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）和相关激动剂的特点是作用于下丘脑弓状核和室旁核（ARH和PVH）中5-羟色胺受体（5HT2CR）的2C异构体，抑制食物摄入并发挥抗肥胖作用。相比之下，5-羟色胺和相关激动剂在ARH和PVH中的特定神经元靶点则没有很好的定义。在最近的研究中，5HT2CR的表达被选择性地恢复到ARH内的前opiomelanocortin （POMC）神经元中，这一独特的神经元亚群是一个强有力的候选靶标。这一观点是基于有证据表明，POMC神经元中5ht2cr的选择性再激活可以挽救5ht2cr缺失小鼠的贪食和肥胖表型。本应用的初步数据还强调PVH中的SIM1神经元共表达5HT2CRs，可能是5-HT和相关激动剂靶向的一种神经元。本课题旨在检测5-HT及相关激动剂是否需要分别在ARH和PVH的POMC和SIM1神经元中表达5HT2CR才能维持正常体重并发挥抗肥胖作用。这将通过结合基因工程小鼠模型，在POMC或SIM1神经元中选择性地删除内源性5HT2CR，综合分析能量稳态和5-HT激动剂间氯苯哌嗪（mCPP）和d-芬氟拉明（d-Fen）的管理来实现。在POMC或SIM1神经元中使用cre-lox技术选择性删除5HT2CRs的小鼠模型为评估这些通路的生理相关性和需求提供了一个强大而独特的模型。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。代谢笼研究也将在喂食食物和高脂肪饮食的小鼠中进行，以评估食物摄入、能量消耗和身体活动。综上所述，这些方法将为5-羟色胺和相关激动剂在中枢神经系统中的作用提供机制见解。预期结果是5-HT及相关激动剂需要POMC和SIM1神经元维持正常体重稳态，并充分介导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.