Mechanistic basis for protection against fatty liver disease by CIDEB loss-of-function mutations

Background & Aims: Somatic and germline CIDEB mutations are associated with protection from chronic liver diseases. The mechanistic basis and whether CIDEB suppression would be an effective therapy against fatty liver disease remain unclear. Methods: 21 CIDEB somatic mutations were introduced into cells to assess functionality. In vivo screening was used to trace Cideb mutant clones in mice fed normal chow, western (WD), and choline-deficient, L-amino acid-defined, high-fat (CDA-HFD) diets. Constitutive and conditional Cideb knockout mice were generated to study Cideb in liver disease. Isotope tracing was used to evaluate fatty acid oxidation and de novo lipogenesis. Transcriptomics, lipidomics, and metabolic analyses were utilized to explore molecular mechanisms. Double knockout models (Cideb/Atgl and Cideb/Ppara) tested mechanisms underlying Cideb loss. Results: Most CIDEB mutations showed that they impair function, and lineage-tracing showed that loss-of-function clones were positively selected with some, but not all fatty liver inducing diets. Cideb KO mice were protected from WD, CDA-HFD, and alcohol diets, but had the greatest impact on CDA-HFD induced liver disease. Hepatocyte-specific Cideb deletion could ameliorate disease after MASLD establishment, modeling the impact of therapeutic siRNAs. Cideb loss protected livers via increased β-oxidation, specifically through ATGL and PPARa activation. Conclusions: Cideb deletion is more protective in some types of fatty liver disease. β-oxidation is an important component of the Cideb protective mechanism. CIDEB inhibition represents a promising approach, and somatic mutations in CIDEB might predict the patient populations that might benefit the most. RNAseq profiling of Cidebfl/fl mice injected with AAV-TBG-GFP or Cre on Western diet and CDA-HFD for 3 months.

研究背景与目的：体细胞与生殖系CIDEB（CIDEB）突变与慢性肝脏疾病的保护效应相关。目前其潜在分子机制，以及抑制CIDEB是否可作为脂肪性肝病的有效治疗手段，仍有待阐明。

研究方法：将21种CIDEB体细胞突变导入细胞以评估其功能活性。采用体内筛选技术，在正常饲料、西方饮食（WD）及胆碱缺乏、L-氨基酸限定高脂饲料（CDA-HFD）喂养的小鼠中示踪Cideb突变克隆。构建组成型及条件性Cideb敲除小鼠，以研究其在肝脏疾病中的作用。利用同位素示踪技术评估脂肪酸氧化与从头脂肪生成。通过转录组学、脂质组学及代谢组学分析，探索其潜在分子机制。构建Cideb/Atgl与Cideb/Ppara双敲除模型，以验证Cideb缺失的作用通路。

研究结果：绝大多数CIDEB突变可损害蛋白功能；谱系示踪结果显示，功能丧失型克隆在部分（而非全部）脂肪性肝病诱导饲料喂养的小鼠中呈现正向选择富集优势。Cideb敲除小鼠可抵御西方饮食、CDA-HFD及酒精饮食诱导的肝脏损伤，其中对CDA-HFD诱导的肝脏疾病保护效应最为显著。在代谢相关脂肪性肝病（MASLD）模型造模成功后，肝细胞特异性Cideb敲除可改善疾病进程，模拟治疗性小干扰RNA（siRNA）的干预效果。Cideb缺失通过增强β氧化发挥肝脏保护作用，该过程具体依赖脂肪甘油三酯脂肪酶（ATGL）与过氧化物酶体增殖物激活受体α（PPARα）的激活。

研究结论：Cideb缺失对部分类型的脂肪性肝病具有更显著的保护效应。β氧化是Cideb介导肝脏保护作用的重要环节。抑制CIDEB是极具潜力的治疗策略，而CIDEB体细胞突变或可用于筛选最能从中获益的患者人群。此外，本研究对在西方饮食及CDA-HFD喂养3个月的Cidebfl/fl小鼠注射AAV-TBG-GFP或Cre重组酶后，开展了RNA测序分析。