Project description:A better understanding of the molecular mechanisms underlying the development and progression of diabetic neuropathy (DN) is essential for the design of mechanism-based therapies. We examined changes in global gene expression to define pathways regulated by diabetes in peripheral nerve. Microarray data for 24 week-old BKS db/db and db/+ mouse sciatic nerve were analyzed to define significantly differentially expressed genes (DEGs); DEGs were further used for functional enrichment analysis and network analysis to identify biological processes and pathways differentially regulated in the db/db nerve. Expression profile clustering was performed to identify co-expressed DEGs. A set of co-expressed lipid metabolism genes was used for promoter sequence analysis.We identified 4,017 DEGs; 2,122 genes were up-regulated and 1,895 genes were down-regulated in the db/db relative to the db+ samples. Over-represented biological processes identified by the functional enrichment analysis include cell cycle, lipid metabolic process, lipid transport, carbohydrate metabolic process, response to stress, apoptosis, axonogenesis and cell adhesion. Pathways regulated in the db/db nerve include lipid metabolism, carbohydrate metabolism, energy metabolism, PPAR signaling, apoptosis, and axon guidance. The majority of DEGs in the glycolysis, TCA cycle, oxidative phosphorylation, fatty acid metabolism, glycerolipid metabolism, mitochondrial fatty acid elongation, lipid transport, adipocytokine signaling, PPAR signaling, and apoptosis pathways are up-regulated, whereas most of the axonogenesis-related genes are down-regulated in db/db nerve. A network of DEGs based on their co-citation in literature identified regulatory relationship between Tnf-α and key genes from the regulated pathways. Promoter sequence analysis identified over-represented transcription factor binding site (TFBS) motifs in the promoter regions of twenty two co-expressed lipid metabolism-related genes suggesting coordinated regulation of these genes by multiple transcription factors (TF). Furthermore, TF binding to these TFBS and differentially regulated in our data are annotated with nervous system development and immune response suggesting possible co-regulation of lipid metabolism, nervous system development and stress response genes. Gene expression changes in our data are consistent with pathological characteristics observed in DN including axon degeneration and demyelination, and support existing hypotheses regarding hyperglycemia mediated nerve damage in DN. Our findings support the role of hyperglycemia-induced oxidative stress and ischemia in nerve injury. Our results also support the hypothesis of oxidized lipid-mediated nerve injury and increased mitochondrial oxidative stress in dyslipidemia. Moreover, our analyses revealed a possible co-regulation mechanism connecting hyperlipidemia, stress response and axonal degeneration.

Project description:A better understanding of the molecular mechanisms underlying the development and progression of diabetic neuropathy (DN) is essential for the design of mechanism-based therapies. We examined changes in global gene expression to define pathways regulated by diabetes in peripheral nerve. Microarray data for 24 week-old BKS db/db and db/+ mouse sciatic nerve were analyzed to define significantly differentially expressed genes (DEGs); DEGs were further used for functional enrichment analysis and network analysis to identify biological processes and pathways differentially regulated in the db/db nerve. Expression profile clustering was performed to identify co-expressed DEGs. A set of co-expressed lipid metabolism genes was used for promoter sequence analysis.We identified 4,017 DEGs; 2,122 genes were up-regulated and 1,895 genes were down-regulated in the db/db relative to the db+ samples. Over-represented biological processes identified by the functional enrichment analysis include cell cycle, lipid metabolic process, lipid transport, carbohydrate metabolic process, response to stress, apoptosis, axonogenesis and cell adhesion. Pathways regulated in the db/db nerve include lipid metabolism, carbohydrate metabolism, energy metabolism, PPAR signaling, apoptosis, and axon guidance. The majority of DEGs in the glycolysis, TCA cycle, oxidative phosphorylation, fatty acid metabolism, glycerolipid metabolism, mitochondrial fatty acid elongation, lipid transport, adipocytokine signaling, PPAR signaling, and apoptosis pathways are up-regulated, whereas most of the axonogenesis-related genes are down-regulated in db/db nerve. A network of DEGs based on their co-citation in literature identified regulatory relationship between Tnf-α and key genes from the regulated pathways. Promoter sequence analysis identified over-represented transcription factor binding site (TFBS) motifs in the promoter regions of twenty two co-expressed lipid metabolism-related genes suggesting coordinated regulation of these genes by multiple transcription factors (TF). Furthermore, TF binding to these TFBS and differentially regulated in our data are annotated with nervous system development and immune response suggesting possible co-regulation of lipid metabolism, nervous system development and stress response genes. Gene expression changes in our data are consistent with pathological characteristics observed in DN including axon degeneration and demyelination, and support existing hypotheses regarding hyperglycemia mediated nerve damage in DN. Our findings support the role of hyperglycemia-induced oxidative stress and ischemia in nerve injury. Our results also support the hypothesis of oxidized lipid-mediated nerve injury and increased mitochondrial oxidative stress in dyslipidemia. Moreover, our analyses revealed a possible co-regulation mechanism connecting hyperlipidemia, stress response and axonal degeneration. Microarray data for 24 week-old BKS db/db and db/+ mouse sciatic nerve were analyzed to define significantly differentially expressed genes

Project description:BACKGROUND:Diabetic polyneuropathy (DPN) is the most common and early developing complication of diabetes mellitus, and the key contributor for foot ulcers development, with no specific therapies available. Different studies have shown that mesenchymal stem cell (MSC) administration is able to ameliorate DPN; however, limited cell survival and safety reasons hinder its transfer from bench to bedside. MSCs secrete a broad range of antioxidant, neuroprotective, angiogenic, and immunomodulatory factors (known as conditioned medium), which are all decreased in the peripheral nerves of diabetic patients. Furthermore, the abundance of these factors can be boosted in vitro by incubating MSCs with a preconditioning stimulus, enhancing their therapeutic efficacy. We hypothesize that systemic administration of conditioned medium derived from preconditioned MSCs could reverse DPN and prevent foot ulcer formation in a mouse model of type II diabetes mellitus. METHODS:Diabetic BKS db/db mice were treated with systemic administration of conditioned medium derived from preconditioned human MSCs; conditioned medium derived from non-preconditioned MSCs or vehicle after behavioral signs of DPN was already present. Conditioned medium or vehicle administration was repeated every 2 weeks for a total of four administrations, and several functional and structural parameters characteristic of DPN were evaluated. Finally, a wound was made in the dorsal surface of both feet, and the kinetics of wound closure, re-epithelialization, angiogenesis, and cell proliferation were evaluated. RESULTS:Our molecular, electrophysiological, and histological analysis demonstrated that the administration of conditioned medium derived from non-preconditioned MSCs or from preconditioned MSCs to diabetic BKS db/db mice strongly reverts the established DPN, improving thermal and mechanical sensitivity, restoring intraepidermal nerve fiber density, reducing neuron and Schwann cell apoptosis, improving angiogenesis, and reducing chronic inflammation of peripheral nerves. Furthermore, DPN reversion induced by conditioned medium administration enhances the wound healing process by accelerating wound closure, improving the re-epithelialization of the injured skin and increasing blood vessels in the wound bed in a skin injury model that mimics a foot ulcer. CONCLUSIONS:Studies conducted indicate that MSC-conditioned medium administration could be a novel cell-free therapeutic approach to reverse the initial stages of DPN, avoiding the risk of lower limb amputation triggered by foot ulcer formation and accelerating the wound healing process in case it occurs.

Dataset Information

Identification of Key Biomarkers and Immune Infiltration in Sciatic Nerve of Diabetic Neuropathy BKS-db/db Mice by Bioinformatics Analysis.

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