Astrocytic regulation of energy balance on high-fat diet

星形胶质细胞对高脂饮食能量平衡的调节

• 批准号: 10734911
• 负责人: BAOJI XU
• 金额: $ 75.47万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-09 至 2027-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10734911
• 关键词: Ablation; Age; Astrocytes; Axon; Binding; Brain; Brain region; Brain-Derived Neurotrophic Factor; Ca(2+)-Transporting ATPase; Cell membrane; Cells; Development; Dimerization; Energy Intake; Energy Metabolism; Fat-Restricted Diet; Gene Deletion; Glutamates; Growth; High Fat Diet; Homeostasis; Human; Hyperactivity; Hyperphagia; Hypothalamic structure; ITPR1 gene; Impairment; Injections; Inositol; Knock-out; Knockout Mice; Lead; Length; Measures; Mediating; Minor; Morbid Obesity; Morphology; Mus; Mutation; NTRK2 gene; Nerve Degeneration; Neurons; Neurotransmitters; Neurotrophic Tyrosine Kinase Receptor Type 2; Nutritional; Nutritional Support; Obesity; Phosphotransferases; Play; Process; Protein Isoforms; RNA Splicing; Reducing diet; Regulation; Reporting; Research Project Grants; Resistance; Role; Signal Pathway; Signal Transduction; Site; Slice; Structure; Structure of nucleus infundibularis hypothalami; Synapses; Synaptic Cleft; Synaptic Transmission; Testing; Therapeutic Intervention; Tropomyosin; Tyrosine Kinase Domain; Variant; antagonist; astrogliosis; attenuation; conditional knockout; density; diet-induced obesity; energy balance; excitotoxicity; experimental study; feeding; knock-down; neuron development; neuronal survival; neurotoxic; neurotransmission; novel; obesity prevention; prevent; receptor; response; rho GTP-Binding Proteins; transmission process; tripolyphosphate; uptake

Summary Brain-derived neurotrophic factor (BDNF) binds to full-length tropomyosin receptor kinase (TrkB.FL), inducing its dimerization and activation. This activates many signaling cascades that cooperatively promote neuronal survival and regulate neuronal development and synaptic transmission in many brain regions. This signaling pathway is also critical for the control of energy balance, as mutations in the TrkB.FL kinase domain or BDNF lead to hyperphagia and severe obesity in mice and humans. In addition to TrkB.FL, the Ntrk2 gene produces two truncated receptors, a predominant TrkB.T1 and a minor TrkB.T2 (we use TrkB.T to refer both isoforms). TrkB.T has a short intracellular sequence and lacks the tyrosine kinase domain. Neurons mainly express TrkB.FL, whereas astrocytes only express TrkB.T. While binding of BDNF to TrkB.T1 induces Ca2+ signals and activates Rho GTPase in cultured astrocytes, it remains unclear if astrocytic TrkB.T plays a role in the control of energy balance. We generated astrocyte specific Ntrk2 conditional knockout (aNtrk2 cKO) mice where Ntrk2 deletion starts at 5 weeks of age and abolishes TrkB.T expression in astrocytes. We found that the Ntrk2 deletion in mature astrocytes blocked astrocytic reactivity in the arcuate nucleus of the hypothalamus (ARH) and gave mice total resistance to diet-induced obesity (DIO) by reducing energy intake and increasing energy expenditure. In addition to nutritional and trophic support to neurons, astrocytes contact synapses through their processes to regulate synaptic transmission by taking up neurotransmitters from the synaptic cleft and releasing gliotransmitters into the synaptic cleft. Thus, we hypothesize that TrkB.T-mediated Ca2+ signals promote astrocytic reactivity in response to high-fat diet (HFD) feeding, which in turn disrupts astrocytic support to neurons and astrocytic regulation of synapses and shifts energy homeostasis to energy surplus. Our studies will focus on astrocytes, AgRP/NPY neurons, and POMC neurons in the ARH. We propose to examine the impact of Ntrk2 gene deletion on astrocytes in the ARH (Aim 1), to determine the impact of astrocytic Ntrk2 deletion on neurons and synaptic transmission (Aim 2), to identify the site where astrocytic TrkB.T ablation blocks diet-induced obesity (Aim 3), and to determine if attenuating astrocytic Ca2+ signals can prevent obesity in HFD-fed mice (Aim 4). In conclusion, this research project will test several novel concepts, including a crucial role for TrkB.T- mediated Ca2+ signals in induction of astrocytic reactivity, an active role for TrkB.T in the regulation of energy balance, and altered astrocytic regulation of synaptic transmission in HFD-fed mice. Our studies will likely show that attenuating TrkB.T-mediated Ca2+ signals in astrocytes can be a novel and effective strategy for therapeutic interventions of DIO, the most common form of obesity in humans.

