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

Abstract 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 intra-abdominal 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 μmol kg−1 h−1 (P < 0·025) and from 35·0 ± 8·4 to 42·6 ± 11·0 μmol kg−1 h−1 (P < 0·05) respectively. Leucine oxidation was significantly higher on BCAA-TPN (24·1 ± 6·3 on AA versus 68·3 ± 37·1 μmol kg−1 h−1, P < 0·025) while tyrosine oxidation was significantly lower (3·7 ± 1·8 μmol kg−1 h−1 on AA versus 2·5 ± 2·0 μmol kg−1 h−1 on BCAA-TPN, P < 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 μmol kg−1 h−1, P < 0·025 and 33·0 ± 8·4 on AA versus 41·3 ± 11·1 μmol kg−1 h−1, P < 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 μmol kg−1 h−1 and from 127·9 ± 33·6 to 167·7 ± 71·2 μmol 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 < 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.