SIRT1对自噬溶酶体形成的调控效应在非酒精性脂肪肝中的作用

Autophagy is a ubiquitous pathway for mobilization of cellular lipid droplets. The level of SIRT1 and autolysosome generation is decreased during the development of Non Alcoholic Fatty Liver Disease (NAFLD), but the interaction mechanism between SIRT1 and autolysosome formation has not been clarified yet. The latest studies showed that SIRT1 alleviates NAFLD through regulation of autophagy. Our preliminary results indicated that overexpression of SIRT1 could restore the flow of autophagy dysfunction caused by lipid overload. Therefore, this project hypothesizes that it is through the regulation of autolysosome formation that SIRT1 affects the development of NAFLD. Zebrafish shows the exactly similar features with human in lipid metabolism and molecular signaling. Moreover, the advantages of high throughput and methodology make zebrafish a powerful tool to study lipid metabolic diseases in recent years. In this study, we will introduce zebrafish NAFLD model to observe the formation of autolysosome in pathological processes with different developmental stages and detect interactions between SIRT1 and the signaling pathways of autolysosome formation. For further study, hepatic SIRT1 overexpression is going to be employed to investigate the role of SIRT1 in the regulation of autolysosome formation in NAFLD. SIRT1-autolysosome formation pathways would offer a new idea for autophagy being involved in NAFLD and may provide novel therapeutic strategies for prevention of NAFLD.

自噬是重要的肝脏脂质降解途径。非酒精性脂肪肝(NAFLD)中，SIRT1水平下降、自噬溶酶体生成减少。研究表明，SIRT1能调控自噬水平改善NAFLD，课题组前期结果显示过表达SIRT1能恢复脂质过载导致的自噬流损伤，但SIRT1与自噬溶酶体形成的关系及其发生机制尚不清楚。因此本课题假设：SIRT1通过调控自噬溶酶体形成影响NAFLD的发展。斑马鱼的脂代谢特征和分子信号与人类高度相似，已成为近年来研究脂代谢相关疾病的有力工具。本课题拟利用斑马鱼建立NAFLD模型，观察不同发育时期、病理进程对自噬溶酶体形成的影响，并探索SIRT1与自噬溶酶体形成相关通路的交互作用。通过肝特异性调节SIRT1表达，进一步研究SIRT1调控自噬溶酶体形成在NAFLD中的作用，包括病理标志物的变化。本项目从新的视角，即SIRT1-自噬溶酶体形成途径阐述自噬参与NAFLD的新机制，为防治NAFLD提供新策略。

自噬是细胞维持自身稳态的重要功能。特异性降解脂质的自噬过程—脂噬是细胞降解脂质的主要途径之一。自噬过程中的自噬体形成以及自噬体-溶酶体融合两方面均至关重要。该功能在肝细胞脂质过量堆积时受损，NAFLD病人表现出肝细胞自噬体形成减少，自噬体-溶酶体融合抑制。本项目旨在研究SIRT1调节自噬体-溶酶体融合的机制及其在NAFLD中的作用。在本项目中，我们首先建立了斑马鱼NAFLD模型，利用RNA-seq，激光共聚焦拉曼成像和三维荧光成像技术展示了斑马鱼NAFLD模型的分子特征，发现了不同饮食诱导的斑马鱼NAFLD模型分子差异；我们发现去乙酰化酶SIRT1可通过Rab7蛋白调节自噬体-溶酶体融合，从而促进脂质分解，其机制与SIRT1影响Rab7蛋白稳定性相关。在非酒精性脂肪肝模型体内外模型中，促进SIRT1活性可以减少肝细胞内脂质堆积，且该作用需要Rab7参与。因此，靶向SIRT1-Rab7途径的药理性调节可能成为治疗NAFLD的新策略。基于该途径可以寻找潜在的防治NAFLD的药物靶点。