The metabolic response to injury, whether a controlled
elective surgical procedure or an
accidental injury, is characterized by the breakdown of skeletal muscle
protein and the translocation of the
amino acids to visceral organs and the
wound. At these sites, the substrate serves to enhance host defenses, and support vital organ function and
wound repair.
Glutamine (GLN) plays a major role in these processes, accounting for approximately one third of the translocated
nitrogen. From available data, GLN-supplemented intravenous nutrition in patients undergoing elective surgery improves
nitrogen balance, helps correct the decreased GLN concentration found in the free intracellular skeletal muscle
amino acid pool and enhances net
protein synthesis (particularly in skeletal muscle). Six randomized blind trials (two multicentered investigations) reported a decreased length in
hospital stay in postoperative patients receiving GLN supplementation. After blunt
trauma, GLN supplementation increased plasma concentrations, attenuated the immunosuppression commonly observed and decreased the rate of
infection. Patients with
burn injury have low GLN plasma and intramuscular concentrations; turnover and synthesis rate are accelerated, yet apparently inadequate to support normal concentrations. These data suggest that GLN supplementation has important effects in catabolic surgical patients, but the exact mechanisms to explain these events remain unknown, and more research is required to explain the apparent benefits of dietary GLN.