Skip to main content
OpenTrials
Recruiting

NCT Number: NCT07317921

Validating IAAO 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.

Recruiting

Interested in participating?

Request Info

Key information

Conditions

Protein Metabolism

Age range

18 year–35 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Kinesiology & Physical Education

Toronto, Ontario, M5S 2C9, Canada

Location status: Recruiting

Location contact

Daniel Moore, Ph.D

PRINCIPAL_INVESTIGATOR

Sabrina T. Barsky, Ph.D.

CONTACT

[email protected]

16475400115

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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)

Treatment and study plan

Protein + Stable Isotope Tracer Beverage

Dietary Supplement

Participants will consume 12 half-hourly (6 hours) isoenergetic, isonitrogenous beverages containing 0.9g/kg fat-free mass/day protein. Drinks will be enriched with stable isotopes [2H5]Phenylalanine and [1-13C]Phenylalanine, which will respectively allow for determination of muscle protein synthesis and whole-body protein synthesis over the subsequent 6 hours of feeding

Primary outcomes

  1. Phenylalanine excretion (umol/kg/h)

    Time frame: 6.5 hours

    Rate of whole-body phenylalanine excretion following orally ingested amino acid tracer [1-13C]Phenylalanine determined from the product of breath 13CO2 enrichment and carbon dioxide production rate (VCO2).

  2. Phenylalanine oxidation (umol/kg/h)

    Time frame: 6.5 hours

    Rate of whole-body phenylalanine oxidation following orally ingested amino acid tracer [1-13C]Phenylalanine determined from the correction of phenylalanine excretion by the phenylalanine precursor enrichment via urine enrichment.

  3. Myofibrillar protein synthesis (%/hr)

    Time frame: 6.5 hours

    Rate of myofibrillar fractional synthesis is determined by rate of incorporation of orally ingested tracer [2H5]Phenylalanine into myofibrillar proteins (isolated from skeletal muscle biopsies) and the enrichment of [2H5]Phenylalanine in plasma collected over the 6 hours protein consumption period. Enrichment will be quantified via tandem LC-MS/MS to derive a rate of incorporation over the 6-hour period.

  4. Sarcoplasmic protein synthesis (%/hr)

    Time frame: 6.5 hours

    Rate of sarcoplasmic fractional synthesis is determined by rate incorporation of orally ingested tracer [2H5]Phenylalanine into sarcoplasmic (ie., soluble) proteins (isolated from skeletal muscle biopsies) and the enrichment of [2H5]Phenylalanine in plasma collected over the 6 hours protein consumption period. Enrichment will be quantified via tandem LC-MS/MS to derive a rate of incorporation over the 6-hour period.

Study contacts

Contact information is provided by the study sponsor or research team.

Sabrina T Barsky, Ph.D.

CONTACT

[email protected]

16475400115

Sponsors and collaborators

Lead sponsor

University of Toronto

Other

Registry information

Official study title

Validating the Indicator Amino Acid Oxidation Technique for Muscle Outcomes

Acronym: VIM

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Jan 5, 2026
Registry last updated
Jan 5, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.