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; 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.

概括 脑衍生的神经营养因子（BDNF）与全长的肌球蛋白受体激酶（TRKB.FL）结合，诱导其诱导其 二聚和激活。这激活了许多协同促进神经元存活的许多信号级联 并调节许多大脑区域的神经元发育和突触传播。这个信号通路是 对于控制能量平衡的控制也至关重要，因为TrkB.fl激酶结构域或BDNF的突变导致 小鼠和人类的肥大和严重的肥胖症。除了trkb.fl，NTRK2基因还产生两个 截短的受体，主要的trkb.t1和一个次要的trkb.t2（我们使用trkb.t参考这两种同工型）。 trkb.t 具有短的细胞内序列，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示TRKB.T.同时BDNF与TRKB.T1结合诱导Ca2+信号并激活 Rho GTPase在培养的星形胶质细胞中，尚不清楚星形胶质细胞TRKB是否在能量控制中起作用 平衡。我们生成了星形胶质细胞特异性NTRK2条件敲除（ANTRK2 CKO）小鼠，其中NTRK2删除 从5周龄开始，废除星形胶质细胞中的TrkB.T表达。我们发现NTRK2删除 成熟的星形胶质细胞阻断了下丘脑（ARH）的弧形核中的星形胶质反应性，并给出了小鼠 通过减少能量摄入和增加能量消耗，完全抵抗饮食诱导的肥胖症（DIO）。在 除了对神经元的营养和营养支持外，星形胶质细胞通过其过程接触突触 通过从突触裂缝中摄取神经递质并释放来调节突触传播 Gliotransmitters进入突触裂缝。因此，我们假设TRKB.T介导的Ca2+信号促进 响应高脂饮食（HFD）进食的星形胶质细胞反应性，进而破坏了对神经元的星形胶质支撑 突触的星形细胞调节，并将能量稳态转移到能量盈余。我们的研究将集中 ARH中的星形胶质细胞，AGRP/NPY神经元和POMC神经元。我们建议检查NTRK2的影响 基因缺失ARH中的星形胶质细胞（AIM 1），以确定星形细胞NTRK2缺失对神经元的影响 和突触传播（AIM 2），以识别星形胶质细胞TRKB的位置。 肥胖症（AIM 3），并确定衰减星形胶质细胞CA2+信号是否可以防止HFD喂养的小鼠肥胖（AIM 4）。总之，该研究项目将测试几种新颖概念，包括TRKB.T-的关键作用 介导的Ca2+信号在诱导星形胶质性反应性中，这是TRKB.T在能量调节中的主动作用 平衡和改变了HFD喂养小鼠突触传播的星形细胞调节。我们的研究可能表明 衰减星形胶质细胞中的TRKB.T介导的Ca2+信号可能是一种新颖有效的治疗策略 DIO的干预措施，是人类肥胖的最常见形式。