Glycated CD59 as a Biomarker for Diabetes

Harvard Medical School, Boston MA

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Abstract

PROJECT SUMMARY/ABSTRACT The goal of this proposal, which responds in full to NIH PA-09-204 [unreadable]Development and Validation of Disease Biomarkers[unreadable], is to validate glycated CD59 (the glucose inactivated form of the complement regulatory protein CD59) in human urine, as 1) a biomarker of diabetic complications, 2) a pathogenically relevant indicator of the glycemic load, and 3) a screening tool for Impaired Glucose Tolerance. This proposal is highly translational and addresses major Public Health priorities because 1) 60% of the ≈16 million Americans with diabetes will develop complications, which are the leading cause of renal transplants, blindness and amputations in adults, dramatically increase the incidence of heart attacks, and stroke, consuming a staggering 15% of the total U.S. healthcare budget. HbA1c, the clinical gold standard for management of diabetes, does not identify individuals at high risk of developing some complications (e.g. nephropathy) and is not sensitive enough to discriminate individuals with IGT. Chronic hyperglycemia is responsible for the complications of human diabetes but the cellular/molecular mechanism(s) by which hyperglycemia causes tissue damage are poorly understood. The applicants have 1) discovered that human CD59 is inactivated by glycation, 2) provided evidence for a link between the complement and the pathogenesis of the complications of diabetes, and 3) developed reagents that allow quantification of glycated hCD59 in human fluids and tissues. Specifically, we have demonstrated that 1) glycated CD59 is present in target organs of diabetic complications, 2) urine glycated CD59 (UglyCD59) can be readily measured in normal urine, and is significantly increased (3-4 fold) in the urine of diabetic subjects. All reagents needed for the validation studies proposed in this application are available, including monoclonal antibodies specific for glycated CD59, assay calibrators, and an archive of well-characterized frozen urine samples from diabetic individuals. To validate UglyCD59 as biomarker for diabetes and its complications we propose to assess: 1) the correlation between UglyCD59 and HbA1c, the dynamics of its changes in relation to the average glucose levels within an individual, and its ability to discriminate ethnic populations at higher risk of vascular complications, 2) UglyCD59 as a marker of impaired glucose tolerance (IGT), and 3) UglyCD59 as a preclinical biomarker to identify diabetic patients at risk of developing complications focusing specifically on diabetic nephropathy (3a) and early small-fiber polyneuropathy (3b). Successful accomplishment of these aims would represent a major advancement in diagnosis, treatment and prevention of the complications of glucose dysmetabolism and diabetes, and should help lower the extremely high costs derived from diabetes and its complications.