Effect Of Phytoecdysteroids On Protein Synthesis And Akt/Mtor Signaling After Downhill Running In Skeletal Muscle Of Mice

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Kevin Hans Goslen (Creator)
Appalachian State University (ASU )
Web Site: https://library.appstate.edu/
Kevin Goslen

Abstract: Phytoecdysteroids are natural plant steroids synthesized by a variety of hardy plants. Phytoecdysteroids, such as 20- hydroxyecdysone (20E), possess anabolic properties and previous research indicates that 20E stimulates protein synthesis in cultured muscle cells and increases grip strength in young rats after 28 days of supplementation. The purpose of this study was to investigate the extent to which 20E stimulates protein synthesis and Akt/mTOR signaling in mouse skeletal muscle after an acute bout of downhill running (DHR). Male C57BL6 mice (3-6 mo old) were randomly assigned to eight groups (n=8- 10/group). