Ornithine-α-Ketoglutarate (OKG) Supplementation Is More Effective than Its Component Salts in Traumatized Rats

Addition of an anabolic stimulus during nutritional support seems to be a reasonable adjunct to augment protein synthesis. Ornithine-a-ketoglutarate (OKG) has been used for this purpose in many patho logical situations, but the mechanism of action is poorly understood. We have evaluated the relative met abolic efficacy of four isonitrogenous diets with or with out the addition of a-ketoglutarate (aKG) or ornithine (ORN), in a rat trauma (bilateral femur fracture) model. Both control and traumatized rats were starved for 2 d. Then for 4 d, the control rats were pair-fed to the traumatized rats, one of the four isonitrogenous diets: the basal diet was a casein-based liquid diet; the ORN and OKG diets were the basal diet in which 10% of the dietary nitrogen was replaced by ORN- or OKG- nitrogen, respectively; the aKG diet contained equiva lent amounts of aKG as were present in the OKG diet. Body weight gain per gram of nitrogen intake was simi lar in all four diet groups of both control and trauma tized rats. The fraction of nitrogen intake that was re tained in the body was significantly higher in OKG- fed traumatized rats (23%) than in the corresponding basal diet-fed rats. Plasma and muscle free amino acid concentrations were comparable in OKG- and ORN-fed rats but not in OKG- and aKG-fed rats. Our data suggest that the mechanism of OKG action may be associated with increases in growth hormone and insulin, as well as the production of metabolites of ORN and aKG. OKG has better metabolic benefits than its two components given separately in the nutri tional support of injured rats. J. Nutr. 126: 2141-