The Role of FoxO1 in the Regulation of the Adipocyte Browning Response

FoxO1 在脂肪细胞褐变反应调节中的作用

• 批准号: 8913161
• 负责人: Joshua Robert Cook
• 金额: $ 4.43万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8913161
• 关键词: Adipocytes; Adipose tissue; Adult; Adverse effects; Animals; Biochemical; Biological Assay; Biometry; Body Composition; Body Temperature; Body Weight; Body Weight decreased; Brown Fat; Burn injury; Cardiovascular Diseases; Cell Line; Cells; Data; Development; Diet; Disease; Eating; Exposure to; FDA approved; Fatty acid glycerol esters; Gene Expression; Genes; Glucose tolerance test; Goals; Health; Heating; Histologic; Hour; Human; In Vitro; Insulin; Insulin Resistance; Knock-out; Knowledge; Laboratories; Left; Link; Lipids; Medical; Metabolic; Metabolic Diseases; Methods; Modeling; Mus; Non-Insulin-Dependent Diabetes Mellitus; Obesity; Organ; Phenotype; Physiological; Prevalence; Process; Protocols documentation; Public Health; Publishing; Regulation; Role; Scientist; Signal Pathway; Temperature; Testing; Therapeutic Agents; Time; Weight; combat; experience; feeding; improved; in vivo; insulin sensitivity; insulin tolerance; interest; mouse model; novel; novel strategies; novel therapeutics; obesity treatment; overexpression; oxidation; practical application; research study; response; targeted treatment; transcription factor

DESCRIPTION (provided by applicant): The rising tide of obesity represents a public health crisis due to its strong association with panoply of disease conditions, notably including insulin resistance leading to type 2 diabetes. Although the mechanism linking obesity and insulin resistance remain controversial, an attractive hypothesis posits that the excess lipid of obesity strains the handling capacity of adipocytes, which then, through various proposed mechanisms, foments insulin resistance. The idea of harnessing the ability of the adipocyte to burn off its own surplus lipid has gained popularity in recent years due to a renewed interest in the study of brown adipose tissue in adults as well as the finding that white adipose tissue can undergo "browning" changes. The proposed project seeks to establish a better understanding of the role of key insulin-responsive transcription factor FoxO1 in the regulation of adipocyte browning. I have already found in a brown-adipocyte cell line as well as in cultured white primary adipocytes that overexpression of FoxO1 selectively represses the expression of "brown" genes - those necessary for engaging in thermo genic lipid oxidation - while leaving unaffected "pan-adipocyte" genes. In order to determine whether these observations hold up in vivo and their potential medical applications, I have generated mice lacking FoxO1 specifically in adipocytes, termed the "A-FoxO1" model. I therefore describe in this proposal two Specific Aims centering on the characterization of the A-FoxO1 model. First, I propose a thorough metabolic phenotyping of the A-FoxO1 mouse, including biometrics (e.g., body weight, body composition, adipose-tissue depot weights) and assays of insulin sensitivity at both the levels of whole-body (e.g., glucose tolerance testing, insulin tolerance testing) and the cell (e.g., activation of insuin signaling pathway components). Next, I will test the adipocyte browning response in A-FoxO1 mice by subjecting animals to cold (4°C), room temperature (22°C), or thermo neutrality (30°C) for various time periods and then performing gene-expression and histologic analyses of white and brown adipose tissue depots. A potentially differential browning response in the absence of FoxO1 suggests a potential application to diet-induced obesity. I will therefore perform the temperature exposure experiments again following high- fat feeding of A-FoxO1 and WT mice and determine whether A-FoxO1 mice differ significantly in their sensitivity to insulin. Particulary of interest is a potential difference in insulin sensitivity that manifests even at room temperatur, suggesting a practical application to human obesity. Finally, I will isolate and culture both A-FoxO1 and WT primary preadipocytes ex vivo in order to perform detailed biochemical and cell- biologic studies of the mechanism underlying the putative regulation of adipocyte browning by FoxO1. These studies represent a set of challenging but reasonable goals that will not only contribute significantly to my development as a scientist but may also prove valuable in the continuing struggle against obesity

描述（由申请人提供）：肥胖率的上升代表着一场公共健康危机，因为它与多种疾病状况密切相关，特别是包括导致 2 型糖尿病的胰岛素抵抗。尽管肥胖和胰岛素抵抗之间的联系机制仍然存在争议，但一个有吸引力的假设认为，肥胖引起的过量脂质会影响脂肪细胞的处理能力，然后通过各种拟议的机制，引发胰岛素抵抗。利用脂肪细胞燃烧自身能力的想法 近年来，由于人们对成人棕色脂肪组织的研究重新产生兴趣，以及发现白色脂肪组织会发生“褐变”变化，多余的脂质越来越受欢迎。该项目旨在更好地了解关键胰岛素反应转录因子 FoxO1 在脂肪细胞褐变调节中的作用。我已经在棕色脂肪细胞系以及培养的白色原代脂肪细胞中发现，FoxO1 的过度表达选择性抑制“棕色”基因（参与产热脂质氧化所必需的基因）的表达，同时留下不受影响的“泛脂肪细胞”基因。为了确定这些观察结果在体内是否成立及其潜在的医学应用，我培育了脂肪细胞中特别缺乏 FoxO1 的小鼠，称为“A-FoxO1”模型。因此，我在本提案中描述了两个以 A-FoxO1 模型特征为中心的具体目标。首先，我建议对 A-FoxO1 小鼠进行彻底的代谢表型分析，包括生物测定（例如体重、身体成分、脂肪组织库重量）以及全身水平（例如葡萄糖耐量测试、胰岛素耐量测试）和细胞水平（例如胰岛素信号通路成分的激活）的胰岛素敏感性测定。接下来，我将通过将动物置于寒冷 (4°C)、室温 (22°C) 或热中性 (30°C) 不同的时间段，然后对白色和棕色脂肪组织库进行基因表达和组织学分析，来测试 A-FoxO1 小鼠的脂肪细胞褐变反应。在缺乏 FoxO1 的情况下，潜在的不同褐变反应表明其可能应用于饮食引起的肥胖。因此，我将在高脂喂养 A-FoxO1 和 WT 小鼠后再次进行温度暴露实验，以确定 A-FoxO1 小鼠对胰岛素的敏感性是否存在显着差异。特别令人感兴趣的是胰岛素敏感性的潜在差异，即使在室温下也会表现出来，这表明其在人类肥胖方面的实际应用。最后，我将离体分离和培养 A-FoxO1 和 WT 原代前脂肪细胞，以便对 FoxO1 假定的脂肪细胞褐变调节机制进行详细的生化和细胞生物学研究。这些研究代表了一系列具有挑战性但合理的目标，这些目标不仅对我作为科学家的发展做出了重大贡献，而且在与肥胖的持续斗争中也可能被证明是有价值的