Effect of enteral glutamine on leucine, phenylalanine and glutamine metabolism in hypercortisolemic subjects

The effect of enteral Gin on protein and Gin metabolism was investigated du ring experimental hypercortisolemia. Four groups of subjects that had recei ved corticosteroids and either enteral Gin (0.5 g.kg(-1).day(-1) for 2 days ) or isonitrogenous Ala-Gly were studied in a fasted or in a fed state. In either state, enteral Gin, compared with Ala-Gly, induced no statistically significant change in the endogenous rate of Leu appearance, an index of pr oteolysis, Leu oxidation, and nonoxidative Leu disposal, an index of protei n synthesis, as studied by kinetics of [1-C-13]Leu. Similar data were obtai ned from kinetics of [H-2(5)]Phe, resulting in an unchanged protein balance in both cases. In contrast, enteral Gin significantly decreased the endoge nous rate of Gin appearance and Gin de novo synthesis in the fed state (P < 0.05) as estimated by the kinetics of [N-15]Gln. This decrease in Gin de n ovo synthesis induced by Gin could contribute to spare amino acids in hyper catabolic patients.