Postoperative Parenteral Nutrition with High Supply of Branched-Chain Amino Acids: Effects on Nitrogen Balance and Liver Protein Synthesis

Abstract

Branched-chain amino acids (BCAA) stimulate muscle and liver protein synthesis in vitro. The significance of this action in catabolic conditions in vivo remains controversial. The effects of a high supply of BCAA in total parenteral nutrition (TPN) on nitrogen balance and liver protein synthesis were studied in a postoperative rat model. After standard operative trauma TPN was commenced with one of two isocaloric programs (I: 20.1% BCAA and II: 50% BCAA) and continued for 48 hr. The relative rate of liver protein synthesis, measured after TPN in vitro by perfusion with ¹⁴C-leucine, was similar in both groups (I: 53.4 ± 17.3 and II: 49.0 ± 27.3 arbitrary units of synthesis rate, mean ± SD). The cumulative nitrogen balance was positive with both regimens and was not improved by the high supply of BCAA (I: 2.02 ± 0.81 and II: 1.87 ± 0.63 gN/kg/48 hr mean ± SD). We conclude that after moderate surgical trauma TPN with a high supply of BCAA offers no advantage over conventional TPN. (Journal of Parenteral and Enteral Nutrition 10:574-577, 1986)