基于URAT1靶点的牛尾菜总皂苷抗高尿酸血症活性成分及作用机制研究

Smilax riparia, a common Chinese herbs with widespread wide resources and large reserves, is widely used for treatment of gout and arthralgiaandmyalgia in folk. Pilot studies sponsored by the applicant revealed that its rhizome is rich in ingredient of steroid saponin with a concentration of as high as 26.5 mg/g crude drug. As a pharmacological test performed on acute hyperuricemia model mice showed, being characteristic of new structure, this ingredient is well active to reduce UA, which is also relative to URAT1 protein expression..Based on the pilot studies, this project is aimed to addressed the following items: to confirm such an active ingredient which is significant active to resist hyperuricemia with a new structure, and try to discover a new medicinal resource; to study the impacts on upstream access of XOD and URAT1 (such as SLC22A12, SLC2A9 and Pdzk1) from this new active ingredient, explore the action mechanism of hyperuricemia resisting, and try to lay a foundation for developing new-type, efficient and safety anti-hyperuricemia medicines. Above items have been achieved via conducting following tests and methods: targeting URAT1 and combining anti-hyperuricemia experiments conducted on hyperuricemia model mice, directed by estimations to materials exploring, isolation and purification methods to natural organic compounds and structure identification methods were employed, respectively.

牛尾菜为我国民间广泛应用于治疗痛风、筋骨疼痛等症的常用中草药。野生资源分布广、蕴藏量大。申请者前期研究发现牛尾菜根茎中富含结构新颖的甾体皂苷类成分（达 26.5mg/g 生药），药理实验证明其对高尿酸血症小鼠具有良好的降低血清尿酸作用，且与 URAT1 蛋白表达相关。. 因此，本项目拟以 URAT1 为靶点并结合高尿酸血症小鼠体内抗高尿酸血症实验，以体内暴露物质评价为导向采用天然有机化合物分离纯化和结构鉴定方法，以期确定牛尾菜总皂苷中具有显著抗高尿酸血症活性、结构新颖的活性成分，发现新的药物资源。并研究活性成分对尿酸生成关键酶XOD的影响和对靶点 URAT1 的上游通路如 SLC22A12、SLC2A9 及 Pdzk1 等的作用，籍以探讨其抗高尿酸血症的作用机制，为应用现代科学实验阐释其功效记载，为开发高效、安全的新型抗高尿酸血症药物奠定基础。

高尿酸血症是痛风发作的重要病理基础。目前的药物治疗以西药为主，但这些药物或价格昂贵( 如苯溴马龙)，或容易发生过敏等不良反应( 如别嘌呤醇、丙磺舒)，使高尿酸血症治疗受到一定限制。本项目我们从牛尾菜总皂苷中分离鉴定16个结构新颖皂苷化合物，多为E环环氧化开裂并二酮或E环环氧化并戊烯烷侧链结构。经模型小鼠抗高尿酸血症药效学实验表明，牛尾菜总皂苷和其中5个皂苷成分均有一定降低模型小鼠血中尿酸水平的作用。5个活性皂苷降低尿酸均与URAT1蛋白相关，不同活性成分的降低尿酸还与XOD酶或GLUT9蛋白等相关。对活性成分针对URAT1靶点上游通路SLC22A12、SLC2A9 和 Pdzk1进行了研究，发现活性成分调控URAT1蛋白都与SLC2A9相关。深入的研究发现牛尾菜总皂苷和其中5个活性成分均有一定降尿酸效果，但效果都不如药效实验对照药别嘌呤醇。意外的是：经金氏Q/等效线法双评价，总皂苷和别嘌呤醇有显著协同降尿酸效果，增效并减毒；其中的化合物Pallidifloside D经金氏Q法初评也和别嘌呤醇也协同作用的苗头。以上结果提示我们：牛尾菜总皂苷中一定具有与别嘌呤醇显著协同活性成分，此类成分能增强别嘌呤醇降尿酸药效且降低其毒副作用；总皂苷与别嘌呤醇协同作用可能是通过此类活性成分和别嘌呤醇协同来实现的。