Gastrointestinal Region Specific Insulin Permeation Enhancement by Aloe vera Gel

Background: The oral administration route is still the most preferred by patients for drug treatment, but is unfortunately not suitable for all drug compounds. For example, protein and peptide drugs (e.g. insulin) are typically administered via injection seeing as they are unstable in the gastrointestinal luminal environment and have poor membrane permeation properties. To overcome this problem, functional excipients such as drug absorption enhancers can be co-administered. Although Aloe vera gel has the ability to improve the permeation of drugs across the intestinal epithelium, its drug permeation enhancing effect has not been investigated in the different regions of the gastrointestinal tract yet.

Objective: The aim of this study was to investigate the insulin permeation enhancing effects of A. vera gel material across excised pig intestinal tissues from different regions of the gastrointestinal tract and to identify the gastrointestinal region where the highest insulin permeation enhancement was achieved.

Methods: Insulin transport across excised pig intestinal tissues from the duodenum, proximal jejunum, medial jejunum, distal jejunum, ileum and colon was measured in the absence and presence of A. vera gel (0.5% w/v) using both the Sweetana-Grass diffusion chamber and everted sac techniques.

Results: The insulin permeation results obtained from both ex vivo techniques showed varied permeation enhancing effects of A. vera gel as a function of the different regions of the gastrointestinal tract. The colon was identified as the gastrointestinal region where A. vera gel was the most effective in terms of insulin permeation enhancement in the Sweetana-Grass diffusion chamber technique with a Papp value of 5.50 x 10-7 cm.s-1, whereas the ileum was the region where the highest permeation enhancement occurred in the everted sac technique with a Papp value of 5.45 x 10-7 cm.s-1.

Conclusion: The gastrointestinal permeation enhancing effects of A. vera gel on insulin is region specific with the highest effect observed in the ileum and colon.