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 during experimental hypercortisolemia. Four groups of subjects that had received 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 proteolysis, Leu oxidation, and nonoxidative Leu disposal, an index of protein synthesis, as studied by kinetics of [1-C-13]Leu. Similar data were obtained from kinetics of [H-2(5)]Phe, resulting in an unchanged protein balance in both cases. In contrast, enteral Gin significantly decreased the endogenous 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 novo synthesis induced by Gin could contribute to spare amino acids in hypercatabolic patients.