Diabetic peripheral neuropathy may be indicated by sensory disorders including spontaneous pain, hyperalgesia or allodynia, by slowed sensory and motor nerve conduction velocities or by structural pathology. Diabetic rats also develop sensory, electrophysiologic and subtle structural disorders. This supports their use as a model of the early stages of hyperglycemia-induced peripheral nerve disorders in the absence of overt structural pathology and allows study of both the etiologic mechanisms linking hyperglycemia to nerve dysfunction and also development of potential therapeutic agents. Recent evidence suggest that peripheral nerve requires ongoing neurotrophic support and that hyperalglycemia disrupts this. Providing exogenous neurotrophic support that either replaces or supercedes diminished endogenous support mechanisms has been proposed as a therapeutic strategy for treating diabetic neuropathy. Prosaposin is the precursor for intracellular saposins but is also secreted in an unprocessed form which has neurotrophic properties. These neurotrophic properties are shared by prosaposin mimetics, small peptides derived from the prosaposin molecule that lack the other properties of saposins. Our preliminary data suggest that prosaposin mimetics called prosaptides prevent or attenuate electrophysiologic, biochemical and structural disorders in the peripheral nerve of diabetic rats, encompassing indices of both sensory and motor function in both large and small fibers. This broad spectrum of efficacy is beneficial for a potential therapeutic because diabetes affects all divisions of the peripheral nervous system. Prosaptides also rapidly ameliorate hyperalgesia in diabetic rats, suggesting a second action distinct from the neurotrophic properties and which may have additional therapeutic benefits to those diabetic patients who develop painful diabetic neuropathy. We propose to establish the therapeutic profiles of prosaptides for treating electrophysiologic and structural disorders of peripheral nerve in diabetic rats that are associated with developing neuropathy and also for treating disorders that reflect pain states. We will also correlate the therapeutic actions of prosaptides with effects on neurochemical abnormalities present in diabetic rats, including investigation of the effect of diabetes on endogenous prosaposin production. The goal is to establish prosaptides as novel therapeutic agents for treating diabetic neuropathy and to provide mechanistic explanations for why hyperglycemia causes nerve disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
3R01NS038855-02S1
Application #
6447349
Study Section
Special Emphasis Panel (ZNS1 (02))
Program Officer
Nichols, Paul L
Project Start
1999-09-30
Project End
2003-08-31
Budget Start
2000-09-01
Budget End
2001-08-31
Support Year
2
Fiscal Year
2001
Total Cost
$1,516
Indirect Cost
Name
University of California San Diego
Department
Pathology
Type
Schools of Medicine
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Jolivalt, Corinne G; Vu, Yvonne; Mizisin, Leah M et al. (2008) Impaired prosaposin secretion during nerve regeneration in diabetic rats and protection of nerve regeneration by a prosaposin-derived peptide. J Neuropathol Exp Neurol 67:702-10
Jolivalt, Corinne G; Ramos, Khara M; Herbetsson, Katrin et al. (2006) Therapeutic efficacy of prosaposin-derived peptide on different models of allodynia. Pain 121:14-21
Calcutt, N A; Freshwater, J D; Mizisin, A P (2004) Prevention of sensory disorders in diabetic Sprague-Dawley rats by aldose reductase inhibition or treatment with ciliary neurotrophic factor. Diabetologia 47:718-24
Mizisin, Andrew P; Vu, Yvonne; Shuff, Michelle et al. (2004) Ciliary neurotrophic factor improves nerve conduction and ameliorates regeneration deficits in diabetic rats. Diabetes 53:1807-12
Sayers, Nicola M; Beswick, Lisa J; Middlemas, Alicia et al. (2003) Neurotrophin-3 prevents the proximal accumulation of neurofilament proteins in sensory neurons of streptozocin-induced diabetic rats. Diabetes 52:2372-80
Calcutt, Nigel A; Allendoerfer, Karen L; Mizisin, Andrew P et al. (2003) Therapeutic efficacy of sonic hedgehog protein in experimental diabetic neuropathy. J Clin Invest 111:507-14
Garcia, Michael L; Lobsiger, Christian S; Shah, Sameer B et al. (2003) NF-M is an essential target for the myelin-directed ""outside-in"" signaling cascade that mediates radial axonal growth. J Cell Biol 163:1011-20
Luo, Z D; Calcutt, N A; Higuera, E S et al. (2002) Injury type-specific calcium channel alpha 2 delta-1 subunit up-regulation in rat neuropathic pain models correlates with antiallodynic effects of gabapentin. J Pharmacol Exp Ther 303:1199-205
Freshwater, Jason D; Svensson, Camilla I; Malmberg, Annika B et al. (2002) Elevated spinal cyclooxygenase and prostaglandin release during hyperalgesia in diabetic rats. Diabetes 51:2249-55
Mizisin, A P; Steinhardt, R C; O'Brien, J S et al. (2001) TX14(A), a prosaposin-derived peptide, reverses established nerve disorders in streptozotocin-diabetic rats and prevents them in galactose-fed rats. J Neuropathol Exp Neurol 60:953-60

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