Dorsomedial Hypothalamic Signaling Pathways and Energy Balance

 描述(申请人提供)：肥胖已成为世界性流行病，并导致严重的公共卫生问题。现在，在美国，大约三分之一的成年人和大约17%的2-19岁的儿童和青少年患有肥胖症。肥胖与威胁生命的疾病有关，如2型糖尿病和心血管疾病。我们应对肥胖症流行的战略在很大程度上是不够的。理论上，肥胖可以通过增加能量消耗和控制饮食来控制，但这些方法的成功率仍然很低。更好地理解能量平衡的控制将有助于我们克服这一问题的能力。来自该实验室和其他实验室的越来越多的数据强调了背内侧下丘脑(DMH)在控制食物摄入量和能量消耗方面的具体作用。这个研究项目的总体目标是更全面地解开这些动作的神经基础。我们发现，在DMH中过度表达食欲素神经肽Y(NPY)会导致过度吞噬和肥胖，而DMH NPY基因敲除会导致食物摄入量减少，白色脂肪中棕色脂肪细胞发育，棕色脂肪产热和身体能量消耗增加，以及体重减轻。这些发现确立了DMH NPY在控制食物摄入量和能量消耗方面的关键作用，但潜在的神经通路仍未确定。该项目旨在通过以下两个具体目标来阐述这些途径。在目标1中，我们建议通过实验来描述DMH NPY摄食效应的神经通路，方法是评估：(1)DMH NPY下行信号是否调节迷走神经传入支配的脑干神经元的活动以控制摄食；(2)DMH NPY支配室旁核中的厌食神经元(如催产素)以调节摄食。目的2中提出的实验是为了确定DMH NPY生热效应的神经机制。我们将首先确定DMH NPY在体温调节中的重要性，并描述潜在的神经元信号转导。鉴于DMH生热区存在促肾上腺皮质激素释放因子(CRF)表达的神经元，目的2的第二部分是评估DMH CRF是否介导DMH NPY对生热的调节，并评价DMH CRF潜在的生热功能。我们将应用多种方法，包括腺相关病毒系统改变DMH中NPY和CRF的表达，胃肠道信号的药理和生理干预，使用c-Fos作为神经元激活标记的神经解剖学分析，追踪神经元投射的绿色荧光蛋白和霍乱无毒B亚单位，通过中枢微量注射受体特异性拮抗剂或激动剂干扰神经信号传递，饮食或营养 冷挑战，并在基因和蛋白质水平上评估神经信号，以实现这些目标。总体而言，该项目的结果不仅将显著促进我们对能量平衡的中央控制的理解，而且还将为开发抗击肥胖及其共病的新策略提供神经基础。

 DESCRIPTION (provided by applicant): Obesity has become a worldwide epidemic and causes serious public health problems. Now about one third of adults and approximately 17% of children and adolescents aged 2-19 years are obese in the United States. Obesity has been linked to life-threatening diseases such as type 2 diabetes and cardiovascular disease. Our strategies for tackling obesity epidemic are largely inadequate. Theoretically, obesity could be controlled by increasing energy expenditure and controlling diet, but the success rates with these approaches remain poor. A better understanding of the control of energy balance will facilitate our capability for overcoming this problem. Growing data from this and other labs have underscored specific roles for the dorsomedial hypothalamus (DMH) in the controls of both food intake and energy expenditure. The overall goal of this research project is to more comprehensively unravel the neural bases of these actions. We have found that overexpression of orexigenic neuropeptide Y (NPY) in the DMH causes hyperphagia and obesity, whereas DMH NPY knockdown results in decreased food intake, brown adipocyte development in white fat, increases in brown fat thermogenesis and body energy expenditure, and weight loss. These findings establish critical roles for DMH NPY in the controls of food intake and energy expenditure, but the underlying neural pathways remain undetermined. This project is aimed at elaborating such pathways by the following two Specific Aims. In Aim 1, we propose experiments to characterize the neural pathways underlying the feeding effects of DMH NPY by assessing whether: (1) DMH NPY descending signals modulate the activity of brainstem neurons innervated by vagal afferents to control food intake, and (2), DMH NPY innervates anorexigenic neurons (such as oxytocin) in the paraventricular nucleus to modulate food intake. Experiments proposed in Aim 2 are to ascertain the neural mechanisms underlying the thermogenic effects of DMH NPY. We will first determine the importance of DMH NPY in thermoregulation and characterize the underlying neuronal signaling. Given the presence of corticotrophin-releasing factor (CRF)-expressing neurons in the thermogenic area of the DMH, the second part of Aim 2 is to assess whether DMH CRF mediates DMH NPY modulation of thermogenesis and to evaluate a potential thermogenic function of DMH CRF. We will apply multiple approaches including an adeno-associated virus system to alter NPY and CRF expression in the DMH, pharmacological and physiological interventions of gastrointestinal signaling, neuroanatomical analyses using c-Fos as a neuronal activation marker and green fluorescent protein and cholera nontoxic B subunit for tracing neuronal projections, interfering neural signaling with central microinjections of receptor-specific antagonists or agonists, diet or cold challenges, and evaluating neural signaling at both gene and protein levels, to achieve these Aims. Overall, the results from this project will not only significantly advance our understanding of the central control of energy balance, but also provide the neural bases for the development of novel strategies for combatting obesity and its comorbidities.