Biomarkers in Diabetic Neuropathy

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DESCRIPTION (provided by applicant): Challenge Area: (03) Biomarker Discovery and Validation Challenge Topic: Discovery of biomarkers for disease risk, progression or response to therapy in diseases of interest to NIDDK. 03-DK-101 Title: Biomarkers in Diabetic Neuropathy Twenty million Americans have diabetes and the incidence is increasing by 5% per year. The most common complication of diabetes is diabetic neuropathy (DN). Current methods used to confirm DN and measure its progression include nerve conduction studies, quantitative sensory measures and decreased sural nerve myelinated fiber density (MFD). The identification of DN biomarkers would greatly enhance our understanding of early events in this complication and could be used to predict its development and rate of progression. No biomarkers have been established for DN leaving this complication to develop unchecked. We hypothesize that a complex network of metabolic changes in type 2 diabetes may predict the onset and progression of DN. Bioinformatics protocols applied to metabolic, neuroanatomical and neurophysiology data from a clinical trial of DN indicate that dyslipidemia, specifically elevated triglyceride levels, is associated with rapid progression of DN. The current proposal employs microarray analyses to examine differentially expressed genes involved in lipid metabolism in both human sural nerve samples and in peripheral nerves from a relevant animal model, the BKS-db/db mouse. Our membership in the National Center for Integrated Biomedical Informatics (NCIBI) at the University of Michigan provides us with a high-powered computing environment and the expertise for computationally intensive analyses. We have two Specific Aims: Hypothesis 1: The application of bioinformatics will identify targets (genes, proteins and metabolic markers) involved in the initiation and progression of DN. Specific Aim 1: Identify genes of interest regulated across species in DN. a. Use microarrays to identify biomarker pathways and targets in human sural nerve samples from patients with type 2 diabetes and DN. b. Perform cross-species validation between sciatic nerve microarrays from mice with type 2 diabetes and the human sural nerve microarrays in Aim 1a. Hypothesis 2: Verified transcriptomics will predict changes in encoded proteins (in peripheral nerve) and metabolites (in plasma and urine) critical to the initiation and progression of DN in human patients and animal models. These functional responses will lead to the identification of biomarkers useful in the diagnosis and therapeutic management of human DN. Specific Aim 2: Validate the biological relevance of identified gene targets in a type 2 murine model with DN a. Localize and quantify target gene products (proteins) in sciatic nerve using immunolocalization and western blotting b. Identify and examine metabolite levels in biological fluids (plasma and urine) PUBLIC HEALTH RELEVANCE: The most common complication of diabetes is peripheral neuropathy (DN). The identification of DN biomarkers would greatly enhance our understanding of early events in this complication and could be used to predict its development and rate of progression. We hypothesize that diabetes directly affects peripheral nerve gene expression and that these data will aid in the identification of useful DN biomarkers. Microarray analyses will compare changes in gene expression between human sural nerve biopsies and BKS-db/db mice, a well-researched model of type 2 diabetes. These data will be used to identify dysregulated intracellular pathways that would result in detectable biomarkers of DN in serum or urine and changes in expression following treatment in animal models.