The effects of short-term parenteral nutrition on human liver protein and amino acid metabolism during laparoscopic surgery

Background: This study was undertaken to elucidate the specific effects of short-term artificial nutrition on human liver protein metabolism. Methods: Thirty patients undergoing elective laparoscopic cholecystectomy were studied: a control group (n = 16) and a group that received total parenteral nutrition (TPN; n = 14). The nutrition consisted of a balanced IV solution of nutrients (17.5 nonprotein kcal/kg body wt, 50% fat, 50% carbohydrates, and 0.1 gN/kg) that was discontinued when the investigation was finished, after a total infusion time of 8.6 +/- 1.0 hours. A liver biopsy specimen was taken as soon as possible after surgery was started, for the determination of the free hepatic amino acid concentrations. In 16 of the patients, L-[H-2(5)]phenylalanine was given by IV to determine the fractional synthesis rate of total liver protein in a second liver biopsy specimen taken approximately 30 minutes later. Results: The frac tional synthesis rate of total liver protein was 15.2% +/- 4.7%/d in the TPN group (n = 7), which was not different from that of the control group (17.7% +/- 3.8%/d, n = 9). However, the free hepatic concentrations of alanine (P < .05) and the essential amino acids increased (p < .001) in the TPN group, whereas the total hepatic amino acid concentrations were comparable between the groups. Conclusion: Thus short-term TPN induced specific changes of the free hepatic amino acid concentrations, whereas total liver protein synthesis remained unaffected by the nutrition.