紫薯多糖干预肠道菌群结构及调节肠道抗炎通路的机制研究

In the long-term coordination evolution process with the host, the intestinal microbiota forms a commensal relationship and stable microenvironment to maintain host health. Recent studies have revealed that natural polysaccharides have beneficial effects on improving gut microbiota composition and also have anti-inflammatory activities in the intestine. However, the relevant mechanisms of these polysaccharides on gut microbiota and anti-inflammatory activities are still unknown, especially in the mechanisms of polysaccharides extracted from purple sweet potato related to prebiotic and anti-inflammatory effects. Based on our previous researches, high-throughput sequencing and Rt-PCR methods are used to explore the effects of polysaccharides from purple sweet potato on gut microbiota composition. Effects of polysaccharides from purple sweet potato on the metabolism of gut microbiota are investigated by microbial molecular ecology and metabolics methods. Anti-inflammatory and immune-regulating effects of polysaccharides from purple sweet potato are unfolded by immunology, proteomics, molecular biology as well as cell biology methods. All these researches will be useful to reveal prebiotic and anti-inflammatory effects of polysaccharides from purple sweet potato. These studies will also be beneficial to elucidate the detailed mechanisms of polysaccharides from purple sweet potato on gut microbiota, intestinal inflammation as well as host immunity, and lay necessary foundation to exploit polysaccharides from purple sweet potato in functional foods.

肠道菌群与宿主间互相依存，形成微生态平衡，维持机体健康。天然多糖具有良好的调节肠道菌群结构和肠道抗炎反应的作用，但相关调节机制尚不明确，尤其在紫薯多糖干预肠道菌群结构、调节肠道抗炎通路的机制研究方面更是空白。在课题组前期研究的基础上，本项目拟采用高通量测序和Rt-PCR技术，探究紫薯多糖对肠道菌群结构的作用机制；基于微生物分子生态学和代谢组学的研究方法，探究紫薯多糖对与肠道炎症相关的肠道菌群及代谢产物的作用机制；基于免疫学、蛋白质组学、分子生物学以及细胞生物学的研究方法，探究紫薯多糖对肠道炎症修复作用及免疫调节机制，最终探明紫薯多糖干预肠道菌群结构以及调节肠道抗炎通路的机制。本项研究不仅为天然多糖、肠道菌群、肠道炎症以及机体免疫等方面的关联性研究提供新的认识，而且为紫薯资源的开发利用提供重要的理论依据。

本研究以紫甘薯块根为试验材料，依次通过水提法和碱提法提取后并纯化获得了高纯度的紫甘薯水溶性多糖和碱溶性多糖，采用NMR等方法解析了紫甘薯多糖的化学结构特性。结果表明，紫甘薯水溶性多糖是主链由→4)-α-D-Glcp-(1→、→6)-α-D-Glcp-(1→、→2)-α-D-Manp-(1→组成，T-β-D-Glcp-(1→残基位于侧链，并通过O-6与主链连接，为线性结构多糖。紫甘薯碱溶性多糖是主链由→4)-α-D-Glcp-(1→组成，T-α-D-Manp-(1→、T-α-D-Rhap-(1→、T-α-L-Araf-(1→和T-β-D-Glcp-(1→残基位于侧链，并通过O-6与主链连接，为复杂的多支链结构多糖。采用脂多糖（LPS）和葡聚糖硫酸钠（DSS）构建炎症模型，研究了紫甘薯多糖的体内外抗炎免疫活性。结果表明，紫甘薯多糖可以抑制炎症细胞释放NO以及促炎细胞因子，促进炎症细胞释放抗炎细胞因子；紫甘薯多糖的干预对炎症小鼠胸腺和脾脏等免疫器官起到一定的修复作用，显现出良好的体内外抗炎特性和对机体的免疫保护作用。以LPS和DSS诱导的炎症模型小鼠为研究对象，采用16s rRNA高通量基因测序技术，研究了紫甘薯多糖对炎症小鼠肠道菌群结构的影响及作用机制。结果表明，紫甘薯多糖的干预可以改善炎症小鼠肠道菌群的丰度，并产生较多的乙酸、丙酸和丁酸等短链脂肪酸。紫甘薯多糖通过刺激炎症小鼠肠道中产短链脂肪酸相关微生物的生长，可能为结肠上皮组织提供更多能量，调节结肠上皮细胞和免疫细胞的生长和凋亡，提高抗炎性能。以DSS诱导的肠炎模型小鼠为研究对象，采用微生物分子生态学和代谢组学方法，研究了紫甘薯多糖对肠炎小鼠肠道代谢化合物及代谢通路的影响。结果表明，紫甘薯多糖通过改善DSS诱导的肠炎小鼠的肠道菌群丰度，优化肠道代谢化合物，发挥其抗炎作用。通过研究，首次解析了紫甘薯水溶性多糖和碱溶性多糖的结构特性，明确了两种紫甘薯多糖的抗炎特性，深入探究了紫甘薯多糖干预肠道菌群结构以及调节肠道抗炎通路的机制，研究成果为紫甘薯多糖资源的开发利用奠定了理论基础。