Characterization of Orexin/Hypocretin Kinetics in Alzheimer's Disease

项目总结 阿尔茨海默病(AD)以淀粉样蛋白(Aβ，Aβ)沉积为不溶性斑块、tau聚集为特征 以及过度磷酸化、神经元变性、突触丢失和最终的认知功能障碍 痴呆症。阿尔茨海默病发病机制关键的蛋白质Aβ和tau的可溶性形式在 有睡眠唤醒活动的脑脊液(CSF)。脑脊液Aβ和tau浓度在 在老鼠和人类的睡眠中，觉醒和减少。根据这些发现，睡眠是 被认为是阿尔茨海默病病理的潜在标志和/或可改变的危险因素 阿尔茨海默氏症。食欲素-A和食欲素-B(也称为下丘脑素-1和下丘脑素-2)是两个尾巴。 促进由一种共同的前体多肽--增食欲素原编码的神经肽。食欲素系统 调节睡眠-觉醒活动、进食行为、能量平衡和奖励系统。食欲素 缺乏会导致嗜睡症，这是一种睡眠障碍，会导致白天过度嗜睡。确凿的证据 支持食欲素系统在阿尔茨海默病病理发展中的作用。击倒了 淀粉样前体蛋白(APP)转基因小鼠中的增食欲素基因导致淀粉样沉积 大脑中淀粉样蛋白病理明显减少。对APP转基因小鼠的研究发现，用 阿莫昔康，一种在受体上阻断食欲素的药物，在给药时降低Aβ浓度 食欲素增加了它们的含量。此外，长期服用阿莫昔康可减少淀粉样蛋白的沉积。在……里面 人类脑脊液食欲素-A还与脑脊液Aβ、tau、磷酸化tau和α-突触核蛋白浓度相关。 患有阿尔茨海默病和其他痴呆症的人。患有发作性睡病(即食欲素缺乏)的患者减少了 脑脊液Aβ，tau，磷酸tau浓度和淀粉样蛋白沉积与年龄和性别的比较- 配对的对照组。这些发现强烈表明增食欲素是一种潜在的阿尔茨海默病 生物标记物和阻断食欲素将调制淀粉样蛋白和潜在的tau在大脑中的病理。 食欲素的动力学(例如，产生率和清除率)尚不清楚，脑脊液的食欲素仍然很差。 在蛋白质结构和异构体水平上具有特征。测量脑脊液食欲素-A的金标准是 放射免疫分析。这项建议的总体目标是充分描述脑脊液中食欲素亚型的特征。 从有和没有AD病理的人类中使用质谱学来定量前PRO- 食欲素、食欲素-A、食欲素-B和13C6-亮氨酸标记和未标记食欲素，并评估 食欲素浓度和动力学在量化AD神经退行性变和睡眠觉醒变化中的作用 活动。这项研究将有助于识别疾病的特定亚型，为未来的生物标志物的使用，改进 了解睡眠障碍的病理生理学，如原发性失眠、发作性睡病和其他 中枢性睡眠亢进，以及了解食欲素系统是如何参与 AD病理以及谁可能对睡眠干预有反应。

PROJECT SUMMARY Alzheimer’s disease (AD) is characterized by deposition of amyloid-β (Aβ) as insoluble plaque, tau aggregation and hyperphosphorylation, neuronal degeneration, synaptic loss, and eventual cognitive dysfunction and dementia. Soluble forms of Aβ and tau, proteins critical to Alzheimer’s disease pathogenesis, change in cerebrospinal fluid (CSF) with sleep-wake activity. CSF Aβ and tau concentrations increase during wakefulness and decrease during sleep in both mice and humans. Based on these findings, sleep is hypothesized to be a potential marker for Alzheimer’s disease pathology and/or a modifiable risk factor for Alzheimer’s disease. Orexin-A and orexin-B (also known as hypocretin-1 and hypocretin-2) are two wake- promoting neuropeptides encoded by a common precursor polypeptide, prepro-orexin. The orexin system regulates sleep-wake activity, feeding behavior, energy homeostasis, and the reward system. Orexin deficiency causes narcolepsy, a sleep disorder resulting in excessive daytime sleepiness. Substantial evidence supports a role for the orexin system in the development of Alzheimer’s disease pathology. Knocking out the orexin gene in amyloid precursor protein (APP) transgenic mice that develop amyloid deposition led to a marked decrease in amyloid pathology in the brain. Studies in APP transgenic mice found that treatment with almorexant, a drug that blocks orexins at their receptors, decreased Aβ concentrations while administration of orexin increased them. Further, prolonged treatment with almorexant decreased amyloid deposition. In humans, CSF orexin-A also correlates with CSF Aβ, tau, phospho-tau, and alpha-synuclein concentrations in individuals with AD and other dementias. Patients with narcolepsy (i.e., with orexin deficiency) have reduced CSF Aβ, tau, phospho-tau concentrations, and amyloid deposition on amyloid PET compared to age- and sex- matched controls. These findings strongly suggest that orexin is a potential Alzheimer’s disease biomarker and that blocking orexin will modulate amyloid and potentially tau pathology in the brain. Orexin kinetics (e.g., production and clearance rates) are not understood and CSF orexin remains poorly characterized at the protein structure and isoform level. The gold standard for measuring CSF orexin-A is a radioimmunoassay. The overall goal of this proposal is to fully characterize orexin isoforms in CSF from humans with and without AD pathology using mass spectrometry in order to quantify prepro- orexin, orexin-A, orexin-B, and 13C6-leucine labeled and unlabeled orexins, and assess the utility of orexin concentrations and kinetics in quantifying AD neurodegeneration and changes in sleep-wake activity. This study will aid in identifying disease specific isoforms for future biomarker use, improve understanding of the pathophysiology of sleep disorders such as primary insomnia, narcolepsy, and other hypersomnias of central origin, as well as allow for an understanding of how the orexin system is involved in AD pathology and who may respond to a sleep intervention.