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.

项目概要 雷帕霉素 (mTOR) 复合物 1 (mTORC1) 活性异常的肝脏机制与 肥胖和胰岛素抵抗。深入了解调节 mTORC1 的生理输入和机制 为了了解肝脏 mTORC1 的调节如何被破坏，需要肝脏中的信号传导 以及这如何导致胰岛素抵抗和代谢疾病。 mTORC1 是细胞的中央调节因子 生长和增殖，促进响应营养物质和生长因子的合成代谢过程。在 肝脏中，mTORC1 活性对禁食和进食期间的生理波动敏感，mTORC1 降低 禁食期间的信号传导以及进食时 mTORC1 的急性诱导。 mTORC1 的这种动态调节 肥胖啮齿类动物的肝脏被废除，凸显了灵活的 mTORC1 信号传导对全身系统的重要性 代谢健康。本研究的目的是确定肝脏中 mTORC1 动态调节的机制， 关注两种荷尔蒙线索。 mTORC1 活性由胰岛素诱导，mTORC1 信号传导和胰岛素 已被证明可以调节肝脏中的葡萄糖和脂质代谢。胰岛素的诱导机制 mTORC1 活性在细胞培养模型中已得到证实。然而，尚不清楚胰岛素如何调节 有助于在进食时诱导肝脏中 mTORC1 活性。相反，已发表的报告和我们的 初步数据表明，原代肝细胞中的胰高血糖素可抑制 mTORC1 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，并且肝脏 mTORC1 活性阻断 多种胰高血糖素介导的代谢变化。然而，胰高血糖素抑制 mTORC1 的机制 禁食期间胰高血糖素是否有助于抑制 mTORC1 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 mTORC1 的动态调节 分别与喂养和禁食。我将通过两个目标来检验这个假设：1）使用新的精度 遗传小鼠模型来定义肝脏胰岛素信号传导至 mTORC1 的作用，在该模型中我将生成和 表征具有 mTORC1 信号传导的小鼠，该信号传导与肝脏中的胰岛素调节无关， 2)确定胰高血糖素介导的mTORC1的生理意义和机制 抑制，其中我将确定胰高血糖素对于肝脏 mTORC1 抑制是否是必要且充分的 禁食期间，以及评估连接胰高血糖素和 mTORC1 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对慢性病的有针对性的见解 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 哈佛大学 T.H.陈公共卫生学院。 Manning博士是mTORC1领域的专家，拥有广泛的研究成果 了解胰岛素-PI3K-Akt 信号传导。此外，许多提出的方法和小鼠模型都是 已经在实验室建立了。