Interleukin-6 Expression and Function in Adipose Cells

脂肪细胞中 IL-6 的表达和功能

• 批准号: 6468798
• 负责人: Joyce B. Harp
• 金额: $ 30.07万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6468798
• 关键词: 3T3 cells; adipocytes; affinity chromatography; athymic mouse; autocrine; biological signal transduction; cell cycle proteins; cell differentiation; colony stimulating factor; corticosterone; disease /disorder model; enzyme linked immunosorbent assay; gene expression; gene targeting; genetically modified animals; glucose metabolism; growth factor receptors; human tissue; interleukin 6; laboratory mouse; ligands; lipid metabolism; messenger RNA; obesity; protein structure function; transcription factor; western blottings

Elevated interleukin-6 (IL-6) is associated with fat wasting in systemic infection and cancer cachexia. However, important new data indicates that circulating IL-6 is also elevated in human obesity, and adipose tissue is the principal source of this elevation. Because obesity is among the most prevalent public health challenges in the United States, it is important to understand IL-6 expression and function in adipose tissue, and to determine whether dysregulated expression of adipose tissue IL-6 is involved in the development of obesity and obesity-related co-morbidities. IL-6 traditionally signals through STAT3 activation, but in differentiating preadipocytes, IL-6 inhibits and STAT3 appears to be necessary for adipocyte formation. In this proposal we propose the following Specific Aims.. Aim 1: To determine mechanisms involved in IL-6-induced inhibition of adipogenesis. We hypothesize that greater than or equal to 10 ng/ml IL-6 inhibits the preadipocyte to adipocyte conversion by altering normal cell cycle progression and subsequent adipogenic transcription factor expression. We will determine in 3T3-L1 preadipocytes the effect of IL-6 on cell cycle progression and differentiation. Using chimeric GM-CSF- gp130 receptor transfections, the signaling mechanisms involved to transduce IL-6 effects will be explored. To explore the physiological relevance of IL-6 in adipose tissue, we will determine whether IL-6 knockout mice have altered adipose tissue growth, glucose, and lipid metabolism on normal and high fat diets. Aim 2: To characterize adipose tissue IL-6 expression in animal models of obesity. We find IL-6 mRNA is expressed in adipose tissue of lean mice, but it has been reported that obese db/db mice do not express IL-6 mRNA in adipose tissue. Since glucocorticoids repress IL-6 expression, we hypothesize that IL-6 expression is depressed in adipose tissue of ob/ob and db/db mice by high systemic corticosterone levels that are characteristic of these models of obesity. We also predict that IL-6 expression is elevated in adipose tissue of diet-induced obese (DIO) mice, similarly to obese humans. DIO mice retain normal corticosterone levels with the development of obesity. We will characterize IL- 6 expression in adipose tissue of lean control, DIO, ob/ob, and db/db all on a C57BL/6J background at baseline and in response to glucocorticoid agonists and antagonists, and thiazolidinediones. Aim 3: To identify the differentiation-induced STAT3 activating ligand. Our new pilot data indicate that IL-6 is not the autocrine factor responsible for MDI-induced STAT3 activation, but that the heparin binding ligand midkine (MK) is. In this Aim, we will confirm our preliminary studies, and determine whether midkine is the sole STAT3 activating ligand released upon MDI stimulation of 3T3-LI cells. Aim 4: To determine the role of STAT3 activation in adipogenesis. We hypothesize that activation of STAT3 is necessary for adipogenesis. We will block MDI-induced STAT3 activation by overexpression of PIAS3. Alternately, we will mimic STAT3 activation by overexpression of a constitutively active STAT3 to determine whether STAT3 activation alone is necessary and sufficient to induce adipogenesis. The role of STAT3 in fat pad formation will be investigated by implantation into the subcutaneous space of nude mice human preadipocytes that express vector, PIAS3, or constitutively active STAT3.

升高的白介素-6（IL-6）与全身感染和癌症恶病质中的脂肪浪费有关。 但是，重要的新数据表明，人类肥胖症中循环IL-6也升高，脂肪组织是该升高的主要来源。 由于肥胖症是美国最普遍的公共卫生挑战之一，因此了解IL-6的表达和功能在脂肪组织中的表达和功能很重要，并确定脂肪组织IL-6的失调表达是否参与肥胖和肥胖相关的共同体的发展。 IL-6传统上通过STAT3激活发出信号，但是在区分前脂肪细胞中，IL-6抑制和STAT3似乎是脂肪细胞形成所必需的。 在此提案中，我们提出以下特定目的。目标1：确定与IL-6诱导的脂肪形成抑制有关的机制。 我们假设这大于或等于10 ng/ml IL-6，通过改变正常的细胞周期进程和随后的脂肪生成转录因子的表达来抑制前脂肪细胞转化的脂肪细胞转化。 我们将在3T3-L1前细胞中确定IL-6对细胞周期进程和分化的影响。 使用嵌合GM-CSF-GP130受体转染，将探索涉及转导IL-6效应的信号传导机制。 为了探索IL-6在脂肪组织中的生理相关性，我们将确定IL-6基因敲除小鼠在正常和高脂肪饮食上是否改变了脂肪组织生长，葡萄糖和脂质代谢。 目标2：表征肥胖动物模型中脂肪组织IL-6表达。 我们发现IL-6 mRNA在瘦小鼠的脂肪组织中表达，但据报道肥胖的DB/db小鼠在脂肪组织中不表达IL-6 mRNA。 由于糖皮质激素抑制IL-6表达，因此我们假设IL-6表达在OB/OB和DB/DB小鼠的脂肪组织中抑制了这些肥胖模型的特征，这是OB/OB和DB/DB小鼠的脂肪组织。 我们还预测，与肥胖人类类似的饮食诱导的肥胖（DIO）小鼠的脂肪组织中IL-6的表达升高。 DIO小鼠随着肥胖的发展保留正常的皮质酮水平。 我们将在基线时在C57BL/6J背景上以及糖皮质激素激动剂和拮抗剂以及噻唑烷化的脂肪对照，dio，ob/ob和db/db的脂肪组织中的IL-6表达。目标3：确定分化诱导的STAT3激活配体。 我们的新试点数据表明，IL-6不是负责MDI诱导的STAT3激活的自分泌因素，而是肝素结合配体中心（MK）是。 在此目标中，我们将确认我们的初步研究，并确定Midkine是否是MDI刺激3T3-LI细胞后释放的唯一STAT3激活配体。 目标4：确定STAT3激活在脂肪形成中的作用。 我们假设STAT3的激活对于成生成是必要的。 我们将通过PIAS3的过表达来阻止MDI诱导的STAT3激活。另外，我们将通过过度表达组成型活性STAT3来模仿STAT3激活，以确定单独使用STAT3激活是否需要诱导脂肪形成。 STAT3在脂肪垫形成中的作用将通过植入裸小鼠的皮下空间进行研究，该裸鼠人类前体前脂肪细胞表达载体，PIAS3或组成性活性STAT3。