DigitalCommons@McMaster

Title

Aerobic Exercise Intensity Affects Skeletal Muscle Myofibrillar Protein Synthesis and Anabolic Signaling in Young Men

Author

Danielle M. Di Donato, McMaster UniversityFollow

Date of Award

Fall 2012

Degree Type

Thesis

Degree Name

Master of Science in Kinesiology

Department

Kinesiology

Supervisor

Stuart Phillips

Language

English

Abstract

Aerobic exercise can stimulate mixed muscle protein synthesis (MPS) acutely post-exercise; however, the types of proteins synthesized as a result of aerobic exercise are not known by studying changes in mixed MPS. We aimed to study the effect of aerobic exercise intensity on the 4 and 24 h post-exercise fractional synthesis rate (FSR) of myofibrillar proteins. Using a within-subject design, eight males (21 ± 1 years, VO_{2 peak}: 46.7 ± 2.0 mL kg^-1 min^-1) underwent 2 trials with a primed constant infusion of L-[ring-¹³C₆]phenylalanine in the fasted state for each work-matched exercise intensity (LOW: cycling for 60 min at 30% W_max and HIGH: 30 min at 60% W_max). Muscle biopsies were obtained to determine resting, 4 and 24 h post-exercise myofibrillar FSR. We also studied the phosphorylation of signaling proteins involved in protein synthesis at each time point using immunoblotting methods. Phospho-p38^{Thr180/Tyr182} was greater at 4.5 h after exercise compared to 0.5, 24 and 28 h post-exercise (p < 0.05). Additionally, a strong trend was present for phospho-mTOR^Ser2448 (p = 0.056) with 0.5 h post-exercise phosphorylation significantly higher after HIGH than after LOW exercise (p < 0.05). Myofibrillar protein synthesis was stimulated 1.5–fold 0.5 – 4 h post-exercise (p < 0.05), returning to rest in the LOW condition 24 h post-exercise, while 6 out of 8 subjects maintained increased myofibrillar FSR 24 h post HIGH exercise (p < 0.05). The increase in myofibrillar FSR 0.5 – 4 h post-exercise was correlated with phospho-mTOR^Ser2448 0.5 h post-exercise (r = 0.698, p < 0.01), indicating the role of this signaling pathway in myofibrillar protein synthesis. It is concluded that aerobic exercise has an effect on myofibrillar protein synthesis and intensity may play a role in the duration of this response.

Recommended Citation

Di Donato, Danielle M., "Aerobic Exercise Intensity Affects Skeletal Muscle Myofibrillar Protein Synthesis and Anabolic Signaling in Young Men" (2012). Open Access Dissertations and Theses. Paper 7299.
http://digitalcommons.mcmaster.ca/opendissertations/7299

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