Molecular mechanisms mediating metabolic benefits of glucagon-like peptide-1 receptor agonists

介导胰高血糖素样肽 1 受体激动剂代谢益处的分子机制

• 批准号: 10583838
• 负责人: Julio E Ayala
• 金额: $ 55.05万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-01 至 2026-11-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10583838
• 关键词: Adipocytes; Adrenergic Receptor; Affect; Agonist; Appetite Depressants; Assessment tool; Binding; Blood Glucose; Body Weight; Body Weight decreased; Brain; Cell physiology; Cells; Chinese Hamster Ovary Cell; Closure by clamp; Complex; Coupled; Cyclic AMP-Dependent Protein Kinases; Data; Development; Diabetes Mellitus; Dose; Drug Side Effects; Effectiveness; Energy Intake; Event; FRAP1 gene; Future; GLP-I receptor; Glucose; Glycolysis; Homeostasis; Human; Hyperglycemia; Hypothalamic structure; Hypoxia Inducible Factor; Impairment; Individual; Knock-in Mouse; Knowledge; Measures; Mediating; Metabolic; Molecular; Molecular Target; Morphology; Mus; Mutation; Neurons; Nutrient; Obesity; Outcome; Pancreas; Pathway interactions; Pharmaceutical Preparations; Phosphorylation; Physiological; Physiology; Predisposition; Pro-Opiomelanocortin; Proteins; Publishing; Receptor Activation; Receptor Signaling; Regulation; Resistance; Role; Signal Transduction; Test Result; Testing; Therapeutic; Therapeutic Effect; Treatment Efficacy; Variant; Weight; cardiometabolism; cell type; clinical effect; clinically relevant; design; detection of nutrient; drug action; energy balance; genetic regulatory protein; glucagon-like peptide 1; glucose tolerance; hypoxia inducible factor 1; improved; in vivo; insulin secretion; islet; liraglutide; metabolic phenotype; mouse model; mutant; novel; personalized medicine; protein activation; receptor; reduced food intake; response; sensor; temporal measurement; transcription factor

PROJECT SUMMARY Although the ability of glucagon-like peptide-1 receptor (Glp1r) agonists to stimulate insulin secretion and reduce caloric intake has been recognized for over two decades, surprisingly little is known about the molecular mechanisms behind these effects. We have previously shown that activation of the hypothalamic Glp1r reduces food intake by engaging key nutrient sensing mechanisms such as mechanistic Target of Rapamycin Complex-1 (mTORC1). Since mTORC1 is also an important regulatory component of -cell function, this suggests that elucidating how Glp1r agonists regulate mTORC1 and its downstream targets will address a key knowledge gap about the mechanism of action of an important class of diabetes and obesity drugs. We have identified a novel interaction stimulated by the clinically relevant Glp1r agonist liraglutide (Lira) whereby the canonical target of Glp1r signaling, cAMP-dependent protein kinase A (PKA), phosphorylates the mTORC1 regulatory protein Raptor resulting in increased mTORC1 signaling. We have also identified the transcription factor Hypoxia- Inducible Factor (HIF) as a target of Glp1r signaling. This is relevant since HIF stimulates glycolysis, a mechanism necessary for the anorectic and insulinotropic effects of Glp1r agonists, and increased HIF expression in the hypothalamus and -cells reduces food intake and stimulates insulin secretion, respectively. We also provide preliminary data showing that Lira no longer reduces body weight or glucose levels in novel knockin mice replacing endogenous Raptor with a PKA-resistant Raptor. Our preliminary data, therefore, lead us to hypothesize that a Glp1r-PKA-mTORC1-HIF-glycolysis axis in the hypothalamus and -cells mediates the ability of Lira to reduce body weight (Aim 1) and stimulate insulin secretion (Aim 2), respectively. The clinical relevance of this is further emphasized by our preliminary data showing that two variants of the Glp1r found in humans that are associated with improved cardiometabolic outcomes and improved responsiveness to Lira also stimulate mTORC1 signaling to a greater degree than wild-type Glp1r. We will, therefore, use mice expressing these human Glp1r variants to test the hypothesis that Lira promotes greater weight loss and improved glucose tolerance in these mice via enhanced mTORC1 signaling (Aim 3). We will complete these Aims by leveraging our extensive expertise in assessing metabolic phenotypes in mice, including real-time measurements of energy balance parameters as well as pancreatic function in isolated islets and in vivo using hyperglycemic clamps. We will apply these approaches to a suite of novel mouse models that allow us to modulate or measure the expression and activity of target proteins in specific cell types. Accomplishing these Aims will delineate specific molecular mechanisms that can be leveraged towards either the improvement of the effectiveness of Lira or the design of more efficient weight-lowering drugs.

项目摘要 尽管胰高血糖素样肽-1受体（Glp 1 r）激动剂刺激胰岛素分泌的能力 和减少热量摄入已经认识到了二十多年，令人惊讶的是， 这些效应背后的分子机制。我们以前已经证明，激活的 下丘脑Glp 1 r通过参与关键的营养感应机制， 雷帕霉素复合物-1（mTORC 1）的机制靶点。由于mTORC 1也是重要的 这表明阐明Glp 1 r激动剂如何调节β-细胞功能， mTORC 1及其下游靶点将解决有关作用机制的关键知识缺口 一类重要的糖尿病和肥胖症药物。我们发现了一种新的相互作用， 通过临床相关的Glp 1 r激动剂利拉鲁肽（里拉）， cAMP依赖性蛋白激酶A（PKA）磷酸化mTORC 1调节蛋白Raptor 导致mTORC 1信号传导增加。我们还鉴定了低氧转录因子- 诱导因子（HIF）作为Glp 1 r信号转导的靶点。这是相关的，因为HIF刺激糖酵解， Glp 1 r激动剂的厌食和促胰岛素作用所必需的机制，以及增加的HIF 下丘脑和胰岛细胞中的表达减少食物摄入并刺激胰岛素分泌， 分别我们还提供了初步数据，显示里拉不再减轻体重或 用PKA抗性Raptor替代内源性Raptor的新型敲入小鼠的葡萄糖水平。我们 因此，初步的数据使我们假设，Glp 1 r-PKA-mTORC 1-HIF-糖酵解轴可能与糖尿病相关。 下丘脑和视神经细胞介导里拉减轻体重（目的1）和刺激 胰岛素分泌（Aim 2）。我们的研究进一步强调了这一点的临床意义。 初步数据显示，在人类中发现的Glp 1 r的两种变体与 改善心脏代谢结局和改善对里拉的反应性也刺激mTORC 1 比野生型Glp 1 r更大程度的信号传导。因此，我们将使用表达这些人类基因的小鼠， Glp 1 r变体用于检验里拉促进更大的体重减轻和改善血糖的假设 通过增强的mTORC 1信号传导，这些小鼠中的耐受性（Aim 3）。我们将通过以下方式实现这些目标： 利用我们在评估小鼠代谢表型方面的广泛专业知识， 测量能量平衡参数以及分离的胰岛中的胰腺功能， 体内使用高血糖钳夹。我们将这些方法应用于一套新颖的小鼠模型 使我们能够调节或测量特定细胞类型中靶蛋白的表达和活性。 实现这些目标将描绘特定的分子机制，可以利用 要么提高里拉的有效性，要么设计更有效的减肥药物。