An interventional study of Fed and Ex-Fed in Dietary Protein, Female Protein Metabolism and Anabolic Sensitivity, sponsored by University of Toronto. Recruiting at 1 site in Canada. Open to female participants aged 18 Years to 35 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2023-07-13.
Sponsored by University of Toronto · Not applicable, Interventional, and Other
The maintenance of lean body mass, especially skeletal muscle, is vital for optimal health and performance across the lifespan. The protein component of lean body mass is in a constant state of turnover, involving the simultaneous breakdown of old and/or damaged proteins and the synthesis of new proteins. These processes collectively determine if someone gains or loses lean body mass. Eating a protein-rich meal or performing resistance exercise can stimulate protein synthesis to gain lean body mass. Stable isotope "tracers" are amino acid building blocks that are slightly heavier than those naturally found in the body. In research, these are often used to assess changes in protein turnover in response to feeding and/or exercise. However, traditional stable isotope tracer methods involve the intravenous delivery of a tracer with blood sampling and muscle biopsies, which may be cumbersome or unfeasible for some for participants.
The investigators have recently developed and validated a non-invasive 'breath test' in males that measures the efficiency of the body for using amino acids in food to build new body proteins. The principle of this method is that leucine, an essential amino acid that the body must acquire from normal diet, can be used to build new body proteins or as a source of energy (i.e., oxidized). Since leucine is preferentially used in skeletal muscle, skeletal muscle protein metabolism can be non-invasively inferred . Any leucine "tracer" that is oxidized can be detected and measured in the carbon dioxide exhaled. It has been observed that less dietary leucine is oxidized when active males perform a bout of resistance exercise, meaning more was used to build muscle proteins. When performed habitually, resistance exercise can help skeletal muscles grow, compared to a rested-state, resulting in greater leucine retention in the body to build new proteins. Therefore, the purpose of this study is to validate this non-invasive breath test in females to increase the validity of the method in a wider range of populations. Ultimately, the results will further validate this non-invasive tool that can potentially detect whether different populations are sensitive to dietary amino acids and in a position to gain or lose lean body mass.
The objective of the present study is to validate the use of an oral L-[13C]-leucine stable isotope tracer, preferentially metabolized within skeletal muscle, to detect an exercise-induced increase in anabolic sensitivity (i.e., reduction in oxidation) in females. It is hypothesized that since resistance exercise enhances skeletal muscle protein synthesis, anabolic sensitivity measured through leucine retention would be greater with feeding after resistance exercise compared to feeding at rest.
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This study's planned enrollment of 10 is below the median of 57 across 1,384 interventional studies indexed under Hypersensitivity.
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Exclusion Criteria:
7-10 days after the onset of menses, determined by self-reports and confirmed with ovulation test kits.
Behavioral: Fed · Behavioral: Ex-Fed
5-7 days after ovulation, determined by self-reports and confirmed with ovulation test kits.
Behavioral: Fed · Behavioral: Ex-Fed
Subjects will be fed a mixed-macronutrient beverage at rest (0.75g/kg lean body mass of carbohydrates; 0.25g/kg lean body mass of protein). Amino acid composition of the protein will be modelled off the composition of egg. Leucine content will be enriched to 5% with \[13C\]-leucine.
Also known as: Feeding at Rest
Participants will be subjected to a full-body resistance exercise protocol, consisting of an upper and lower body circuit. The upper body circuit will be a chest press and dumbbell row superset, whereas the lower body circuit will be leg press and leg extension (4 sets of 10 repetitions @ 75% of their 1 repetition max, respectively). The inter-set rest period will be 90 seconds. Subjects will be fed a mixed-macronutrient beverage at rest (0.75g/kg lean body mass of carbohydrates; 0.25g/kg lean body mass of protein). Amino acid composition of the protein will be modelled off the composition of egg. Leucine content will be enriched to 5% with \[13C\]-leucine.
Also known as: Exercise with Feeding
Net-Leucine Retention (umol/kg)
Whole-Body Net Leucine Retention determined from the difference between exogenous leucine oxidation and leucine ingestion the 6 hour measurement period.
Time frame: 6 hours
Exogenous Leucine Oxidation (umol/kg)
Exogenous Leucine Oxidation determined from breath 13CCO2 enrichment. Breath samples will be collected every 20-30min after test drink ingestion to determine breath 13CO2 enrichment. Total leucine oxidation will be determined from the area under the 13CO2 enrichment by time curve.
Time frame: 6 hours
Plan to share: No
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