Health, Exercise, and Sports Sciences ETDs

Publication Date

Summer 7-16-2018

Abstract

Purpose: 1) To compare the effects of an acute bout of HIIT exercise (treadmill running) on autophagy to MICT exercise in human skeletal muscle 3 hours post exercise, and 2) to test an in vitro model of muscle contraction-induced autophagy using electrical pulse stimulation in C2C12 myotubes. Methods: Study 1: Ten recreationally active males and females completed a bout of high intensity interval training (HIIT) exercise and moderate intensity continuous exercise (MICT) exercise in a fasted state. Muscle biopsies from the vastus lateralis were taken pre and 3 hours post-exercise. Muscle tissue was analyzed for protein expression of markers of autophagy (LC3I, LC3II) and autophagy signaling (p38MAPK). Study 2: C2C12 myoblasts were differentiated into myotubes and underwent 8 hours of low-frequency electrical pulse stimulation (EPS) and starvation (St) and EPS+St conditions with and without bafilomycin A1 (Baf) or non-treatment control conditions (Con). Cells were harvested immediately following EPS and analyzed for protein expression of markers of autophagy (LC3I, LC3II, and p62). Results: Study 1: No differences were detected for LC3I, LC3II, and p38MAPK at the 3h time point vs. pre-exercise in both HIIT and MICT conditions. The LC3II:LC3I ratio increased 3-h post exercise in the HIIT (162.4, SE: 45.9%), which was significantly higher than the 3h timepoint in the MICT (48.8, SE: 9.4%; p<0.05) Study 2: LC3II (324.4, SE: 29.8%) LC3II:I (258.2, SE: 323.3%), and p62 (437.8, SE: 9.7%) were significantly higher in EPS+Baf conditions compared to control (100%, SE: 9.3, 8.8, 22.6%, respectively) and EPS alone (127.7, SE: 24.3%; 95.5, SE: 13.2%, 251.2, SE: 33.2%) . p62 protein expression was also higher in EPS compared to Con and in St+Baf (320.9, SE: 65.9%) compared Con and St (91, SE: 20.3%). There were no differences between EPS and St alone vs. combined EPS+St conditions in LC3I, LC3II, LC3II:I or p62. Conclusions: HIIT stimulates autophagy in a distinct fashion compared to MICT. Additionally, EPS may serve as an in vitro model for muscle contraction-induced autophagy in C2C12 myotubes in fed and fasted conditions.

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Keywords

training, proteostasis, LC3, cell culture, muscle contraction

Sponsors

the University of New Mexico Women in STEM Faculty Development Fund; New Mexico Graduate and Professional Student Association

Document Type

Dissertation

Language

English

Degree Name

Physical Education, Sports and Exercise Science

Level of Degree

Doctoral

Department Name

Health, Exercise, and Sports Sciences

First Committee Member (Chair)

Fabiano Amorim

Second Committee Member

Christine Mermier (co-chair)

Third Committee Member

Carlos Hiroshi Nitta

Fourth Committee Member

Trisha VanDusseldorp

Fifth Committee Member

Micah Zuhl

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