Hydrolyzed casein and whey protein meals comparably stimulate net whole-body protein synthesis in COPD patients with nutritional depletion without an additional effect of leucine co-ingestion.
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BACKGROUND & AIMS: Muscle wasting commonly occurs in COPD, negatively affecting outcome. The aim was to examine the net whole-body protein synthesis response to two milk protein meals with comparable absorption rates (hydrolyzed casein (hCAS) vs. hydrolyzed whey (hWHEY)) and the effects of co-ingesting leucine. METHODS: Twelve COPD patients (GOLD stage II-IV) with nutritional depletion, were studied following intake of a 15 g hCAS or hWHEY protein meal with or without leucine-co-ingestion, according to a double-blind randomized cross-over design. The isotopic tracers L-[ring-(2)H5]-Phenylalanine, L-[ring-(2)H2]-Tyrosine, L-[(2)H3]-3-Methylhistidine (given via continuous intravenous infusion), and L-[(15)N]-Phenylalanine (added to the protein meals) were used to measure endogenous whole-body protein breakdown (WbPB), whole-body protein synthesis (WbPS), net protein synthesis (NetPS), splanchnic extraction and myofibrillar protein breakdown (MPB). Analyses were done in arterialized-venous plasma by LC/MS/MS. RESULTS: WbPS was greater after intake of the hCAS protein meal (P < 0.05) whereas the hWHEY protein meal reduced WbPB more (P < 0.01). NetPS was stimulated comparably, with a protein conversion rate greater than 70%. Addition of leucine did not modify the insulin, WbPB, WbPS or MPB response. CONCLUSIONS: Hydrolyzed casein and whey protein meals comparably and efficiently stimulate whole-body protein anabolism in COPD patients with nutritional depletion without an additional effect of leucine co-ingestion. This trial was registered at clinicaltrials.gov as NCT01154400.