Enhanced anabolic response to milk protein sip feeding in elderly subjects with COPD is associated with a reduced splanchnic extraction of multiple amino acids

Abstract

Background & aims: We previously observed in elderly subjects with Chronic Obstructive Pulmonary Disease (COPD) an enhanced anabolic response to milk protein sip feeding, associated with reduced splanchnic extraction (SPE) of phenylalanine. Milk proteins are known for their high Branched-chain Amino Acids (BCAA) content, but no information is present about splanchnic extraction and metabolism of the individual BCAA in COPD.

Objective: To investigate whether BCAA metabolism and SPE of the individual BCAA are altered in COPD during milk protein sip feeding.

Design: 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-[(2)H(3)]-LEU, l-[1-(13)C]-ILE and l-[1-(13)C]-VAL were given on two separate test days orally or intravenously. Simultaneously, l-[ring-(2)H(5)]-phenylalanine (PHE) and l-[ring-(2)H(2)]-tyrosine (TYR) were given to determine the whole body protein breakdown (WbPB), synthesis (WbPS) and NetPS.

Results: 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.

Conclusion: 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.

Conflict of interest statement

CONFLICT OF INTEREST

There is no Conflict of Interest to declare.

Copyright © 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Figures

Figure 1

Splanchnic extraction of phenylalanine (SPE-PHE, fig 1a), tyrosine (SPE-TYR, fig 1b), leucine (SPE-LEU, fig 1c), isoleucine (SPE-ILE, fig 1d), and valine (SPE-VAL, fig 1e) in young (n=8, striped bar) and elderly healthy controls (n=8, closed bar) and COPD patients (n=8, open bar) during enteral intake of the whey protein meal. Mean values ± SE are shown. Significance of difference between the COPD and healthy elderly group **:P<0.01, ***:P<0.001. Significance of difference between the healthy elderly and young group ###: P<0.001.

Figure 2

Raendo in the postabsorptive state (=WbRa, open bar) and the prandial state (closed bar) of phenylalanine (PHE, fig 2a), tyrosine (TYR, fig 2b), leucine (LEU, fig 2c), isoleucine (ILE, fig 2d) and valine (VAL, fig 2e) in young (n=8) and elderly healthy controls (n=8), and in COPD patients (n=8) during enteral intake of the whey protein meal. Mean values ± SE are shown. Significance of difference in postabsorptive Raendo between the COPD and the healthy elderly group *:P<0.05, **:P<0.01. For the COPD vs. elderly comparison, there was a group effect for Raendo PHE, TYR, LEU, ILE and VAL (P<0.001) and a feeding effect for Raendo PHE, ILE and VAL (P<0.05). For the elderly vs. young comparison, there was a group effect for PHE, ILE, VAL (P< 0.01), and TYR (P< 0.05) and a feeding effect for Raendo PHE (P< 0.05). There was no significant group × time interaction for Raendo for Phe, Tyr, or the three BCAAs Leu, Ile or Val.

Figure 3

Absolute change (prandial-postabsorptive) in whole body protein synthesis (PS, fig 3a), endogenous rate of appearance (Raendo, fig 3b) and NetPS (=PS-Raendo, fig 3c) during intake of the whey protein meal in young (n=8, striped bar) and elderly healthy controls (n=8, closed bar) and COPD patients (n=8, open bar). Mean values ± SE are shown. Significance of difference between the COPD and healthy elderly group **:P<0.01, ***:P<0.001. Significance of difference between the healthy elderly and young group #:P<0.05.