Requirement of 5-HT2CRs in POMC and SIM1 neurons to Regulate Energy Homeostasis

描述（由申请人提供）：5-羟色胺（5-HT）和相关激动剂被充分表征为作用于下丘脑弓状核和室旁核（ARH和PVH）中其受体（5-HT 2CR）的2C同种型，以抑制食物摄入并发挥抗肥胖作用。与此相反，这种作用所需的ARH和PVH中的5-HT和相关激动剂的特定神经元靶点尚未明确。最近的工作中，5 HT 2CR的表达被选择性地恢复到前阿黑皮素（POMC）神经元内的ARH确定，这个独特的神经元子集是一个强有力的候选目标。该观点基于POMC神经元中5 HT 2CR的选择性再活化拯救5 HT 2CR缺失小鼠的过度吞噬和肥胖表型的证据。本申请中的初步数据还强调了PVH中的头脑简单1（SIM 1）神经元共表达5 HT 2CR，并且可能是5-HT和相关激动剂靶向的一种类型的神经元。目前的建议旨在测试5-HT和相关激动剂是否需要在POMC和SIM 1神经元的ARH和PVH，分别表达5 HT 2CR，以维持正常的体重和发挥抗肥胖作用。这将通过结合基因工程小鼠模型来实现，其中内源性5 HT 2CR在POMC或SIM 1神经元中被选择性地删除，并对能量稳态进行全面分析，并给予5-HT激动剂间氯苯基哌嗪（mCPP）和D-芬氟拉明（d-Fen）。所提出的小鼠模型，其中使用cre-lox技术在POMC或SIM 1神经元中选择性地删除5 HT 2CR，提供了一个强大而独特的模型来评估这些途径的生理相关性和需求。分析这些小鼠表型的综合方法将包括小鼠模型的组织学验证以及大脑发育和神经存活的评估。还将在喂食普通饲料和高脂肪饲料的小鼠中进行代谢笼研究，以评估摄食量、能量消耗和体力活动。总之，这些方法将提供5-HT和相关激动剂在中枢神经系统中的作用机制的见解。预期的发现是，5-HT和相关激动剂将需要POMC和SIM 1神经元来维持正常的体重稳态，并完全介导mCPP和d-Fen的抗肥胖作用。这些发现将提高我们对身体如何控制能量稳态的理解，并可能提供新的治疗靶点。

DESCRIPTION (provided by applicant): Serotonin (5-HT) and related agonists are well characterized to act upon the 2C isoform of its receptor (5HT2CR) in the arcuate and paraventricular nuclei of the hypothalamus (ARH and PVH) to suppress food intake and exert anti-obesity effects. The specific neuronal targets of 5-HT and related agonists in the ARH and PVH required for such effects are, in contrast, not well defined. Recent work in which 5HT2CR expression was selectively restored to pro-opiomelanocortin (POMC) neurons within the ARH identifies that this distinct neuronal sub-set is a strong candidate to be a target. This notion is based on evidence that selective re- activation of 5HT2CRs in POMC neurons rescues the hyperphagic and obese phenotype of 5HT2CR-null mice. Preliminary data in this application also highlights that simple-minded 1 (SIM1) neurons in the PVH co-express 5HT2CRs and may be one type of neuron targeted by 5-HT and related agonists. The current proposal aims to test whether 5-HT and related agonists require 5HT2CR expression in POMC and SIM1 neurons in the ARH and PVH, respectively, to maintain normal body weight and to exert anti-obesity effects. This will be accomplished by combining genetically engineered mouse models in which endogenous 5HT2CR are selectively deleted in either POMC or SIM1 neurons with comprehensive analyses of energy homeostasis and administration of 5-HT agonists m-chloro-phenylpiperazine (mCPP) and D-fenfluramine (d-Fen). The proposed mouse models in which 5HT2CRs will be selectively deleted using cre-lox techniques in either POMC or SIM1 neurons provide a powerful and unique model to assess the physiological relevance and requirement for these pathways. The comprehensive approach to analyze the phenotype of these mice will include histological validation of the mouse model as well as assessments of brain development and neural survival. Metabolic cages studies will also be performed in mice fed chow and high-fat diet to assess food intake, energy expenditure, and physical activity. Taken together, these approaches will provide mechanistic insight into the effects of 5-HT and related agonists in the CNS. The expected findings are that 5-HT and related agonist will require POMC and SIM1 neurons to maintain normal body weight homeostasis and to fully mediate the anti- obesity effects of mCPP and d-Fen. These findings would improve our understanding about how the body controls energy homeostasis and potentially offer new therapeutic targets.