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迟钝原因。乙醇通过两个主要机制损害神经元的存活和功能：1)它抑制存活、代谢、突触形成和乙酰胆碱生成所需的胰岛素信号；2)它作为一种神经毒物，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通过胰岛素受体（IR）介导的，并由结合受损和随之而来的生存信号传递减少引起。此外，逆转IR酪氨酸激酶和pi3k活性的磷酸酶的激活增加加剧了乙醇对神经元存活的抑制作用。相反，乙醇的神经毒性作用促进DNA损伤，并且可能是由于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的遗传或化学缺失导致fasd样的形态、生化和分子缺陷；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）治疗而减轻；3)青少年中fasd相关的中枢神经系统异常可能持续或发展，导致功能缺陷。在这一竞争性的更新应用中，在三个特定目标中提出的实验将描述慢性妊娠期乙醇暴露的长期后果，重点是青春期早期和晚期，并确定PPAR激动剂治疗预防或减少慢性子宫内乙醇暴露引起的长期中枢神经系统异常的程度和机制。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将利用由对照和乙醇暴露的大鼠幼崽产生的初级小脑神经元体外培养模型来表征PPAR激动剂对神经元存活和功能的影响。Aim #3将利用Aim #2中获得的信息，优化PPAR激动剂治疗性抢救慢性子宫内乙醇暴露与青春期早期和晚期CNS神经元存活和功能相关的长期不良反应的体内方法。分级子宫内乙醇暴露将用于确定PPAR激动剂的治疗效果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激动剂的反应性方面的作用。该实验设计具有转译性，因为它采用了一种可以实际应用于人类的治疗策略。我们已经将胎儿酒精谱系障碍相关的大脑异常与胰岛素抵抗和神经元氧化应激联系起来。初步数据表明，产前酒精暴露可能导致青少年大脑持续或进行性神经元损伤，因此，我们现在建议确定产前酒精暴露对大脑功能造成长期不利影响的程度。我们的第二个目标是

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. PUBLIC HEALTH RELEVANCE We have linked fetal alcohol spectrum disorder-associated brain abnormalities to insulin resistance and oxidative stress in neurons. Preliminary data suggest that prenatal alcohol exposure may cause persistent or progressive neuronal injury in adolescent brains, and therefore, we now propose to characterize the degree to which pre-natal alcohol exposure causes long-lasting adverse effects on brain function. Our second goal is to evaluate treatments that target the underlying causes of ethanol-mediated brain abnormalities and assess their effectiveness in preventing structural and functional impairments in adolescent brains following chronic prenatal alcohol exposure.