Department of Animal Science, Chonnam National University, Gwangju, Republic of Korea.
Department of Physiology, Keimyung University School of Medicine, Daegu 42601, Republic of Korea.
Mol Cell. 2021 Sep 16;81(18):3820-3832.e7. doi: 10.1016/j.molcel.2021.06.003. Epub 2021 Jul 6.
A metabolic imbalance between lipid synthesis and degradation can lead to hepatic lipid accumulation, a characteristic of patients with non-alcoholic fatty liver disease (NAFLD). Here, we report that high-fat-diet-induced sterol regulatory element-binding protein (SREBP)-1c, a key transcription factor that regulates lipid biosynthesis, impairs autophagic lipid catabolism via altered HS signaling. SREBP-1c reduced cystathionine gamma-lyase (CSE) via miR-216a, which in turn decreased hepatic HS levels and sulfhydration-dependent activation of Unc-51-like autophagy-activating kinase 1 (ULK1). Furthermore, Cys951Ser mutation of ULK1 decreased autolysosome formation and promoted hepatic lipid accumulation in mice, suggesting that the loss of ULK1 sulfhydration was directly associated with the pathogenesis of NAFLD. Moreover, silencing of CSE in SREBP-1c knockout mice increased liver triglycerides, confirming the connection between CSE, autophagy, and SREBP-1c. Overall, our results uncover a 2-fold mechanism for SREBP-1c-driven hepatic lipid accumulation through reciprocal activation and inhibition of hepatic lipid biosynthesis and degradation, respectively.
脂质合成和降解之间的代谢失衡可导致肝脂质堆积,这是非酒精性脂肪性肝病(NAFLD)患者的特征。在这里,我们报告说,高脂肪饮食诱导的固醇调节元件结合蛋白(SREBP)-1c,一种调节脂质生物合成的关键转录因子,通过改变 HS 信号来损害自噬性脂质分解代谢。SREBP-1c 通过 miR-216a 降低半胱氨酸γ-裂解酶(CSE)的表达,进而降低肝 HS 水平和依赖巯基化的 UNC-51 样自噬激活激酶 1(ULK1)的激活。此外,ULK1 的 Cys951Ser 突变减少了自噬溶酶体的形成,并促进了小鼠的肝脂质堆积,表明 ULK1 的巯基化丧失与 NAFLD 的发病机制直接相关。此外,在 SREBP-1c 敲除小鼠中沉默 CSE 增加了肝脏甘油三酯,证实了 CSE、自噬和 SREBP-1c 之间的联系。总的来说,我们的研究结果揭示了 SREBP-1c 驱动肝脂质堆积的双重机制,分别是通过对肝脂质生物合成和降解的相互激活和抑制。