Background: Insulin, like most peptides, is classified as a hydrophilic and macromolecular
drug that is considered as a low permeable and unstable compound in the gastrointestinal (GI) tract.
The acidic condition of the stomach can degrade insulin molecules. Moreover, the presence of proteolytic
activities of some enzymes such as trypsin and chymotrypsin can hydrolyze amide-bonds between
various amino-acids in the structures of peptides and proteins. However, due to its simplicity
and high patient compliance, oral administration is the most preferred route of systemic drug delivery,
and for the development of an oral delivery system, some obstacles in oral administration of peptides
and proteins including low permeability and low stability of the proteins in GI should be overcome.
Objective: In this study, the effects of orally insulin nanoparticles (INPs) prepared from quaternerized
N-aryl derivatives of chitosan on the biochemical factors of the liver in diabetic rats were studied.
Methods: INPs composed of methylated (amino benzyl) chitosan were prepared by the PEC method.
Lyophilized INPs were filled in pre-clinical capsules, and the capsules were enteric-coated with Eudragit
L100. Twenty Male Wistar rats were randomly divided into four groups: group1: normal control
rats, group 2: diabetic rats, group 3: diabetic rats received capsules INPs(30 U/kg/day, orally), group 4:
the diabetic rats received regular insulin (5 U/kg/day, subcutaneously). At the end of the treatment, serum,
liver and kidney tissues were collected. Biochemical parameters in serum were measured using
spectrophotometric methods. Also, oxidative stress was measured in plasma, liver and kidney. Histological
studies were performed using H and E staining .
Results: Biochemical parameters, and liver and kidney injury markers in serum of the diabetic rats that
received INPs improved significantly compared with the diabetic group. INPs reduced oxidative toxic
stress biomarkers in serum, liver and kidney of the diabetic treated group. Furthermore, a histopathological
change was developed in the treated groups.
Conclusion: Capsulated INPs can prevent diabetic liver and oxidative kidney damages (similar regular
insulin). Therefore oral administration of INPs appears to be safe.
Lay Summary: Although oral route is the most preferred route of administration, but oral delivery of
peptides and proteins is still a challenging issue. Diabetes Mellitus may lead to severe complications,
which most of them are life-threatening. In this study, we are testing the toxicity of oral insulin nanoparticles
in kidney and liver of rats. For this investigation, we will prepare insulin nanoparticles
composed of a quaternized derivative of chitosan. The nanoparticles will be administered orally to
rats and the level of oxidative stress in their liver and kidney will be determined. The data will be
compared to the subcutaneous injection of insulin.