Validating IAAO for Muscle Outcomes

Validating the Indicator Amino Acid Oxidation Technique for Muscle Outcomes

Consuming dietary protein stimulates whole-body and muscle protein synthesis, the latter of which is typically measured using invasive primed constant infusions of stable isotopes with concurrent muscle biopsies. Alternative non-invasive methodologies have been developed (namely the indicator amino acid oxidation (IAAO) technique) to estimate the impact of protein ingestion on whole-body protein synthesis as a proxy for determining dietary protein requirements. Given that the IAAO technique is based on principles of protein metabolism which occur in the liver, it is unclear how representative the IAAO outcomes of whole-body protein synthesis is to skeletal muscle protein synthesis. Validation of the IAAO technique against gold-standard, biopsy-derived measures of muscle metabolism (i.e., muscle protein synthesis) would assist in mitigating the invasiveness of muscle physiology and nutrition research.

Inclusion Criteria:

• Participants will be aged 18-35 years old
• Participants will have a BMI within the normal range (i.e., 18.5-24.9) and waist-to-hip circumference ratio of <0.95 for males and <0.8 for circumference for females to ensure homogeneity of the sample population
• Participants are willing to abide by the compliance rules of this study (e.g., abstain from extraneous physical activity 48h prior to session 4
• Self-reported regular menstrual cycle (25-35d) within the last 3 months (female participants)
• Physical activity score of ≥24 units as measured by the Godin leisure time exercise questionnaire

Exclusion Criteria:

• Inability to adhere to any of the compliance rules judged by principal investigator
• Self-reported regular tobacco or illicit drug use (e.g., growth hormone or testosterone)
• Current use of hormonal contraceptives
• Individuals with a history of allergy to local anesthetics (e.g., lidocaine)