Effects of fatty ethers and stearic acid on the gastrointestinal absorption of insulin

Insulin degradation and inactivation occurs when the protein is given to an animal through oral route. The following compounds were assessed to determine their potential effect in increasing insulin absorption: polyoxyethylene (20) oleyl ether (Brij 99), polyoxyethylene lauryl ether and polyoxyethylene (20) cetyl ether (Brij 58). In this study the above compounds, along with stearic acid, were used to prepare granules with or without addition of insulin and were given orally to rabbits. Both glucose and insulin levels in blood were measured at different time intervals, the former with a glucometer and the latter using radioimmunoassay (RIA). To determine if there was a relationship between the glucose and the insulin levels in blood, a highly sensitive radioimmunoassay method was used to detect any small changes in the level of insulin in blood. A significant decrease in glucose blood levels (P less than 0.05) was obtained after oral administration of each of granules containing insulin. The greatest reduction was observed after half an hour of the oral administration of the granules. A similar response was obtained with the hypodermal injection of 1/5 of the oral insulin dose. Granules prepared with Brij 58 and containing insulin was the only formula that showed increase of insulin level in the blood. This was equivalent to 1/10 of the change produced after hypodermal injection of the hormone. In these experiments the changes in blood insulin levels were not directly proportional to the corresponding changes in blood glucose.