Consequences of astrocytic leptin receptor upregulation on obesity

星形细胞瘦素受体上调对肥胖的影响

• 批准号: 8158608
• 负责人: ABBA J KASTIN
• 金额: $ 37万
• 依托单位: LSU PENNINGTON BIOMEDICAL RESEARCH CTR
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-26 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8158608
• 关键词: Acute; Address; Adult; Affect; Astrocytes; Attention; Attenuated; Binding; Biological Markers; Body Weight; Brain; Brain Injuries; Calcium; Calcium Signaling; Cardiovascular system; Cell Communication; Cell Nucleus; Cells; Conditioned Culture Media; Cultured Cells; Data; Diet; Eating; Endocytosis; Energy Metabolism; Fatty acid glycerol esters; Gliosis; Glutamates; Hormones; Hyperlipidemia; Hypothalamic structure; Image; Incidence; Insulin Resistance; Knock-out; Knockout Mice; Leptin; Link; Lipids; Messenger RNA; Metabolic; Metabolic syndrome; Metabolism; Modeling; Molecular Weight; Mus; Neuroglia; Neurons; Neurosecretory Systems; Obesity; Phase; Phenotype; Play; Process; Production; Proteins; Regulation; Resistance; Role; Series; Serum; Signal Pathway; Signal Transduction; Sleep Apnea Syndromes; System; Testing; Time; Tissues; Up-Regulation; Weight; Weight maintenance regimen; astrogliosis; cancer complication; combat; cytokine; design; fluorocitrate; inhibitor/antagonist; leptin receptor; mouse model; nerve injury; neuroinflammation; new therapeutic target; novel; receptor upregulation; research study; response

DESCRIPTION (provided by applicant): The proposed study aims to determine how astrocytic leptin receptors (ObR, or LR) affect obesity regulation. Obesity, like neural injury, results in regional astrogliosis. We observed that knockout of ObR in astrocytes leads to partial resistance of the mice to diet-induced obesity, a finding opposite to the obesity found in mice with knockout of ObR in neurons. Moreover, mice with adult-onset obesity show both astrogliosis and robust upregulation of astrocytic ObR in selective nuclei of the hypothalamus. These ObR are functional, as leptin treatment activates multiple signaling pathways in primary astrocytes. We, therefore, hypothesize that the ObR (+) astrocytes provide negative regulation to facilitate obesity in two main ways: (a) reducing availability of leptin to neurons by accelerating leptin turnover; (b) modulating neuronal function by alterations of the profile of glial transmitters released. Such a role for astrocytes provides a direct mechanism linking neuroinflammatory processes and body weight control. We will test the hypotheses in three specific aims. (1) To show that reactive astrocytes facilitate the turnover of leptin and attenuate neuronal leptin signaling in the brain, Aim 1 will use an established model of reactive astrogliosis - adult-onset obesity - to determine the distribution of fluorescently conjugated leptin and pSTAT3 signaling after intracerebroventricular delivery of leptin. The results will be compared with those from astrocyte specific leptin receptor knockout mice, and after pretreatment with the astrocyte inhibitor fluorocitrate. (2) In Aim 2, we will test the hypothesis that leptin modulates the production profile of gliotransmitters, including glutamate and ATP in the acute phase and cytokines at a later time. Primary astrocytes and neurons will be used for calcium imaging, and the effects of astrocyte conditioned medium and mixed neuron-glial culture will be tested. (3) Aim 3 will identify functional consequences of astrocyte specific leptin receptor knockout on the metabolic phenotype and correlate this with serum biomarkers of neuroinflammation. Overall, the results will demonstrate an essential role of ObR(+) astrocytes in the regulation of neuronal leptin signaling. As astrocytes are crucially involved in neural injury and an integral part of the neuroimmune axis, these studies will provide tangible mechanisms by which neuroinflammation can regulate body weight. PUBLIC HEALTH RELEVANCE: Leptin is a hormone mainly produced by fat tissue. Hyperleptinemia is seen in obesity and the metabolic syndrome. The incidence of obesity and its associated hyperlipidemia, cardiovascular complications, cancer, and sleep apnea have been on a steep rise nationally and globally. This study will address how astrocytes participate in delivering leptin to neurons and modulating its actions. Astrocytes are the most abundant cells in the brain, clearly involved in brain injury, but very few studies have addressed whether they are involved with leptin and obesity. We recently found that both the mRNA and protein of leptin receptors are indeed present in astrocytes. Moreover, the expression level of these leptin receptors increases in mouse models of adult-onset obesity. This suggests an important role of the astrocytic leptin system in the regulatory changes in obese subjects. A series of experiments with mice and cultured cells are designed to address how these ObR(+) astrocytes affect neuronal function and overall metabolic phenotype. Thus, their relevance lies in (a) better understanding of how astrocytes affect obesity onset and progression; (b) better understanding of cell-cell interactions in the brain; and (c) potential identification of novel therapeutic targets to better combat obesity.

