Fasting and Exercise-induced Changes in Human Skeletal Muscle

Study Overview
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Brief Summary
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This study examines the impact of increasing energetic stress during an 8-hour fast on metabolic pathways in human skeletal muscle. Specifically, participants will undergo two 8-hour fasting sessions in a randomized crossover fashion, with the addition of low-intensity arm exercise in one of the sessions. Changes in metabolic pathways will be examined in resting (leg) muscle before, during, and after the fast.

Official Title
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Impact of Exercise-induced Energetic Stress During an 8-hour Fast on Metabolic Regulation in Resting Human Skeletal Muscle

Conditions
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Skeletal Muscle Energetics

Intervention / Treatment
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* Other: FAST+EX
* Other: FAST


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: recreationally active (no more than 3 hours of weekly physical activity) not currently involved in a systematic training program body mass index < 30 kg/m2 Exclusion Criteria: presence of cardiometabolic disease taking regular oral medication current smoker

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: FAST+EX - FAST<br>FAST+EX then FAST alone | Other: FAST+EX<br>* Participants will perform 2-hours of low-intensity arm exercise (8 x 15 min bouts of arm ergometer exercise separated by 10 min of rest) during an 8-hour fast.<br>Other: FAST<br>* Participants will complete an 8-hour fast.<br>|
| Experimental: FAST - FAST+EX<br>FAST alone then FAST+EX | Other: FAST+EX<br>* Participants will perform 2-hours of low-intensity arm exercise (8 x 15 min bouts of arm ergometer exercise separated by 10 min of rest) during an 8-hour fast.<br>Other: FAST<br>* Participants will complete an 8-hour fast.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peroxisome proliferator activated receptor gamma co-activator 1-alpha (PGC-1α) messenger ribonucleic acid (mRNA) expression | PGC-1α gene expression (indirect indicator of PGC-1α activity) | 15 min before fast; after 4 and 8 hours of fasting | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Catecholamine concentrations | Epinephrine and norepinephrine concentrations in plasma samples | 15 min before fast; after exercise; after 4 and 8 hours of fasting | 
| Glucose and insulin concentrations | Glucose and insulin concentrations in plasma samples | 15 min before fast; after 4 and 8 hours of fasting | 
| total and phosphorylated AMP activated protein kinase (AMPK) | active AMPK relative to total AMPK protein content | 15 min before fast; after 4 and 8 hours of fasting | 
| total and phosphorylated SIRT-1 | active SIRT-1 relative to total SIRT1 protein content | 15 min before fast; after 4 and 8 hours of fasting | 
| total and phosphorylated mammalian target of rapamycin (mTOR) | active mTOR relative to total mTOR protein content | 15 min before fast; after 4 and 8 hours of fasting | 
| total and phosphorylated Akt/Protein Kinase B | active Akt relative to total Akt protein content | 15 min before fast; after 4 and 8 hours of fasting | 
| total and phosphorylated acetyl coenzyme A carboxylase (ACC) | active ACC relative to total ACC protein | 15 min before fast; after 4 and 8 hours of fasting | 
| total and phosphorylated p38 mitogen activated protein kinase (MAPK) | active p38 MAPK relative to total p38 MAPK protein | 15 min before fast; after 4 and 8 hours of fasting | 
| phosphorylated protein kinase A (PKA) substrates | phosphorylated PKA substrates (indirect measure of PKA activity) | 15 min before fast; after 4 and 8 hours of fasting | 
| acetylated p53 | p53 acetylation status (indirect measure of SIRT-1 deacetylase activity) | 15 min before fast; after 4 and 8 hours of fasting | 
| Sirtuin 1 (SIRT1) mRNA expression | gene expression of the deacetylase enzyme SIRT1 | 15 min before fast; after 4 and 8 hours of fasting | 
| Sirtuin 3 (SIRT3) mRNA expression | gene expression of the deacetylase enzyme SIRT3 | 15 min before fast; after 4 and 8 hours of fasting | 
| Pyruvate dehydrogenase kinase isoenzyme 4 (PDK4) mRNA expression | gene expression of the PGC-1α target PDK4 | 15 min before fast; after 4 and 8 hours of fasting | 
| p53 mRNA expression | gene expression of the tumour suppressor protein p53 | 15 min before fast; after 4 and 8 hours of fasting | 
| Leucine rich pentatricopeptide repeat containing protein (LRP130) mRNA expression | gene expression of RNA-binding protein LRP130 | 15 min before fast; after 4 and 8 hours of fasting | 
| General control non-repressible 5 (GCN5) mRNA expression | gene expression of the acetyltransferase GCN5 | 15 min before fast; after 4 and 8 hours of fasting | 
| PGC-1α protein content | Protein content of the transcriptional co-activator PGC-1α | 15 min before fast; after 4 and 8 hours of fasting | 
| Cytochrome C oxidase subunit 4 (COX-IV) protein content | Protein content of the mitochondrial enzyme COX subunit 4 | 15 min before fast; after 4 and 8 hours of fasting | 
| Intramuscular glycogen content | Muscle glycogen content | 15 min before fast; after 4 and 8 hours of fasting | 
| Intramuscular triglyceride (IMTG) content | Muscle IMTG content | 15 min before fast; after 4 and 8 hours of fasting |