Branched chain amino acids as the protein component of parenteral nutrition in cancer cachexia.

A prospective randomized trial was conducted to determine the effects of branched chain amino acids (BCAA) as the protein component of total parenteral nutrition (TPN) on protein kinetics in patients with intraabdominal adenocarcinoma. Nine malnourished patients were given both conventional TPN containing 19 per cent BCAA (AA) and isocaloric, isonitrogenous TPN containing 50 per cent BCAA (BCAA-TPN), in random order. Both [13C]leucine and [14C]tyrosine were employed as tracers to avoid the potential bias due to the different amino acid composition of the two TPN solutions. With BCAA-TPN, leucine and tyrosine flux increased significantly from (mean +/- s.d.) 158.0 +/- 37.2 to 243.5 +/- 75.8 mumol kg-1 h-1 (P less than 0.025) and from 35.0 +/- 8.4 to 42.6 +/- 11.0 mumol kg-1 h-1 (P less than 0.05) respectively. Leucine oxidation was significantly higher on BCAA-TPN (24.1 +/- 6.3 on AA versus 68.3 +/- 37.1 mumol kg-1 h-1, P less than 0.025) while tyrosine oxidation was significantly lower (3.7 +/- 1.8 mumol kg-1 h-1 on AA versus 2.5 +/- 2.0 mumol kg-1 h-1 on BCAA-TPN, P less than 0.05). Whole body protein synthesis and breakdown was significantly higher on BCAA-TPN by the tyrosine tracer (31.3 +/- 7.3 on AA versus 40.1 +/- 9.3 mumol kg-1 h-1, P less than 0.025 and 33.0 +/- 8.4 on AA versus 41.3 +/- 11.1 mumol kg-1 h-1, P less than 0.05) respectively. Using the leucine tracers both synthesis and breakdown were increased, but not significantly, from 133.8 +/- 40.0 to 175.3 +/- 65.1 mumol kg-1 h-1 and from 127.9 +/- 33.6 to 167.7 +/- 71.2 mumol kg-1 h-1 respectively. The fractional albumin synthetic rate increased significantly on BCAA-TPN from 4.3 +/- 2.9 on AA to 8.0 +/- 5.1 per cent per day (P less than 0.05). The reduction in tyrosine oxidation, suggesting improved protein utilization, coupled with an increase in protein and albumin synthesis, strongly support a positive benefit from BCAA-TPN in cancer cachexia.