Quantification of protein metabolism in Vivo for skin, wound, and muscle in severe burn patients

Background: In response to injury, muscle catabolism can be extensive, and in theory, the wound consumes amino acids to support healing. The purpose of this study is to assess a technique by which in vivo protein kinetics of muscle, wound, and normal skin can be quantified in burn-injured patients. Methods: Study protocol consisting of infusion of d ₅ phenylalanine; biopsies of skeletal muscle, skin, and donor-site wound on the leg; quantification of blood flow to total leg, wound, and skin; and sequential blood sampling from the femoral artery and vein. Five-compartment modeling was used to quantify the rates of protein synthesis, breakdown, and phenylalanine transport between muscle, wound, and skin. Results: The study results demonstrated a net release of phenylalanine from muscle yet a net consumption of phenylalanine by the wound. Compared with skin, the wound had a substantially increased rate of protein synthesis and a reduced rate of protein breakdown (p < .01). Transport rates into and out of muscle were significantly higher than those for wound (p < .01). Conclusions: This novel methodology enables in vivo quantification of the integrated response of muscle, wound, and skin protein/amino acid metabolism and confirms the long-held theory of a net catab-olism of muscle and a net anabolism of wound protein in patients after injury. This methodology can be used to assess the metabolic impact of such measures as nutrition, pharma-cologic agents, and surgical procedures. (Journal of Parenteral and Enteral Nutrition 30:331-338, 2006)