Food First Approach to Stimulate Muscle Protein Synthesis in Healthy Adults

Food First Approach to Stimulate Muscle Protein Synthesis in Healthy Adults

In a crossover design 10 young healthy adults (20-35 y) will receive stable isotope tracer infusions and perform a single bout of resistance exercise. Immediately after exercise participants will ingest either 3.5 oz of Salmon fillet or its constituent macronutrients as isolated amino acids and fat. Repeated blood and breath samples as well as muscle biopsies will be collected to determine whole body amino acid kinetics, muscle amino acid transporters, anabolic signalling 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, the participant will fill out a questionnaire and a baseline breath sample will be collected to determine 13CO2 enrichment by isotope ratio mass spectrometry. A Teflon catheter will be inserted into the antecubital vein for a baseline blood sample (t=-210) 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 solution 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) and maintained over the infusion trials. A second Teflon catheter will be inserted into a heated dorsal vein for repeated arterialized blood sampling and remained patent by a 0.9% saline drip. Breath samples and arterialized blood samples will be collected every 30 to 60 minutes 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 10-12 repetitions or to muscular failure at 65-70% of 1-RM for both leg press and leg extension exercise.

Immediately after the completion of the exercise bout, participants will ingest either 3.5 oz of Salmon fillet or a matched isolated amino acid and fat mixture (t=0). Completion of the meal will mark the start of the postprandial stage and additional muscle biopsies will be collected at t=120 and t=300.

Inclusion Criteria:

• Age 20-35 years
• Recreationally-active adults: ≥ 30 min of physical activity at moderate intensity ≥ 3 times per week
• English fluency

Exclusion Criteria:

• Smoking
• Known allergies to fish consumption
• Vegans
• Diagnosed GI tract diseases
• Arthritic conditions
• A history of neuromuscular problems
• Diagnosed cognitive impairments
• Recent (1 year) participation in amino acid tracer studies
• Predisposition to hypertrophic scarring or keloid formation
• Individuals on any medications known to affect protein metabolism (i.e. corticosteroids, non-steroidal anti-inflammatories, or prescription strength acne medications).
• High blood pressure (Systolic > 140 mm HG; Diastolic > 90 mm HG)
• Alcohol consumption >10 drinks per week
• Metabolic disorders (e.g., Metabolic Syndrome, diabetes, thyroid diseases)
• Consumption of thyroid, androgenic or other medications known to affect endocrine function
• Consumption of ergogenic-leves of dietary supplements that may affect muscle mass (e.g., creatine, HMB), insulin-like substances, or anabolic/catabolic pro-hormones (e.g., DHEA) within 6 weeks prior to participation
• Currently pregnant
• A suboptimal diet quality score as assessed by ASA24 dietary records
• Asthma
• Hypogonadism
• Cardiovascular disease, arrhythmias