Endoplasmic Reticulum Chaperone as a Regulator of Obesity and Diabetes

内质网伴侣作为肥胖和糖尿病的调节剂

• 批准号: 7896679
• 负责人: AMY S LEE
• 金额: $ 37.93万
• 依托单位: UNIVERSITY OF SOUTHERN CALIFORNIA
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-20 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7896679
• 关键词: Adipocytes; Adipose tissue; Affect; Alleles; Apoptotic; Binding; Body Composition; Body Weight; Breeding; Calnexin; Cell Culture Techniques; Cells; Chemicals; Chronic; Chronic stress; Data; Development; Diabetes Mellitus; Diabetic mouse; Diet; Disease; Eating; Employee Strikes; Endoplasmic Reticulum; Energy Metabolism; Euglycemic Clamping; Exhibits; Fatty acid glycerol esters; Foundations; Future; GRP78 gene; GRP94; Gene Proteins; Genetic; Genetic Models; Glucose; Glucose Clamp; Health; Homeostasis; Hormones; Human; Hyperglycemia; Immunoglobulin binding proteins; In Vitro; Incidence; Inflammation; Inflammatory; Inflammatory Response; Insulin; Insulin Resistance; Insulin Signaling Pathway; Knock-out; Laboratories; Lead; Leptin; Link; Lipids; Maintenance; Measurement; Measures; Membrane; Membrane Proteins; Metabolic; Metabolic Diseases; Metabolism; Mitochondria; Molecular; Molecular Chaperones; Molecular Weight; Mouse Strains; Mus; Mutant Strains Mice; Mutation; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Obesity; Organ; Organelles; Peripheral; Phenotype; Physical activity; Process; Protein Conformation; Protein Disulfide Isomerase; Proteins; Regulatory Pathway; Resistance; Role; Serum; Signal Pathway; Signal Transduction; Skeletal Muscle; Stimulus; Stress; System; Testing; Therapeutic Intervention; Tissues; Up-Regulation; Wild Type Mouse; absorption; attenuation; awake; base; blood glucose regulation; body system; calreticulin; clinically relevant; cytokine; endoplasmic reticulum stress; energy balance; feeding; glucose metabolism; glucose uptake; glucose-regulated proteins; improved; in vivo; insulin sensitivity; insulin signaling; lipid metabolism; mouse model; mutant; new therapeutic target; novel; overexpression; oxidation; prevent; protein degradation; protein folding; public health relevance; research study; response; sensor; trafficking

DESCRIPTION (provided by applicant): The endoplasmic reticulum (ER) is a cellular organelle where secretory and membrane-associated proteins are synthesized and modified. It has been proposed that obesity promotes nutrient stress and chronic inflammation that involve increased demand on the synthetic machinery of the cells in many secretory organ systems, such as adipose tissue. Thus, obesity acts as a chronic stimulus for ER stress in peripheral tissues, triggering insulin resistance and type 2 diabetes. The multifunctional ER chaperone protein GRP78/BiP, is a master regulator of ER homeostasis due to its control of protein folding and the activation of trans-membrane ER stress sensors. Serendipitously, we discovered that the Grp78 mice in the C57BL/6 background exhibit resistance to high-fat diet (HFD)-induced obesity and improved insulin sensitivity. Our preliminary studies revealed that HFD-fed Grp78 mice showed increased energy expenditure without changes in food intake and lipid absorption. Preliminary euglycemic clamp studies showed a striking increase in insulin-stimulated glucose uptake most prominently in the white adipose tissue of the Grp78 mice (P<0.001). We further discovered that in adipose tissue, Grp78 heterozygosity leads to diet-induced upregulation of ER chaperones. In contrast, glucose metabolism was not altered in skeletal muscle and no chaperone upregulation was observed. Thus, Grp78 mice offer new opportunities to investigate the basic mechanisms linking ER integrity to energy balance, glucose homeostasis and adipocyte stress. We propose that during chronic stress induced by HFD, Grp78 heterozygosity in adipose tissue triggers compensatory and protective measures, such as upregulation of chaperones and increase in mitochondrial function, which lead to enhanced energy expenditure, attenuation of ER stress and inflammatory responses resulting in improved insulin sensitivity. Based on our preliminary data that the Grp78mice are more insulin sensitive than the wild-type littermates on chow diet with similar body weights, Aim 1 will identify the mechanism by which Grp78 improves insulin sensitivity. Aim 2 will determine how obesity affects the unfolded protein response signaling and how Grp78 heterozygosity alters energy expenditure and causes resistance to diet-induced obesity. Aim 3 will generate and characterize mouse models with white adipose tissue-specific overexpression or knockout of GRP78 to determine its role in energy balance and insulin sensitivity. Aim 4 will determine the functional contribution of other ER chaperones upregulated in adipose tissue of HFD-fed Grp78 mice in adipocyte metabolic function, utilizing primary adipocytes and MEFs from the Grp78 and mice, as well as the 3T3-L1 adipocyte culture system. The clinical relevance of our studies is that they may identify novel regulatory pathways for diet- induced obesity and insulin resistance which may represent new therapeutic targets for human metabolic diseases. PUBLIC HEALTH RELEVANCE: The dramatic increase in the incidence of obesity, insulin resistance and type 2 diabetes has become one of the most serious threats to human health. Hence, understanding the molecular mechanisms underlying these diseases is critical. This proposal is based on the serendipitous observation from a novel mouse model recently created in the laboratory that may provide clues to prevent high-fat diet-induced obesity and subsequent insulin resistance. This proposal will fully characterize the metabolic phenotypes of the mutant mice and investigate the underlying mechanisms for increased energy expenditure and improved insulin sensitivity of these mice under the chronic stress of high-fat diet. If validated, our findings may lead to new targets for therapy against obesity and type 2 diabetes in humans.

