米糠膳食纤维中结合态酚类物质的消化代谢特征及其影响机制

Bound phenolics (BPs), Which are bound to dietary fiber (DF) covalently, are important bioactive components accounting for the health benefits of whole grain. Our previous results indicated that BPs in the whole grain brown rice are mainly ferulic acid (FA) and p-coumaric acid (CA). But how are the BPs released from DF during digestion to exhibit activity? In this project, BP rich rice bran DF (DFRP) or an equivalent level of mixture of CA and FA are used as experiment materials. LC-MSn method will be used to analyze the changes of phenolics and their metabolites in different phases of in vitro simulated digestion and gut microbial fermentation. The distribution of phenolic metabolic substances in blood, urine and feces will also be analyzed in rats fed with DFRB or CA and FA enriched diets for 24 hours or 12 weeks. Meanwhile, the distribution of phenolic metabolic substances in liver, kidney and intestines of rats will be analyzed through MSI. The gut microbial diversity of the rats will be analyzed through 16s rRNA High-throughput Sequencing and metagenomic analysis. We will also determine the activity of cellulase in cecal contents and characterize the fine structure of dietary fiber extracted from rat feces. The mechanism by which BPs are released from DF and then absorbed and metabolized will be elucidated from the perspective of the interaction of gut microbiota with DF. The results will be of great importance for illuminating the action mechanism of whole grain for health promotion and guiding the people to establish whole-grain dietary patterns.

与膳食纤维(DF)共价结合的结合态酚类物质(BP)是全谷物健康效应的重要成分。项目组前期发现物糙米中BP主要为阿魏酸(FA)和对香豆酸(CA)，但其如何被消化酵解从纤维中释放出来而被吸收代谢发挥活性尚不清楚。本项目以富含BP的米糠DF(DFRP)或相当水平的FA和CA混合物为材料，通过体外消化和微生物酵解、大鼠短期和长期强化膳食摄入实验，采用LC-MSn法分析不同体外消化阶段以及动物血、尿、粪便中FA和CA等及其代谢物组成含量变化，通过质谱成像技术明确酚类代谢物在组织器官的分布，探究以FA和CA为主的BP在体内的消化和吸收代谢特征；通过16s rRNA高通量测序、宏基因组测序分析肠道微生物构成，结合分解DF相关酶活性分析和粪便DF精细结构解析，围绕DF和肠道微生物的互作揭示结合态酚类物质的体内释放和吸收代谢机制。研究结果对于全面揭示全谷物的健康效应机制和引导民众全谷物健康膳食模式有重要意义

本项目围绕米糠膳食纤维结合酚的消化代谢特征及肠道微生物在米糠膳食纤维调节酚类物质代谢和生物活性中的作用开展研究。通过碱水解法释放结合色谱分离-波谱分析，鉴定出米糠膳食纤维结合态酚类化合物的结构特征，通过体外模拟胃、肠消化以及消化残渣的结肠体外发酵实验，明确了结合酚主要在肠道微生物酵解作用下被释放为游离态的阿魏酸和对香豆酸，二者进一步在微生物作用下代谢转化为小分子酚酸；体内代谢实验研究表明游离态摄入的阿魏酸和对香豆酸主要经尿液排泄，而结合态酚酸则主要经粪便排出，微生物对结合酚的释放作用使肠腔中的游离多酚含量是摄入游离酚的8-15倍，形成高浓度酚酸含量的结肠内环境可能是米糠膳食纤维发挥改善糖、脂代谢生物活性的重要机制。进而以特殊的全谷物糙米——黑米为材料，通过体外粪便菌群酵解实验，探明了黑米米糠膳食纤维IDF通过增加Prevotella和Paraprevotella的丰度，在其分泌的糖苷水解酶作用下促进其主要花色苷Cy3G代谢转化生成矢车菊素和原儿茶酸，二者是Cy3G的代谢产物中主要的活性代谢产物，IDF存在情况下，二者的浓度在发酵反应体系中始终保持在较未添加IDF更高的水平，表明IDF通过调节菌群结构进而改变了Cy3G的代谢动力学特征。动物实验结果表明，Cy3G和IDF对降低代谢综合征小鼠的体重增长、血脂和血糖水平存在显著的协同增效作用，二者通过协同改善小鼠外周组织的瘦素抵抗，减轻不健康膳食引起的肠道炎症反应和屏障受损，增加norank_Muribaculaceae、Romboutsia、Akkermansia Mucispirillum代谢综合征改善特征微生物丰度，发挥协同作用。上述结果表明全谷物中膳食纤维在调节其结合态以及游离态多酚的代谢动力学特征，基于调节肠道微生物结果增强酚类物质的生物活性中发挥了重要作用。.项目共发表论文学术论文12篇，其中SCI论文10篇，申请并获授权发明专利6件，培养研究生3人。项目主持人张名位带领的功能食品研究团队2019年入选广东省特支计划本土创新团队、主持人入选国家农业农村部“神农领军英才”。