Lipid Binding in Obesity/Diabetes Syndromes

描述（由申请人提供）：代谢综合征将内脏脂肪组织的积累与高脂血症、胰岛素敏感性受损、血栓形成易感性、炎症和内皮功能受损联系起来，导致2型糖尿病、心血管疾病和高血压的风险增加。各种分子和生理研究已经确定细胞内游离脂肪酸（FFA）是关键代谢产物，将脂质代谢与信号转导、胰岛素抵抗、炎症和脂肪细胞因子的产生联系起来。脂肪酸结合蛋白（FABP）是细胞内FFA受体，在脂肪细胞和巨噬细胞中高水平表达。脂肪细胞高水平表达脂肪细胞FABP (AFABP/aP2)，低水平表达上皮细胞FABP （EFABP/mal1）。相比之下，巨噬细胞表达较高水平的EFABP/mal1和较低水平的AFABP/aP2。当被喂食高脂肪食物时，FABP基因敲除小鼠（缺乏AFABP/aP2或EFABP/mal1）表现出代谢综合征的减弱特征，包括TNF α降低、脂联素表达增加、胰岛素敏感性提高、NF-kB激活降低和动脉粥样硬化潜力降低。相比之下，脂肪组织中过表达FABP的小鼠表现出代谢综合征的增强特征，包括胰岛素抵抗加剧，脂联素分泌减少，心脏组织脂质积累。本应用的重点是细胞内FABP水平的变化如何导致代谢综合征特征的减弱或增强的机制基础。我们假设FABPs作为细胞内受体，作为FFA的传感器，介导炎症和激素信号通路在肥胖相关的胰岛素抵抗中失调。这种调节是通过holo-FABPs（配体结合形式）和靶蛋白（包括JAK2和IKK β）之间的蛋白质相互作用介导的。为了验证这一假设，我们提出：A.确定定义fabp靶蛋白相互作用的结构参数。

DESCRIPTION (provided by applicant): The metabolic syndrome links accumulation of visceral adipose tissue to hyperlipidemia, impaired insulin sensitivity, susceptibility to thrombosis, inflammation, and impaired endothelial function resulting in increased risk for type 2 diabetes, cardiovascular disease and hypertension. A variety of molecular and physiological studies have identified intracellular free fatty acids (FFA) as key metabolites, linking lipid metabolism to signal transduction, insulin resistance, inflammation and adipocytokine production. Fatty acid binding proteins (FABP) are intracellular FFA receptors found expressed to high levels in adipocytes and macrophages. Adipocytes express high levels of Adipocyte FABP (AFABP/aP2) and low levels of Epithelial FABP (EFABP/mal1). In contrast, macrophages express higher levels of EFABP/mal1 and low levels of AFABP/aP2. When placed on high fat diets, FABP knockout mice (devoid of either AFABP/aP2 or EFABP/mal1) exhibit attenuated characteristics of the metabolic syndrome including reduced TNF alpha and increased adiponectin expression, improved insulin sensitivity, decreased NF-kB activation and atherogenic potential. In contrast, mice overexpressing FABP in adipose tissue exhibit potentiated characteristics of the metabolic syndrome included exacerbated insulin resistance, decreased adiponectin secretion, and accumulation of lipids in cardiac tissue. The focus of this application is on the mechanistic basis for how changes in the FABP level within the cell leads to attenuated or potentiated characteristics of the metabolic syndrome. We hypothesize that FABPs serve as intracellular receptors that function as sensors for FFA and mediate inflammatory and hormonal signaling pathways dysregulated in obesity linked insulin resistance. Such regulation is mediated via protein-protein interactions between holo-FABPs (ligand bound forms) and target proteins including JAK2 and IKK beta. To test this hypothesis we propose to: A. Determine the structural parameters defining the FABP-target protein interactions. B. Assess the functional significance of the FABP-target protein interactions on signal transduction and metabolic process in adipocytes and macrophages. C. Evaluate the role of FABP-target protein interaction in vivo using transgenic mice.