To investigate whether BCAA metabolism and SPE of the individual BCAA are altered in COPD during milk protein sip feeding.
In elderly subjects with COPD and in healthy age-matched elderly SPE, endogenous rate of appearance (Raendo) of the leucine (LEU), isoleucine (ILE) and valine (VAL) were measured before and during sip feeding of a Whey protein meal. To study the effect of aging, the healthy elderly were compared to a group of healthy young subjects. Stable isotopes of l-[2H3]-LEU, l-[1-13C]-ILE and l-[1-13C]-VAL were given on two separate test days orally or intravenously. Simultaneously, l-[ring-2H5]-phenylalanine (PHE) and l-[ring-2H2]-tyrosine (TYR) were given to determine the whole body protein breakdown (WbPB), synthesis (WbPS) and NetPS.
SPE of all BCAA, TYR, and PHE (p?<?0.01) were lower in the COPD group, and the increase in netPS during feeding was higher in the COPD group (P?<?0.01) due to higher values for PS (P?<?0.001). Raendo of all BCAA, PHE and TYR were higher in the COPD than the healthy elderly group (P?<?0.05) before and during feeding (P?<?0.001). Sip feeding resulted in a reduction of Raendo of PHE, ILE and VAL (P?<?0.05). Postabsorptive Raendo was not different for any of the measured amino acids between the healthy elderly and young group, while sip feeding resulted in a reduction of Raendo of PHE. Only SPE of TYR was higher in the elderly (P?<?0.05) and the increase in netPS during sip feeding was independent of aging.
The enhanced anabolic response to milk protein sip feeding in normal-weight COPD patients is associated with a reduced splanchnic extraction of multiple amino acids including all branched-chain amino acids.
Registration ClinicalTrials.gov?=?NCT01418469.