Joint Center for Translational Medicine, Fengxian District Central Hospital, Fengxian District, Shanghai, China; Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai, China.
The Key Laboratory of Metabolism and Molecular Medicine of the Ministry of Education, Department of Endocrinology and Metabolism, Zhongshan Hospital, Fudan University, Shanghai, China.
J Hepatol. 2021 Jul;75(1):150-162. doi: 10.1016/j.jhep.2021.01.042. Epub 2021 Feb 4.
BACKGROUND & AIMS: Chronic endoplasmic reticulum (ER) stress in the liver has been shown to play a causative role in non-alcoholic fatty liver disease (NAFLD) progression, yet the underlying molecular mechanisms remain to be elucidated. Forkhead box A3 (FOXA3), a member of the FOX family, plays critical roles in metabolic homeostasis, although its possible functions in ER stress and fatty liver progression are unknown.
Adenoviral delivery, siRNA delivery, and genetic knockout mice were used to crease FOXA3 gain- or loss-of-function models. Tunicamycin (TM) and a high-fat diet (HFD) were used to induce acute or chronic ER stress in mice. Chromatin immunoprecipiation (ChIP)-seq, luciferase assay, and adenoviral-mediated downstream gene manipulations were performed to reveal the transcriptional axis involved. Key axis protein levels in livers from healthy donors and patients with NAFLD were assessed via immunohistochemical staining.
FOXA3 transcription is specifically induced by XBP1s upon ER stress. FOXA3 exacerbates the excessive lipid accumulation caused by the acute ER-inducer TM, whereas FOXA3 deficiency in hepatocytes and mice alleviates it. Importantly, FOXA3 deficiency in mice reduced diet-induced chronic ER stress, fatty liver, and insulin resistance. In addition, FOXA3 suppression via siRNA or adeno-associated virus delivery ameliorated the fatty liver phenotype in HFD-fed and db/db mice. Mechanistically, ChIP-Seq analysis revealed that FOXA3 directly regulates Period1 (Per1) transcription, which in turn promotes the expression of lipogenic genes, including Srebp1c, thus enhancing lipid synthesis. Of pathophysiological significance, FOXA3, PER1, and SREBP1c levels were increased in livers of obese mice and patients with NAFLD.
The present study identified FOXA3 as the bridging molecule that links ER stress and NAFLD progression. Our results highlighted the role of the XBP1s-FOXA3-PER1/Srebp1c transcriptional axis in the development of NAFLD and identified FOXA3 as a potential therapeutic target for fatty liver disease.
The molecular mechanisms linking endoplasmic reticulum stress to non-alcoholic fatty liver disease (NAFLD) progression remain undefined. Herein, via in vitro and in vivo analysis, we identified Forkhead box A3 (FOXA3) as a key bridging molecule. Of pathophysiological significance, FOXA3 protein levels were increased in livers of obese mice and patients with NAFLD, indicating that FOXA3 could be a potential therapeutic target in fatty liver disease.
慢性内质网（ER）应激在非酒精性脂肪性肝病（NAFLD）的进展中起着因果作用，但潜在的分子机制仍有待阐明。叉头框 A3（FOXA3）是 FOX 家族的成员，在代谢稳态中发挥着关键作用，尽管其在 ER 应激和脂肪肝进展中的可能功能尚不清楚。
使用腺病毒传递、siRNA 传递和基因敲除小鼠来创建 FOXA3 获得或缺失功能模型。使用衣霉素（TM）和高脂肪饮食（HFD）诱导小鼠急性或慢性 ER 应激。进行染色质免疫沉淀（ChIP）-seq、荧光素酶测定和腺病毒介导的下游基因操作，以揭示涉及的转录轴。通过免疫组织化学染色评估健康供体和 NAFLD 患者肝脏中的关键轴蛋白水平。
FOXA3 转录是 ER 应激后 XBP1s 特异性诱导的。FOXA3 加剧了急性 ER 诱导剂 TM 引起的过度脂质积累，而肝细胞和小鼠中的 FOXA3 缺失则减轻了这种积累。重要的是，小鼠中的 FOXA3 缺失可减少饮食诱导的慢性 ER 应激、脂肪肝和胰岛素抵抗。此外，siRNA 或腺相关病毒递送抑制 FOXA3 可改善 HFD 喂养和 db/db 小鼠的脂肪肝表型。在机制上，ChIP-Seq 分析表明，FOXA3 直接调节 Period1（Per1）转录，进而促进包括 Srebp1c 在内的脂肪生成基因的表达，从而增强脂质合成。具有病理生理学意义的是，肥胖小鼠和 NAFLD 患者肝脏中的 FOXA3、PER1 和 SREBP1c 水平增加。
本研究确定 FOXA3 是连接 ER 应激和 NAFLD 进展的桥接分子。我们的结果强调了 XBP1s-FOXA3-PER1/Srebp1c 转录轴在 NAFLD 发展中的作用，并确定 FOXA3 是治疗脂肪肝疾病的潜在治疗靶点。
将内质网应激与非酒精性脂肪性肝病（NAFLD）进展联系起来的分子机制尚不清楚。在此，通过体外和体内分析，我们确定了 Forkhead box A3（FOXA3）是一个关键的桥接分子。具有病理生理学意义的是，肥胖小鼠和 NAFLD 患者肝脏中的 FOXA3 蛋白水平增加，表明 FOXA3 可能是治疗脂肪肝疾病的潜在治疗靶点。
