Author(s): VAN LIESHOUT, G., TROMMELEN, J., HENDRIKS, F., NYAKAYIRU, J., VAN KRANENBURG, J., SENDEN, J., GOESSENS, J., GIJSSEN, A., VERDIJK, L., BRAGT, M., VAN LOON, L., Institution: MAASTRICHT UNIVERSITY, Country: NETHERLANDS, Abstract-ID: 406

INTRODUCTION:
Industrial processing and storage of milk products can strongly increase protein glycation level. Previously, we have reported that a high protein glycation level compromises protein digestion, resulting in an attenuated post-prandial rise in circulating plasma lysine concentrations. The compromised post-prandial lysine availability may restrict the anabolic properties of such a highly glycated protein. The present study assessed the impact of the level of milk protein glycation on post-prandial plasma amino acid availability and subsequent muscle protein synthesis rates during recovery from a single bout of exercise.
METHODS:
45 recreationally active, healthy young men participated in this randomized parallel study. Immediately after performing a single bout of whole-body resistance-type exercise, subjects ingested either 20 g milk protein with a low (4%; LOW) or high (47%; HIGH) glycation level plus 2 g free leucine, or a non-caloric placebo (PLA). Continuous intravenous infusions of L-[ring-13C6]-phenylalanine were applied, with blood and muscle tissue samples being collected during a 6 h post-prandial period to evaluate plasma amino acid concentrations and post-prandial muscle protein synthesis rates. Incremental area under the curve and peak concentration for plasma amino acid concentrations and muscle protein synthesis rates were compared between treatments using a one-way ANOVA with a Bonferroni correction. Plasma amino acid concentrations were compared between treatments by two-factor repeated-measures ANOVA with time as within-subject factor and treatment as between-subject factor.
RESULTS:
Protein ingestion increased plasma total and essential amino acid concentrations compared to placebo (time*treatment effect: P<0.001), with no significant differences between the milk protein with the low or high glycation level. Post-prandial plasma lysine concentrations were higher following protein ingestion (time*treatment effect: P<0.001), with on average 28% lower peak lysine concentrations following ingestion of the protein with the high versus low glycation level (191±23 vs 266±47 mmol·L-1, respectively, P<0.001). Post-prandial plasma lysine availability, assessed over the full 6 h period, was substantially lower following ingestion of the protein with the high versus low glycation level (-5±7 vs 10±9 mmol·L-1·6 h-1, respectively, P<0.001). Post-prandial muscle protein synthesis rates did not differ between treatments (0.059±0.016, 0.061±0.012, and 0.061±0.018 %·h-1, in LOW, HIGH and PLA, respectively, P=0.939).
CONCLUSION:
Ingestion of a protein with a higher glycation level compromises the post-prandial increase in plasma lysine availability. Milk protein glycation does not seem to modulate the post-prandial muscle protein synthetic response during recovery from resistance exercise in healthy men.