大豆皂甙经调控肝脏-胆汁酸-肠道菌群代谢轴预防非酒精性脂肪肝病活性与机理研究

Nonalcoholic fatty liver disease (NAFLD) seriously threats human health. No specific medicine is currently available. Latest studies suggest that the Liver-Bile acid-Gut Microbiota Metabolic Axis (LBGMA) plays vital roles in the occurrence and development of NAFLD, which provides new clues for NAFLD's prevention and therapy. Existing evidences show that phytochemical soyasaponin (SS) have many biological activities (eg. hepatoprotection, anti-inflammation, etc.) which can help to reduce or clear the risk factors of NAFLD. We previously found that SS reduced hepatic steatosis and inflammation in high fat diet-induced obese mice. This suggests that SS may have the potential abilities to prevent and treat NAFLD. Moreover, we and others have shown that SS can be metabolized by gut microbiota and interacted with bile acids in the intestine. However, no report is available regarding SS's preventive abilities against NAFLD and its mechanism. In this study, we are going to firstly establish the methionine and choline deficiency (MCD) feed-induced NAFLD mice model and then investigate the effects of SS with three different chemical structures on the occurrence and development of NAFLD and further study their regulation on LBGMA. The purpose of the study is to confirm the preventive bioactivities of SS against NAFLD, uncover their chemical structure-bioactivity relationships and clarify the underlying mechanism. Accomplishment of this program will provide theoretical basis for using phytochemical soyasaponins to prevent NAFLD in nutrition and potential clues for developing therapeutic medicine in pharmacy.

非酒精性脂肪肝病（NAFLD）严重威害人类健康，目前尚无特效治疗药。最新研究显示肝脏-胆汁酸-肠道菌群代谢轴（LBGMA）在NAFLD发生发展中起重要作用，为其防治提供了新思路。已有研究表明植物化学物大豆皂甙（SS）具有肝保护、抗炎等多种可减轻或消除NAFLD危险因素的生物活性，我们前期在高脂诱导的肥胖小鼠模型中发现SS可减轻肝脏脂肪变性和炎症，提示其可能具有防治NAFLD的效果，且我们和他人的研究均表明SS在肠道内会被菌群代谢并与胆汁酸发生互作，但目前未见有关SS预防NAFLD及其机理的报道。本课题拟运用蛋氨酸-胆碱缺乏饲料诱导小鼠建立NAFLD模型，用三种不同化学结构SS进行预防性干预，进一步研究它们对LBGMA的调控作用，旨在证实SS预防NAFLD的活性，揭示其构效关系，并阐明其作用机理，为从营养学上合理运用SS类植物化学物预防NAFLD提供理论依据，也为药学上开发治疗药物提供线索。

非酒精性脂肪肝病（NAFLD）严重威害人类健康，肝脏-胆汁酸-肠道菌群代谢轴在NAFLD发生发展中起重要作用。我们和他人研究发现植物化学物大豆皂甙具有肝保护、抗炎等多种生物学活性，但其预防NAFLD的作用与机理不明。本项目运用蛋氨酸-胆碱缺乏（MCD）饲料诱导C57BL/6雄性小鼠建立NAFLD模型，用三种不同化学结构大豆皂甙（SS-A1、SS-A2和SS-Bb）预防性干预4周和16周，检测分析肝脏NAFLD活动度（NAS）和纤维化评分、肠道菌群、胆汁酸及其信号通路，分别观察大豆皂甙对非酒精性单纯性脂肪肝（NAFL）和非酒精性脂肪肝炎（NASH）的影响。研究发现：1）SS-A1、SS-A2和SS-Bb预防性干预NAFLD小鼠，均显著降低了肝脏NAS评分、脂肪变、小叶炎症、气球样变以及纤维化，同时改善了肝脏和血清中的脂质水平、降低了炎症和肝损伤等指标，表明SS-A1、SS-A2和SS-Bb均具有预防NAFLD的生物学活性，但它们预防NAFLD的生物学活性之间无统计学显著性差异，说明不存在化学结构-活性效应。2）SS-A1、SS-A2和SS-Bb增加了NAFLD小鼠肠道菌群的多样性，改善了肠道菌群结构；同时改变了肝脏、血清和粪便中的胆汁酸组成和含量，促进了粪便中胆汁酸的排泄，而且肠道菌群与胆汁酸具有相关性；升高了回肠中法尼酯X受体（FXR）和成纤维细胞生长因子15（FGF-15）的表达，表明大豆皂甙可以经调控肝脏-胆汁酸-肠道菌群代谢轴发挥预防NAFLD的生物学活性。3）大鼠代谢笼实验发现SS-Bb体内吸收率很低，被转化为大豆皂苷元B，但可能还存在其他代谢产物；人肠上皮Caco-2细胞模型研究发现SS-Bb为被动转运，存在细胞内蓄积。本项目研究结果为从营养学上合理运用大豆皂甙类植物化学物预防NAFLD提供了理论依据，也为药学上开发大豆皂甙类似结构的NAFLD治疗药物提供了线索。