植酸（磷酸肌醇）对沙棘黄酮肠道转运吸收的促进作用及其机制

Hippophae rhamnoides is a traditional ethnic-minority medicine with long application history. Total flavones of Hippophae rhamnoides L. demonstrated wide pharmacology effects such as anti-ischemic, antiarrhythmic, ehancing oxygen resistance ability and lowing serum cholesterol, etc. Xin Da Kang Tablets were the main dosage forms applying in clinic. However, its pharmacological actions were limited by its poor in vitro dissolution and low oral bioavailablity. Therefore, it is necessary to improve the poor intestinal transport and absorption and low oral bioavailability of this preparations, in order to reduce the administering doses and enhance the whole efficacy. Based on the good absorption enhancing effects of phytic acid on the representative components in total flavones of Hippophae rhamnoides L. founded in our previous researches, the oral absorption enhancement effects of phytic acid on total flavones of Hippophae rhamnoides L. would be comprehensively investigated in this study by the combined model of system-in situ-cell. Additonally, the safety of phytic acid also would be evaluated and the absorption enhancing mechanisms would be explored by the three different aspects of chemistry-cell-molecule. The whole research would develop the new application of phytic acid in drug research fields, provide the example for improving oral bioavailability of flavonoids in ethnic-minority medicine and some references for the application of absorption enhancers in more ethnic-minority medicine and its compound prescription preparations with poor oral absorption, and also provide guidances for the studies on intestinal transport and absorption enhancers of traditonal ethnic-minority medicine.

沙棘是一种应用历史悠久的传统民族药物，沙棘黄酮具有抗心肌缺血、抗心律失常，提高耐缺氧能力、降低血清胆固醇等广泛的药理作用。临床上常用的制剂以心达康片为主，但因体外溶出与口服生物利用度均不理想，限制了其药效发挥，迫切需要解决该类制剂肠道转运吸收差、口服生物利用度低的问题，从而减少服药剂量、提高制剂的整体疗效。 本研究在前期发现植酸对沙棘黄酮中代表性成分均具有较好吸收促进作用的基础上，拟通过"整体-在体-细胞"相结合模式全面研究植酸对沙棘黄酮肠道转运吸收的促进作用，评价其安全性，并从"化学-细胞-分子"三种不同角度对植酸促吸收机制进行探讨。以期拓展植酸在药物研究领域的新用途，为解决含黄酮类化合物民族药物的口服生物利用度问题提供范例，为吸收促进剂能够应用到更多吸收较差的民族药物乃至复方制剂提供参考，为传统民族药物的肠道转运吸收促进剂研究提供借鉴。

沙棘黄酮具有抗心肌缺血等广泛药理作用，但其临床制剂因体外溶出与口服生物利用度均不理想，限制了其药效发挥。本项目通过植酸对沙棘黄酮活性成分的吸收促进作用及其机制研究，开发植酸在药物研究领域的新用途，为口服药物促吸收机制的研究方法提供借鉴。本项目结合整体药动学、单向灌流模型、Caco-2细胞单层模型考察植酸对沙棘黄酮活性成分的吸收促进作用，并进行植酸的细胞毒性和肠粘膜毒性评价，在此基础上，从沙棘黄酮理化性质、肠粘膜屏障、肠外排蛋白三个方面进行植酸对各黄酮成分吸收促进作用的机制研究。整体药动学研究显示，植酸在50-200 mg/kg范围内，对沙棘黄酮各成分的吸收促进作用与其剂量呈正相关，植酸剂量为200 mg/kg时促吸收作用最佳；植酸浓度在50-200 μg/mL范围内，沙棘黄酮中有效成分在空肠上的Peff提高了21.20%-41.20%，回肠上的Peff值提高了25.67%-41.76%；在Caco-2细胞单层上的表观渗透系数提高了69%-111%。另外，植酸在0-400 μg/mL浓度范围内细胞毒性小，在50-200 mg/kg内无肠粘膜毒性。随给予植酸浓度增加，Caco-2细胞的跨膜电阻值迅速降低至初始值的6.31%，荧光素钠的透过量由低于0.01 nM/cm2提高至0.68 nM/cm2，表明植酸可以打开紧密连接；激光共聚焦和免疫印迹法分析表明植酸能通过减弱紧密连接蛋白occludin、ZO-1和claudin-1分布和下调紧密连接蛋白表达，降低Caco-2细胞单层膜的完整性；此外，二价阳离子也参与了植酸对紧密连接蛋白的调节，能减弱植酸引起的单层细胞膜完整性降低作用。植酸对外排蛋白P-gp的调节作用及机制研究表明，给予植酸后，P-gp底物R123在大鼠回肠的Peff值增加至151.51%，结肠的Peff值增加至200.59%，且在两种细胞的跨膜转运降低，摄取增加。植酸能增加P-gp的转录水平，却抑制P-gp的蛋白合成环节，从而降低P-gp蛋白表达水平；非竞争性抑制P-gp ATPase活性，且具有浓度依赖性；降低UIC2抗体的结合能力，从而导致空间构象的改变；能够与P-gp的调控部位结合，导致P-gp转运能力下降。