Metabolic Effect of Short‐Term Total Parenteral Nutrition Highly Enriched With Leucine or Valine in Rats Recovering From Severe Trauma

Abstract

The metabolic impact of infusing a large amount of leucine (Leu) or valine (Val) was examined with regard to the corrective effect of total parenteral nutrition (TPN). Rats recovering from severe sepsis received either Leu- or Val-enriched TPN solution for 30 hours. The in vivo behavior of the amino acids administered was explored by a pulse injection of 14C-labeled Leu or Val. The recovery of 14CO2 from Leu increased by 64% in the septic rats of Leu-TPN group (41% of dose; p less than .01), as compared with control rats receiving the same TPN solution, whereas no significant rise in the 14CO2 recovery from Val occurred in the septic rats given Val-TPN (45% of dose) in comparison with the corresponding controls. The enhancement of Leu catabolism to CO2 in the Leu-TPN group was compatible with the alterations of urinary nitrogen excretion, plasma Leu level, and metabolite contents of liver and muscle. The only difference in metabolite levels observed between the two TPN groups was in hepatic total adenine nucleotides. Plasma amino acid levels were largely unaffected by infusion of these TPN solutions highly enriched with branched-chain amino acids (45%), except for an approximately threefold elevation of the Val level in Val-TPN rats. Thus, when administered in a large quantity during such short-term TPN, Leu can exert its metabolic effect without causing an imbalance in plasma amino acids under severe catabolic conditions.