Carboxyl ester lipase (CEL), a pivotal enzyme involved in lipid metabolism, is recurrently mutated in obese mice. Here, we aimed to elucidate the functional significance, molecular mechanism, and therapeutic potential of CEL in metabolic dysfunction-associated steatohepatitis (MASH). Hepatocyte-specific carboxyl ester lipase gene (Cel) knockout (CelΔHEP) and wildtype (WT) littermates were fed with choline-deficient high-fat diet (CD-HFD) for 16 weeks, or methionine- and choline-deficient diet (MCD) for three weeks to induce MASH. Liquid chromatography–mass spectrometry and co-immunoprecipitation were employed to identify the downstream targets of CEL. CD-HFD/MCD-fed WT mice received intravenous injections of CEL-adeno-associated viral, serotype 8 (AAV8) to induce specific overexpression of CEL in the liver. We observed a decrease in CEL protein levels in MASH induced by CD-HFD or MCD in mice. CelΔHEP mice fed with CD-HFD or MCD exhibited pronounced hepatic steatosis, inflammation, lipid peroxidation, and liver injury compared to WT littermates, accompanied by increased hepatic nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) activation. Consistently, Cel knockdown in mouse primary hepatocytes and AML12 cells aggravated lipid accumulation and inflammation, whereas CEL overexpression exerted the opposite effect. Mechanistically, CEL directly bound to fatty acid synthase (FASN), resulting in reduced FASN SUMOylation, which in turn promoted FASN degradation through the proteasome pathway. Furthermore, inhibition of FASN ameliorated hepatocyte lipid accumulation and inflammation induced by Cel knockdown in vivo and in vitro. Hepatocyte-specific CEL overexpression using AAV8-Cel significantly mitigated steatohepatitis in mice fed with CD-HFD or MCD. CEL protects against steatohepatitis development by directly interacting with FASN and suppressing its expression for de novo lipogenesis. CEL overexpression confers a therapeutic benefit in steatohepatitis.

中文翻译：

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羧酯脂肪酶通过与脂肪酸合酶结合来预防代谢功能障碍相关的脂肪性肝炎


羧酯脂肪酶 （CEL） 是一种参与脂质代谢的关键酶，在肥胖小鼠中反复发生突变。在这里，我们旨在阐明 CEL 在代谢功能障碍相关脂肪性肝炎 （MASH） 中的功能意义、分子机制和治疗潜力。肝细胞特异性羧酸酯脂肪酶基因 （Cel） 敲除 （CelΔHEP） 和野生型 （WT） 同窝同窝小鼠用胆碱缺乏高脂饮食 （CD-HFD） 喂养 16 周，或蛋氨酸和胆碱缺乏饮食 （MCD） 喂养 3 周以诱导 MASH。采用液相色谱-质谱和免疫共沉淀鉴定 CEL 的下游靶点。CD-HFD/MCD 喂养的 WT 小鼠接受静脉注射 CEL 腺相关病毒血清型 8 （AAV8） 以诱导肝脏中 CEL 的特异性过表达。我们观察到小鼠 CD-HFD 或 MCD 诱导的 MASH 中 CEL 蛋白水平降低。与 WT 同窝小鼠相比，饲喂 CD-HFD 或 MCD 的 CelΔHEP 小鼠表现出明显的肝脂肪变性、炎症、脂质过氧化和肝损伤，并伴有肝核因子 κ 轻链增强子活化 B 细胞 （NF-κB） 激活。一致地，小鼠原代肝细胞和 AML12 细胞中的 Cel 敲低加剧了脂质积累和炎症，而 CEL 过表达则发挥了相反的作用。从机制上讲，CEL 直接与脂肪酸合酶 （FASN） 结合，导致 FASN SUMOylation 减少，进而促进 FASN 通过蛋白酶体途径降解。此外，抑制 FASN 在体内和体外改善了 Cel 敲除诱导的肝细胞脂质积累和炎症。使用 AAV8-Cel 的肝细胞特异性 CEL 过表达可显著减轻饲养 CD-HFD 或 MCD 小鼠的脂肪性肝炎。 CEL 通过与 FASN 直接相互作用并抑制其从头脂肪生成的表达来防止脂肪性肝炎的发生。CEL 过表达在脂肪性肝炎中具有治疗益处。