EFFECTS OF ETHANOL ON INSULIN SIGNALING IN THE BRAIN

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Fetal alcohol spectrum disorder (FASD) is the most common preventable cause of mental retardation in the USA. Ethanol impairs neuronal survival and function by two major mechanisms: 1) it inhibits insulin signaling required for viability, metabolism, synapse formation, and acetylcholine production; and 2) it functions as a neurotoxicant, causing oxidative stress, DNA damage and mitochondrial dysfunction. Ethanol inhibition of insulin signaling is mediated at the insulin receptor (IR), and caused by impaired binding and attendant reductions in the transmission of survival signals. In addition, increased activation of phosphatases that reverse IR tyrosine kinase and PI3 K activities, exacerbates ethanol¿s inhibitory effects on neuronal survival. In contrast, the neurotoxicant effects of ethanol promote DNA damage, and are likely caused by DNA adduct formation through production and accumulation of acetaldehyde, a major metabolite of ethanol. Therefore, chronic in utero ethanol exposure produces a dual state of CNS insulin resistance and oxidative stress. Preliminary studies showed that: 1) genetic or chemical depletion of CNS IR causes FASD-like morphologic, biochemical, and molecular defects; 2) CNS insulin resistance-related impairments can be reduced by treatment with insulin-sensitizers i.e. PPAR agonists; and 3) FASD-associated CNS abnormalities may persist or progress leading to functional deficits in adolescents. In this competing renewal application, experiments proposed in 3 specific aims will characterize the long-term consequences of chronic gestational exposure to ethanol, focusing on early and late adolescence, and determine the degrees and mechanisms in which PPAR agonist treatments prevent or reduce long-term CNS abnormalities caused by chronic in utero exposure to ethanol. Aim #1 will characterize the long-term consequences of brain insulin resistance in early and late adolescent rats following chronic in utero exposure to ethanol. Aim #2 will utilize an in vitro model of primary cerebellar neuron cultures generated from control and ethanol-exposed rat pups to characterize the effects of PPAR agonists on neuronal survival and function. Aim #3 will take advantage of information gained in Aim #2 to optimize an in vivo approach for PPAR agonist therapeutic rescue of the long-term adverse effects of chronic in utero ethanol exposure in relation to CNS neuronal survival and function in early and late adolescence. Graded in utero ethanol exposures will be used to determine if the therapeutic effectiveness of PPAR agonists varies with ethanol dose. In addition, experiments will address the role of gender in relation to the nature and severity of ethanol-induced CNS abnormalities and responsiveness to PPAR agonists. The experimental design is translational because it utilizes a therapeutic strategy that realistically could be applied to humans.