应用拟人化仓鼠模型探讨卵磷脂胆固醇酰基转移酶在非酒精性脂肪肝中的作用和机制

Dyslipidemia is not only a predominant risk factors in atherosclerosis (AS), but also closely relates to non-alcoholic fatty liver disease (NAFLD). Lecithin cholesterol acyltransferase (LCAT) is the only free cholesterol esterase in plasma which is secreted by liver. In LCAT mutant patients, there was a decreased high-density lipoprotein content and raised free cholesterol in plasma. In several clinical studies, it was a reduction of LCAT activity in many liver diseases including NAFLD. However, the relationship between LCAT and NAFLD has been controversial in mouse model..Therefore, we successfully created the unique human-like LCAT knockout hamster model. We found that the features of lipid metabolism in LCAT knockout hamster was much closer to patients and when fed with high fat diet (HFD), it was elicited severe dyslipidemia and accelerated the process of NAFLD. These evidences suggested that LCAT might play an important role in preventing from NAFLD. To clarify the impact of LCAT in NAFLD, we used the human-like LCAT knockout hamster to reveal the influence of LCAT in process of NAFLD in vivo and in vitro. We hypothesized that LCAT deficiency might lead to increased FC content in liver, and then triggered the NLRP3/caspase-1 pathway to promote steatosis and inflammation. Through this project, we could reveal the influence of LCAT in NAFLD and discover the detail mechanism. Finally, we could provide the new ideal in clinical NAFLD therapeutic.

脂代谢紊乱不仅是动脉粥样硬化（AS）的危险因子，也与非酒精性脂肪肝（NAFLD）密切相关。卵磷脂胆固醇酰基转移酶（LCAT）是肝脏分泌入血浆的唯一游离胆固醇（FC）酯化酶，LCAT突变患者的血浆HDL降低，FC明显升高。临床研究发现，多种肝脏疾病包括NAFLD的LCAT活性降低；但以小鼠为模型开展的LCAT与NAFLD关系的研究却存在争议。.因此我们前期成功制备了独特的拟人化LCAT敲除仓鼠模型，其表型比小鼠更接近人类，喂饲高脂饲料后加重了脂代谢紊乱，并诱发了明显的NAFLD， 提示LCAT可能对NAFLD具有保护作用。本项目拟应用LCAT敲除仓鼠为模型，从细胞和整体动物水平，研究LCAT敲除后，导致FC在肝脏异常沉积，激活NLRP3/caspase-1通路，加重NAFLD的作用及机制。通过本研究，可阐明LCAT影响NAFLD的作用及机制，为NAFLD的临床干预提供新思路。

脂肪肝是非常重要的代谢类疾病，我国目前的患病人数每年持续增高，患者的脂肪肝的知晓率仍然很低，临床上目前仍然缺乏脂肪肝有效早期诊断的方式。在以往关于脂肪肝的研究中，主要集中在总胆固醇，总甘油三酯等脂质分子。对于一些非酯化的脂类研究仍然比较少，游离胆固醇（FC）是一类非常重要的非酯化脂类，在血浆中可通过卵磷脂胆固醇酰基转移酶（LCAT）被催化形成酯化胆固醇（CE），血清中FC的增加在脂肪肝的病变过程中的作用与机制目前仍然不清楚。本研究项目旨在研究非酯化脂质——游离胆固醇在脂肪肝的发生发展中的作用，通过动物实验和细胞实验明确升高的游离胆固醇加重脂肪肝的作用与机制，提示血浆游离胆固醇可能成为脂肪肝发生与发展过程重要的生物分子。项目自开展以来，我们按照研究计划完成了一系列的实验与相关工作，并取得成果，主要包括：1.通过临床横断面研究发现，游离胆固醇明显升高，与肝功能的改变明显相关；2利用LCAT敲除仓鼠，明确游离胆固醇升高后加重脂肪肝；3. 探讨LCAT敲除后加重NAFLD的相关机制，我们利用mRNA-seq等技术，寻找LCAT敲除后加重脂肪肝的可能机制，我们发现LCAT敲除后游离胆固醇升高，肝脏组织内炎症细胞（以中性粒细胞，巨噬细胞为主）浸润增加，相关炎症因子明显增加，同时肝脏组织的纤维化加重。本项目从临床研究，动物实验和细胞实验等不同的层面揭示了LCAT敲除后，血浆游离胆固醇升高能够明显加重脂肪肝的，这种现象主要通过肝脏细胞内游离胆固醇负荷增加，引起肝脏组织炎症反应和纤维化增加为主。为临床上脂肪肝的早期诊断提供新的候选分子。

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