总结 脑源性神经营养因子（BDNF）与全长原肌球蛋白受体激酶（TrkB.FL）结合，诱导其表达。 二聚化和活化。这激活了许多信号级联，协同促进神经元存活 并调节许多脑区的神经元发育和突触传递。这种信号通路是 对于能量平衡的控制也是至关重要的，因为TrkB.FL激酶结构域或BDNF中的突变导致 食欲过盛和严重肥胖。除了TrkB.FL，Ntrk 2基因还产生两个 截短的受体，主要的TrkB. T1和次要的TrkB. T2（我们使用TrkB.T来指两种亚型）。TrkB.T 具有短的细胞内序列并且缺乏酪氨酸激酶结构域。神经元主要表达TrkB.FL， 而星形胶质细胞仅表达TrkB. T。而BDNF与TrkB.T1的结合诱导Ca 2+信号并激活 尽管Rho GT3在培养的星形胶质细胞中表达，但仍不清楚星形胶质细胞TrkB.T是否在能量控制中发挥作用。 平衡我们产生星形胶质细胞特异性Ntrk 2条件性敲除（aNtrk 2 cKO）小鼠，其中Ntrk 2缺失 从5周龄开始，并消除星形胶质细胞中的TrkB.T表达。我们发现Ntrk 2缺失在 成熟的星形胶质细胞阻断了下丘脑弓状核（ARH）中的星形胶质细胞反应， 通过减少能量摄入和增加能量消耗来完全抵抗饮食诱导的肥胖（DIO）。在 除了对神经元的营养和营养支持外，星形胶质细胞通过它们的过程接触突触， 通过从突触间隙摄取神经递质并释放 神经胶质递质进入突触间隙。因此，我们假设TrkB. T介导的Ca 2+信号促进了细胞内Ca 2+的表达。 星形胶质细胞对高脂饮食（HFD）喂养的反应性，这反过来又破坏了星形胶质细胞对神经元的支持 和星形胶质细胞调节突触，并将能量稳态转变为能量盈余。我们的研究将集中在 对ARH中的星形胶质细胞、AgRP/NPY神经元和POMC神经元的影响。我们建议研究Ntrk 2的影响 ARH中星形胶质细胞上的基因缺失（目的1），以确定星形胶质细胞Ntrk 2缺失对神经元的影响 和突触传递（Aim 2），以确定星形胶质细胞TrkB.T消融阻断饮食诱导的 肥胖（Aim 3），并确定减弱星形胶质细胞Ca 2+信号是否可以预防HFD喂养小鼠的肥胖（Aim 4）。总之，这项研究项目将测试几个新的概念，包括TrkB的关键作用。 TrkB. T介导的Ca 2+信号诱导星形胶质细胞反应性，TrkB.T在能量调节中的积极作用 平衡，以及HFD喂养小鼠中突触传递的星形胶质细胞调节改变。我们的研究可能会显示 在星形胶质细胞中减弱TrkB. T介导的Ca 2+信号可能是一种新的有效的治疗策略， DIO是人类最常见的肥胖形式。