白扁豆多糖通过“小肠-大脑对话”控制葡萄糖吸收及其代谢通路研究

White Hyacinth Bean, one of the Chinese traditional foods, has been confirmed to possess health benefits on maintaining glucose homeostasis. Meanwhile, our previous study has elucidated that White Hyacinth Bean polysaccharide (WBHP) could trigger the protective effects against neuron injury in brain. Interestingly, in a recent research, Yale University scientists demonstrated that brain neurons exerted a vital effect in glucose homeostasis via sensing blood glucose signal feedback. However, it remains unclear whether WBHP could control glucose absorption by the cell-cell contact between intestine and brain. Therefore, the present study is designed to investigate the effect of WBHP in intestinal epithelial cells involved in glucose absorption both in vivo and in vitro on the basis of glycemic signal. Various technological methods are integrated in this work like metabonomics, biochemistry and nutrition. Furthermore, we extend the innovative view of “the dialogue between intestine and brain” to neuronal excitation-mitochondrial energy metabolism coupling signal molecules---AMPK. Therefore, AMPK is applied as a spot to discover the differential metabolites-related pathways-the host response (plane) via the correlation of metabolic transformative principles. And subsequently to propose the mitochondrial mechanism and targeted metabolic pathway referring to WBHP control glucose via “the dialogue between intestine and brain”. In brief, our study elucidates a unique nutritional value of White Hyacinth Bean and provides a novel target and strategy for the research of blood glucose control in regard to the overall effect and material basis through dietary pattern.

白扁豆是中国的传统食品，具有血糖稳定作用。项目组前期研究亦发现白扁豆多糖（WBHP）具有脑保护作用。有趣的是，最近耶鲁大学科学家，突破传统观念，证实大脑神经细胞能感受到血糖水平的改变，在血糖稳定中起重要作用。然而WBHP能否通过细胞与细胞的直接对接，通过“小肠-大脑对话”共同发挥血糖稳定作用亟待进一步研究。本研究基于血糖感受信号，拟将大脑和小肠关联，以葡萄糖吸收为主线，整合代谢组学、生物化学和营养学研究手段，体内、外研究WBHP对小肠上皮细葡萄糖吸收影响。在此基础上，进一步基于 “小肠-大脑对话” 的新视角，以神经元兴奋-线粒体能量代谢偶联信号分子AMPK为点，关联代谢转化规律，研究差异代谢物-相关通路-整体效应（面），阐明WBHP通过“小肠-大脑对话”调控血糖的线粒体机制及靶向代谢通路，最终诠释白扁豆的独特营养价值；为解决膳食稳定血糖的整体效应和物质基础提供新靶标和新方法。

(1)白扁豆多糖（WHBP）的理化性质鉴定：WHBP 具有吡喃环结构，平均分子质量 2.3×105 Da，其单糖组成由葡萄糖、鼠李糖、半乳糖醛酸、半乳糖、木糖、阿拉伯糖组成，质量百分比（%）为 23.23:6.2:5.09:2.76:2.4:0.48，电镜扫描结果显示该多糖表面微观形貌为片状。 WHBP 具有一定的抗氧化和抑菌性能，可为白扁豆的深加工和进一步研究开发奠定理论基础。 .(2) 高脂高糖饮食结合尾静脉注射链脲佐菌素（STZ）建立II型糖尿病(T2DM)大鼠模型，研究WHBP降血糖作用及代谢通路。实验发现，WHBP能够显著降低T2DM大鼠FBG水平和血清INS含量，改善T2DM大鼠体重减轻和糖耐量受损症状；WHBP能够降低T2DM大鼠血清TC、TG和LDL-C含量，同时提高血清HDL-C含量。WHBP可通过调节血脂代谢水平.WHBP可通过减轻胰腺氧化应激和炎症水平发挥胰腺保护作用，抑制胰岛素抵抗（Insulin Resistance, IR）水平，进而发挥降血糖作用。通过建立UPLC-Q-TOF/MS代谢组学方法，分析PSG对T2DM大鼠血液、尿液中代谢物的影响。PSG通过调控T2DM大鼠体内甲基化途径、三羧酸循环和尿液代谢、维生素B12代谢、色氨酸代谢、脂代谢吸收和胆固醇的分解过程、脂肪酸的合成、碳水化合物代谢、脂肪和脂蛋白代谢等途径发挥其降血糖和糖尿病并发症保护作用。.(3)基于肠脑对话白扁豆多糖通过“小肠-大脑对话”控制葡萄糖吸收作用。.WHBP显著提高了紧密连接相关蛋白（ZO-1）的表达，增加了短链脂肪酸（SCFAs）含量，减轻了肠道氧化应激并改善了T2DM大鼠的肠道病理性损伤。此外，WHBP显著改变了T2DM大鼠的肠道菌群，包括门水平的厚壁菌门和拟杆菌门，以及属水平的乳酸杆菌属和变形杆菌属，使菌群组成趋近于正常水平。白扁豆多糖能够显著降低 II 型糖尿病大鼠血清 CRH、ACTH 和 CORT水平，调控下丘脑-垂体-肾上腺轴亢进及AMPK的活性。同时，WHBP能显著抑制小肠组织中的高血糖介导的 SGLT1 mRNA 高表达水平。因此，WHBP 可通过调控肠脑对话抑制高血糖介导的下丘脑-垂体-肾上腺轴亢进和小肠组织 SGLT1 的高表达，减少葡萄糖吸收入血，改善 II 型糖尿病大鼠胰岛素抵抗水平，发挥降血糖作用。