基于肠道菌群的肉苁蓉抗痴呆作用机制与药效物质基础研究

Cistanches Herba is one of the most commonly used herbs with anti-dementia effect in traditional Chinese medicines (TCMs). Its clinic application and pharmacological studies have shown that it has obvious anti-dementia activity, including anti-Alzheimer’s disease (AD). The total glycosides from C. Herba has been launched as an anti-dementia new drug in China. The phenylethanoid glycosides are its active ingredients, and echinacoside is the main active compound of it. It has been reported that the oral bioavailability of echinacoside is just 0.83%. Therefore it is a key scientific issue how to play the efficacy of the Chinese herbs with low oral bioavailability. Recent research demonstrated that dementia was closely related to gut microflora, and the gut microflora is becoming a new promising target for anti-dementia drug research and development. We present the hypothesis that "Cistanches Herba can play anti-dementia effect through gut microflora". In this study, we observe the anti-dementia activity of C. Herba in APP/PS1 double transgenic mice. At the same time, we investigate the changes in composition and diversity of the gut microflora affected by C. Herba. Then we isolate and culture bacterial strains which are in connection with AD to confirm the growth regulatory effect of main compounds and metabolites from C. Herba. In addition, we explore the possible mechanism of growth regulation by metabolomic analysis of the strains, so as to comprehensively elucidate the anti-dementia mechanism based on gut microflora regulation and the active ingredients of C. Herba. This study will provide a new perspective for understanding the effectiveness of TCMs with low bioavailability.

肉苁蓉为一常用中药，临床及药理研究证实其具有显著抗痴呆作用，从中开发的“苁蓉总苷胶囊”已批准上市，有研究显示其中主要活性成分松果菊苷的口服生物利用度仅为0.83%。口服生物利用度如此低的中药及其成分如何发挥作用一直是困扰人们的一个关键科学问题。近年研究显示，肠道菌群与包括阿尔茨海默病（AD）在内的多种痴呆密切相关，肠道菌群也成为抗痴呆药物研究开发的一个新靶点。我们提出“肉苁蓉通过调节肠道菌群发挥抗痴呆作用”的假说。本课题利用APP/PS1双转基因AD模型小鼠观察肉苁蓉改善学习记忆的药理活性，同时研究肉苁蓉对肠道菌群组成及多样性的影响，分离和培养痴呆相关菌株，证实肉苁蓉主要成分及其代谢产物对相关菌株的促进或抑制作用，并通过代谢组学分析探索菌株生长调节的机理，从而阐明肉苁蓉抗痴呆的肠道菌群调节机制及药效物质基础，为理解低生物利用度中药的有效性提供一个新的视角。

近年研究显示，肠道菌群在阿尔茨海默病（Alzheimer’s disease, AD）的发生和发展过程中起关键作用，调节肠道菌群及其代谢产物有望作为治疗AD的新途径。中药肉苁蓉中的苯乙醇苷类成分抗痴呆作用明确，但其口服生物利用度低，作用机制尚未完全阐明。本项目基于APP/PS1双转基因AD模型小鼠，从肠道菌群的角度探讨了肉苁蓉抗痴呆的作用机制。取得的主要进展如下：（1）荒漠肉苁蓉70%乙醇提物具有良好的抗痴呆作用，可显著提高AD模型小鼠在水迷宫实验中的目标象限停留时间，降低海马组织中p-Tau和AβA4表达。（2）16S rRNA基因测序表明，AD模型小鼠的肠道菌群多样性较C57BL/6野生型小鼠显著降低，且肠道菌群组成结构发生明显改变。肉苁蓉干预可调节与AD相关的肠道菌群紊乱，显著回调在AD模型小鼠中异常升高的厚壁菌门与拟杆菌门的相对丰度比，纠正AD模型小鼠中多种肠道菌丰度的异常升高或降低，并促进毛螺菌属、普雷沃氏菌属等肠道益生菌的富集。（3）基于LC-MS/MS的靶向代谢组学分析发现，肉苁蓉提取物可有效调控痴呆相关的肠道菌群代谢紊乱，显著回调了26个在AD模型小鼠粪便中含量异常的代谢物，其中22个为氨基酸类成分，涉及丙氨酸、天冬氨酸和谷氨酸代谢等多条氨基酸代谢通路，提示肉苁蓉可能通过调节肠道菌群的氨基酸代谢而发挥抗痴呆作用。（4）同时，我们建立了肉苁蓉提取物的体外化学成分谱，并鉴定了其中25个主要化学成分。本项目从肠道菌群的结构和功能两方面初步探究了肉苁蓉的抗痴呆作用机制，相关研究结果可为抗痴呆药物研发提供靶点和基础，也为阐明低生物利用度中药的药效物质基础提供了科学依据。