Sano Akitoshi, Kakazu Eiji, Hamada Shin, Inoue Jun, Ninomiya Masashi, Iwata Tomoaki, Tsuruoka Mio, Sato Kosuke, Masamune Atsushi
Division of Gastroenterology, Tohoku University Graduate School of Medicine, Aobaku, Sendai, Japan.
Hepatology. 2021 Sep;74(3):1271-1286. doi: 10.1002/hep.31808.
NAFLD is a lipotoxic disease wherein hepatic steatosis and oxidative stress are key pathogenic features. However, whether free amino acids (FAAs) are associated with the oxidative stress response against lipotoxicity has yet to be determined. We hypothesized that an imbalance of FAAs aggravates hepatic steatosis by interfering with the oxidative stress sensor.
C57BL/6 mouse immortalized hepatocytes, primary hepatocytes, and organoids were employed. Steatotic hepatocytes treated with oleic acid (OA) were cultured under FAA-modifying media based on the concentrations of FAAs in the hepatic portal blood of wild-type (WT) mice. As in vivo experiments, WT hepatocyte-specific Kelch-like ECH-associated protein 1 (Keap1) knockout mice (Keap1 ) and Cre- control mice (Keap1 ) were fed high-fat (HF) diets with modified amino acid content. The correlations were analyzed between the areas of lipid droplets (LDs) around central vein and plasma OA/FAA ratio in 61 patients with NAFLD. Mice fed an HF, Met-restricted, and tyrosine (Tyr)-deficient diet showed the NAFLD-like phenotype in which the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), triglyceride-rich VLDL, and fumarate were decreased in liver, but Keap1 ameliorated these phenomena. Reactive oxygen species and LDs induced by the deprivation of Met and Tyr were prevented in hepatic organoids generated from Keap1 . Dimethyl fumarate, an Nrf2 inducer, ameliorated the steatosis and increased the hepatic fumarate reduced by the deprivation of Met and Tyr in vitro. OA/Met or Tyr ratio in peripheral blood was associated with the hepatic steatosis in patients with NAFLD.
An imbalance between free fatty acids and Met and Tyr induces hepatic steatosis by disturbing the VLDL assembling through the Keap1-Nrf2 system.
非酒精性脂肪性肝病（NAFLD）是一种脂肪毒性疾病，肝脂肪变性和氧化应激是其关键的致病特征。然而，游离氨基酸（FAA）是否与针对脂肪毒性的氧化应激反应相关仍有待确定。我们假设FAA失衡通过干扰氧化应激传感器加重肝脂肪变性。
使用C57BL/6小鼠永生化肝细胞、原代肝细胞和类器官。根据野生型（WT）小鼠肝门静脉血中FAA的浓度，用油酸（OA）处理的脂肪变性肝细胞在FAA修饰培养基中培养。作为体内实验，给WT肝细胞特异性 Kelch样ECH相关蛋白1（Keap1）基因敲除小鼠（Keap1-/-）和Cre对照小鼠（Keap1+/+）喂食氨基酸含量改变的高脂肪（HF）饮食。分析了61例NAFLD患者中央静脉周围脂滴（LD）面积与血浆OA/FAA比值之间的相关性。喂食HF、蛋氨酸限制和酪氨酸（Tyr）缺乏饮食的小鼠表现出NAFLD样表型，即肝脏中核因子红细胞2相关因子2（Nrf2）的核转位、富含甘油三酯的极低密度脂蛋白（VLDL）和富马酸减少，但Keap1基因敲除改善了这些现象。在由Keap1-/-产生的肝类器官中，蛋氨酸和酪氨酸缺乏诱导的活性氧和脂滴被阻止。富马酸二甲酯，一种Nrf2诱导剂，改善了脂肪变性，并增加了体外因蛋氨酸和酪氨酸缺乏而降低的肝脏富马酸。NAFLD患者外周血中的OA/蛋氨酸或酪氨酸比值与肝脂肪变性相关。
游离脂肪酸与蛋氨酸和酪氨酸之间的失衡通过Keap1-Nrf2系统干扰VLDL组装，从而诱导肝脂肪变性。
