Cholesterol and Sphingolipid Metabolism in Alzheimer's Disease

描述(由申请人提供)：我们的长期研究兴趣是提供细胞脂代谢和神经病理学之间的机械联系。在一份新的手稿(包括在附录中)和初步研究部分，我们描述了以下线索：1.我们发现，在三重转基因阿尔茨海默病小鼠(AD小鼠)中，酰基辅酶A：胆固醇酰基转移酶1(ACAT1)的遗传失活增加了24(S)-羟基胆固醇的含量，减少了脑中胆固醇的合成，并改善了淀粉样蛋白的病理。2.与非转基因小鼠相比，AD小鼠的胆固醇含量、调控胆固醇生物合成相关基因的转录因子SREBP2的mRNA、胆固醇生物合成限速酶HMGR的mRNA以及两种相互作用的转录因子血清反应因子(SRF)和肌钙蛋白(MYOCD)的mRNAs均显著升高。基于这些线索，在当前的方案中，我们设计了实验来验证两个假设。首先是测试大脑中编码胆固醇酯化酶ACAT1的基因失活是否对治疗阿尔茨海默病有治疗价值。第二个是测试特定的鞘磷脂(S)是否通过刺激大脑中胆固醇的生物合成来介导淀粉样β多肽1-42(Abeta1-42)的作用。我们征集了三个特定的目的：特定的目的1：检测失活的24酶(S)-羟基酶CYP46A1，对ACT1-/-(A1-)介导的AD小鼠神经元HAPP、HMGR和ABCA1的调节作用。特定目的2：检测AD小鼠不同时期脑内Acat1的失活效果。具体目的3：研究Abeta1-42对原代神经元和星形胶质细胞胆固醇和鞘磷脂代谢的影响。 公共卫生相关性：阿尔茨海默病(AD)导致老年人记忆丧失和认知障碍，是发达国家最常见的神经退行性疾病。细胞脂代谢异常已被认为与AD有关。这一提议的结果可能会导致基于脂代谢的新疗法来减缓这种疾病的进展。

DESCRIPTION (provided by applicant): Our long-term research interest is to provide mechanistic links between cellular lipid metabolism and neuropathology. In a new manuscript (included in the Appendix) and in the PRELIMINARY STUDIES section, we describe the following leads: 1. We show that genetic inactivation of acyl-CoA: cholesterol acyltransferase 1 (ACAT1) increases 24(S)-hydroxycholesterol content, reduces cholesterol synthesis in the brain, and ameliorates amyloid pathology in the triple transgenic Alzheimer's mice (AD mice). 2. We show that the cholesterol content, the mRNA of SREBP2 (the transcription factor that controls genes involved in cholesterol biosynthesis), the mRNA of HMGR (the rate-limiting enzyme in cholesterol biosynthesis), and the mRNAs of two interacting transcription factors, serum response factor (SRF) and myocardin (MYOCD) are elevated in the AD mice compared to nontransgenic mice. Based on these leads, in the current proposal, we design experiments to test two hypotheses. The first is to test whether inactivating the gene that encodes the cholesterol esterification enzyme ACAT1 in the brain has therapeutic value for treating AD. The second is to test if specific sphingolipid(s) mediate the action of amyloid beta peptide 1-42 (Abeta1-42) by stimulating cholesterol biosynthesis in the brain. We enlist three specific aims: Specific Aim 1: To test the effect of inactivating the enzyme 24(S)-hydroxylase CYP46A1, on Acat1-/- (A1-) mediated modulations on hAPP, HMGR and ABCA1 in AD mice neurons. Specific Aim 2: To test the effect of inactivating Acat1 in AD mouse brains at different time during life. Specific Aim 3: To study the effects of Abeta1-42 on cholesterol and sphingolipid metabolism in primary neurons and astrocytes. PUBLIC HEALTH RELEVANCE: Alzheimer's disease (AD) causes memory loss and cognitive deficits in the elderly, and is the most prevalent neurodegenerative disease in developed countries. Abnormalities in cellular lipid metabolism have been implicated in AD. The outcomes of this proposal may lead to novel, lipid metabolism-based therapies to slow down the progression of this disease.