Acute Propranolol and Insulin Infusion Stimulates Synthesis and Deposition of Muscle Protein Post Partial Thickness Donor Site Wound

Abstract

Introduction Severe burn injury induces muscle catabolism. Harvesting of normal skin from non-burned donor sites is a preferred surgical option in severe burns, but it may provoke additional muscle breakdown. The aim of this study was to test whether propranolol or insulin administration improve muscle protein synthesis after surgical creation of partial thickness skin donor wounds. Methods A partial-thickness skin donor wound was created on the back of 21 rabbits. Catheters were placed in the carotid artery and jugular vein. A nasogastric feeding tube was placed for enteral feeding. On day 5, stable isotope tracers were infused. Animals were randomly assigned to control, insulin (2.5 mU/kg/min) or propranolol groups (1 mg/kg/h) (n=7 each). Arterial blood and leg muscle were collected during tracer infusion. The difference between groups was evaluated by non-parametric tests (Kruskal-Wallis and Wilconxon Rank-sum tests). A P value of < .05 was considered significant. Results The propranolol infusion decreased heart rate by 21%. The protein fractional synthetic rate in muscle was greater in the insulin and propranolol group (4.42 ± 0.26, 3.66 ± 0.20 vs. 3.10 ± 0.21 %/day, P < 0.05). Muscle protein fractional breakdown rates were not significantly different (P=0.092). The rate of protein deposition (synthesis - breakdown) was increased in both the insulin and propranolol groups vs. control (3.15 ± 0.39, 0.43 ± 1.13 vs. −0.22 ± 0.7%/day, P= 0.022). Conclusions Propranolol and Insulin infusion increased muscle protein synthetic rate and increased muscle protein deposition rate. These changes reflect a systemic response to the β-adrenergic blockade and to insulin treatment after surgical stress inflicted by harvesting of skin.