柑橘黄烷酮调控β-胡萝卜素肠道吸收作用机制及构效关系研究

Low bioavailability of carotenoids appears to be critical factor for carotenoids and vitamin A deficiency. An increase of intestinal uptake action contributes to high bioavailability of carotenoids. The presence of citrus flavanones can facilitate the absorption of carotenoids both in vitro and in vivo, however, the underlying mechanisms have not yet been exaimined. The project intends to investigate the effects of citrus flavanones on β-carotene cellular uptake using the Caco-2 cell monolayer. A total of twelve citrus flavanones will be used to combine with β-carotene. The changes about cell membrane permeability, and upstream and downstream targets of scavenger receptor class B, type I protein, meanwhile, the related changes of β-carotene cellular uptake will be analyzed comprehensively. Paired comparison will be carried out to understand the roles of number and position of hydroxyl groups and 7-O-glycoside moiety in relation to the regulation effects of citrus flavanones. Then, the inherent mechanisms of citrus flavanones for β-carotene cellular uptake and the structure-activity relationship could be revealed. This project may provide scientific evidences to formulate valuable nutrition strategies for supplement of β-carotene and vitamin A, and also to develop commercial carotenoids mixtures.

类胡萝卜素生物利用率低是导致人们类胡萝卜素及维生素A缺乏的重要原因，增加在肠粘膜的吸收是提高其生物利用率的有效途径。柑橘黄烷酮促进类胡萝卜素吸收在体内外研究中均被证实，但调控机制尚不清楚。本项目构建Caco-2细胞模型，拟选用12种柑橘黄烷酮分别与β-胡萝卜素配伍，研究柑橘黄烷酮调控β-胡萝卜素跨肠道细胞膜水平上的吸收促进机制。系统解析柑橘黄烷酮在此过程中调控细胞膜通透性、膜载体蛋白B类I型清道夫受体上下游信号分子的表达及由此带来的β-胡萝卜素细胞吸收变化的机理，通过组合配对进行结构-效应关系研究，揭示黄烷酮羟基数量、位置及C7位羟基糖苷化所发挥的作用，进而从细胞层次阐明柑橘黄烷酮调控β-胡萝卜素肠道吸收的作用机制及构效关系。研究成果将有助于为人们提出科学的补充类胡萝卜素及维生素A的膳食配伍方案，亦可为研发类胡萝卜素复配营养剂提供理论基础。

食物中营养素非随机的组合，人们食用会产生显著的协同增效作用，然而同时补充两种以上营养素又会影响各自的吸收。类黄酮促进β-胡萝卜素吸收已在体内外研究中被证实，但具体调控机制尚不清楚。本项目构建Caco-2细胞模型，选用12种柑橘黄烷酮分别与β-胡萝卜素配伍，研究柑橘黄烷酮调控β-胡萝卜素跨肠道细胞膜水平上的吸收促进机制及效应关系。研究结果表明柑橘黄烷酮C7位羟基与细胞膜亲和力更强，更利于增加细胞膜流动性，促进β-胡萝卜素细胞吸收；而C3位、C4位羟基与细胞膜亲和力较弱，且结构中羟基数量越多对紧密连接蛋白ZO-1、claudin-1表达影响越小，对β-胡萝卜素细胞吸收作用不显著。柑橘黄烷酮激活重要转录因子PPARγ增加细胞膜受体蛋白SR-BI的表达促进β-胡萝卜素肠道吸收，其中C7位糖基化显著增加SR-BI表达，B环具有邻苯二酚结构对SR-BI的表达促进作用降低。研究成果将有助于为人们提出科学的补充类胡萝卜素及维生素A的膳食配伍方案，亦可为商业研发类胡萝卜素复配营养品提供理论基础，实现类胡萝卜素及维生素A补充人群的精准营养。