1D (n = 68) and T2D (n = 42) was employed, enabling identification of 131 biomarker candidates (40 were sequenced) differentially regulated between T1D and T2D. These biomarkers distinguished T1D from T2D in an independent validation set of normoalbuminuric patients (n = 108) with 88% (95% CI: 81–94%) accuracy, and in patients with impaired renal function (n = 369) with 85% (95% CI: 81–88%) accuracy. Specific collagen fragments were associated with diabetes and type of diabetes indicating changes in collagen turnover and extracellular matrix as one hallmark of the molecular pathophysiology of diabetes. Additional biomarkers including inflammatory processes and pro-thrombotic alterations were observed.Conclusions/SignificanceThese findings, based on the largest proteomic study performed to date on subjects with DM, validate the previously described biomarkers for DM, and pinpoint differences in the urinary proteome of T1D and T2D, indicating significant differences in extracellular matrix remodeling.

Renal Allograft Fibrosis: Biology and Therapeutic Targets

“…Urinary peptidome and proteome also suggested that collagen fragments are potential biomarkers for renal fibrosis (407)(408)(409). Global analyses of urinary proteins and peptides could be superior to analyses of single markers (407)(408)(409)(410)(411), and a number of studies have used this approach (412)(413)(414). At the moment, proteomic analyses are not yet feasible for broad clinical application.…”

A peptidomic approach to biomarker discovery for bovine mastitis

“…There have been a number of studies, especially using urine, that have developed biomarkers models for a number of different diseases using capillary electrophoresis (CE) and mass spectrometry (MS). Those investigated so far range from renal disorders [16,17] to cardiovascular disease [18] and diabetes [19]. Many of these biomarker profiles have been recorded in a database made up from over 13,000 samples [20].…”

Urinary biomarkers of diabetic nephropathy

“…88 In the largest multicenter study to date, involving 902 participants at ten different centers using capillary electrophoresis coupled mass spectrometry, Maahs et al reported that 131 urinary biomarker candidates were differentially regulated between type 1 and type 2 DM. 89 Specifically, a decrease in urinary level of fragments of collagen α-1 (I) and (III) was found in type 2 DM as compared with type 1 DM. This suggests that a disturbance in the physiologic degradation of the extracellular matrix occurs, perhaps due to decreased activity of certain matrix metalloproteases in diabetes.…”

“…90,91 On the other hand, fragments of fibrinogen α and β were increased in type 2 DM as compared with type 1 DM. 89 Other proteins sequenced include fragments of α-1 antitrypsin, membrane-associated progesterone receptor component 1, and uromodulin. This panel of biomarkers distinguished type 1 DM from type 2 DM in an independent validation set of normoalbuminuric patients with 88% (95% confidence interval 81%-94%) accuracy and in patients with impaired renal function with 85% (95% confidence interval 81%-88%) accuracy.…”

“…This panel of biomarkers distinguished type 1 DM from type 2 DM in an independent validation set of normoalbuminuric patients with 88% (95% confidence interval 81%-94%) accuracy and in patients with impaired renal function with 85% (95% confidence interval 81%-88%) accuracy. 89 In a longitudinal cohort study of type 1 and type 2 DM, Zurbig et al reported that a previously validated panel of 273 biomarkers, consisting mostly of collagen fragments, was able to detect subsequent progression to macroalbuminuria in normoalbuminuric subjects (area under the curve 0.93). This panel identified progressors in the majority of the cases earlier than the traditional albuminuria (area under the curve 0.67).…”