Impact of aging, sex, vitamin D deficiency and high cholesterol on beta-amyloid peptide accumulation in brains of guinea pigs

衰老、性别、维生素 D 缺乏和高胆固醇对豚鼠大脑中 β-淀粉样肽积累的影响

• 批准号: RGPIN-2020-06112
• 负责人: Pang, KSandy
• 金额: $ 2.4万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741026
• 关键词: Impact; aging; sex; vitamin; deficiency

A major puzzle with aging is the loss of brain function. ß-Amyloid peptides of 40 and 42 amino acid lengths (Aß40 and Aß42) are pathologic cleavage products that are being formed increasingly from the amyloid precursor protein (APP) with aging. Other modulating factors may be sex, vitamin D-deficiency and high cholesterol. The synthesis of Aß from APP occurs via sequential cleavage by the ß- and ?- secretases. The Aß monomers progress to oligomers then aggregate to plaques. Removal of Aß occurs via efflux by P-glycoprotein (P-gp, gene product of the multidrug resistance protein 1, MDR1) and the low-density lipoprotein receptor-related protein 1 (LRP1) at the blood brain barrier; Aß returns to the brain via the receptor for advanced glycation end products (RAGE). Other efflux transporters - the breast cancer resistance protein (BCRP) and multidrug resistance associated proteins (MRP1/4) - also facilitate Aß efflux from brain. Aß is degraded mostly by neprilysin, then the insulin degrading enzyme, and is phagocytosed by the microglia. With normal and pathological aging, ß-secretase protein (BACE-1) is elevated towards the amyloidogenic pathway and neprilysin, P-gp, LRP1 and vitamin D levels are decreased, and RAGE, elevated. High cholesterol levels catalyze Aß42 formation and render lower CYP46A1 expression in brain that benefits brain BACE-1 activity. Although the peripheral and brain cholesterol are independent pools, peripheral but not brain cholesterol levels correlate strongly with brain Aß accumulation. The guinea pig (GP) is chosen for study. Its size is well-suited for serial plasma and CSF collection. There is 100% sequence correspondence of the GP Aß peptide and a high homology of the Mdr1 with that in humans. The GP carries most of its cholesterol in low density lipoprotein and possesses cholesterol ester transfer protein and lipoprotein lipase activities that result in reverse cholesterol transport and delipidation cascades similar to those in men. This proposed program focuses on defining the cellular changes in GP enzymes and transporters that form and remove Aßs with aging and altered vitamin D/cholesterol status, and the scientific investigation falls under the purview of NSERC. We will Aim 1: develop an improved method to assay for Aß40 and Aß42 by solid phase extraction, SPE-ELISA Aim 2: examine the changes in genes involved in Aß homeostasis among GPs of different ages, sexes, and vitamin D/cholesterol status Aim 3: examine the pharmacokinetics of Aß in brain and liver among GPs of different ages, sexes, and vitamin D/cholesterol status Aim 4: develop a physiologically-based pharmacokinetic model for the prediction of Aß changes in aging and altered vitamin D/cholesterol status  The aims collectively test the hypothesis that age, vitamin D deficiency and high cholesterol are risk factors for Aß accumulation in the brain. The scientific data will lead to remedial measures to ameliorate the outcomes to improve brain health.

衰老的一个主要难题是大脑功能的丧失。长度为 40 和 42 个氨基酸的 ß-淀粉样肽（Aß40 和 Aß42）是病理性裂解产物，随着衰老，淀粉样前体蛋白 (APP) 越来越多地形成这些产物。其他调节因素可能包括性别、维生素 D 缺乏和高胆固醇。 APP 中 Aß 的合成是通过 ß- 和 β- 分泌酶的连续裂解进行的。 Aß 单体发展成低聚物，然后聚集成斑块。 Aß 的去除是通过 P-糖蛋白（P-gp，多药耐药蛋白 1，MDR1 的基因产物）和低密度脂蛋白受体相关蛋白 1 (LRP1) 在血脑屏障处的流出而发生的； Aß 通过晚期糖基化终末产物 (RAGE) 受体返回大脑。其他外排转运蛋白 - 乳腺癌耐药蛋白 (BCRP) 和多药耐药相关蛋白 (MRP1/4) - 也促进 Aß 从大脑中外流。 Aß 主要被脑啡肽酶降解，然后是胰岛素降解酶，并被小胶质细胞吞噬。在正常和病理性衰老过程中，β-分泌酶蛋白 (BACE-1) 向淀粉样蛋白生成途径升高，脑啡肽酶、P-gp、LRP1 和维生素 D 水平降低，而 RAGE 升高。高胆固醇水平会催化 Aß42 的形成并降低大脑中 CYP46A1 的表达，从而有利于大脑 BACE-1 的活性。尽管外周胆固醇和脑胆固醇是独立的池，但外周胆固醇水平与脑 Aß 积累密切相关，而脑胆固醇水平则不然。 选择豚鼠（GP）进行研究。其尺寸非常适合连续血浆和脑脊液采集。 GP Aß 肽序列 100% 一致，Mdr1 与人类序列高度同源。 GP以低密度脂蛋白形式携带大部分胆固醇，并具有胆固醇酯转移蛋白和脂蛋白脂肪酶活性，导致胆固醇反向转运和脱脂级联，类似于男性。该计划的重点是确定 GP 酶和转运蛋白的细胞变化，这些变化随着衰老和维生素 D/胆固醇状态的改变而形成和去除 Aßs，并且科学研究属于 NSERC 的职权范围。我们的目标 1：开发一种改进的方法，通过固相萃取、SPE-ELISA 测定 Aß40 和 Aß42 目标 2：检查不同年龄、性别和维生素 D/胆固醇状态的 GP 中 Aß 稳态相关基因的变化 目标 3：检查不同年龄、性别和维生素 D/胆固醇状态的 GP 中 Aß 在脑和肝脏中的药代动力学 目标 4： 开发基于生理学的药代动力学模型，用于预测衰老过程中 Aß 的变化和维生素 D/胆固醇状态的改变。目的是共同检验年龄、维生素 D 缺乏和高胆固醇是 Aß 在大脑中积累的危险因素这一假设。科学数据将导致采取补救措施，以改善结果，从而改善大脑健康。