Defining Mechanisms of Dynamic mTORC1 Regulation in the Liver with Fasting and Feeding

禁食和进食时肝脏动态 mTORC1 调节的定义机制

• 批准号: 10386461
• 负责人: Krystle Kalafut
• 金额: $ 3.94万
• 依托单位: HARVARD SCHOOL OF PUBLIC HEALTH
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10386461
• 关键词: Acute; Alanine; Anabolism; Biological Assay; Cell Culture Techniques; Cell Proliferation; Cells; Chronic; Complex; Coupling; Cues; Data; Disease; FRAP1 gene; Fasting; Genetic; Genetic Transcription; Glucagon; Glucagon Receptor; Goals; Growth Factor; Health; Hepatic; Hepatocyte; Hormonal; Hormones; Human; Insulin; Insulin Resistance; Knowledge; Link; Liver; Measures; Mediating; Mediator of activation protein; Metabolic; Metabolic Diseases; Metabolic dysfunction; Metabolism; Methods; Modeling; Molecular; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Obesity; Phosphorylation; Phosphorylation Site; Physiological; Process; Protein Kinase; Public Health Schools; Publishing; Regulation; Reporting; Repression; Rodent; Role; Signal Transduction; TSC2 gene; Testing; Tissues; Tuberous Sclerosis; Tuberous sclerosis protein complex; Up-Regulation; Work; cell growth; experimental study; fatty acid oxidation; feeding; flexibility; glucose metabolism; hormonal signals; in vivo; innovation; insight; insulin regulation; insulin signaling; ketogenesis; lipid metabolism; mouse model; mutant; novel; precision genetics; protein complex; response

PROJECT SUMMARY Aberrant hepatic mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) activity is associated with obesity and insulin resistance. Insights into the physiological inputs and mechanisms that regulate mTORC1 signaling in the liver are needed in order to understand how regulation of hepatic mTORC1 becomes disrupted and how this contributes to insulin resistance and metabolic disease. mTORC1 is a central regulator of cellular growth and proliferation that promotes anabolic processes in response to nutrients and growth factors. In the liver, mTORC1 activity is sensitive to physiologic fluctuations during fasting and feeding, with reduced mTORC1 signaling during fasting and acute induction of mTORC1 upon feeding. This dynamic regulation of mTORC1 in the liver is abolished in obese rodents, highlighting the importance of flexible mTORC1 signaling for systemic metabolic health. The goal of this study is to define mechanisms of dynamic mTORC1 regulation in the liver, with a focus on two hormonal cues. mTORC1 activity is induced by insulin, and both mTORC1 signaling and insulin have been shown to regulate glucose and lipid metabolism in the liver. The mechanism by which insulin induces mTORC1 activity is well-established in cell culture models. However, it is not known how insulin regulation contributes to the induction of mTORC1 activity in the liver upon feeding. Conversely, published reports and our preliminary data demonstrate that mTORC1 signaling is suppressed by glucagon in primary hepatocytes. Glucagon signaling orchestrates an adaptive response to fasting in the liver, and hepatic mTORC1 activity blocks multiple glucagon-mediated metabolic changes. However, the mechanism of mTORC1 repression by glucagon and whether glucagon contributes to the repression of mTORC1 during fasting are unknown. I hypothesize that the glucoregulatory hormones insulin and glucagon contribute to the dynamic regulation of mTORC1 in the liver with feeding and fasting, respectively. I will test this hypothesis through two aims: 1) Use of a new precision genetic mouse model to define the role of liver insulin signaling to mTORC1, in which I will generate and characterize mice with mTORC1 signaling that is disconnected from insulin regulation specifically in the liver, and 2) Determine the physiological significance and mechanism of glucagon-mediated mTORC1 suppression, in which I will determine if glucagon is necessary and sufficient for hepatic mTORC1 suppression during fasting, as well as evaluate potential downstream mediators connecting glucagon and mTORC1 signaling in primary hepatocytes. The proposed experiments have the potential to identify targetable insights into chronic mTORC1 activation in metabolic disease. The study will be conducted in the lab of Dr. Brendan Manning at the Harvard T.H. Chan School of Public Health. Dr. Manning is an expert in the mTORC1 field and has extensive knowledge of insulin-PI3K-Akt signaling. Additionally, many of the proposed methods and mouse models are already established in the lab.

项目摘要 雷帕霉素（mTOR）复合物1（mTORC 1）活性的异常肝脏机制靶点与以下因素相关： 肥胖和胰岛素抵抗。深入了解调节mTORC 1的生理输入和机制 为了了解肝脏mTORC 1的调节是如何被破坏的， 以及这是如何导致胰岛素抵抗和代谢疾病的。mTORC 1是一种细胞凋亡的中枢调节因子， 促进合成代谢过程以响应营养物和生长因子的生长和增殖。在 肝脏，mTORC 1活性对禁食和进食期间的生理波动敏感， 禁食期间的信号传导和进食时mTORC 1的急性诱导。这种mTORC 1的动态调节， 肥胖啮齿动物的肝脏被破坏，突出了灵活的mTORC 1信号传导对系统性免疫的重要性。 代谢健康本研究的目的是确定mTORC 1在肝脏中的动态调节机制， 关注两种荷尔蒙信号mTORC 1活性由胰岛素诱导，mTORC 1信号传导和胰岛素 已经显示出调节肝脏中的葡萄糖和脂质代谢。胰岛素诱导的机制 mTORC 1活性在细胞培养模型中已得到充分确立。然而，目前尚不清楚胰岛素调节如何 有助于在进食时诱导肝脏中的mTORC 1活性。相反，已发表的报告和我们的 初步数据表明，在原代肝细胞中，胰高血糖素抑制mTORC 1信号传导。 胰高血糖素信号传导协调肝脏对禁食的适应性反应，并阻断肝脏mTORC 1活性 多种胰高血糖素介导的代谢变化。然而，胰高血糖素抑制mTORC 1的机制 以及胰高血糖素是否有助于禁食期间mTORC 1的抑制尚不清楚。我假设 葡萄糖调节激素胰岛素和胰高血糖素有助于肝脏中mTORC 1的动态调节 喂食和禁食。我将通过两个目标来检验这个假设：1）使用新的精度 遗传小鼠模型，以确定肝脏胰岛素信号传导对mTORC 1的作用，在该模型中， 表征mTORC 1信号传导与胰岛素调节特异性地在肝脏中断开的小鼠， 2）探讨胰高血糖素介导的mTORC 1的生理意义和作用机制 抑制，其中我将确定胰高血糖素是否是肝脏mTORC 1抑制所必需和充分的 以及评估连接胰高血糖素和mTORC 1信号传导的潜在下游介质 在原代肝细胞中。拟议的实验有可能确定慢性疾病的有针对性的见解。 代谢性疾病中的mTORC 1活化。该研究将在Brendan Manning博士的实验室进行， 哈佛T. H.陈氏公共卫生学院。曼宁博士是mTORC 1领域的专家， 胰岛素-PI 3 K-Akt信号传导的知识。此外，许多所提出的方法和小鼠模型是 已经在实验室中建立。