Healthy Adult Males
Conditions
Brief summary
Previous studies have used a combination of oral L-\[1-13C\]leucine and intravenous labeled L-\[5,5,5-2H3\]leucine to assess the acute postprandial changes in whole-body protein turnover (12, 19). Intravenous and dietary-labeled amino acid tracers have also been used in tandem to assess rates of myofibrillar protein synthesis in response to bolus protein ingestion and resistance exercise (46). By validating whole-body net balance to myofibrillar protein synthesis, our proposed multi-tracer approach will develop minimally invasive models to study protein turnover in a variety of populations in which traditional infusions and/or repeated blood samples are not possible (i.e. pediatric, free-living populations).
Detailed description
The primary objective of the proposed study is to validate the use of a novel oral tracer model to accurately and reliably measure myofibrillar protein synthesis. It is hypothesized that oral L-\[1-13C\]leucine and L-\[ring-2H5\]phenylalanine, ingested as a bolus to mimic an intravenous 'pulse dose' administration (51, 65), will reveal similar rates of myofibrillar protein synthesis when compared to traditional intravenous L-\[5,5,5-2H3\]leucine infusion. Moreover, it is hypothesized that both methods will reveal the expected graded changes in myofibrillar protein synthesis in response to feeding and resistance exercise (i.e. fasted\<feeding\<exercise & feeding). The secondary objective of the proposed study is to develop and validate non-invasive models to measure whole-body amino acid oxidation and net balance in response to feeding and resistance exercise. It is hypothesized that whole-body net balance, as determined by a novel oral tracer model (i.e. L-\[1-13C\]leucine) , will align with traditional intravenous tracer methodology (i.e. L-\[5,5,5-2H3\]leucine) and reveal the expected physiological changes in whole-body protein turnover in response to feeding and resistance exercise (i.e. fasted\<feeding\<exercise & feeding).
Interventions
DIETARY_SUPPLEMENTCrystalline amino acids to assess myofibrillar protein synthesis rates
Amino acid dose = 0.25g/kg bodyweight
DIETARY_SUPPLEMENTCrystalline amino acids to assess whole-body protein turnover, amino acid oxidation, and net protein balance
Amino acid dose = 0.25g/kg bodyweight
Sponsors
University of Toronto
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Intervention model description
Three groups: Fast, Fed, Ex-Fed Two trials per group
Eligibility
Sex/Gender
MALE
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* Male * Currently performing structured physical activity 2-5 days per week
Exclusion criteria
* Unable to safely perform exercise as per PARQ+ guidelines * Currently using tobacco products * Currently using or have history of anabolic steroid use * Diagnosed with medical condition including type 2 diabetes, cancer, heart disease * Unable to abstain from supplement use (HMB, branched chain amino acids, phosphatidic acid) for at least three weeks prior to trial * currently using medications known to affect protein metabolism e.g. corticosteroids, NSAID, prescription-strength acne medication * allergic to local anesthetics * female: Hormonal fluctuations associated with the menstrual cycle have been reported to alter protein metabolism during exercise and may influence indices of the post-exercise myofibrillar protein synthetic response. Accordingly, the study will include males to ensure a stable hormonal environment and to increase the homogeneity of the physiological response.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Myofibrillar protein synthesis rates | 5 hours | Myofibrillar protein synthesis rates assessed by oral and intravenous tracers during Fast, Fed, and Ex-Fed |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Whole-body protein turnover | 5 hours | Whole-body protein turnover assessed by oral and intravenous tracers during Fast, Fed, and Ex-Fed |
| Amino acid oxidation and net protein balance | 5 hours | Amino acid oxidation and net protein balance assessed by oral tracers during Fast, Fed, and Ex-Fed. Net protein balance is derived from the difference between amino acid intake (known) and total amino acid oxidation over the 5h measurement period. |
| Muscle anabolic signalling | 2 and 5 hours | Immunoblotting for mTORC1/key downstream targets of mTORC1 |
| Amino acid transporter expression | 2 and 5 hours | Immunoblotting for amino acid transporters LAT1/SNAT2 |
Countries
Canada
Outcome results
None listed