通过“肠道菌群移植”重建粘膜免疫稳态对非酒精性脂肪性肝炎的防治研究

The increasing incidence of nonalcoholic steatohepatitis (NASH) has qualified it to be one of the most important liver diseases in China. Abnormal fecal microbiota, which is introduced by high-fat diet (HFD), has recently been reported to induce NASH on the basis of mucosal immunity disturbance and then intestine-liver lymphocyte homing. We thus attempt to restore the fecal microbiota in HFD-induced NASH by 'fecal microbiota transplantation'. The effects of fecal microbiota regulation are evaluated by means of Th1/Th2 and Th17/Treg proportion, intestine-liver lymphocyte homing/recycle, and resultantly hepatic immune response. This research may uncover the critical role and underlying mechanisms of fecal microbiota, being mediated by mucosal immunity system, in the genesis and development of NASH, and normalization of fecal microbiota may highlight a novel prevention and treatment for NASH.

近年来非酒精性脂肪性肝炎（nonalcoholic steatohepatitis, NASH）发病率不断增高，已成为我国的重要肝病之一。国内外研究显示，高脂饮食导致的肠道菌群结构紊乱可能破坏肠粘膜免疫稳态，并募集肠道的活化淋巴细胞向肝脏归巢，进而诱发NASH。为此，本研究尝试在高脂饮食诱导小鼠NASH模型基础上，通过"肠道菌群移植"恢复正常的肠道菌群结构；观察肠道菌群调控对纠正肠粘膜Th1/Th2、Th17/Treg细胞比例，抑制肠-肝间淋巴细胞归巢/再循环，以及阻断肝脏免疫反应的作用。以期揭示肠道菌群经粘膜免疫系统介导对NASH发生发展的影响及其确切机制，从而为NASH防治提供新手段。

非酒精性脂肪性肝病（non-alcoholic fatty liver disease, NAFLD）是已成为我国乃至全世界慢性肝病主要病因，疾病谱包括单纯性脂肪肝（nonalcoholic fatty liver，NAFL）、非酒精性脂肪性肝炎（nonalcoholic steatohepatitis, NASH）、肝硬化甚至原发性肝癌。NASH是NAFLD 疾病谱的重要拐点，早期识别并干预NASH成为了重中之重。近年多项报道提示肠道菌群作为人体内不可或缺的一个特殊共生“器官”，参与生命代谢活动，调控免疫系统活性。紊乱的肠道菌群经由释放内毒素和内生性乙醇、诱导免疫细胞分化、刺激炎性细胞增殖等多条途径促进NASH 的发生与发展。因此，肠道菌群是否可作为NASH防治一重要突破口值得探索。.本研究旨在以肠道菌群作为靶向干预，为NASH 的预防与治疗开辟全新的途径。经过 16周实验周期，高脂饮食造模组小鼠出现显著代谢紊乱，NASH发病率为100%；造模组肝内及附睾脂肪炎症因子水平及相关免疫因子水平、血清及肝脏内毒素水平较正常组显著升高。经过8周FMT或CB或NaB干预后，各组小鼠代谢指标、肝酶等较造模组均显著改善，肝脏病理较造模组显著减轻，NAS积分均显著下降；肝内及附睾脂肪炎症因子水平与造模组相比显著下降，相关免疫因子趋于平衡；粪便菌群分析提示造模组肠道菌群整体结构显著偏离正常组，而三种干预均使整体菌群更接近于正常对照组，同时显著增加了有益菌的水平如Lactobacillus、Christensenellaceae等；与正常组和造模组相比，三个干预组肠道内丁酸的含量均显著升高。体外研究显示NaB可以通过对HDAC抑制作用调控CD4+ T细胞的分化，同时促进肝细胞表达GLP-1R。上述结果提示以肠道菌群为靶向的干预包括粪菌移植、CB益生菌及NaB主要或部分通过改善HFD引起的小鼠肠道菌群紊乱，纠正HFD引发的炎症与免疫微环境失衡，增强肠道粘膜屏障，促进肠源性激素GLP-1分泌及增强肝脏对GLP-1反应性，进而改善HFD诱导的NASH。