Chapter 7
Hypoglycemic Effect of Insulin in Oil Preparation by Oral Administration
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M . X. Duan, J. H . Guo, H. Ma, Y. Zuo, and C. X. Zheng Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing, 100084, Peoples Republic of China
Since the discovery of insulin, attempts have been made to find the best route of administration of insulin. In addition to injection, various routes of administration have been proposed to control diabetes. However, oral administration of insulin is most convenient, if insulin is protected from proteolytic degradation in the gastrointestinal tract and transported into the circulation system effectively. A n oil formulation was developed and it seemed to be effective by oral route. The use of oil solution for insulin delivery has recently been tested. A system, called IIOP, involves amphiphiles to maintain insulin fully dispersed in oil. The stability of insulin in oil was studied in different pH buffers. This kind of oil phase solution was found to be effective in diabetic rats and normal mice. [1],[2]
[3]
Experimental Materials.
Crystalline porcine insulin was purchased from Xuzhou Biopharmaceutical Company, PRC. Amphiphiles were purchased from Sigma. The oil (such as P E C E O L , L A B R A F A C C C , L A B R A F I L M 1944 CS, P L U R O L O L E I Q U E C C 497, etc.) was generously donated by G A T T E F O S S E Company, France. The insulin radioimmunoassay (RIA) kit was purchased from Beijing Nuclear Energy Institute. The glucose analysis kit was purchased from Beijing Zhongsheng High-tech Bioengineering Company,PRC.
© 2000 American Chemical Society
In Controlled Drug Delivery; Park, Kinam, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
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66 Methods. The insulin, amphiphiles, and o i l were carefully m i x e d together to obtain a clear o i l solution ( H O P ) in the absence o f water. E a c h male W i s t a r rat was injected with streptozocin (65 m g / k g body weight) to destroy β cells in pancreas islets. T h e rats were considered diabetic when fasted g l y c e m i a was more than 300 mg/dl two weeks 141
after the treatment . The H O P was dispersed and stirred in 0.1 M H C l (pH=1.0) solution, P B S buffer (pH=7.4) and N a C 0 - N a H C 0 2
3
3
buffer ( p H = l 1.8), respectively, up to 24 hours.
Samples were extracted at 0, 1, 2, 24 hours after dispersion. The mixture was then
Downloaded by UNIV OF QUEENSLAND on January 30, 2016 | http://pubs.acs.org Publication Date: May 15, 2000 | doi: 10.1021/bk-2000-0752.ch007
centrifuged at 15,000 rpm for 10 minutes until complete separation o f the o i l phase from the water phase. The amount o f insulin in the water phase was measured with R I A by the method described by R I A kit instruction. Diabetic rats were treated with 0.5 m l o f H O P at the dose o f 50 I U / k g body weight after over night fasting. The concentration o f serum glucose was measured with glucose and R I A kits. N o r m a l mice were fed with glucose orally and then with H O P at the dose o f 50 I U / k g body weight. T h e i r serum glucose level was also measured with the glucose analysis kit.
Results and Discussion A s shown in Table 1, insulin was not released from the o i l solution even after being dispersed in bulk buffer o f different p H over 24 hours. This might explain w h y the activity o f insulin in H O P is still retained after flowing through the gastrointestinal tract. W h e n dispersed in the aqueous environment o f the gut, the o i l is emulsified to small droplets w h i c h still contain insulin.
Table 1. Effects of Buffer of Different pH on the Stability of OOP Percentage o f T o t a l Insulin Entering into the Aqueous Phase 0 hour
1 hour
2 hours
24 hours
pH=l H C l