描述（由申请人提供）：拟议的研究旨在确定星形胶质细胞瘦素受体（ObR或LR）如何影响肥胖调节。肥胖，像神经损伤，导致局部星形胶质细胞增生。我们观察到，敲除星形胶质细胞中的ObR导致小鼠对饮食诱导的肥胖的部分抵抗，这一发现与敲除神经元中的ObR的小鼠中发现的肥胖相反。此外，患有成年型肥胖症的小鼠在下丘脑的选择性核中显示星形胶质细胞增生和星形胶质细胞ObR的强烈上调。这些ObR是功能性的，因为瘦素治疗激活了初级星形胶质细胞中的多种信号通路。因此，我们假设ObR（+）星形胶质细胞通过两种主要方式提供负调节以促进肥胖：（a）通过加速瘦素周转来减少瘦素对神经元的可用性;（B）通过改变释放的胶质递质的分布来调节神经元功能。星形胶质细胞的这种作用提供了连接神经炎症过程和体重控制的直接机制。我们将在三个具体目标中检验这些假设。(1)为了显示反应性星形胶质细胞促进瘦素的周转并减弱脑中神经元瘦素信号传导，Aim 1将使用已建立的反应性星形胶质细胞增生-成人发病肥胖症-模型来确定脑室内递送瘦素后荧光缀合的瘦素和pSTAT 3信号传导的分布。将结果与星形胶质细胞特异性瘦素受体敲除小鼠的结果以及用星形胶质细胞抑制剂氟柠檬酸预处理后的结果进行比较。(2)在目标2中，我们将测试瘦素调节胶质递质的产生概况的假设，包括急性期的谷氨酸和ATP，以及稍后的细胞因子。原代星形胶质细胞和神经元将用于钙成像，并将测试星形胶质细胞条件培养基和混合神经元-胶质细胞培养物的效果。(3)目的3将确定星形胶质细胞特异性瘦素受体敲除对代谢表型的功能后果，并将其与神经炎症的血清生物标志物相关联。总之，这些结果将证明ObR（+）星形胶质细胞在神经元瘦素信号调节中的重要作用。由于星形胶质细胞在神经损伤中起着至关重要的作用，并且是神经免疫轴的组成部分，这些研究将提供神经炎症可以调节体重的切实机制。 公共卫生相关性：瘦素是一种主要由脂肪组织产生的激素。高瘦素血症见于肥胖和代谢综合征。肥胖及其相关的高脂血症、心血管并发症、癌症和睡眠呼吸暂停的发病率在全国和全球范围内急剧上升。本研究将探讨星形胶质细胞如何参与将瘦素传递给神经元并调节其作用。星形胶质细胞是大脑中最丰富的细胞，显然与脑损伤有关，但很少有研究涉及它们是否与瘦素和肥胖有关。我们最近发现瘦素受体的mRNA和蛋白质确实存在于星形胶质细胞中。此外，这些瘦素受体的表达水平在成年型肥胖小鼠模型中增加。这表明星形胶质细胞瘦素系统在肥胖受试者的调节变化中起重要作用。设计了一系列小鼠和培养细胞的实验，以解决这些ObR（+）星形胶质细胞如何影响神经元功能和整体代谢表型。因此，它们的相关性在于（a）更好地理解星形胶质细胞如何影响肥胖症的发作和进展;（B）更好地理解脑中的细胞-细胞相互作用;和（c）潜在地鉴定新的治疗靶点以更好地对抗肥胖症。