膳食纤维-淀粉拟谷粒结构体的构建及其对血糖平衡的作用机制

Glucose homeostasis is essential to life. Cereal starch, as the main glucose provider in cereal-based foods, its nutritional properties have a significant impact on glucose homeostasis，particularly its slow digestion property. Literature reports have shown that whole grain foods are beneficial to glucose homeostasis and the prevention of metabolic diseases, and dietary fiber is considered as the main functional component. However, the contribution and mechanism of endosperm starch (the major component of whole grain) to the beneficial effects of whole grain foods have rarely been investigated. Thus, according to the principle of bionics and the natural arrangement of cell wall and starch in whole grain, the current project is to imitate the cellular microstructure of intact whole grain to produce a kernel-like structural form through interaction between dietary fiber and starch.The kernel-like structural form will be used as a model system to investigate the slow digestion proprty of starch and related mechanism and the structural form's impact on postprandial glycemic response. Finally,the metabolic synergy between the two components in kernel-like structural forms and its influence and mechanism on glucose homeostasis regulation will be explored. This project can not only provide insights regarding the slow digestion property of starch in whole grain foods,but also reveal the contribution of the endosperm starch to the health benefits of whole grain foods through its synergistic interaction with dietary fiber. The research of the kernel-like structural form will provide theoretical and technological guidance to produce healthy foods with the physiological functions of whole grain foods.

血糖平衡是维持生命正常运转的基础。研究证实，在谷物食品中，淀粉作为提供葡萄糖的主要成分，其慢消化性对血糖平衡至关重要。全谷物食品也具有平衡血糖和预防疾病的功能，其中膳食纤维被认为是其生理功效的重要基础，而作为主要成分的淀粉（50-70%）在全谷物食品健康功效中可能的作用和机制未见深入的研究和报道。因此，本项目将依据仿生学原理和全谷粒中细胞壁和淀粉的排列方式，采用膳食纤维来模拟细胞壁，并通过与淀粉的相互作用，创建膳食纤维-淀粉拟谷粒结构体，同时作为一种全新的模式体系来研究结构体中淀粉的慢消化性及机理，检测拟谷粒结构体对餐后血糖和肠道反馈系统的影响，并探索结构体中两组分在调节血糖平衡中的作用和机制。本研究可揭示全谷物食品中淀粉慢消化的机理，阐明膳食纤维与淀粉协同作用对全谷物食品健康功效的贡献，并可为设计和制造具有全谷物食品生理功效的健康食品提供理论依据和技术指导。

肥胖发病率的持续上升已经成为一个日益严重的公共健康问题，而糖尿病、高血压、动脉粥样硬化等许多慢性病都与肥胖有密切的关系。研究证实，全谷物食品具有抗肥胖和调节血糖平衡的功能，其中膳食纤维和植物化学物被认为是其发挥生理功效的主要物质，而淀粉虽然是谷物食品中提供葡萄糖的主要营养素，但其对全谷物食品健康功效的影响和作用机制却没有深入的研究。因此，我们首先仿造全谷粒的微观结构，通过钙离子交联海藻酸钠和β-葡聚糖成为‘细胞壁’包裹淀粉，构成了拟谷粒体，扫描电子显微镜（SEM）和激光共聚焦显微镜（CLSM）观察到淀粉颗粒嵌入β-葡聚糖-海藻酸钠-Ca2+形成的凝胶基质中，具有细胞壁样结构，就像具有较高淀粉含量的燕麦麸皮一样具有较高的慢消化性(淀粉)，而且可以显著减低餐后血糖反应和发酵速率。进一步以拟谷粒体代替高脂食品中50%的淀粉作为膳食干预和预防的饲料对于肥胖小鼠进行了研究，研究结果表明干预和预防都显著降低了小鼠体重的增加量，下丘脑中抑制食欲的POMC基因表达的增加和促进食欲的NPY基因表达的下调，说明拟谷粒结构体可通过增加能量消耗、抑制食欲而有利于能量平衡，达到抗肥胖作用，而PPARα表达的增加和SREBP-1c、FAS表达的降低，和AMPK通路的激活也证实了拟谷粒结构体的抗肥胖作用。其次拟谷粒体降低了炎症因子的表达，降低糖异生关键酶PEPCK和G-6-Pase，降低了葡糖糖的合成，肝糖原的合成增加，不仅改善了糖代谢，而且提高了小鼠肝胰岛素抵抗。进一步通过代谢组分析小鼠血液，发现拟谷粒体小鼠血液中丁酸含量明显高于高脂组，而生糖氨基酸如精氨酸、亮氨酸等明显低于高脂组，说明拟谷粒体能够通过丁酸等途径拮抗高脂膳食带来的糖脂代谢紊乱。肠道菌群发现拟谷粒体组小鼠粪便中与抑制肥胖相关的Bacteroidetes 菌群丰度高于高脂组，而其中促进糖尿病发生与发展的Lachnospiraceae细菌丰度低于高脂组，说明拟谷粒结构体能够通过改善肠道菌群对机体健康产生有益作用。