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（MTORC1）活性的异常肝机械靶标与 肥胖和胰岛素抵抗。对调节MTORC1的生理输入和机制的见解 需要在肝脏中发出信号，以了解肝MTORC1的调节如何破坏 以及这如何有助于胰岛素抵抗和代谢疾病。 MTORC1是细胞的中央调节剂 生长和增殖促进了响应养分和生长因素的合成代谢过程。在 肝脏，MTORC1活性对禁食和进食过程中的生理波动敏感，MTORC1降低 喂食后禁食和急性诱导MTORC1的信号传导。 MTORC1的这种动态调节 肥胖啮齿动物消除了肝脏，突出了灵活的MTORC1信号对全身性的重要性 代谢健康。这项研究的目的是定义肝脏中动态MTORC1调节的机制，并用 专注于两个荷尔蒙提示。 MTORC1活性由胰岛素诱导，MTORC1信号传导和胰岛素均诱导 已证明可以调节肝脏中的葡萄糖和脂质代谢。胰岛素诱导的机制 MTORC1活性在细胞培养模型中良好。但是，尚不知道胰岛素调节如何 进食后有助于肝脏中MTORC1活性的诱导。相反，已发表的报告和我们的 初步数据表明，在原发性肝细胞中，胰高血糖素抑制了MTORC1信号。 胰高血糖素信号传导协调对肝脏禁食的自适应反应，肝MTORC1活性阻滞 多种胰高血糖介导的代谢变化。但是，胰高血糖素MTORC1抑制的机制 以及胰高血糖素是否有助于禁食期间MTORC1的抑制。我假设这一点 葡萄糖调节激素胰岛素和胰高血糖素有助于MTORC1的动态调节 分别进行喂食和禁食。我将通过两个目的来检验这一假设：1）使用新的精度 遗传小鼠模型来定义肝胰岛素信号对MTORC1的作用，在其中我将产生和 用MTORC1信号传导与胰岛素调节断开的MTORC1信号的表征， 2）确定胰高血糖素介导的MTORC1的生理意义和机制 抑制作用，在其中我将确定胰高血糖素是否需要肝MTORC1抑制 在禁食期间，并评估连接胰高血糖素和MTORC1信号的潜在下游介质 在原发性肝细胞中。提出的实验有可能识别慢性的目标见解 代谢疾病中的MTORC1激活。该研究将在布伦丹·曼宁博士的实验室进行 哈佛T.H.陈公共卫生学院。曼宁博士是MTORC1领域的专家，并且有广泛的 胰岛素-PI3K-AKT信号传导的知识。此外，许多提出的方法和鼠标模型是 已经在实验室中建立。