Validating IAAO for Muscle Outcomes (VIM)

December 18, 2025 updated by: Daniel Moore, University of Toronto

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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

8

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • Canada
    • Ontario
      • Toronto, Ontario, Canada, M5S 2C9
        • Recruiting
        • Kinesiology & Physical Education
        • Contact:
        • Principal Investigator:
          • Daniel Moore, Ph.D

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

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)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Protein + Stable Isotope Tracer Beverage
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.
Dietary supplement: Protein + Stable Isotope Tracer Beverage
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

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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).
6.5 hours
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.
6.5 hours
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.
6.5 hours
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.
6.5 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Toronto

Investigators

  • Principal Investigator: Daniel Moore, Ph.D, University of Toronto, Faculty of KPE

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 1, 2025

Primary Completion (Estimated)

March 20, 2026

Study Completion (Estimated)

May 20, 2026

Study Registration Dates

First Submitted

December 18, 2025

First Submitted That Met QC Criteria

December 18, 2025

First Posted (Actual)

January 5, 2026

Study Record Updates

Last Update Posted (Actual)

January 5, 2026

Last Update Submitted That Met QC Criteria

December 18, 2025

Last Verified

December 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • VIM

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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