Role of the Interleukin12/STAT4 Pathway in Insulin Resistance and Atherosclerosis

描述(由申请人提供)：有证据表明，在内脏脂肪组织(AT)增加的状态下，免疫细胞激活和胰岛素抵抗(IR)之间存在重要联系。白介素12(IL-12)家族的细胞因子在细胞免疫反应和下游炎症基因诱导中具有重要作用。IL-12已被证明直接参与动脉粥样硬化的进展。信号转导和转录激活子4(STAT4)由IL-12激活，诱导动脉粥样硬化和代谢综合征中与炎症相关的几个主要基因的表达。中心假说是IL-12/Stat-4途径在内脏和主动脉周围脂肪组织IR的诱导中起关键作用，这将影响主动脉的免疫反应，进一步加速动脉粥样硬化。目的：1.研究IL-12/STAT4在造血细胞和非造血细胞中缺乏对肥胖诱导的胰岛素抵抗和脂肪组织炎症的保护作用机制。我们的假设是，STAT4缺乏通过改变脂肪组织中T细胞的丰度、表型和巨噬细胞极化，以及通过减少炎症和改善内脏脂肪细胞的胰岛素敏感性来预防饮食诱导的肥胖的IR。目的1.1：探讨IL-12或STAT4缺乏在体内造血室(T细胞、NK细胞)与非造血室(脂肪细胞)在胰岛素抵抗和肥胖发病中的作用。目的1.2：探讨IL-12/STAT4缺陷对体内外脂肪组织T细胞迁移、T细胞和巨噬细胞表型、极化和促炎细胞因子产生的影响。目的1.3：从机制上研究IL-12/STAT4缺乏对高脂饮食和细胞因子刺激下脂肪细胞葡萄糖摄取和胰岛素信号转导的作用。目的2.检测IL-12/Stat-4通路抑制对AT炎症相关动脉粥样硬化的影响。主动脉周围和内脏血管紧张素转换酶在脂肪组织相关动脉粥样硬化中的具体作用是什么？目的2.1：观察Stat-4缺乏对伴和不伴AT炎症的小鼠动脉粥样硬化的影响。采用糖尿病饮食(DD)诱导IR和DD加胆固醇(DDC)诱导AS和AT炎症。目的2.2：检测血管紧张素转换酶(AT)炎症、血管紧张素转换酶-4(STAT-4)缺乏对血管周围、内脏AT和主动脉内白细胞募集的影响。目的2.3：探讨血管紧张素转换酶炎症、血管紧张素转换酶4缺乏及血管紧张素转换酶炎症相关动脉粥样硬化对主动脉周围、内脏血管紧张素转换酶和主动脉局部免疫反应的影响。目的：探讨抑制IL-12对DDC饮食小鼠AT-炎症加速动脉粥样硬化Stat-4+/+和Stat-4缺乏模型的影响及其特异性。完成的项目应该确定一种创新的治疗目标，可能导致新的治疗方法，以减少与中心性肥胖、胰岛素抵抗和糖尿病相关的动脉粥样硬化。

DESCRIPTION (provided by applicant): Evidence suggests an important link between immune cell activation and insulin resistance (IR) in states associated with increases in visceral adipose tissue (AT). The interleukin-12 (IL-12) family of cytokines is particularly relevant given their importance in cell-mediated immune responses and downstream inflammatory gene induction. IL-12 has been shown to be directly involved in the progression of atherosclerosis. Signal transducer and activator of transcription 4 (STAT4), which is activated by IL-12, induces the expression of several major genes linked to inflammation in atherosclerosis and the metabolic syndrome. The central hypothesis is that IL-12/Stat-4 pathway plays a critical role in the induction of IR in visceral and peri-aortic adipose tissue and this will affect the immune response in aortas and further accelerate atherosclerosis. Aims to address this include: Aim 1. Determine mechanisms related to IL-12/STAT4 deficiency in hematopoetic and non-hematopoetic cells on protection against obesity induced insulin resistance, and adipose tissue inflammation. Our hypothesis is that STAT4 deficiency prevents IR in diet-induced obesity by changes in T cell abundance and phenotype and macrophage polarization in adipose tissue and by reducing inflammation and improving insulin sensitivity in visceral adipocytes. Aim 1.1: Determine the in vivo effect of IL-12 or STAT4 deficiency in the hematopoietic (T cells, NK cells) vs. non-hematopoetic compartment (adipocyte) for the development of IR and obesity. Aim 1.2: Determine role of IL-12/STAT4 deficiency on in vivo and in vitro T cell migration in adipose tissue, T cell and macrophage phenotype and polarization and production of pro-inflammatory cytokines. Aim 1.3: Mechanistically investigate functional roles of IL-12/STAT4 deficiency in adipocytes on glucose uptake and insulin signaling in response to high fat diet and cytokine stimulation. Aim 2. Determine effects of IL-12/Stat-4 pathway inhibition on AT inflammation-associated atherosclerosis. What is the specific role of peri-aortic and visceral AT in adipose tissue-related atherosclerosis? Aim 2.1: Examine effects of Stat-4 deficiency on atherosclerosis with and without AT inflammation in Stat -4-/- Ldlr-/- mice fed a diabetogenic diet (DD) to induce IR and DD with additional cholesterol (DDC) to induce atherosclerosis and AT inflammation. Aim 2.2: Test the effects of AT inflammation, Stat-4 deficiency on leukocyte recruitment into peri-aortic, visceral AT and aortas. Aim 2.3: Determine the involvement of AT inflammation, Stat-4 deficiency and the conditions of AT inflammation-related atherogenesis on local immune response in peri-aortic, visceral AT and aortas. Aim 2.4: Investigate effects and specificity of IL-12 inhibition on Stat-4+/+ and Stat-4 deficient model of AT- inflammation accelerated atherosclerosis in mice fed DDC diet. The completed project should identify an innovative therapeutic target that could lead to new treatment to reduce atherosclerosis associated with central obesity insulin resistance and diabetes.