Reduction of Corticosterone-Induced Muscle Proteolysis and Growth Retardation by a Combined Treatment with Insulin, Testosterone and High-Protein-High-Fat Diet in Rats

Abstract

An experiment was conducted to clarify the combined effect of simultaneous administrations of insulin (Ins, 4 units/100g body weight/day) and testosterone propionate (TP, 2mg/100g body weight/day) and feeding a high-protein-high-fat (HPHF) diet (50% protein, 36% fat) on corticosterone (CTC, 10mg/100g body weight/day)-induced muscle proteolysis or growth retardation in young growing male rats. After 6 days prefeeding of the standard (STD) diet (25% protein, 9% fat) and the HPHF diet, hormones were injected subcutaneously for 4 days. Urine was collected every day for the 4-day experimental period to measure N^τ-methylhistidine excretions. The results were as follows. The growth was markedly inhibited and muscle proteolysis was accelerated by the CTC treatment. Feeding HPHF diet reduced CTC-induced muscle proteolysis and the growth retardation, and administrations of Ins and TP further reduced the proteolysis and the growth retardation. From these results, it is thought that administrations of Ins and TP and feeding HPHF diet minimize the muscle protein wasting by counteracting insulin resistance caused by CTC, and masking the CTC receptor.