Lipid Binding Proteins in Obesity and Diabetes Syndromes

描述(申请人提供)：脂肪酸结合蛋白(FABP)是在脂肪细胞和巨噬细胞中高水平表达的细胞内游离脂肪酸受体。FABP结合多种未酯化脂肪酸和其他脂质第二信使，并调节它们的细胞内代谢。当给予高脂饮食时，FABP基因敲除小鼠表现出代谢综合征的特征，包括脂肪细胞脂解减少，肿瘤坏死因子减少，脂联素表达增加，改善胰岛素敏感性，降低核因子？B活性，防止哮喘和降低动脉粥样硬化能力。相比之下，在脂肪组织中过度表达FABP的小鼠表现出代谢综合征的强化特征，包括脂肪分解增加，胰岛素抵抗加剧，脂联素分泌减少，以及轻度心肌肥厚。脂肪细胞FABP降低的人(由AFABP/aP2启动子的多态性引起)显示出患高甘油三酯血症、2型糖尿病和心血管疾病的风险降低。在NIH DK053189的研究中，我们已经证明了脂肪组织的FABP是炎症性白三烯生物合成所必需的。由于LTA4是单核细胞募集因子LTB4和炎症性半胱氨酰白三烯(LTC4、LTD4和LTE4)的前体，FABP缺失小鼠和FABP缺失巨噬细胞系的脂肪组织中炎性二十烷类化合物的水平降低。用白三烯处理巨噬细胞后，iNOS和MCP1的表达增加，PPAR？此外，LTC4处理脂肪细胞后，Akt的磷酸化程度降低，葡萄糖转运减弱，而基础和Forsklin刺激的脂解作用增加。这些发现导致了这样的假设：来自饮食或脂肪细胞脂肪分解的脂肪酸刺激驻留的巨噬细胞，导致脂肪酸结合蛋白依赖的白三烯合成。LTC4和LTC4促进巨噬细胞炎症基因的表达和细胞因子的分泌，LTC4抑制胰岛素信号转导，改变脂肪因子的分泌，增加脂肪细胞的脂解作用。为了验证这一假设，我们提出了以下四个具体目标：1.利用细胞培养模型确定脂肪酸和脂肪酸结合蛋白在巨噬细胞白三烯生物合成中的作用。2.利用动物模型评价脂肪酸和脂肪酸结合蛋白在脂肪组织白三烯生物合成中的作用。3.评价FABPs与LTA4和LTA4代谢酶的相互作用。4.检测白三烯对巨噬细胞和脂肪细胞信号转导及细胞因子合成的影响。 与公共卫生相关：炎症是包括糖尿病、哮喘和过敏在内的各种代谢性疾病状态的共同主题。本申请中详述的工作描述了分析脂肪组织中依赖脂肪酸结合蛋白的炎性脂类的产生，并检验了白三烯在胰岛素抵抗的发展中起重要作用的假设。总之，这些研究为脂肪组织生物学、炎性脂类在调节胰岛素抵抗发展中的作用(S)以及确定分子治疗的新部位开辟了新的途径。

DESCRIPTION (provided by applicant): Fatty acid binding proteins (FABPS) are intracellular free fatty acid receptors found expressed at high levels in adipocytes and macrophages. FABPs bind a variety of unesterified fatty acids and other lipid second messengers and mediate their intracellular metabolism. When placed on high fat diets, FABP knockout mice exhibit attenuated characteristics of the metabolic syndrome including diminished adipocyte lipolysis, reduced TNF¿ and increased adiponectin expression, improved insulin sensitivity, decreased NF-?B activation, protection from asthma and diminished atherogenic capacity. In contrast, mice over-expressing FABP in adipose tissue exhibit potentiated characteristics of the metabolic syndrome included increased lipolysis, exacerbated insulin resistance, decreased adiponectin secretion, and mild cardiac hypertrophy. Humans with decreased adipocyte FABP (arising via a polymorphism in the AFABP/aP2 promoter) exhibit reduced risk for hypertriglyceridemia, type 2 diabetes and cardiovascular disease. In work carried out under NIH DK053189 we have demonstrated that the FABPs of adipose tissue are required for inflammatory leukotriene biosynthesis. Since LTA4 is a precursor to the monocyte recruitment factor LTB4 and the inflammatory cysteinyl leukotrienes (LTC4, LTD4 and LTE4), adipose tissue from FABP null mice and FABP null macrophage cell lines exhibit reduced levels of inflammatory eicosanoids. Treatment of macrophages with leukotrienes results in an increase in iNOS and MCP1 expression while decreasing PPAR?. Moreover, LTC4 treatment of adipocytes results in decreased phosphorylation of Akt and attenuated glucose transport while increasing basal and forskolin-stimulated lipolysis. These findings lead to the hypothesis that: fatty acids, either fro diet or from adipocyte lipolysis, stimulate resident macrophages resulting in fatty acid binding protein-dependent leukotriene synthesis. LTB4 and LTC4 promote inflammatory gene expression and cytokine secretion by macrophages, and LTC4 impairs insulin signaling, alters adipokine secretion and increases lipolysis in adipocytes. To test this hypothesis, we propose the following four specific aims: 1. Determine the role of fatty acids and fatty acid binding proteins in macrophage leukotriene biosynthesis using cell culture models. 2. Assess the role of fatty acids and fatty acid binding proteins in adipose tissue leukotriene biosynthesis using animal models. 3. Evaluate the interaction of FABPs with LTA4 and LTA4 metabolizing enzymes. 4. Examine the effects of leukotrienes on macrophage and adipocyte signal transduction and cytokine synthesis. PUBLIC HEALTH RELEVANCE: Inflammation is a common theme in a variety of metabolic disease states including diabetes, asthma and allergy. Work detailed in this application describes the analysis of fatty acid binding protein dependent production of inflammatory lipids in adipose tissue and tests the hypothesis that leukotrienes play a prominent role in the development of insulin resistance. The studies in sum open new avenues into the biology of adipose tissue, the role(s) of inflammatory lipids in mediating the development of insulin resistance and identification of new sites for molecular therapies.