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智力低下原因。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) 它具有神经毒剂的作用，导致氧化应激、DNA 损伤和线粒体功能障碍。乙醇对胰岛素信号的抑制是在胰岛素受体 (IR) 介导的，是由结合受损和随之而来的生存信号传递减少引起的。此外，逆转 IR 酪氨酸激酶和 PI3 K 活性的磷酸酶激活增加，会加剧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会促进 DNA 损伤，并且可能是由于乙醛（乙醇的主要代谢物）的产生和积累形成 DNA 加合物而引起的。因此，子宫内慢性乙醇暴露会产生中枢神经系统胰岛素抵抗和氧化应激的双重状态。初步研究表明：1）CNS IR的遗传或化学耗竭导致FASD样形态、生化和分子缺陷； 2) 中枢神经系统胰岛素抵抗相关的损伤可以通过胰岛素增敏剂（即 PPAR 激动剂）治疗来减少； 3) FASD 相关的中枢神经系统异常可能持续或进展，导致青少年功能缺陷。在这项竞争性的更新申请中，在3个具体目标中提出的实验将描述妊娠期长期接触乙醇的长期后果，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因子宫内长期接触乙醇引起的长期中枢神经系统异常的程度和机制。目标#1将描述青春期早期和晚期大鼠在子宫内长期接触乙醇后大脑胰岛素抵抗的长期后果。目标 #2 将利用对照大鼠和乙醇暴露大鼠幼仔产生的原代小脑神经元培养体外模型来表征 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 中获得的信息来优化 PPAR 激动剂的体内方法，以缓解宫内慢性乙醇暴露对青春期早期和晚期中枢神经系统神经元存活和功能的长期不利影响。子宫内乙醇暴露分级将用于确定 PPAR 激动剂的治疗效果是否随乙醇剂量变化。此外，实验还将探讨性别与乙醇引起的中枢神经系统异常的性质和严重程度以及对 PPAR 激动剂的反应的关系。该实验设计是可转化的，因为它采用了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.