Role of ATGL in lipid droplet and nuclear lipidomes

非酒精性脂肪性肝病(NAFLD)由脂滴(LD)蓄积定义，是一种普遍存在的疾病，与肥胖、糖尿病和心血管疾病等多种代谢性疾病的病因有关。尽管TAG代谢的重要性以及对TAG合成途径的深入了解，但调节肝脏TAG水解的机制及其在疾病病因学中的作用尚不清楚。这一行政补充的目的是描述动态的肝脏LD和核脂体如何响应代谢刺激的变化，如高脂肪喂养、ATGL催化的脂解和B-肾上腺素能信号。我们假设和ATGL独一无二地改变LD和核脂体，ATGL产生的特定脂类参与Sirt1的调节和下游对细胞信号的影响。我们基于我们实验室的初步研究表明，ATGL诱导Sirt1活性以控制PGC1-A/PPAR-a信号，介导B-肾上腺素能信号对Sirt1/PGC1-a/PPAR-a信号的影响，并以Sirt1依赖的方式诱导线粒体生物发生和脂肪酸氧化。这项研究的基本原理是，识别LD和核脂体的变化将极大地促进我们对这些细胞器及其脂体在疾病病因学中的作用的理解，并可能有助于确定ATGL调节Sirt1的机制。这一假说将通过两个特定的目的进行验证：1)确定高脂喂养如何改变肝脏LD和核脂体，以及ATGL在改变这些变化中的重要性；2)确定LD和核脂体如何响应B-肾上腺素能信号的变化，以及ATGL/脂解在介导这些影响中的作用。在第一个目标下，我们将对对照组或ATGL shRNA饲喂对照组或高脂饮食3个月的小鼠的肝细胞核和LDS进行脂肪组学分析。第二个目的将描述B-肾上腺素能信号和ATGL的慢性(ShRNA)或急性(化学)抑制对原代小鼠肝细胞LD和核脂体的影响。这些研究具有创新性，因为它们将把脂肪组学的强大技术平台应用到LD生物学和细胞器特异性脂质组学这一未被充分研究的领域。这项建议的工作意义重大，因为它将进一步加深我们对LD积聚(即脂肪变性)、能量信号通路和NAFLD和2型糖尿病病因之间的联系的理解。

Non-alcoholic fatty liver disease (NAFLD), defined by lipid droplet (LD) accumulation, is a prevalent disorder that is involved in the etiology of numerous metabolic diseases including obesity, diabetes and cardiovascular disease. Despite the importance of TAG metabolism and the advancements into our understanding of the TAG synthetic pathway, the mechanisms regulating hepatic TAG hydrolysis and their effects on disease etiology are unknown. The objective of this administrative supplement is to characterize how the dynamic hepatic LD and nuclear lipidomes change in response to metabolic stimuli such as high fat feeding, ATGL-catalyzed lipolysis and B-adrenergic signaling. We hypothesis and ATGL uniquely alters LD and nuclear lipidomes and that specific lipid species generated by ATGL contribute to Sirt1 regulation and the downstream effects on cell signaling. We base this hypothesis on Preliminary Studies from our laboratory showing that ATGL induces Sirt1 activity to control PGC1-A/PPAR-a signaling, mediates the effects of B-adrenergic signaling on Sirt1/PGC1- a/PPAR-a signaling, and induces mitochondrial biogenesis and fatty acid oxidation in a Sirt1 dependent manner. The rationale for the proposed research is that identifying changes in LD and nuclear lipidomes will greatly advance our understanding of the contribution of these organelles and their lipidomes in disease etiology and may help identify the mechanism through which ATGL regulates Sirt1. The hypothesis will be tested using two specific aims: 1) to determine how high fat feeding alters the hepatic LD and nuclear lipidome and the importance of ATGL in altering these changes and 2) to determine how LD and nuclear lipidomes change in response to B-adrenergic signaling and the role of ATGL/lipolysis in mediating these effects. Under the first aim, we will perform lipidomic profiling of hepatic nuclei and LDs in mice treated with control or ATGL shRNA fed control or high fat diets for 3 months. The second aim will characterize the effects of B-adrenergic signaling and chronic (shRNA) or acute (chemical) inhibition of ATGL on the LD and nuclear lipidomes of primary mouse hepatocytes. These studies are innovative because they will employ the powerful technical platform of lipidomic profiling to the understudied area of LD biology and organelle-specific lipidomics. The proposes work is significant because it will further our understanding into the link between LD accumulation (i.e. steatosis), energy signaling pathways and the etiology of NAFLD and Type 2 Diabetes.