Integration of Peripheral and Central Appetite Signals by Brainstem Neurons

描述(申请人提供)：肥胖是美国的一个主要健康问题，也是心血管疾病、糖尿病和中风的主要诱因。肥胖研究中知之甚少的领域之一是神经元对有关能量状态的中枢和外周信号的反应、整合和传递的机制，以及这些信号通路在肥胖中是如何改变的。我们的长期目标是了解脑干孤束核(NTS)神经元控制体重的分子和细胞机制，以及这些机制在肥胖中是如何改变的。携带饱腹感信息的内脏传入，包括胃传入，终止于NTS。因此，NTS神经元起着闸门的作用，决定了传入神经元中包含的哪些信息被传递到大脑的其他区域。损毁表达儿茶酚胺的NTS神经元(NTS-CA神经元)可干扰包括Ghrelin和CCK(CCK)在内的多种激素对食物摄取的控制。这项建议的总体目标是确定NTS-CA神经元在正常和肥胖条件下对食欲调节输入做出反应的机制。我们的中心假设是，NTS-CA神经元的输出是传入和激素输入的整合，并且它会被不同的能量状态改变，如禁食或肥胖。我们将通过以下三个具体目标来检验这一假设。(1)确定传入信息对NTS-CA神经元的调节作用。我们的工作假设是，NTS-CA神经元的放电频率是由内脏传入，包括胃传入，通过直接和间接输入控制的。(2)明确关键激素食欲调节剂对孤束核CA区神经元的调控机制(S)。为此，我们的工作假设是，抑制食物摄取的CCK和刺激食物摄取的Ghrelin调节NTS-CA神经元的输出。(3)确定NTS-CA神经元对不同能量状态的适应情况。为此，我们的工作假设是NTS-CA神经元适应长期暴露在激素或能量状态改变的条件下。我们已经为开展拟议的研究做好了充分的准备，因为我们已经开发出一种小鼠水平脑片，它允许我们在使用电生理膜片钳技术记录已识别的NTS-CA神经元的同时，选择性地刺激内脏传入。这是一个非常强大的系统，可以解决NTS-CA神经元整合神经元和激素反应的细胞和分子机制，以及这些机制在肥胖中是如何改变的。此外，我们将使用标记技术来识别接受胃传入输入的NTS-CA神经元，并利用药理学来剖析分子信号通路和行为范式，以检验这些通路/机制在不同能量状态下是如何改变的。这项工作的贡献预计将是重大的，因为增加我们对食欲控制的分子机制以及这些机制在不同能量状态下是如何改变的理解，将导致更精确的针对性方法来预防和治疗肥胖症。公共健康相关性：这项拟议的研究与公共健康相关，因为肥胖是美国的一个主要健康问题，也是心血管疾病、糖尿病和中风的主要贡献者。这些研究的预期贡献将是确定一组关键神经元控制体重调节的分子机制，以及这些机制在肥胖中是如何改变的。人们相信，增加我们对这些机制的理解将导致更精确地有针对性地预防和治疗肥胖。

DESCRIPTION (provided by applicant): Obesity is a major health problem in the United States and is a leading contributor to cardiovascular disease, diabetes mellitus and stroke. One of the less well understood areas of obesity research are the mechanisms by which neurons respond to, integrate and pass on central and peripheral signals about energy state and how these signaling pathways are altered in obesity. Our long-range goal is to understand the molecular and cellular mechanisms by which neurons in the nucleus of the solitary tract (NTS) of the brainstem control body- weight and how these mechanisms are altered in obesity. Visceral afferents, including gastric afferents, carrying information about satiety terminate in the NTS. As such, NTS neurons act as gates, determining what information contained in afferents is passed onto other brain regions. Ablation of NTS neurons expressing catecholamines (NTS-CA neurons) disrupts control of food intake by several hormones, including ghrelin and cholecystokinin (CCK). The overall objective of this proposal is to identify the mechanisms by which NTS-CA neurons respond to appetite-regulating inputs under normal and obese conditions. Our central hypothesis is that the output of NTS-CA neurons is an integration of afferent and hormonal inputs and that it is altered by different energy states, such as fasting or obesity. We will test this hypothesis with the following three specific aims. (1) Determine how afferent inputs regulate NTS-CA neurons. Our working hypothesis for this aim is that the firing rate of NTS-CA neurons is controlled by visceral afferents, including gastric afferents, both through direct and indirect inputs. (2) Identify mechanism(s) by which key hormonal appetite modulators regulate NTS- CA neurons. Our working hypothesis for this aim is that CCK, which inhibits food intake and ghrelin, which stimulates food intake, regulate the output of NTS-CA neurons. (3) Determine how NTS-CA neurons adapt to different energy states. Our working hypothesis for this aim is that NTS-CA neurons adapt to prolonged exposure to hormones or conditions of altered energy states. We are well prepared to undertake the proposed research because we have developed a mouse horizontal brain slice that allows us to selectively stimulate visceral afferents while recording from identified NTS-CA neurons using electrophysiological patch clamp techniques. This is an extremely powerful system to address the cellular and molecular mechanisms by which NTS-CA neurons integrate neuronal and hormonal responses and how these mechanisms are altered in obesity. In addition, we will use labeling techniques to specifically identify NTS-CA neurons receiving gastric afferent inputs, pharmacology to dissect out molecular signaling pathways and behavioral paradigms to examine how these pathways/mechanisms are altered in different energy states. The contribution of this work is expected to be significant, because increasing our understanding of the molecular mechanisms underlying appetite control and how these mechanisms are altered in different energy states, will lead to more precisely targeted approaches for the prevention treatment of obesity. PUBLIC HEALTH RELEVANCE: The proposed research is relevant to public health because obesity is a major health problem in the United States and is a leading contributor to cardiovascular disease, diabetes mellitus and stroke. The expected contribution of these studies will be the identification of molecular mechanisms by which one group of critical neurons control weight regulation and how these are altered in obesity. The belief is that increasing our understanding of these mechanisms will lead to more precisely targeted approaches for the prevention and treatment of obesity.