Antiproteolytic Action of Insulin in Burn-Injured Rats

Abstract

Background. Negative nitrogen balance is a typical metabolic response to burn injury resulting in decreased muscle mass and activity. Since insulin is an anabolic hormone, using insulin as a prophylactic agent in burned patients has received some attention. The present study was carried out to investigate the systemic effect of insulin on burn injury-induced muscle wasting.Patients and methods. A 15–20% total body surface area (TBSA) scald burn injury was inflicted on the shaved dorsum of rats. Rats were treated with a daily subcutaneous insulin injection for 3 days (0.25–1.0 U/day). After the treatment, a variety of insulin-dependent physiological parameters were monitored. Overall body protein degradation rates were determined by measuring the urinary tyrosine. Also, protein degradations were measured in diaphragm muscles, splenocytes, and peripheral blood mononuclear cells to directly confirm the antiproteolytic activity of insulin.Results. Administration of insulin to burn-injured rats restored body weight primarily by reducing accelerated protein degradation and regaining the intracellular protein content in individual skeletal muscle. The measured physiological parameters showed no possible side effects. Protein degradation in immune cells was also suppressed after the therapy.Conclusion. Results indicate that lower dose insulin particularly suppresses protein degradation without causing secondary effects. It may be a useful approach to preventing burn injury-induced muscle wasting and also has a potential to improve immune response.