Muscle Protein Synthesis After Whole Egg vs. Egg White Consumption

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.