自噬调控Sirt1/PGC-1α信号对肥胖症脂肪组织糖脂代谢的作用机制研究

Autophagic activity has been reported to be significantly elevated in adipose tissue of obesity, yet the therapeutic potential of decreasing adipose autophagic levels in obese and insulin-resistant adult mice, and the underlying mechanisms remain unclear. We found that suppression of autophagy in adipocytes was accompanied by increased expression of Sirt1 and PGC-1α protein, which are both key regulators of energy metabolism. Therefore, we proposed that the therapeutic potential of decreasing adipose autophagy against obesity-induced metabolic dysfunction might be achieved by Sirt1/PGC-1α dependent manner. To test this hypothesis, adipoq-CreER:Atg7flox/flox and Atg7flox/flox mice will be first fed a high fat diet for 8 weeks to induce obesity and insulin resistance, and then tamoxifen was administered to induce adipose specific deletion of Atg7. By using GTT、ITT、immunoblotting、immunofluorescence、transmission electron microscopy, etc., we will investigate the role of adipose-specific autophagy deficiency on histological characteristics of adipose, insulin sensitivity, adipogenesis, mitochondrial function, fatty acid β-oxidation at the onset of obesity. Then we will focus on the role of autophagy on regulating Sirt1/PGC-1α pathway in cells with over-expressed/defective autophagy. Finally we will clarify the molecular mechanisms of how autophagy interacts with the adipose glucose and lipid metabolism with shRNAs using an adenovirus-mediated approach in vivo. The study will lead to a better understand of the functional mechanism of autophagy in adipose insulin resistance, and may provide a new target for the prevention and treatment of insulin resistance.

自噬活性在肥胖症脂肪组织中显著增强，但抑制其水平是否缓解肥胖症及胰岛素抵抗进展尚不清楚，相关作用机制亟待阐明。我们发现抑制脂肪细胞自噬可上调Sirt1及PGC-1α表达，提示其可能通过Sirt1/PGC-1α通路调控肥胖诱发的代谢异常。本项目拟在高脂饮食诱导的肥胖小鼠模型中，利用他莫昔芬诱导脂肪组织特异性Atg7基因敲除抑制自噬，采用GTT、ITT、免疫印迹、免疫荧光、透射电镜等方法，明确抑制自噬对肥胖症脂肪组织形态、胰岛素敏感性、脂质生成、线粒体功能、β氧化等的作用；在上述小鼠模型中分析抑制自噬对肥胖症脂肪组织Sirt1及PGC-1α表达的影响，并运用多种干扰表达/过表达细胞模型，明确自噬对Sirt1/PGC-1α通路的调控作用；利用腺病毒shRNA干扰技术，阐明自噬调控脂肪组织功能和糖脂代谢的分子机制。本项目有助于明确自噬在脂肪组织胰岛素抵抗中的作用机制，为胰岛素抵抗的治疗提供新靶点。

近年来，肥胖与胰岛素抵抗等代谢紊乱呈不断加剧的流行趋势， 严重影响人类生活与健康。自噬活性在肥胖症脂肪组织中显著增强，但抑制其水平是否缓解肥胖症及胰岛素抵抗进展尚不清楚，相关作用机制亟待阐明。我们发现抑制脂肪细胞自噬可上调Sirt1及PGC-1α表达，提示其可能通过Sirt1/PGC-1α通路调控肥胖诱发的代谢异常。本项目拟在高脂饮食诱导的肥胖小鼠模型中，利用他莫昔芬诱导脂肪组织特异性Atg7基因敲除抑制自噬，明确抑制自噬对肥胖症脂肪组织形态、胰岛素敏感性、脂质生成、线粒体功能、β氧化等的作用；明确颗粒蛋白前体PGRN对脂肪组织炎性反应的调控作用及分子机制；自噬调控的骨稳态与能量代谢的相互作用。本项目明确了抑制自噬活性小鼠体重减轻、脂肪变少，脂肪细胞体积变小，肝脏及肌肉脂滴聚集减少，脂肪细胞线粒体数目增多，线粒体相关基因表达增加、胰岛素敏感性增强；脂肪组织SIRT1缺陷缺陷引起小鼠体重与脂肪量显著增加、胰岛素敏感性显著降低及糖脂代谢紊乱，小鼠外泌体分泌量显著增多， 抑制外泌体分泌能够有效改善Sirt1 缺陷引起的代谢异常；PGRN处理脂肪细胞炎性因子Il6, TNFa等分泌增加，SIRT1表达减少、NF-kB乙酰化水平增加，通过SIRT1-NF-kB信号通路促进脂肪组织炎症发生并介导脂肪组织的胰岛素敏感性；成骨自噬缺陷诱导内质网应激并导致骨量减少，骨钙素表达减少，揭示调控骨源性因子骨钙素分泌的分子机制，也为后续骨稳态与能量代谢间的关联研究提供了研究基础。