The identification of protective factors for Diabetic Retinopathy (DR) and Diabetic Nephropathy (DN) could provide important biomarkers and therapeutic agents to prevent and halt these two toxic complications from significantly diminishing quality of life. Using a unique population of type 1 diabetic (T1DM) patients with more than 50 years of disease (Medalists), we have begun to identify potential protective factors for DR and DN through pre and post mortem studies. We have extensively characterized over 600 Medalists through clinical examination, mixed meal tolerance test, extensive ophthalmic examination, and medical history questionnaires. Surprisingly, 35% have no or only mild DR (ETDRS <53), and less than 14% have DN (ACR <70 mcg/mg). Post-mortem histologic examinations confirm these findings. Thus far, post-mortem specimens from over 16 Medalist Study participants have been donated. Proteomic mapping of the specimens from the retina, vitreous, and renal glomeruli have identified a first set of potential protective factors for DR and DN. This was done by comparing protein expression between affected and unaffected tissues. According to pathway mapping and literature review, the fourteen candidate proteins identified in the glomerular analysis are all involved in fuel metabolism. The 10 factors identified in the retina analysis are involved in membrane recycling, transport, recovery of phototransduction, and retinal function. Bioinformatic pathway analyses demonstrate that the candidates identified for DR do not overlap with those for DN; however, both sets of protective factors suggest that more vibrant and metabolically active tissues exist in Medalists without DR or DN compared to those with the respective conditions. This study proposes to measure all of the identified and validated candidates in the plasma and circulating cells in the Medalists and in another unusual group of diabetic patients with ultra-fast progression. Additionally, the ability to protect against hyperglycemic exposure will be studied in cultured retinal vascular and renal glomerular and tubular cell models of DR and DN. We will also be able to determine the biological actions of these potential protective factors both in cell culture models and in vivo animal models of diabetes. From these translational studies, we will be able to identify and confirm potential protective factors associated with DR and DN.
Clinically, studies in diabetic patients who have survived greater than 50 years of disease duration clearly have demonstrated that endogenous protective factors can prevent and delay for extreme periods of time the onset of diabetic microvascular complications. Thus, therapeutic approach in the future for diabetic vascular complications needs to decrease the toxic effects of hyperglycemia as well as increase the actions of protective/survival factors in order to be effective.
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