Date of Award

2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular and Cellular Biology and Pathobiology

College

College of Graduate Studies

First Advisor

John Arthur

Second Advisor

Michael Janech

Third Advisor

Lauren Ball

Fourth Advisor

Rick Schnellmann

Fifth Advisor

Elizabeth Hill

Abstract

Background: Acute kidney injury is a cause of significant morbidity and mortality in hospitalized patients. Prognostic biomarkers that predict at the time of diagnosis which patients will develop severe AKI and its complications would facilitate timely intervention and could lead to improved outcomes. The urinary proteome is a logical source of candidate biomarkers of kidney injury. Methods: Urine was collected from rodents and human subjects with AKI secondary to diverse etiologies, including cardiac surgery, ischemic/hypoxic injury, and nephrotoxicity. Shotgun proteomics was used to identify candidate biomarkers in four separate discovery phase experiments. These candidates were then verified in a larger cohort and case-control studies, in which they were measured using ELISA and a multiplex, quantitative mass spectrometry assay. Results: A total of 22 candidate prognostic biomarkers of AKI were identified by shotgun proteomic analysis of urine from rodents and humans with AKI. Of these, urinary angiotensinogen was the most promising. The prognostic predictive power of urinary angiotensinogen was verified in a cohort of post-cardiac surgery human subjects with AKI (n = 204), which found that it was a strong predictor of progression from Acute Kidney Injury Network (AKIN) stage 1 AKI to the composite endpoint AKIN stage 3 or death, having an area under the ROC curve of 0.75, 95% CI [0.65, 0.85]. In the same cohort, urinary renin concentration had an AUC of 0.7, 95% CI [0.57, 0.83] for the outcome. A classification tree model found that the combination of these biomarkers could predict the outcome with a positive predictive value of 80.4%. The quantitative mass spectrometry assay was able to successfully measure 11 of the 22 candidate biomarkers, and using this assay, the prognostic predictive power of urinary superoxide dismutase [Cu-Zn], myoglobin was confirmed in a subset of the aforementioned cohort of post-cardiac surgery AKI patients (n =156). SOD and myoglobin predicted progression from AKIN stage 1 to AKIN stage 3 or death with an AUC of 0.76 and 0.77, respectively. Urinary angiotensinogen was also included in the assay, and it had an AUC of 0.74 for the outcome. The performance characteristics of these novel biomarkers compared favorably with urinary liver-type fatty acid binding protein (AUC = 0.69), a more established AKI biomarker which was also included in the assay.

Rights

All rights reserved. Copyright is held by the author.

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