Mechanism of Integrative Metabolic Regulation by Iron and Hypoxia

铁和缺氧综合代谢调节机制

• 批准号: 10004944
• 负责人: DONALD A. MCCLAIN
• 金额: --
• 依托单位: W G HEFNER VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-10-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10004944
• 关键词: Adipose tissue; Affect; Altitude; Beta Cell; Blood Donations; Blood Glucose; CREB1 gene; Cell Respiration; Cell physiology; Cells; Complex; Data; Dependence; Diabetes Mellitus; Diabetes prevention; Diet; Dietary Iron; EP300 gene; Elements; Enzymes; Exposure to; FOXO1A gene; FRAP1 gene; Fatty acid glycerol esters; Gene Activation; Genetic Transcription; Genus Hippocampus; Glucosamine; Glucose; Goals; Habits; Harvest; Health; Hepatic; Hexosamines; Homeostasis; Human; Hypoxia; Hypoxia Pathway; Impairment; Individual; Insulin; Insulin Resistance; Iron; Iron Overload; Leptin; Link; Mediating; Metabolic; Metabolic Pathway; Metabolism; Mitochondria; Mixed Function Oxygenases; Modification; Molecular; Mus; Non-Insulin-Dependent Diabetes Mellitus; Normal Range; Nutrient; Obesity; Oxidation-Reduction; Oxidative Stress; Oxygen; Pathogenesis; Pathologic; Pathway interactions; Pharmacology; Phosphorylation; Physiology; Post-Translational Protein Processing; Production; Proteins; Proteomics; Publishing; Regulation; Risk Factors; Sea; Signal Pathway; Signal Transduction; Signal Transduction Pathway; Sirtuins; Sum; System; Technology; Testing; Tissues; Transcriptional Regulation; Work; adiponectin; base; blood glucose regulation; detection of nutrient; diabetes mellitus therapy; glucose metabolism; glucose production; glycosylation; human tissue; insulin secretion; insulin sensitivity; islet; modifiable risk; mouse model; normoxia; novel; oxidant stress; oxidation; personalized medicine; pleiotropism; promoter; recruit; response; sensor; sugar; transcription factor; transcriptome sequencing

PROJECT SUMMARY Insulin resistance, excess hepatic glucose production, and impaired insulin secretion are the hallmarks of type 2 diabetes mellitus (T2DM), and tissue iron levels significantly affect all three. In mice and humans, we have shown that high iron impairs insulin secretion and down regulates leptin and adiponectin. Our preliminary data show further that these effects of iron are fuel-dependent, with much of this difference based on higher iron levels supporting higher levels of fat oxidation. Our mechanistic work on these effects of iron has revealed the involvement of numerous pathways, including transcriptional regulation (notably by CREB, FoxO1, and PGC1α) and nutrient/metabolite signaling (AMPK, sirtuins, and mTOR). Thus, the effects of iron are complex, pleiotropic, and cannot be explained by invoking a single linear signal transduction pathway. Recently our work on the mechanism by which iron regulates leptin secretion has revealed a unifying concept for these pleiotropic effects: High tissue iron down-regulates a central integrator of nutrient and redox status, the O-linked N-acetyl glucosamine (O-GlcNAc) pathway. This pathway results in the O-GlcNAc modification of most transcription factors and numerous enzymes that regulate metabolism. Activation of the pathway is often a direct readout of cellular nutrient fluxes, and we have shown it to be sufficient to induce changes in insulin sensitivity, insulin secretion, and hepatic glucose metabolism in ways that recapitulate T2DM. A second pathway that responds to both nutrient and oxidative stresses is the hypoxia-sensing pathway. Like the O-GlcNAc pathway, it functions at both ends of two metabolic spectra—low glucose and low oxygen as well as high glucose and oxidative stress. The pathways regulate one another and interact in determining hepatic glucose production, insulin sensitivity, and insulin secretion. Importantly, both the O- GlcNAc and hypoxia pathways are not only relevant to pathologic iron overload and hypoxia, but regulate metabolism in normal physiology, across the very broad range of “normal” iron and in individuals at sea level. In sum, the O-GlcNAc and hypoxia pathways cooperate to sense the availability or excess of two essential elements required for oxidative metabolism, iron and oxygen. Based on the above, our published work, and Preliminary Data, we therefore hypothesize that these two pathways integrate these signals to regulate several metabolic pathways involved in the pathogenesis of T2DM. Modulation of the O-GlcNAc pathway by iron affects numerous signal transduction pathways, leading to broad-based changes in metabolism that globally alter fuel utilization to confer adaptive responses to either a lack or excess of iron. In parallel, the hypoxia pathway performs a parallel function based on oxygen availability or excess oxidant stress. Crosstalk between the two pathways can amplify their effects, resulting in integration and a “fine-tuning” of metabolism based on nutrient availability, iron and oxygen levels, and oxidant stress. To test these hypotheses, we propose the following Specific Aims: 1. Determine the mechanism by which O-GlcNAc mediates the regulation of leptin secretion by iron. 2. Define the effects of dietary iron on β-cell function in mice, in normoxia and hypoxia. 3. Determine the mechanism for the effects of iron on O-GlcNAc protein modification. The significance and impact of these studies is that they aim to define ideal levels of tissue iron that may be narrower than the broad “normal” range in humans, and tissue iron is easily modifiable by diet or blood donation. Ideal iron levels may also differ based on oxygen status (i.e. in those with different habitation altitudes), ultimately allowing personalized therapy for diabetes in those individuals. Finally, the studies will also identify new pathways to treat diabetes: For example, the HIF hydroxylases can be pharmacologically manipulated, and advances are also being made in doing so for the O-GlcNAc pathway. !

