Lipid Metabolism in Fat Cells

描述（由申请人提供）：肥胖是一种主要的健康问题，容易导致2型糖尿病和其他严重疾病。更全面地了解脂肪细胞如何调节脂肪合成，对于指导合理开发治疗肥胖及其并发症的新方法至关重要。在上一个资助期，我们证明了中链脂肪酸（辛酸盐）刺激β -氧化并抑制脂肪细胞中甘油三酯的合成，模拟了禁食的一些代谢作用。在用TNFalpha处理的脂肪细胞中发现了类似的抗脂肪生成作用。我们证明了三种应激源，体内禁食，辛酸盐和体外TNFalpha，诱导许多相同的细胞反应。其中包括活性氧（ROS）的产生增加，map -激酶（MAPK）和amp活化蛋白激酶（AMPK）的激活，核转录因子PPARgamma和相关脂肪生成基因的表达减少。鉴于这些发现，我们计划使用这三种压力源来操纵脂肪细胞中的脂肪生成，以剖析调节机制。我们假设关键信号（ROS或ROS无关）是由于β -氧化增加而产生的。这些信号分子激活应激反应激酶，使PPARgamma失活，减弱脂肪合成所需基因的表达。为了验证这一假设，我们提出以下具体目标：(1)确定ROS是否对脂肪生成的调节至关重要；(2)测试β -氧化的变化是否会产生导致PPARgamma失活的关键信号；(3)确定PPARgamma是否是控制应激诱导的抗脂作用的信号汇聚点，PPARgamma失活的机制是什么，以及哪些代谢基因对应激操作最敏感。每个目标都将通过细胞生物学和分子生物学的综合应用，结合代谢和生化方法，利用培养小鼠和人类脂肪细胞以及啮齿动物模型来解决。总之，这些研究将为应激诱导的脂肪细胞脂肪生成调控提供新的见解，这是调节能量平衡的潜在重要途径。

DESCRIPTION (provided by applicant): Obesity is a major health problem that predisposes to type 2 diabetes and other serious conditions. A more complete understanding of how fat synthesis is regulated in adipocytes is critical to guide rational development of new approaches for treating obesity and its complications. In the last grant period, we demonstrated that medium-chain fatty acids (octanoate) stimulate beta-oxidation and inhibit triglyceride synthesis in adipocytes, mimicking some of the metabolic effects of fasting. Analogous anti-lipogenic effects have been found in adipocytes treated with TNFalpha. We demonstrated that the three stressors, fasting in vivo, octanoate, and TNFalpha in vitro, induce many of the same cellular responses. These include increased generation of reactive oxidative species (ROS), activation of MAP-kinases (MAPK) and AMP-activated protein kinase (AMPK), and decreased expression of the nuclear transcription factor PPARgamma and associated lipogenic genes. In light of these findings, we plan to use these three stressors to manipulate lipogenesis in adipocytes to dissect mechanisms of regulation. We hypothesize that critical signals (ROS or ROS-independent) are generated as a result of increased beta-oxidation. These signaling molecules activate stress-responsive kinases, which inactivate PPARgamma, attenuating expression of genes necessary for fat synthesis. To test this hypothesis, we propose the following specific aims: (1) to determine whether ROS is crucial for regulation of lipogenesis; (2) to test if changes in beta-oxidation generate critical signals that cause inactivation of PPARgamma; and (3) to determine if PPARgamma is the point at which signals converge that control stress-induced anti-lipogenic effects, what is the mechanism of PPARgamma inactivation, and which metabolic genes are most sensitive to the stress manipulation. Each aim will be addressed with comprehensive and integrated application of cell biology and molecular biology in combination with metabolic and biochemical approaches, using culture murine and human adipocytes as well as rodent models. Together, these studies will provide new insights into the stress-induced regulation of lipogenesis in adipocytes, a potentially important avenue for modulating energy balance.