描述（由申请人提供）：内质网（ER）是一种细胞器，分泌和膜相关蛋白在其中合成和修饰。有人提出，肥胖会促进营养应激和慢性炎症，这涉及对许多分泌器官系统（例如脂肪组织）中细胞合成机制的需求增加。因此，肥胖是外周组织ER应激的慢性刺激，引发胰岛素抵抗和2型糖尿病。多功能ER伴侣蛋白GRP 78/BiP由于其控制蛋白质折叠和跨膜ER应激传感器的激活而成为ER稳态的主要调节剂。偶然地，我们发现C57 BL/6背景中的Grp 78小鼠表现出对高脂饮食（HFD）诱导的肥胖的抗性和改善的胰岛素敏感性。我们的初步研究表明，HFD喂养的Grp 78小鼠显示出增加的能量消耗，而食物摄入和脂质吸收没有变化。初步的正葡萄糖钳夹研究显示，在Grp 78小鼠的白色脂肪组织中，胰岛素刺激的葡萄糖摄取显著增加（P<0.001）。我们进一步发现，在脂肪组织中，Grp 78杂合性导致饮食诱导的ER伴侣上调。与此相反，葡萄糖代谢没有改变骨骼肌和没有伴侣上调观察。因此，Grp 78小鼠为研究ER完整性与能量平衡、葡萄糖稳态和脂肪细胞应激的基本机制提供了新的机会。我们认为，在HFD诱导的慢性应激过程中，脂肪组织中的Grp 78杂合性触发了补偿和保护措施，如分子伴侣的上调和线粒体功能的增加，这导致能量消耗增加，ER应激和炎症反应的减弱，从而改善胰岛素敏感性。基于我们的初步数据，即Grp 78小鼠比具有相似体重的食物饮食的野生型同窝小鼠更胰岛素敏感，目的1将鉴定Grp 78改善胰岛素敏感性的机制。目的2将确定肥胖如何影响未折叠蛋白反应信号，以及Grp 78杂合性如何改变能量消耗并导致对饮食诱导的肥胖的抵抗。目的3将产生和表征具有白色脂肪组织特异性过表达或GRP 78敲除的小鼠模型，以确定其在能量平衡和胰岛素敏感性中的作用。目的4将利用来自Grp 78和小鼠的原代脂肪细胞和MEF，以及3 T3-L1脂肪细胞培养系统，确定HFD喂养的Grp 78小鼠的脂肪组织中上调的其他ER分子伴侣在脂肪细胞代谢功能中的功能贡献。我们的研究的临床相关性在于，它们可以确定饮食诱导的肥胖和胰岛素抵抗的新的调节途径，这可能代表人类代谢疾病的新的治疗靶点。公共卫生相关性：肥胖、胰岛素抵抗和2型糖尿病发病率的急剧增加已成为人类健康最严重的威胁之一。因此，了解这些疾病的分子机制至关重要。这项提议是基于最近在实验室中创建的一种新型小鼠模型的偶然观察，该模型可能为预防高脂饮食诱导的肥胖和随后的胰岛素抵抗提供线索。该提案将充分表征突变小鼠的代谢表型，并研究这些小鼠在高脂饮食慢性应激下增加能量消耗和改善胰岛素敏感性的潜在机制。如果得到验证，我们的研究结果可能会为人类肥胖和2型糖尿病的治疗带来新的靶点。