Regulation and consequences of hepatic lipid droplet catabolism

项目总结 非酒精性脂肪性肝病(NAFLD)是全球最常见的肝病，与 大量的代谢性疾病。脂滴是细胞内的主要储存细胞器 三酰甘油(TAG)和，因此，是NAFLD的定义特征。与历史观点不同的是 LDS仅仅是一种惰性的能量储存形式，最近的研究已经确定LDS是重要的细胞器， 除了调节TAG的含量和周转外，还影响细胞功能和信号转导。给定 非酒精性脂肪肝的流行及其在世界范围内的巨大负担，了解管理酒精性脂肪肝的机制 如果我们的目标是发展到有效的饮食、生活方式或药物治疗，新陈代谢是最重要的 瞄准非酒精性脂肪肝及其并发症。此应用程序将以我们实验室的最新发现为基础 关于脂肪甘油三酯脂肪酶(ATGL)在肝脏能量代谢中的作用。我们出版的和 初步数据显示，ATGL是一种主要的肝脂酶，可以促进水解性脂肪酸的氧化 (Fas)，并将cAMP/PKA信号与sirtuin 1(SIRT1)介导的PGC-1a及其转录的诱导联系起来 结合伙伴(例如PPAR-a和FoxO1)。一旦被激活以响应ATGL，SIRT1将 自噬/脂噬，进而导致肝脏LDS的大量降解和随后的 FAs外流。基于这一数据，这项建议的目的是阐明生理和 溶酶体源性FAs吞噬和运输的机械调节。我们假设ATGL，VIA 油酸在细胞内的运输，激活SIRT1控制导致LD分解代谢的脂噬特定臂 溶酶体介导的FA外流。为了验证我们的假设，我们将进行以下具体目标：1) 研究ATGL和脂溢性/FA外流的生理调节及相互作用；2)确定 ATGL与SIRT1信号和脂噬诱导的联系机制；3)阐明ATGL的调控和 溶酶体介导的FA外流对肝脏能量代谢的影响。目标1将使用细胞，灌流 肝脏和小鼠模型，以表征生理因素如何调节吞脂性。AIM 2将同时使用两个单元格 和小鼠模型，解剖出将ATGL与自噬/脂噬调节联系起来的信号网络 和FA外排。目标3将重点放在溶酶体融合到质膜上作为治疗靶点来增加 吞脂性。这些研究具有创新性，因为它们将回答有关学习障碍监管的新问题 分解代谢和信号传递。这项工作具有重要意义，因为它促进了我们对定义 NAFLD的特点，将对实现以下目标产生积极和持久的影响 预防或治疗非酒精性脂肪性肝病及相关并发症。

PROJECT SUMMARY Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide and is tightly linked to numerous metabolic diseases. Lipid droplet (LDs) are the major storage organelles of intracellular triacylglycerol (TAG) and, therefore, are the defining characteristic of NAFLD. In contrast to historical views of LDs as simply inert forms of energy storage, recent studies have identified LDs as important organelles that influences cellular function and signaling in addition to the regulation of TAG content and turnover. Given the prevalence of NAFLD and its massive burden worldwide, understanding the mechanisms governing LD metabolism is paramount if we aim to progress to effective dietary, lifestyle or pharmaceutical therapies targeting NAFLD and its comorbidities. This application will build upon recent findings from our laboratory regarding the role of adipose triglyceride lipase (ATGL) in liver energy metabolism. Our published and preliminary data show that ATGL is a major hepatic lipase that promotes oxidation of hydrolyzed fatty acids (FAs) and links cAMP/PKA signaling to sirtuin 1 (SIRT1)-mediated induction of PGC-1a and its transcriptional binding partners (e.g. PPAR-a and FoxO1). Once activated in response to ATGL, SIRT1 promotes autophagy/lipophagy, which in turn is responsible for bulk degradation of hepatic LDs and the subsequent efflux of FAs. Based on this data, the objective of this proposal is to elucidate the physiological and mechanistic regulation of lipophagy and trafficking of lysosome-derived FAs. We hypothesize that ATGL, via intracellular trafficking of oleate, activates SIRT1 to control specific arms of lipophagy leading to LD catabolism and lysosomal-mediated FA efflux. To test our hypothesis, we will conduct the following specific aims: 1) to characterize the physiological regulation of and interplay between ATGL and lipophagy/FA efflux; 2) to define the mechanism linking ATGL to SIRT1 signaling and lipophagy induction; and 3) to elucidate the regulation and consequences of lysosomal-mediated FA efflux on hepatic energy metabolism. Aim 1 will employ cell, perfused liver and mouse models to characterize how physiological factors regulate lipophagy. Aim 2 will use both cell and mouse models to dissect out the signaling network linking ATGL to the regulation of autophagy/lipophagy and FA efflux. Aim 3 will focus on lysosome fusion to the plasma membrane as a therapeutic target to increase lipophagy. These studies are innovative in that they will answer novel questions about the regulation of LD catabolism and signaling. This work is significant because it advances our understanding of the defining characteristic of NAFLD (i.e. LDs), which will have a positive and sustained impact towards the goal of preventing or treating NAFLD and related comorbidities.