Probing an Unexplored Intracellular Pathway in Diabetes Pathogenesis

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ABSTRACT Diabetic nephropathy and other diabetes complications impose enormous burdens on patients and healthcare systems, making it imperative to define actionable etiologic factors and develop effective, low-cost therapeutic interventions. Nonenzymatic protein glycation and the formation of advanced glycation end products (AGEs) are strongly implicated in pathogenesis. The driver of AGE formation is 3-deoxyglucosone (3DG), a highly reactive dicarbonyl species that also causes acute cellular toxicities by damaging enzymes and DNA and inflaming the vasculature. Accordingly, the ability to accurately measure 3DG levels and understand its etiology are paramount to elucidating pathogenesis, limiting its pathogenic effects, and improving clinical management of diabetic complications. Endogenous 3DG was deemed to arise nonenzymatically from the slow disintegration of glycated proteins in the body or absorbed from ingested heat-processed foods. We developed new methods to study the enzymatic activity of fructosamine-3-kinase (FN3K), an enzyme thought to repair glycated proteins and prevent AGE, but an end-product of FN3K activity is 3DG. We discovered that 3DG levels in kidney are higher than previously anticipated. Our core hypothesis is that FN3K-mediated 3DG formation in cells is a key pathogenic driver in diabetic complications. Specific Aim 1: we will measure 3DG arising in tissues in relationship to pathogenesis in the KK.Cg-Ay/J murine model of type-2 diabetes. Specific Aim 2: the impact of a high glycation diet on 3DG levels will be measured in tissues sensitive to diabetic complications, including in the kidney, heart, and liver of the diabetic mice. Specific Aim 3: We will define the pharmacodynamic properties and modes of action for meglumine, an agent, already proven safe, that we discovered has unrecognized medicinal effects, having provided nephroprotection and prevented triglyceride accumulation in diabetic mice. Specific Aim 4: a series of FN3K antagonists that we discovered will be characterized to identify a preclinical drug development candidate. This proposal offers several major innovative elements of high significance and impact in diabetes translational research. Aim 1 will provide new data developed with methodology we refined to measure FN3K activity and 3DG formation more accurately, addressing key gaps in knowledge. Aim 2 will explore the linkage between intracellular 3DG elevation and the consumption of ‘Western’ diets rich in fructosamines—the substrate for FN3K. Drug safety is paramount for any new diabetes drug. The data from Aim 3 will accelerate the development of meglumine as an innovative treatment modality—a compound proven extremely safe for chronic administration—to ameliorate diabetic nephropathy, fatty liver, and potentially other diabetic complications. Aim 4 offers opportunity to deliver first-in-class enzyme inhibitors as potential drug lead candidates. In summary, this research program will illuminate an unexplored intracellular pathway in diabetes pathogenesis and deliver unprecedented tools for broader research into the role of 3DG in diabetic nephropathy and other diabetes complications.