Extremity hyperinsulinemia stimulates muscle protein synthesis in severely injured patients

Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77555 Submitted 10 June 2003 ; accepted in final form 19 November 2003 Insulin has a well-recognized anabolic effect on muscle protein, yet critically ill, severely injured patients are often considered "resistant" to the action of insulin. The purpose of this study was to assess the in vivo effects of hyperinsulinemia on human skeletal muscle in severely injured patients. To accomplish this goal, 14 patients with burns encompassing >40% of their body surface area underwent metabolic evaluation utilizing isotopic dilution of phenylalanine, femoral artery and vein blood sampling, and sequential muscle biopsies of the leg. After baseline metabolic measurements were taken, insulin was infused into the femoral artery at 0.45 mIU·min -1 ·100 ml leg volume -1 to create a local hyperinsulinemia but with minimal systemic perturbations. Insulin administration increased femoral venous concentration of insulin ( P < 0.01) but with only a 4% (insignificant) decrease in the arterial glucose concentration and a 7% (insignificant) decrease in the arterial concentration of phenylalanine. Extremity hyperinsulinemia significantly increased leg blood flow ( P < 0.05) and the rate of muscle protein synthesis ( P < 0.05). Neither the rate of muscle protein breakdown nor the rate of transmembrane transport of phenylalanine was significantly altered with extremity hyperinsulinemia. In conclusion, this study demonstrates that insulin directly stimulates muscle protein synthesis in severely injured patients. insulin resistance; phenylalanine; burns; muscle catabolism; critical illness; hypermetabolic response Address for reprint requests and other correspondence: D. C. Gore, The Univ. of Texas Medical Branch, 301 Univ. Boulevard, Galveston, TX 77555-1172 (E-mail: dcgore{at}utmb.edu ).