A kinetic study of L-2H3-methyl-1-13C-methionine in patients with severe burn injury.

To explore the consequences of severe burn injury on methionine metabolism we carried out tracer studies, using [1-13C, 2H3-methyl] methionine, given by continuous intravenous infusion, in 12 adult patients. Each was studied in the "fasted" and in the fed state while receiving parenteral nutrition. Compared with findings obtained in our previous studies in healthy adults using a similar protocol, the rates of transmethylation (Tm), homocysteine remethylation (Rm), and methionine oxidation (C) were all substantially increased in burn patients. From the relationships between these systems, it appears that there is a relative increase in the recycling of methionine carbon via Rm during the fasted state. This implies active methyl group transfer and utilization in burn patients. Parenteral feeding increased methylmethionine flux (Qm) and the rates of Tm, Rm, and C. However, the Tm/Qm ratio did not change with feeding in the patients, whereas it increased in healthy young adults. This may not necessarily reflect the consequences of burn injury, but may be due to differences in the route of methionine intake or its level relative to requirement, compared with the conditions of study in healthy adults. Further studies on methionine-cysteine interrelationships, using an isotopic approach, in burned patients are needed to evaluate these possibilities.