Amplification of satiation signaling by melanocortin-4 receptors in the nucleus tractus solitarius

项目摘要 令人震惊的肥胖率带来了重大的公共健康和经济后果。这个 开发更有效的减肥疗法是至关重要的，需要基础科学研究 描述摄食行为的神经控制。黑素皮质素信号通路--通过黑素皮质素4受体 孤束核(NTS)中的MC4Rs通过以下途径参与食物摄取控制： 放大餐内胃肠(GI)衍生的饱腹感信号。然而，MC4R的作用机制 NTS内部的信号转导不清楚以及NTS之间相互作用的翻译意义 黑素皮质素信号和其他激素系统在NTS水平上还没有得到充分的研究。 这项拟议的研究旨在检验内源性突触前和突触后NTS MC4R的假设 活动调节NTS神经信号和GI引起的食物摄取和体重抑制 衍生的饱腹症信号为CCK和GLP-1。具体目标我会 应用体内纤维光度法检测CCK和GLP-1诱发的NTS神经活动的双向调制 后脑注射MC4R激动剂MTII或拮抗剂Shu9119。我们假设神经活动 这两种饱和信号中的任何一种都会被外源MTII放大，并被Shu9119减弱。AS 我们假设NTS神经活动的增强将导致饱和信号的放大，我们预计NTS 提供MTII，以提高外周给药的食物摄入量和体重抑制效果 CCK或GLP-1。特殊目的II将使用腺相关病毒(AAV)编码有效的shRNA构造 对于MC4R，传递到迷走神经的结状神经节或NTS，选择性地击倒 MC4Rs分别表达于迷走神经突触前传入神经元和突触后NTS神经元。我们将分析 在每组大鼠的日常饮食模式中分离前和后两者的内源性贡献 突触后NTS MC4Rs与摄食和体重控制有关。我们将继续使用这一策略来检查 突触前、后MC4Rs在介导外源性NTS MTII摄取抑制效应中的作用 递送和增强CCK和GLP-1的厌食作用。最后，我们将开始描述 NTS内MTII激活神经元的表型。通过确定功能相关性和机制 对于NTS内MC4R信号的研究，这些研究将有助于识别一种新的NTS MC4R激活的 可以通过药理学方法控制的循环，以减少食物摄入量和体重。

Project Summary The astounding prevalence of obesity presents major public health and economic consequences. The development of more effective therapeutics for weight loss is paramount and requires basic science research to characterize the neural control of feeding behavior. Melanocortin signaling, through melanocortin 4 receptors (MC4Rs) in the nucleus tractus solitarius (NTS) contributes to food intake control by reducing meal size via amplification of within-meal gastrointestinally (GI)-derived satiation signals. However, the mechanism of MC4R signaling within the NTS is not clear and the translational significance of the interaction between NTS melanocortin signaling and other hormonal systems at the level of the NTS has not been adequately explored. The proposed research aims to test the hypothesis that endogenous pre- and postsynaptic NTS MC4R activity modulates NTS neural signaling and food intake and body weight suppression evoked by the GI- derived satiation signals cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1). Specific Aim I will use in vivo fiber photometry to examine bidirectional modulation of CCK- and GLP-1-evoked NTS neural activity by hindbrain delivery of the MC4R agonist MTII or antagonist Shu9119. We hypothesize that neural activity evoked by either of these satiation signals will be amplified by exogenous MTII and attenuated by Shu9119. As we hypothesize that potentiation of NTS neural activity will result in amplified satiation signaling, we expect NTS delivered MTII to also enhance the food intake and body weight suppressive effects of peripherally administered CCK or GLP-1. Specific Aim II will utilize an adeno-associated virus (AAV)-encoding a validated shRNA construct for the MC4R, delivered to either the nodose ganglion of the vagus nerve or to the NTS, to selectively knockdown MC4Rs expressed on vagal presynaptic afferents or postsynaptic NTS neurons, respectively. We will analyze day-to-day meal patterns in each of these groups of rats to dissociate the endogenous contribution of pre- and postsynaptic NTS MC4Rs to food intake and body weight control. We will go on to use this strategy to examine the role of pre- and postsynaptic MC4Rs in mediating the intake-suppressive effects of exogenous NTS MTII delivery and in potentiating the anorectic actions of CCK and GLP-1. Finally, we will begin to characterize the phenotype of MTII-activated neurons within the NTS. By determining the functional relevance and mechanism of MC4R signaling within the NTS, these studies will contribute to identification of a novel NTS MC4R-activated circuit that may be manipulated through pharmacological approaches to reduce food intake and body weight.