Post-Developmental Adipocyte Autophagy in Control of Insulin-Glucose Homeostasis

发育后脂肪细胞自噬控制胰岛素-葡萄糖稳态

• 批准号: 8733685
• 负责人: TIMOTHY E. GRAHAM
• 金额: $ 32.41万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-13 至 2018-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8733685
• 关键词: Adipocytes; Adipose tissue; Adult; Affect; Age; Animal Model; Area; Aurothioglucose; Autophagocytosis; Biogenesis; Biological Process; Body Composition; Body Weight; Cells; Cellular Stress; Communication; Death Rate; Development; Diet; Eating; Embryo; Embryonic Development; Exhibits; Fatty acid glycerol esters; Functional disorder; Genetic; Genetic Transcription; Genetically Engineered Mouse; Glucose; Glucose Intolerance; Glycogen; Glycolysis; Health; Homeostasis; Hypothalamic structure; Impairment; In Vitro; Infiltration; Inflammation; Insulin; Insulin Resistance; Islets of Langerhans; Knock-out; Knockout Mice; Life; Lipolysis; Liver; Measures; Mediating; Metabolic; Metabolic syndrome; Metabolism; Mitochondria; Modeling; Molecular; Multivesicular Body; Mus; Muscle; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Obesity; Organ; Pathogenesis; Pathway interactions; Phenotype; Play; Prevention; Production; Regulation; Reporting; Role; Signal Transduction; Skeletal Muscle; Stem cells; Stress; Structure of beta Cell of islet; Tamoxifen; Testing; Time; Time Study; Tissues; Tracer; Wild Type Mouse; Work; adipocyte biology; adipocyte differentiation; biological adaptation to stress; blood glucose regulation; feeding; glucose production; glucose transport; glucose uptake; glycogenolysis; in vivo; insulin secretion; insulin sensitivity; insulin signaling; late endosome; lipid biosynthesis; macrophage; mortality; mouse model; novel; oxidation; prevent; progenitor; public health relevance; response; trafficking; treatment strategy

DESCRIPTION (provided by applicant): Obesity, Metabolic Syndrome, and Type 2 diabetes are characterized by insulin resistance affecting multiple tissues (e.g., liver, muscle, and fat). Recent studies determined that intracellular autophagy plays an important role maintaining the metabolic health of tissues involved in the pathogenesis of insulin resistance. Autophagy is the intracellular lysosomal trafficking pathway that maintains energy homeostasis and counteracts multiple forms of cellular stress. In addition, autophagy is the sole mechanism for mitochondrial degradation and turnover in cells. Autophagy functions in skeletal muscle, liver, pancreatic beta cells, and hypothalamus to maintain insulin-glucose homeostasis; in addition, autophagy is required for lipolysis in liver. Prior studies examining the role of autophagy in adipose tissue utilized mouse models in which adipocyte autophagy was impaired during embryogenesis. These mice were lean and protected from diet-induced obesity, and exhibited enhanced insulin sensitivity and glucose intolerance. Such observations led to speculations that inhibiting autophagy in adipocytes might provide a promising strategy for treating or preventing obesity and its metabolic consequences. However, despite their apparently favorable metabolic phenotype, the mice with embryonic impairment of autophagy were not healthy: they exhibit increased rates of death (40% at 12 weeks of age) and inflammation and macrophage infiltration in adipose tissue. Due to the extreme alterations of adipocyte development and adipose tissue depot formation in these mice, they are not adequate models for assessing the post-developmental role of autophagy in the mature adipocyte. We hypothesize autophagy plays an important, protective function in mature adipocytes, and post-developmental impairment of adipocyte autophagy will induce intracellular stress and insulin-resistance via established signaling mechanisms; in addition, we predict "autophagic stress" will cause release of unique circulating factors from adipocytes that drive systemic insulin-resistance and glucose intolerance via direct effects on other organs (e.g., liver, muscle, and pancreatic beta cells). The Overall Objectives of this project are: (i) to determine the role of adipocyte autophagy in the pathogenesis of insulin-resistance and glucose intolerance in vivo by defining specific target tissues and molecular actions through which adipocyte autophagy regulates systemic metabolism in the adult; and (ii) to define the normal regulation and metabolic functions of autophagy in mature adipocytes, independently of the role of autophagy in adipocyte development/differentiation. We genetically engineered mice so that autophagy can be turned off in adulthood, after the developmental period of intense adipogenesis, via a tamoxifen- inducible genetic impairment. Preliminary findings with "mature adipocyte autophagy knockout mice" indicate autophagy does not regulate adiposity but is necessary for healthy insulin-glucose homeostasis. In the proposed work we will extend these observations to a systematic assessment of the tissue specific-mechanisms through which impairment of autophagy in mature adipocytes causes insulin resistance and glucose intolerance in mice in vivo (Aim #1); and we will make use of cultured primary adipocyte progenitor cells to study how the timing of autophagy impairment during adipogenesis influences the metabolic phenotype of adipocytes in vitro (Aim #2).

