Protein Metabolism
Conditions
Keywords
Muscle biopsy, Protein Metabolism, Stable isotopes, Protein oxidation, Indicator amino acid oxidation, Protein synthesis
Brief summary
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.
Interventions
DIETARY_SUPPLEMENTProtein + 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
Sponsors
University of Toronto
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
Single group: Eight healthy young (18-35 years, 4 females and 4 males) will be subjected to 2 skeletal muscle biopsies, collection of blood and urine samples, and a non-invasive 13CO2 breath-test over a 6.5-hour period while ingesting half-hourly protein beverages with stable isotope tracers. The breath-test is based on the indicator amino acid oxidation (IAAO) method.
Eligibility
Sex/Gender
ALL
Age
18 Years to 35 Years
Healthy volunteers
Yes
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)
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Phenylalanine excretion (umol/kg/h) | 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). |
| Phenylalanine oxidation (umol/kg/h) | 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. |
| Myofibrillar protein synthesis (%/hr) | 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. |
| Sarcoplasmic protein synthesis (%/hr) | 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. |
Countries
Canada
Contacts
Primary ContactSabrina T Barsky, Ph.D.
Outcome results
None listed