第二型鈉離子依賴型葡萄糖轉運蛋白抑制劑之臨床前活性及藥動性質研究

Abstract

第二型鈉離子依賴型轉運蛋白 (sodium-dependent glucose transporter-2，SGLT2) 抑制劑被認為具有調控血糖的功能，而利用結構與活性關係的探討，可了解最適合之抑制劑結構。本研究嘗試利用不同結構之糖苷類化合物，分別探討其糖基及非糖基結構對鈉離子依賴型轉運蛋白功能之影響。其轉運功能利用大鼠腎臟及小腸刷狀外緣細胞膜微粒配合放射性物質及快速過濾技術來測定。同時，為評估抑制劑是否可發展為有效之口服降血糖藥物，以人類肝臟微粒體系統檢視其代謝狀況，並利用大鼠之原位小腸灌流試驗評估其腸道穿透性，配合溶解度試驗進行生物藥劑學分類，以了解其腸道吸收之特性。 研究結果顯示，非糖基之芳香環需與糖基呈一定距離且具有適當之取代基以達到選擇性抑制第二型鈉離子依賴型轉運蛋白之作用。此外，糖基結構與鈉離子依賴型轉運蛋白的交互作用對其抑制效果是必要的，而將dapagliflozin 之糖基修改為五元環之新化合物core 1 亦具有抑制腎臟刷狀外緣細胞膜微粒轉運葡萄糖的功能，兩者IC50 分別是19.2 ± 7.1 (μM) 及9.0 ± 3.7 (μM)。Core 1 與dapagliflozin 同樣可能經由phase II 代謝酵素作用而降解，而推算其人體腸道吸收分率約為90 %，顯示在口服吸收的過程中可能會受到腸道穿透性不佳的限制。由以上藥效及藥動學之探討，本研究提供第二型鈉離子依賴型轉運蛋白抑制劑之結構特性，並討論發展為口服降血糖藥物必要的考量，可作為此類藥物後續研究方向之參考。

Sodium-dependent glucose transporter-2 (SGLT2) inhibitors are proved to have antihyperglycemic effect. With the approach of structure-activity relationship, the optimal structure of SGLT2 inhibitors can be revealed. In the present study, glucosides of different structures are used to evaluate the effect of aglycones or “glucose” moieties modification on SGLTs inhibition. The transport activity of SGLTs in the presence of glucosides was measured using brush border membrane vesicles (BBMV) isolated from rat kidneys or intestines. Furthermore, in order to evaluate the suitability of inhibitors for oral administration, human liver microsomes and rat in situ perfusion were used to study the sensitivity to metabolic enzymes and intestinal permeability, respectively. With the results of solubility test, the biopharmaceutics classification system (BCS) of inhibitors was discussed. The results suggested that a certain distance between the “glucose” moiety and the distal aromatic ring as well as appropriate substituents on aromatic rings were necessary for selective SGLT2 inhibition. In addition, the “glucose” moiety was important to interact with SGLTs. Finally, core 1, a new compound formed by replacing the pyranose of dapagliflozin with furanose, had similar inhibitory effect as dapagliflozin, with the IC50 values of 9.0 ± 3.7 (μM) and 19.2 ± 7.1 (μM), respectively. Like dapagliflozin, core 1 might be degraded by phase II metabolic enzymes, and its predicted fraction absorbed in human was about 90 % indicating that its oral absorption might be limited by poor intestinal permeability. In conclusion, the study provided suitable structure characteristics and considerations relating to oral application of SGLT2 inhibitors, which could be of use for further investigation.