Gating of Leptin Transport into the Cerebrospinal Fluid at the Choroid Plexus

项目摘要 该建议的中心目标是阐明瘦素如何转运到脑脊液（CSF） 而大脑在脉络丛（ChP）是门控的，这种门控如何影响瘦素对奖励的作用- 相关的多巴胺能神经元，以及饱和ChP转运如何可能有助于瘦素抵抗， 肥胖能量消耗和摄食的调节对动物的生存和维持能力至关重要 生理稳态瘦素是脂肪细胞分泌的一种内分泌因子，参与调节 食物摄入量和体重。瘦素作用于大脑中的受体，发挥整体作用， 喂养，增加能量消耗，并促进瘦肉型。瘦素必须进入大脑， 受体。在肥胖症中，循环瘦素水平升高，但CSF与血清瘦素的比率降低， 瘦素在中枢给药而非外周给药时抑制食物摄取。这表明， 瘦素转运到CSF中是肥胖症发展的潜在因素。前期工作已 暗示通过ChP上皮的血-脑脊液屏障的转胞吞作用是关键途径 瘦素进入大脑的过程。事实上，内吞受体的局部缺失与低密度脂蛋白受体有关 ChP上皮中的蛋白1（LRP 1）削弱外周瘦素的摄食抑制，同时保持完整的 减少食物摄入量，以响应中枢传递的瘦素。然而，这其中的真实的时间动态 在中国药典提出的转胞吞转运知之甚少。我建议将新的活体成像技术 研究瘦素通过ChP上皮细胞的转胞吞作用以及其进入和作用的技术 在清醒状态下真实的时间， 行为老鼠在目标1中，我将完善最近开发的工具，以真实的可视化中国药典中的瘦素转胞吞作用 时间（见初步数据），并定量评估LRP 1缺失或过表达对瘦素的影响 从血液进入脑脊液。一旦瘦素到达大脑，它就会与许多神经系统发生联系。 电路.腹侧被盖区的多巴胺能神经元编码食物的动机显著性，并且通常被抑制 瘦素的作用，导致食物消费动机降低。然而，在肥胖症患者中， 多巴胺能活动促进强迫性进食。在目标2中，我将扩展成像工具包来跟踪访问 与记录单个腹侧被盖区多巴胺能神经元的活性平行， 并严格评估ChP的瘦素转胞吞作用和VTA多巴胺能反应之间的相互作用 在瘦老鼠和胖老鼠身上找到可口的食物。此外，我将确认LRP 1在ChP上皮中的过表达是否 可以预防肥胖的发展。这些研究将提供新的见解， 瘦素进入大脑的途径和机制，评估瘦素的动力学和下游效应 以前所未有的精确度发出信号，并为肥胖和其他疾病提出新的治疗方法。 代谢紊乱

Project Summary The central goal of this proposal is to elucidate how leptin transport into the cerebrospinal fluid (CSF) and brain is gated at the choroid plexus (ChP), how such gating influences the action of leptin on reward- related dopaminergic neurons, and how saturated ChP transport may contribute to leptin resistance in obesity. Regulation of energy expenditure and feeding are crucial to an animal’s ability to survive and maintain physiological homeostasis. Leptin is an endocrine factor secreted by adipocytes that participates in the regulation of food intake and body weight. Acting on receptors in the brain, leptin exerts an overall effect to decrease feeding, increase energy expenditure, and promote a lean phenotype. Leptin must enter the brain to reach its receptors. In obesity, circulating leptin levels are elevated, but the ratio of CSF to serum leptin is reduced, and leptin suppresses food intake when administered centrally but not peripherally. This suggests insufficient transport of leptin into the CSF as a potential contributor to the development of obesity. Preliminary work has implicated transcytosis through the blood-cerebrospinal fluid barrier of the ChP epithelium as a critical pathway of leptin entry into the brain. In fact, local deletion of endocytic receptor low density lipoprotein receptor-related protein 1 (LRP1) in the ChP epithelium impairs feeding suppression by peripheral leptin while keeping intact the decrease in food intake in response to centrally delivered leptin. However, the real time dynamics of this proposed transcytotic transport at the ChP are poorly understood. I propose to apply novel in vivo imaging techniques to study leptin transcytosis through the ChP epithelium as well as its access to and effects on leptin-sensitive dopaminergic circuitry in the ventral tegmental area (VTA) in real time in awake, behaving mice. In Aim 1, I will refine recently developed tools to visualize leptin transcytosis at the ChP in real time (see preliminary data) and quantitatively assess the effects of LRP1 deletion or overexpression on leptin transport from the blood into the CSF. Once it reaches the brain, leptin is known to engage a number of neural circuits. Dopaminergic neurons in the VTA encode the motivational salience of food and are normally inhibited by leptin, leading to reduced motivation for food consumption. In obesity, however, dysregulated VTA dopaminergic activity promotes compulsive eating. In Aim 2, I will extend the imaging toolkit to track the access of leptin to the VTA parenchyma in parallel with recording the activity of individual VTA dopaminergic neurons, and rigorously assess the interplay between leptin transcytosis at the ChP and the VTA dopaminergic responses to palatable food in lean and obese mice. Additionally, I will confirm if LRP1 overexpression in the ChP epithelium could be protective against the development of obesity. These studies will provide novel insights into the pathways and mechanisms of leptin entry into the brain, assess the dynamics and downstream effects of leptin signaling with unprecedented precision, and propose new therapeutic approaches for obesity and other metabolic disorders.