Effect of enrichment of infusion solutions with branched chain amino acids in parenteral nutrition of rats.

The effect of enrichment of the branched chain amino acids (BCAAs) leucine, isoleucine and valine on total parenteral nutrition was studied in rats. Experimental infusion solutions with a sufficient, marginal or deficient level of glucose contained either the conventional amino acid composition (22.6% BCAAs) or a BCAA-enriched amino acid composition (36% BCAAs). Rats were infused with experimental solutions for 4 days and several parameters of protein metabolism were evaluated in various tissues. Under conditions of sufficient energy supply, BCAA-enriched and conventional groups showed similar body weight gains and muscle protein degradations as measured by urinary 3-methylhistidine excretion. Polysome profiles in the liver and gastrocnemius muscle of the BCAA-enriched group were more heavily aggregated than those of the conventional group. Under the conditions of marginal or deficient energy supply, beneficial effects of BCAA enrichment over the conventional amino acid composition became more evident in terms of better body weight retention, higher RNA/DNA ratio and heavier polysome profile in both liver and muscle, and reduced protein catabolism in muscle. The present study suggests that enrichment of BCAAs, particularly valine and isoleucine, may be useful for nutritional support under hypercatabolic or stressed conditions.