描述(申请人提供)：肥胖、代谢综合征和2型糖尿病的特征是胰岛素抵抗影响到多种组织(如肝脏、肌肉和脂肪)。最近的研究表明，细胞内自噬在维持胰岛素抵抗发病机制中的组织代谢健康方面起着重要作用。自噬是细胞内溶酶体的运输途径，维持能量平衡并抵消多种形式的细胞应激。此外，自噬是细胞内线粒体降解和周转的唯一机制。自噬在骨骼肌、肝脏、胰岛β细胞和下丘脑中发挥作用，以维持胰岛素-葡萄糖的动态平衡；此外，肝脏中的脂肪分解需要自噬。先前的研究利用脂肪细胞自噬在胚胎发育过程中受损的小鼠模型来研究自噬在脂肪组织中的作用。这些小鼠很瘦，不受饮食诱导的肥胖的影响，并表现出更高的胰岛素敏感性和葡萄糖耐量。这些观察结果导致人们猜测，抑制脂肪细胞的自噬可能会为治疗或预防肥胖及其代谢后果提供一种很有前途的策略。然而，尽管有明显有利的代谢表型，胚胎自噬受损的小鼠并不健康：它们表现出更高的死亡率(12周龄时为40%)以及脂肪组织中的炎症和巨噬细胞浸润。由于这些小鼠脂肪细胞发育和脂肪组织库形成的极端变化，它们不是评估自噬在成熟脂肪细胞发育后的作用的适当模型。我们假设自噬在成熟脂肪细胞中起着重要的保护作用，发育后的脂肪细胞自噬功能障碍将通过已建立的信号机制诱导细胞内应激和胰岛素抵抗；此外，我们预测“自噬应激”将导致脂肪细胞释放独特的循环因子，通过直接作用于其他器官(如肝脏、肌肉和胰腺β细胞)而导致全身胰岛素抵抗和葡萄糖耐受不良。本项目的总体目标是：(I)通过确定脂肪细胞自噬调节成人全身代谢的特定靶组织和分子作用，确定脂肪细胞自噬在体内胰岛素抵抗和糖耐量减低发病机制中的作用；(Ii)确定成熟脂肪细胞自噬的正常调节和代谢功能，独立于自噬在脂肪细胞发育/分化中的作用。我们对小鼠进行了基因改造，这样在成年后，在强烈脂肪生成的发育期之后，可以通过他莫昔芬诱导的遗传损伤来关闭自噬。“成熟脂肪细胞自噬基因敲除小鼠”的初步发现表明，自噬不能调节肥胖，但对健康的胰岛素-葡萄糖稳态是必要的。在拟议的工作中，我们将把这些观察扩展到组织特异性的评估-成熟脂肪细胞自噬受损导致体内小鼠胰岛素抵抗和葡萄糖耐受的机制(目标#1)；我们将利用培养的原代脂肪细胞前体细胞来研究脂肪形成过程中自噬受损的时间如何影响体外脂肪细胞的代谢表型(目标#2)。