The effect of insulin and growth hormone on full thickness wound of guinea pigs

Abstract

Insulin is a hormone known primarily for regulating sugar levels in the blood. It was suggested that insulin accelerated wound healing due to its chemical similarity to insulin-like growth factor 1(IGF-1). In order to justify whether or not insulin correlates with IGF-1 and share the same healing property, this study compared the effect of insulin and growth hormone (as the source for IGF) in full thickness wound. This is an animal based study whereby thirty six male guinea pigs were used as animal model and classified into three major groups consist of twelve guinea pigs and each group were subdivided into two smaller groups. Full thickness wound were created on these animals and treated with insulin (Humulin N), recombinant growth hormone (Saizen) and distilled water as control. Each subgroup represented two different mode of administration namely instillation (drop by drop) and subcutaneous injection. Wound healing progress were analysed based on rate of contraction, histological descriptions and macroscopic observations. Statistical analysis indicated that type of agent and mode of administration used has significant effect on rate of contraction. Growth hormone administered by instillation at the dose of 0.6 I.U daily for five days gave a significant result in promoting wound healing as compared to control. Furthermore, histopathological findings both in quantitative as well as macroscopic in this group showed minimal infiltrate exudates with fibrous granulation tissue and mature collagen deposition as compared to other groups. This study provides evidence that insulin failed to promote wound healing although it has the same chemical similarity with IGF-1. Presence of insulin degrading enzyme in wound fluid, insulin physicochemical properties and insulin delivery were identified as negative factors affecting wound healing results in insulin group. Mode of administration has an important role in determining drug delivery to the wound site. Subcutaneous injection has the ability to promote faster wound contraction however the issue of systemic effect that it may produce causes difficulty in finding the most optimum dose for wound healing in both agents.