Modulation of immune response with ornithine alpha-ketoglutarate in burn injury: An arginine or glutamine dependency?

Enterally administered ornithine alpha-ketoglutarate (OKG) is an efficient complement of nutritional support in trauma situations, especially after bu rn injury. A typical feature observed in this intense catabolic state is in sufficient production of glutamine (Gln) and arginine (Arg), two amino acid s (AAs) involved in the immune response. As OKG in vivo metabolism generate s these two AAs, we investigated, in burned rats, the action of OKG with re gard to modulation of immunity. Male Wistar rats were randomly allocated to four groups. On day 0, 12 rats were burned with boiling water (20% body su rface area). After a 24-h fast, they were enterally refed for 48 h using Os molite, as a low-calorie low-nitrogen regimen, supplemented with either 5 g OKG . kg(-1) . d(-1) (n = 6) or an equivalent amount of nitrogen in the fo rm of glycine (n = 6). Non-burned pair-fed controls treated with glycine (n = 6) and healthy rats fed ad libitum (n = 6) were also studied. Nitrogen b alance was assessed from daily measurement of total nitrogen excretion. On day 3, thymus, Anterior tibialis muscle and proximal jejunum weights were r ecorded. Muscle and intestinal AA concentrations were also quantified. OKG counteracted (P < 0.01) the thymic involution that occurs with burn injury. and increased the concentrations of Gin and Arg in both the muscle (P < 0. 01 and P < 0.05, respectively) and the jejunum (P < 0.01 for Gin). When all groups were taken together, a positive correlation was found between thymu s weight, and Gin and Arg muscle concentrations (r = 0.71, P < 0.001 and r = 0.58, P < 0.01, respectively). Furthermore, as expected, OKG improved nit rogen balance. As it is known that total number of thymocytes parallels thy mic weight, and as Gin and Arg are essential nutrients for activated immune cells, our results suggest that Gin and Arg derived from OKG are responsib le for the immunomodulating properties of this molecule in burn injury. Nut rition 1999;15:773-777. (C) Elsevier Science Inc. 1999.