项目概要 胰岛素抵抗、肝葡萄糖生成过多和胰岛素分泌受损是其标志 在小鼠和人类中，组织铁水平对 2 型糖尿病 (T2DM) 的影响显着。 我们的初步研究表明，高铁会损害胰岛素分泌并下调瘦素和脂联素。 数据进一步表明，铁的这些影响取决于燃料，其中大部分差异基于更高的 我们对铁的这些作用的机制研究揭示了铁水平支持更高水平的脂肪氧化。 许多途径的参与，包括转录调控（特别是 CREB、FoxO1 和 PGC1α）和营养/代谢物信号（AMPK、sirtuins 和 mTOR）因此，铁的作用是复杂的。 多效性，并且不能通过调用单个线性信号转导途径来解释。 最近，我们对铁调节瘦素分泌机制的研究揭示了一个统一的机制 这些多效性效应的概念：高组织铁下调营养和氧化还原的中央整合器 状态，O-连接的 N-乙酰氨基葡萄糖 (O-GlcNAc) 途径 该途径产生 O-GlcNAc。 大多数转录因子和许多调节代谢激活的酶的修饰。 途径通常是细胞营养通量的直接读数，我们已经证明它足以诱导 胰岛素敏感性、胰岛素分泌和肝葡萄糖代谢的变化概括如下 T2DM 响应营养和氧化应激的第二条途径是缺氧感知。 与 O-GlcNAc 途径一样，它在两个代谢谱的两端发挥作用——低葡萄糖和低葡萄糖。 氧以及高葡萄糖和氧化应激这些途径相互调节并相互作用。 确定肝葡萄糖产生、胰岛素敏感性和胰岛素分泌，重要的是，O-。 GlcNAc 和缺氧途径不仅与病理性铁超载和缺氧相关，而且还调节 正常生理代谢，跨越非常广泛的“正常”铁范围以及海平面个体的代谢。 总之，O-GlcNAc 和缺氧途径协同感知两种物质的可用性或过量。 基于上述，我们发表了氧化代谢所需的必需元素铁和氧。 工作和初步数据，因此我们认为这两条途径将这些信号整合到 调节参与 T2DM 发病机制的多种代谢途径。 铁途径影响许多信号转导途径，导致广泛的变化 新陈代谢会整体改变燃料利用率，从而对铁缺乏或过量做出适应性反应。 同时，缺氧途径根据氧气可用性或过量氧化剂执行并行功能 两条通路之间的串扰可以放大它们的影响，从而导致整合和“微调”。 基于营养可用性、铁和氧水平以及氧化应激来测试这些。 假设，我们提出以下具体目标： 1.确定O-GlcNAc介导铁调节瘦素分泌的机制。 2. 确定膳食铁在常氧和缺氧条件下对小鼠 β 细胞功能的影响。 3.确定铁对O-GlcNAc蛋白修饰影响的机制。 这些研究的意义和影响在于，它们的目的是确定组织铁的理想水平， 可能比人类广泛的“正常”范围更窄，并且组织铁很容易通过饮食或血液改变 理想的铁水平也可能因氧气状况而异（即居住地不同的人）。 海拔），最终允许对这些人进行糖尿病的个性化治疗。 还确定了治疗糖尿病的新途径：例如，HIF 羟化酶可以在药理学上 O-GlcNAc 途径的操作也取得了进展。 ！