Diabetic nephropathy is the leading cause of end-stage renal disease in the United States. Non-invasive biomarkers to evaluate the initiation and progression of disease are currently limited. The goal of this project is to develop hyperpolarized (HP) 13C magnetic resonance (MR) spectroscopic imaging methods that interrogate key metabolic changes underlie diabetic nephropathy, namely altered oxidative stress and glycolytic metabolism, which may improve the early diagnosis and monitoring of targeted treatment of diabetic renal injury. HP 13C MR is a new molecular imaging technique that provides an unprecedented gain in sensitivity (>10,000-fold increase) for detecting 13C-labeled bio-molecules, and allows rapid detection of alterations in metabolic and physiologic processes noninvasively. Recently, we have developed two novel HP probes: (1) the redox sensor HP 13C-dehydroascorbate (DHA), an oxidized version of Vitamin C, and (2) HP 13C-fructose, a hexose probe that evaluates the early steps of glycolysis. We will apply these new probes to a 3D perfused cell culture or "bioreactor" platform, and a well-characterized murine model of diabetes in order to carry out the Specific Aims of this proposal.
In Aim 1, we will determine the key molecular mechanism underlying in vivo HP 13C-DHA reduction to Vitamin C, and examine renal redox states using HP 13C-DHA during the progression of renal injury from diabetes.
In Aim 2, we will investigate the renal glycolytic metabolism in diabetes using HP 13C-fructose, and relate the observed metabolic flux to the enzymatic activity of glyceraldehydes-3 phosphate dehydrogenase (GAPDH). Inactivation of GAPDH with accumulation of glycolytic intermediates is critically linked to the many damaging pathways in diabetic nephropathy.
In Aim 3, we will monitor treatment response to an angiotensin converting enzyme inhibitor (Ramipril), a nuclear factor erythroid 2-related factor 2 (Nrf2) pathway activator (Sulforaphane), and a transketolase activator (Thiamine) using the HP probes, with particular attention to the agents'targeted effects on oxidative stress and glycolytic metabolism. The HP probes in this study are comprised of endogenous bio-molecules that are anticipated to have minimal toxicities in humans, and therefore have high potential for clinical translation. Successful completion of the aims will lead to noninvasive biomarkers that may enhance monitoring the onset and progression of diabetic nephropathy, and response to therapy.

Public Health Relevance

Diabetic nephropathy is the leading cause of end-stage renal disease in the United States. Current clinical markers of diabetic nephropathy have significant limitations. In this proposal, we aim to develop a new magnetic resonance imaging (MRI) technology to noninvasively detect the alterations in oxidative stress and glucose metabolism that are critically linked to diabetic renal injury. Such approach has the potential to enhance the diagnosis and therapy monitoring of this devastating disease.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Medical Imaging Study Section (MEDI)
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Flessner, Michael Francis
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University of California San Francisco
Schools of Medicine
San Francisco
United States
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