Effect of Branched-Chain Amino Acids and Insulin on Postinjury Protein Catabolism in Growing Animals

Abstract

Muscle proteolysis continues to occur in hyper-catabolic states despite the administration of carbohydrates and proteins. Recent clinical and experimental studies have demonstrated that, under catabolic conditions, treatment with either branched-chain amino acids (BCAA) or insulin may decrease negative nitrogen balance. However, the use of BCAA-enriched solutions to inhibit muscle proteolysis has never been tested in growing animals. A study was therefore undertaken to assess the effectiveness of such solutions, with or without insulin, as compared to a more balanced amino acid solution, in preventing or diminishing postinjury protein catabolism in growing animals. Fifteen-day-old rabbits, exposed to standard moderate trauma in the form of crushing the muscle mass of one rear thigh, received one of two amino acid formulations— a balanced amino acid solution (18.8% BCAA) or a 35% BCAA-enriched solution—for 96 hr. Insulin was given to subgroups of both series. The results indicate that: (1) nitrogen balance in nontraumatized animals is clearly superior when balanced amino acids are administered; (2) BCAA-enriched solutions may decrease postinjury muscle protein catabolism; (3) after trauma, insulin also has a nitrogen-conserving effect, which is demonstrated when it is combined both with BCAA-enriched (35%) and balanced amino acid (18.8%) solutions. However, a better nitrogen balance is achieved when insulin is associated with the balanced amino acid solution. (Journal of Parenteral and Enteral Nutrition 8:416-420, 1984)