Development of Oral Amino Acid Tracers to Study Protein Turnover in Humans

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).

Study Overview

• Status: Completed
• Conditions: Healthy Adult Males
• Intervention / Treatment: Dietary supplement: Crystalline amino acids to assess myofibrillar protein synthesis rates; Dietary supplement: Crystalline amino acids to assess whole-body protein turnover, amino acid oxidation, and net protein balance

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).

• Study Type: Interventional
• Enrollment (Actual): 22
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5S2C9
      • Goldring Centre for High Performance Sport at the University of Toronto

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 35 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: Male

Description

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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Healthy, recreationally-active adult males - Muscle Trial; Subjects receive 0.25g/kg crystalline amino acids modelled after egg protein, enriched with L-[1-13C]leucine and L-ring-[2H5]phenylalanine with a primed-constant infusion of L-[555-2H3]leucine to assess myofibrillar protein synthesis rates	Dietary supplement: Crystalline amino acids to assess myofibrillar protein synthesis rates; Amino acid dose = 0.25g/kg bodyweight
Experimental: Healthy, recreationally-active adult males - Whole Body Trial; Subjects receive 0.25g/kg crystalline amino acids modelled after egg protein, enriched with L-[1-13C]leucine with a primed-constant infusion of L-[555-2H3]leucine to whole-body protein turnover, amino acid oxidation, and net protein balance	Dietary supplement: Crystalline amino acids to assess whole-body protein turnover, amino acid oxidation, and net protein balance; Amino acid dose = 0.25g/kg bodyweight

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Myofibrillar protein synthesis rates	Myofibrillar protein synthesis rates assessed by oral and intravenous tracers during Fast, Fed, and Ex-Fed	5 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Whole-body protein turnover	Whole-body protein turnover assessed by oral and intravenous tracers during Fast, Fed, and Ex-Fed	5 hours
Amino acid oxidation and net protein balance	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.	5 hours
Muscle anabolic signalling	Immunoblotting for mTORC1/key downstream targets of mTORC1	2 and 5 hours
Amino acid transporter expression	Immunoblotting for amino acid transporters LAT1/SNAT2	2 and 5 hours

Collaborators and Investigators

• Sponsor: University of Toronto

Publications and helpful links

General Publications

• Mazzulla M, Hodson N, West DWD, Kumbhare DA, Moore DR. A non-invasive (13)CO(2) breath test detects differences in anabolic sensitivity with feeding and heavy resistance exercise in healthy young males: a randomized control trial. Appl Physiol Nutr Metab. 2022 Aug 1;47(8):860-870. doi: 10.1139/apnm-2021-0808. Epub 2022 May 24.

Study record dates

Study Major Dates

• Study Start (Actual): February 25, 2019
• Primary Completion (Actual): August 31, 2019
• Study Completion (Actual): August 31, 2019

Study Registration Dates

• First Submitted: May 5, 2021
• First Submitted That Met QC Criteria: May 10, 2021
• First Posted (Actual): May 14, 2021

Study Record Updates

• Last Update Posted (Actual): May 14, 2021
• Last Update Submitted That Met QC Criteria: May 10, 2021
• Last Verified: May 1, 2021

More Information

Terms related to this study

• Other Study ID Numbers: Connaught

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No