Utilization of D-methionine during total parenteral nutrition in postsurgical patients

Utilization of intravenously administered D-methionine was measured by morbidly obese subjects fed parenterally after elective gastric bypass surgery. Five patients were infused with a 25% glucose--4.25% amino acid solution containing DL-methionine, and four were treated with a 25% glucose--3.5% amino acid solution containing only L-methionine. Mean (+/- SD) total daily methionine excretion was 0.06 +/- 0.04 mmoles (of 28 +/- 4 mmoles infused) in patients treated with the L-methionine containing solution, and was 15.2 +/- 4.2 mmoles/day (of 45.2 +/- 5 mmoles DL-isomer infused) in patients treated with the DL-methionine containing solution. In these latter patients, 90 to 98% of the excreted methionine was the D-isomer. The data indicate 64 +/- 23% of infused D-methionine is excreted in the urine. Four patients excreted between 70 to 85% of infused D-methionine in the urine, but one patient excreted only 35 to 55%, suggesting better utilization. Plasma methionine levels were higher (9.9 +/- 1.9 mumoles/100 ml) in patients infused with solutions containing DL-methionine than those infused with the L-methionine solution (4.5 +/- 1.0 mumoles/100 ml). In the former case, 49% of plasma methionine was the D-isomer. The data indicate poor D-methionine utilization by postsurgical patients during total parenteral nutrition when given as DL-methionine in the presence of other amino acids and glucose.