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Mechanism of mitochondrial dysfunction in diabetic sensory neuropathy
Author(s) -
Fernyhough Paul,
Huang TzeJen,
Verkhratsky Alex
Publication year - 2003
Publication title -
journal of the peripheral nervous system
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 67
eISSN - 1529-8027
pISSN - 1085-9489
DOI - 10.1111/j.1085-9489.2003.03028.x
Subject(s) - neurotrophic factors , creb , diabetic neuropathy , neurotrophin , peripheral neuropathy , mitochondrion , endocrinology , biology , medicine , diabetes mellitus , sensory neuron , sensory system , neuroscience , microbiology and biotechnology , transcription factor , gene , receptor , genetics
Symmetrical sensory polyneuropathy, the most common form of diabetic neuropathy in humans, is associated with a spectrum of structural changes in peripheral nerve that includes axonal degeneration, paranodal demyelination, and loss of myelinated fibers – the latter probably the result of a dying‐back of distal axons. Mitochondrial dysfunction has recently been proposed as an etiological factor in this degenerative disease of the peripheral nervous system. Lack of neurotrophic support has been proposed as a contributing factor in the etiology of diabetic neuropathy based on studies in animal models of Type I diabetes. We have recently demonstrated that insulin and neurotrophin‐3 (NT‐3) modulate mitochondrial membrane potential in cultured adult sensory neurons. We therefore tested the hypothesis that diabetes‐induced mitochondrial dysfunction is caused by impairments in neurotrophic support. We have used real‐time fluorescence video microscopy to analyze mitochondrial membrane potential in cultured adult sensory neurons isolated from normal and diabetic rats. Diabetes caused a significant loss of mitochondrial membrane potential in all sub‐populations of sensory neurons which can be prevented by in vivo treatment with insulin or NT‐3. The mechanism of insulin and NT‐3‐dependent modulation of mitochondrial membrane potential involves the activation of the phosphoinositide 3 kinase (PI 3 kinase) pathway. Downstream targets of PI 3 kinase, such as Akt and the transcription factor cAMP response element‐binding protein (CREB), are activated by insulin and NT‐3 and regulate sensory neuron gene expression. These alterations in gene expression modulate critical components of metabolite pathways and the electron transport chain associated with the neuronal mitochondrion. Our results show that in adult sensory neurons, treatment with insulin can elevate the input of reducing equivalents into the mitochondrial electron transport chain, which leads to greater mitochondrial membrane polarization and enhanced ATP synthesis.