Meng Dongxiao, Chang Minghui, Dai Xianling, Kuang Qin, Wang Guangchuan
Department of Gastroenterology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, 250021, PR China.
Tumor Research and Therapy Center, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, 250021, PR China.
Free Radic Biol Med. 2025 Mar 1;229:312-332. doi: 10.1016/j.freeradbiomed.2024.09.044. Epub 2024 Sep 26.
Nonalcoholic steatohepatitis (NASH) is emerging as a major cause of liver transplantation and hepatocellular carcinoma (HCC). Regrettably, its pathological mechanisms are still not fully comprehended. GTP-binding protein 8 (GTPBP8), belonging to the GTP-binding protein superfamily, assumes a crucial role in RNA metabolism, cell proliferation, differentiation, and signal transduction. Its aberrant expression is associated with oxidative stress and mitochondrial dysfunctions. Nevertheless, its specific functions and mechanisms of action, particularly in NASH, remain elusive. In our current study, we initially discovered that human hepatocytes L02 displayed evident mitochondrial respiratory anomaly, mitochondrial damage, and dysfunction upon treatment with palmitic acids and oleic acids (PO), accompanied by significantly reduced GTPBP8 expression levels through RNA-Seq, RT-qPCR, western blotting, and immunofluorescence assays. We then demonstrated that GTPBP8 overexpression mediated by adenovirus vector (Ad-GTPBP8) markedly attenuate lipid accumulation, inflammatory response, and mitochondrial impair and dysfunction in hepatocytes stimulated by PO. Conversely, adenovirus vector-mediated GTPBP8 knockdown (Ad-shGTPBP8) significantly accelerated lipid deposition, inflammation and mitochondrial damage in PO-treated hepatocytes in vitro. Furthermore, we constructed an in vivo NASH murine model by giving a 16-week high fat high cholesterol diet (HFHC) diet to hepatocyte specific GTPBP8-knockout (GTPBP8) mice. We firstly found that HFHC feeding led to metabolic disorder in mice, including high body weight, blood glucose and insulin levels, and liver dysfunctions, which were accelerated in these NASH mice with GTPBP8 deficiency in hepatocytes. Consistently, GTPBP8 remarkably exacerbated the progression of NASH phenotypes induced by HFHC, as proved by the anabatic lipid accumulation, inflammation, fibrosis and reactive oxygen species (ROS) production in liver tissues, which could be largely attributed to the severe mitochondrial damage and dysfunction. Mechanistically, we further identified that GTPBP8 interacted with peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in hepatocytes. Importantly, the hepaprotective effects of GTPBP8 against mitochondrial dysfunction, oxidative stress and inflammation was largely dependent on PGC-1α expression. Collectively, GTPBP8 may exert a protective role in the progression of NASH, and targeting the GTPBP8/PGC-1α axis may represent a potential strategy for NASH treatment by improving mitochondrial functions.
非酒精性脂肪性肝炎（NASH）正逐渐成为肝移植和肝细胞癌（HCC）的主要病因。遗憾的是，其病理机制仍未被完全理解。GTP结合蛋白8（GTPBP8）属于GTP结合蛋白超家族，在RNA代谢、细胞增殖、分化和信号转导中起关键作用。其异常表达与氧化应激和线粒体功能障碍有关。然而，其具体功能和作用机制，尤其是在NASH中的作用，仍不清楚。在我们目前的研究中，我们首先发现，在用棕榈酸和油酸（PO）处理后，人肝细胞L02表现出明显的线粒体呼吸异常、线粒体损伤和功能障碍，通过RNA测序、RT-qPCR、蛋白质免疫印迹和免疫荧光分析发现GTPBP8表达水平显著降低。然后我们证明，腺病毒载体（Ad-GTPBP8）介导的GTPBP8过表达显著减轻了PO刺激的肝细胞中的脂质积累、炎症反应以及线粒体损伤和功能障碍。相反，腺病毒载体介导的GTPBP8敲低（Ad-shGTPBP8）显著加速了体外PO处理的肝细胞中的脂质沉积、炎症和线粒体损伤。此外，我们通过给肝细胞特异性GTPBP8敲除（GTPBP8-/-）小鼠喂食16周的高脂肪高胆固醇饮食（HFHC）构建了一个体内NASH小鼠模型。我们首先发现，HFHC喂养导致小鼠代谢紊乱，包括高体重、血糖和胰岛素水平以及肝功能障碍，而这些在肝细胞中缺乏GTPBP8的NASH小鼠中加速出现。一致的是，GTPBP8显著加剧了HFHC诱导的NASH表型的进展，肝脏组织中脂质积累、炎症、纤维化和活性氧（ROS）产生的增加证明了这一点，这在很大程度上归因于严重的线粒体损伤和功能障碍。机制上，我们进一步确定GTPBP8在肝细胞中与过氧化物酶体增殖物激活受体γ辅激活因子1α（PGC-1α）相互作用。重要的是，GTPBP8对线粒体功能障碍、氧化应激和炎症的肝保护作用在很大程度上依赖于PGC-1α的表达。总的来说，GTPBP8可能在NASH的进展中发挥保护作用，靶向GTPBP8/PGC-1α轴可能代表一种通过改善线粒体功能来治疗NASH的潜在策略。
