EFFECTS OF ETHANOL ON INSULIN SIGNALING IN THE BRAIN

描述（由申请人提供）：胎儿酒精谱系障碍（FASD）是美国最常见的可预防的精神发育迟滞原因。乙醇通过两种主要机制损害神经元的存活和功能：1）它抑制活力、代谢、突触形成和乙酰胆碱产生所需的胰岛素信号传导; 2）它作为神经毒物发挥作用，引起氧化应激、DNA损伤和线粒体功能障碍。乙醇对胰岛素信号传导的抑制是在胰岛素受体（IR）处介导的，并且是由受损的结合和伴随的存活信号传递的减少引起的。此外，增加的磷酸酶的激活，逆转IR酪氨酸激酶和PI 3 K的活动加剧了乙醇对神经元存活的抑制作用。相比之下，乙醇的神经毒性作用促进DNA损伤，并且可能是由通过乙醇的主要代谢物乙醛的产生和积累形成DNA加合物引起的。因此，子宫内长期乙醇暴露会产生CNS胰岛素抵抗和氧化应激的双重状态。初步研究表明：1）CNS IR的遗传或化学消耗导致FASD样形态学、生物化学和分子缺陷; 2）CNS胰岛素抵抗相关损伤可通过胰岛素增敏剂（即PPAR激动剂）治疗减轻; 3）FASD相关CNS异常可能持续或进展，导致青少年功能缺陷。在这一竞争性更新申请中，3个具体目标中提出的实验将表征长期妊娠期暴露于乙醇的长期后果，重点关注青春期早期和晚期，并确定PPAR激动剂治疗预防或减少子宫内长期暴露于乙醇引起的长期CNS异常的程度和机制。目的#1将描述早期和晚期青春期大鼠在子宫内长期暴露于乙醇后脑胰岛素抵抗的长期后果。目的#2将利用对照和乙醇暴露大鼠幼仔产生的原代小脑神经元培养物的体外模型来表征PPAR激动剂对神经元存活和功能的影响。 目标#3将利用目标#2中获得的信息，优化用于PPAR激动剂治疗性挽救子宫内长期乙醇暴露对青春期早期和晚期CNS神经元存活和功能的长期不良作用的体内方法。将使用子宫内乙醇暴露分级来确定PPAR激动剂的治疗有效性是否随乙醇剂量而变化。此外，实验将解决性别在乙醇诱导的CNS异常的性质和严重程度以及对PPAR激动剂的反应性方面的作用。实验设计是平移的，因为它利用了一种实际上可以应用于人类的治疗策略。

DESCRIPTION (provided by applicant): 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.