山药多糖调节肠道菌群生长的构效关系及其作用机制研究

Dioscorea opposita Thunb. is widely used as functional food and traditional Chinese medicine in China for its activity of regulating spleen and stomach. Proteins, amino acids, flavonoids, allantoin, dopamine, polysaccharides and glycoproteins were reported to isolate from D. opppsita. Polysaccharides from the rhizome of D. opposita (yam polysaccharides) were found to have the activity of regulating the growth of gut microbiota as prebiotics. However, the composition and structure of crude polysaccharides are still unknown. The structure-activity relationship and mechanism are not clear either. In this project, homogeneous polysaccharides will be separated and purified from the crude polysaccharides of D. opposita. Chemical and physical modification will be used to obtain derivatives with different molecular weight and different modified groups. The structure-activity relationship will be illustrated by the relationship between molecular weight, the differential structure of the polysaccharides and the growth of gut microbiota. On the basis of this, the pharmacodynamics evaluation will be evaluated using the model of mice and the mechanism of the effect of yam polysaccharides to gut bacteria will be elucidated by the detection of molecular diversity, functional diversity and diversity of intestinal microorganisms in mice. All these results would provide the theoretical basis for the treatment of intestinal flora disorder based on carbohydrate drugs. Meanwhile, it will further expand the field of medicinal use of traditional Chinese yam and provide the theoretical basis for further development of yam resources.

山药是一种药食两用的中药材，具有补脾养胃、生津益肺的功效。山药中的有效成分种类比较多，其中，山药多糖作为一种益生元可以调节肠道菌群的生长。本实验室前期研究发现山药粗多糖具有调节肠道菌群生长的作用，但是所用粗多糖的组成与结构均不明确，其构效关系与作用机制也不清晰。本项目将通过分离纯化，得到具有调节菌群生长的山药均一多糖，采用化学和物理法得到不同分子量和不同修饰基团的衍生多糖。通过研究差异结构对该多糖调节肠道菌群生长作用的影响，阐明山药多糖调节菌群生长的功能结构域及其构效关系。在此基础上利用小鼠模型对山药多糖进行药效学评价，并通过山药多糖对小鼠肠道微生物分子多样性、功能多样性以及菌群多样性的影响情况，研究其作用机制。该项目的成功实施，将为基于糖类药物治疗或缓解肠道菌群紊乱提供重要的理论基础，同时也将进一步拓展中药山药的药用领域，为深入开发山药的药用资源价值提供理论基础。

山药是一种药食两用的中药，据《本草纲目》记载，山药可治疗脾胃虚弱、湿热虚泄、肿毒初起等症状。前期研发现山药粗多糖具有调节肠道菌群生长的作用，但是所用粗多糖的组成与结构均不明确，其构效关系与作用机制也不清晰 。本项目首先采用水提醇沉得到了山药粗多糖DOP。采用DEAE SepharoseTM Fast Flow将DOP分成了DOP0.1和DOP0.2两个组分。其中，DOP0.2组分主要由半乳糖和半乳糖醛酸组成，它在体外特异性促进阿奇霉素作用下的多形拟杆菌的增殖，这种保护作用机制可能是通过其代谢产物半乳糖醛酸来影响局部阿奇霉素对肠道拟杆菌的抑制作用。DOP0.2在体内也可降低阿奇霉素对小鼠肠道菌群及代谢产物造成的炎症副作用。通过Sephacryl S-300HR我们从DOP0.1组分中分离到一个均一多糖，DOP0.1-S-1，它的分子量为10kDa，由半乳糖组成。通过核磁和甲基化结果，DOP0.1-S-1被确定为1,4-α-GalAp连接的聚糖，是一个没有任何甲基酯化的HG型果胶。DOP0.1-S-1通过促进几种拟杆菌的增殖并产生短链脂肪酸来达到调节肠道菌群的效果。通过Sephacryl S-300HR我们又从DOP0.2组分中分离到一个均一多糖，DOP0.2-S-3，它的分子量为14kDa，为一均一的半乳糖醛酸聚糖。DOP0.2-S-3能显著降低抗生素相关性腹泻引起的小鼠粪便含水量和排便次数，同时它还显著减弱小鼠结肠组织中IL-1β和IL-6的细胞因子表达。此外，它还降低了小鼠肠道中潜在的病原体同时增加了拟杆菌的数量。本项目的成功实施，为基于糖类药物治疗或缓解肠道菌群紊乱提供重要的理论基础，同时 也进一步拓展了中药山药的药用领域，为深入开发山药的药用资源价值提供理论基础。