Milk Protein Glycation Compromises Postprandial Lysine Bioavailability but does not Modulate Postprandial Muscle Protein Synthesis Rates In Vitro in Males: A Double-blind, Randomized Parallel Trial.

Abstract

Background: Industrial processing and storage of milk products can strongly increase protein glycation level. Previously, we have reported that a high protein glycation level impairs protein digestion, thereby compromising lysine bioavailability. The lower postprandial lysine availability may restrict the anabolic properties of a high glycated protein.

Objectives: The objective of this study was to assess the impact of milk protein glycation on postprandial plasma amino acid availability and subsequent postprandial muscle protein synthesis rates during recovery from a single bout of resistance-type exercise.

Methods: Forty-five recreationally active, healthy young males participated in this double-blinded, randomized parallel study. After performing a single bout of whole-body resistance-type exercise, subjects ingested 20 g milk protein with either a low (4%; LOW-GLYC) or high (47%; HIGH-GLYC) glycation level or a noncaloric placebo (PLA). Continuous intravenous infusion of L-[ring-¹³C₆]-phenylalanine was combined with the collection of blood and muscle tissue samples during a 6-h postprandial period to assess plasma amino acid concentrations and muscle protein synthesis rates.

Results: Protein ingestion increased plasma total and essential amino acid concentrations compared with placebo (time × treatment interaction: P < 0.001), with no differences between the low and high glycated milk protein. Plasma lysine availability, assessed over the full 6 h postprandial period, was substantially lower following ingestion of the protein with the high versus low glycation level (-5 ± 7 compared with 10 ± 9 mmol · L^-1 · 360 min, respectively, P < 0.001). Postprandial 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-GLYC, HIGH-GLYC and PLA, respectively, P = 0.939).

Conclusions: Ingestion of protein with a higher glycation level attenuates postprandial plasma lysine availability. Milk protein glycation does not modulate postprandial muscle protein synthesis rates during recovery from resistance exercise in healthy, young males. This trial was registered at the Dutch Trial Register as NL8690; https://onderzoekmetmensen.nl/nl/trial/49398.