从代谢角度发现罗汉果皂苷抗肥胖型2型糖尿病物质基础及作用机制

Mounting evidence indicates gut microbiota in diabetes and obesity may make possible the development of integrated strategies to prevent and treat these metabolic disorders. As a widely used non-nutritive sweetener, an edible Chinese medicinal material, Siraitiae Fructus was reported that the anti-diabetes activity on experimental animal, and no effect on normal human’s blood sugar concentration in clinic. Based on our previous studies, we aim to separate and screen the active compositions from total saponins of Siraitiae Fructus, used multilevel pharmacodynamics evaluation system of anti-T2DM. The strategy of metabolomics combined T2DM related microbiota was employed to compare investigate the absorption, distribution, metabolism and excretion of the active compositions in T2DM with obesity model and normal animal groups, and the influence of the endogenous component, in order to clarified the difference of the efficacy and effective substances between on T2DM with obesity model to normal groups, and the relevance of active components and microbiota. Furthermore, it will be illuminated that the anti- T2DM mechanism of active compositions of Siraitiae Fructus at three levels: the metabolism of exogenous components, microbiota and the transformation of endogenous components. This study will lay the foundation for the research of pharmacodynamic material, mechanism, and metabolic pathway of active components in vivo, and provide new idea to research and discovery natural products have anti-diabetic activity based on metabolic aspect.

近年研究显示肥胖、2型糖尿病（Type 2 Diabetes Mellitus, T2DM）与肠道微生物改变密切相关。作为甜味剂广泛应用、药食兼用罗汉果具有抗糖尿病作用，且对正常人血糖无影响。基于T2DM与代谢、肠道菌群的密切关系，本课题在前期研究基础上，拟采用抗T2DM多层次药效评价体系，对罗汉果总皂苷进行分离和活性筛选；以代谢组学为手段，结合T2DM相关肠道菌群变化，考察活性组分群在正常和模型动物体内的吸收、分布、代谢、排泄）变化过程，及其对机体内源性成分的影响，阐明其在正常、模型动物中的作用差异，以及活性组分群与肠道菌群间相互关系；从外源性成分代谢、肠道菌群和内源性成分变化三个层面阐明其功效物质发挥抗糖尿病活性的作用机制。本课题的实施为药食兼用药材罗汉果抗T2DM的功效物质基础、作用机制和体内过程奠定基础；为从机体代谢角度研究和发现抗糖尿病的活性天然产物提供借鉴。

本研究以罗汉果皂苷为研究对象，在表征罗汉果总皂苷及其不同分离组分群的化学组成基础上，采用高糖高脂饲料结合链脲佐菌素（STZ）诱导的肥胖型2型糖尿病（T2DM）大鼠模型，以抗T2DM多层次药效评价指标体系筛选并确证含1-3个糖基罗汉果皂苷为罗汉果抗TDM潜在的功效物质基础；结合药动学、组织分布和代谢研究（包括体外模拟人肠道代谢技术），全面勾勒出罗汉果皂苷活性组分群在正常和TDM大鼠体内的吸收、分布、代谢和排泄的过程，主要分布在肝、胰腺、小肠、肾脏、脾脏和肺中，在肠道中经氧化、脱氢、脱氧、异构化的代谢反应生成罗汉果苷III+O、罗汉果苷IA1、罗汉果苷IE1和罗汉果苷II异构体等，其中罗汉果苷IIIA2及其异构化产物、罗汉果苷IIA2及其脱氢产物能够经胆汁和尿液排泄；同时发现该代谢途径与产物与其在人源肠道菌群的代谢一致。高通量测序分析T2DM相关肠道菌变化结合代谢组学手段阐明了活性组分群对肠道菌群及其代谢物的影响，恢复T2DM大鼠失调的肠道菌群结构、增加SCFAs含量、降低次级胆汁酸（deoxycholic acid和1β-hydroxycholic acid），进一步通过皮尔森（Pearson’s）相关分析发现，其中Lachnospiraceae_UCG-004、Family_XIII_AD3011_group、Escherichia-Shigella、Desulfovibrio、Elusimicrobium、1β- hydroxycholic acid、乙酸和丁酸是活性组分群发挥抗糖尿病作用的关键菌属和代谢物；特别是通过对T2DM患者肠道菌群结构特征和SCFAs含量的分析比较，T2DM大鼠与T2DM患者失调的肠道菌群结构和SCFAs含量相似。综上，从代谢角度明确罗汉果抗肥胖型2型糖尿病的功效物质基础及作用机制，为罗汉果皂苷的临床应用提供了科学依据，为从机体代谢角度研究和发现活性天然产物提供了借鉴。