肠道菌群多样性与人参皂苷代谢差异相关性及其作用机制研究

Ginsenosides are the main active components of ginseng. After oral administration of ginseng and its products, naturally occurring ginsenosides will metabolic and hydrolysis into rare ginsenosides by intestinal bacteria to play its pharmacological role. Due to the intestinal microflora settlers affected by many factors, its diversity and structures are quite different. For the populations who are lack of intestinal microflora to metabolize ginseng saponins, they can not reach the corresponding effect after oral administration of ginseng. Thus, intestinal microbial diversity is closely related to absorption and metabolism of ginsenosides in vivo. In the previous study, we found significant differences in the metabolism of ginsenosides in rats. In this study, we use rat colon contents that have significant differences as the research object to explore and identify the bacteria species or genus involved in the metabolism of ginsenosides, and clarify the correlation between individual intestinal flora diversity and metabolic differences of ginsenosides, to reveal the reason of different efficacy of different individuals taking ginseng. Establish intestinal microflora metagenomic library, screen and identify the key of the functional genes. Furthermore, screen the active strains of metabolism of ginsenosides to providing valuable clues for studies on metabolic mechanism of ginsenosides.

人参皂苷是人参的主要活性成分，人参及其制品经口服后，天然人参皂苷需经肠道菌代谢后被水解成稀有人参皂苷而发挥其药理作用。由于肠道内定居的微生物菌群受诸多因素影响，个体间肠道菌群多样性和结构组成差异较大。对于肠道内缺少代谢人参皂苷菌群的人群，口服人参后无法达到预期的疗效。因此，肠道菌群多样性与人参皂苷在体内的代谢吸收密切相关。在前期研究中，我们发现大鼠个体间人参皂苷的代谢存在明显差异。在本课题中，我们以人参皂苷代谢具有显著差异的大鼠大肠内容物为研究对象，采用宏基因组学方法研究其肠道微生物多样性、种群结构、功能活性等，探寻并鉴定参与代谢人参皂苷的菌属或菌种，阐明个体间肠道菌群多样性与人参皂苷代谢差异的相关性，揭示不同个体服用人参后的效果差异原因；构建肠道微生物宏基因组文库，筛选、鉴定关键功能基因；筛选代谢人参皂苷的活性菌株，为人参皂苷代谢机制研究提供有价值的线索。

肠道菌群多样性及群落结构与人参皂苷在体内代谢与吸收密切相关。本项目中，体外模拟肠道微生物生物转化人参总皂苷提取物的研究结果表明，人参二醇类皂苷经肠道微生物主要代谢成compound K，而原人参三醇类皂苷主要代谢成PPT。药代动力学研究结果表明，compound K的Tmax, Cmax, 和AUC 血液中明显高于其他皂苷，人参主皂苷主要以稀有人参皂苷compound K的形式被体内吸收。对人参皂苷代谢活性较强的大鼠（HEM）和代谢活性较弱的大鼠（LEM）的肠道微生物分析结果显示，两组间大鼠肠道微生物组成结构差异较为显著，在门水平上HEM组放线菌（Actinobacteria）的数目显著高于LEM组，而拟杆菌（Bacteroidetes）的数目在HEM组中显著低于LEM组，在属水平两组间差异显著的OTUs共有114个，在HEM组中75个OTUs显著高于LEM组，HEM组较高的75个OTUs中，其中51 个OTUs属于S24-7科，8个OTUs属于产碱菌科（Alcaligenaceae）。在大鼠结肠内容物中分离了代谢人参皂苷的活性菌株Enterococcus gallinarum GM2，该菌株把人参皂苷Rb1转化成绞股蓝皂苷XVII。进一步我们从活性菌株Enterococcus gallinarum GM2中筛选了代谢人参皂苷的关键功能基因bgy3，重组酶Bgy3能够把人参皂苷Rb1转化成人参皂苷F2。本项目的研究结果阐明了肠道菌群多样性与人参皂苷代谢差异的相关性，揭示了不同个体服用人参后效果差异的原因，为人参皂苷代谢机制研究提供了有价值的线索。