Muscle Protein Synthesis After Whole Egg vs. Egg White Consumption

Hypertrophy

In crossover trials, ten (N=10) young men (18-35 y) will receive stable isotope tracer infusions and perform a single bout of resistance exercise. Immediately after resistance exercise, participants will ingest stable isotope labeled whole eggs (18 g protein, 17 g fat) or egg whites (18 g protein, 0 g fat) cooked in scrambled form. Repeated blood and muscle biopsies will be collected to determine whole body amino acid kinetics, muscle amino acid transporters, anabolic signaling and myofibrillar protein synthesis rates during the trials.

On both infusion trials, participants will report to the laboratory at 0700 h after an overnight fast. Upon arrival to the lab, a baseline breath sample will be collected for determination of 13CO2 enrichment by isotope ratio mass spectrometry. A Teflon catheter will be inserted into an antecubital vein for baseline blood sample collection (t=-210 min) and then participants will receive priming doses of NaH13CO2 (2.35 µmol·kg-1), L-\[1-13C\]leucine (7.6 µmol·kg-1), and L-\[ring-2H5\]phenylalanine (2.0 µmol·kg-1). Subsequently, a continuous intravenous infusion of L-\[1-13C\]leucine (0.10 µmol·kg-1·min-1) and L-\[ring-2H5\]phenylalanine (0.05 µmol·kg-1·min-1) will be initiated (t=-210 min) and maintained over the infusion trials. A second Teflon catheter willinserted into a heated dorsal hand vein for repeated arterialized blood sampling and remained patent by a 0.9% saline drip. Breath samples and arterialized blood samples and will be collected every 30 or 60 min during the postabsorptive- and postprandial states. In the post-absorptive state of infusion trial 1, muscle biopsies will be collected at t=-150 and -30 min of infusion to determine basal-state myofibrillar protein synthesis rates, relative skeletal muscle amino acid transporter content, and anabolic-related signaling. In the subsequent cross-over trial only 1 muscle biopsy will be collected at t=-30 for Western blot analysis and postabsorptive myofibrillar protein-bound tracer enrichment. After collection of the resting muscle biopsy at t=-30 for both trials, the participants will perform resistance exercise that consists of 4 sets of 10 repetitions at 80% of 10-RM for both leg press and leg extension exercise. Immediately after completion of the exercise bout, participants will consume 3 whole eggs or an equivalent amount of protein from egg whites (t=0 min). Completion of the meal will mark the start of the postprandial phase (t=0 min) and additional muscle biopsies will be collected at t=120 and 300 min.

United States