Lipophagy is the autophagic degradation of lipid droplets. Dysregulated lipophagy has been implicated in the development of non-alcoholic fatty liver disease (NAFLD). Ajugol is an active alkaloid isolated from the root of Rehmannia glutinosa which is commonly used to treat various inflammatory and metabolic diseases. This study aimed to investigate the effect of ajugol on alleviating hepatic steatosis and sought to determine whether its potential mechanism via the key lysosome-mediated process of lipophagy. Our findings showed that ajugol significantly improved high-fat diet-induced hepatic steatosis in mice and inhibited palmitate-induced lipid accumulation in hepatocytes. Further analysis found that hepatic steatosis promoted the expression of LC3-II, an autophagosome marker, but led to autophagic flux blockade due to a lack of lysosomes. Ajugol also enhanced lysosomal biogenesis and promoted the fusion of autophagosome and lysosome to improve impaired autophagic flux and hepatosteatosis. Mechanistically, ajugol inactivated mammalian target of rapamycin and induced nuclear translocation of the transcription factor EB (TFEB), an essential regulator of lysosomal biogenesis. siRNA-mediated knockdown of TFEB significantly abrogated ajugol-induced lysosomal biogenesis as well as autophagosome-lysosome fusion and lipophagy. We conclude that lysosomal deficit is a critical mediator of hepatic steatosis, and ajugol may alleviate NAFLD via promoting the TFEB-mediated autophagy-lysosomal pathway and lipophagy.

脂肪吞噬是脂滴的自噬降解。脂肪吞噬失调与非酒精性脂肪肝疾病 (NAFLD) 的发展有关。Ajugol 是一种从地黄根中分离出来的活性生物碱常用于治疗各种炎症和代谢疾病。本研究旨在研究 ajugol 对减轻肝脏脂肪变性的作用，并试图通过关键的溶酶体介导的脂肪吞噬过程确定其潜在机制。我们的研究结果表明，ajugol 显着改善了高脂饮食诱导的小鼠肝脂肪变性，并抑制了棕榈酸酯诱导的肝细胞脂质积累。进一步分析发现，肝脂肪变性促进了自噬体标志物 LC3-II 的表达，但由于缺乏溶酶体而导致自噬通量阻断。Ajugol 还增强了溶酶体的生物合成，促进了自噬体和溶酶体的融合，从而改善受损的自噬通量和肝脂肪变性。机械地，ajugol 使雷帕霉素的哺乳动物靶点失活并诱导转录因子 EB (TFEB) 的核转位，这是溶酶体生物发生的重要调节因子。siRNA 介导的 TFEB 敲低显着消除了 ajugol 诱导的溶酶体生物发生以及自噬体-溶酶体融合和脂肪吞噬。我们得出结论，溶酶体缺陷是肝脂肪变性的关键介质，而 ajugol 可能通过促进 TFEB 介导的自噬-溶酶体途径和脂肪吞噬来缓解 NAFLD。