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.

项目总结 雷帕霉素(MTOR)复合体1(MTORC1)活性的异常肝机制靶点与 肥胖和胰岛素抵抗。对调节mTORC1的生理输入和机制的洞察 需要肝脏中的信号才能理解肝脏mTORC1的调节是如何被破坏的 以及这如何导致胰岛素抵抗和代谢性疾病。MTORC1是细胞内的一种中枢调节因子 促进营养物质和生长因子的合成代谢过程的生长和增殖。在 肝脏，mTORC1活性对禁食和喂食期间的生理波动敏感，mTORC1活性降低 禁食时的信号和进食时mTORC1的急性诱导。MTORC1在体内的这种动态调节 在肥胖的啮齿动物中，肝脏被废除，突显了灵活的mTORC1信号对全身性 新陈代谢健康。这项研究的目标是确定肝脏中mTORC1的动态调节机制， 关注两个荷尔蒙线索。MTORC1的活性是由胰岛素诱导的，mTORC1信号和胰岛素都是如此 已被证明可以调节肝脏中的葡萄糖和脂肪代谢。胰岛素诱导的机制 MTORC1活性在细胞培养模型中得到了很好的证实。然而，目前尚不清楚胰岛素是如何调节的。 有助于在摄食时诱导肝脏中mTORC1的活性。相反，已发布的报告和我们的 初步数据表明，在原代肝细胞中，胰高血糖素抑制mTORC1信号转导。 胰高血糖素信号协调肝脏对禁食的适应性反应，肝脏mTORC1活动被阻断 多个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 而胰高血糖素是否在禁食期间对mTORC1的抑制起到了作用尚不清楚。我假设 血糖调节激素胰岛素和高血糖素参与肝脏mTORC1的动态调节 分别进食和禁食。我将通过两个目标来检验这一假设：1)使用新的精确度 遗传性小鼠模型，以确定肝脏胰岛素信号对mTORC1的作用，在该模型中，我将生成和 描述mTORC1信号与胰岛素调节脱节的小鼠，特别是在肝脏， 2)确定胰高血糖素介导的mTORC1的生理意义和机制 抑制，我将确定胰高血糖素是否是肝脏mTORC1抑制的必要条件和充分条件 在禁食期间，以及评估连接胰高血糖素和mTORC1信号的潜在下游介质 在原代肝细胞中。拟议中的实验有可能确定对慢性病的有针对性的见解 代谢性疾病中mTORC1的激活。这项研究将在布伦丹·曼宁博士的实验室进行 哈佛大学公共卫生学院。曼宁博士是mTORC1领域的专家，拥有广泛的 胰岛素-PI3K-Akt信号转导知识。此外，许多建议的方法和鼠标模型都是 已经在实验室建立了。