酪蛋白和鱼精蛋白对胰岛素酶降解和口服降血糖作用的影响

Effect of casein and protamine on the enzymatic degradation and the orally hypoglycemic action of insulin

目的 研究酪蛋白和鱼精蛋白对酶降解胰岛素(INS)的保护作用及对大鼠灌胃给予INS溶液和微球后降血糖作用的影响。方法 采用HPLC法测定α-糜蛋白酶和胰蛋白酶溶液中INS的残余量,考察酪蛋白和鱼精蛋白对体外酶降解INS的保护作用;制备INS溶液及肠溶微球,在促吸剂M-[8-(2-羟基苯甲酰基)氨基]辛酸钠(SNAC)存在下,大鼠灌胃给药研究酪蛋白和鱼精蛋白单独及合并使用对INS溶液和微球降血糖作用的影响。结果 酪蛋白对α-糜蛋门酶体外降解INS有较好的抑制作用,鱼精蛋白不能抑制α-糜蛋白酶对INS的降解,但对胰蛋白酶降解INS的抑制作用优于酪蛋白。鱼精蛋白和酪蛋白均可增加INS溶液和肠溶微球的降血糖作用,两者合用效果更佳。在SNAC、鱼精蛋白和酪蛋白存在下,INS肠溶微球比INS溶液有更强而持久的降血糖作用。结论 酪蛋白和鱼精蛋白可通过竞争性与酶结合机制增加INS在肠道消化酶中的稳定性,对INS口服吸收有利。

Aim To study the protection of casein and protamine against degradation of insulin (INS) by proteolysis enzymes and the effect of these two kinds of protein on the hypoglycemic action of INS solution and enteric-microspheres after administrated orally to rats. Methods HPLC was used to determine the remained INS in the solution of α-chymotrypsin and trypsin with or without casein or protamine; INS solution and enteric-microspheres were prepared and adiministrated orally to rats together with the absorption enhancer sodium N-[8-(2-hydroxybenzoyl) amino] caprylate ( SNAC ) . At the same time , casein or protamine or both of these two kinds of protein were administrated together in order to study their influence on the hypoglycemic effect of INS and microspheres. Results Casein had a good protection against degradation of INS by α-chymotrypsin, but protamine had no protection effect. However, the degradation of INS by trypsin is concerned, the protection effect of protamine on INS was better that of casein. Both of protamine and casein can increase the hypoglycemic effect of INS solution and enteric-microspheres. Co-administrated these two kinds of protein had a better effect. In addition, co-administrated with SNAC, casein and protamine, INS enteric-microspheres had a longer and more potent hypoglycemic effect than that of the solution. Conclusion Casein and protamine can increase the stability of INS in the intestinal fluid by the mechanism of competition and combine with proteolysis enzymes, which will benefit to INS oral administration.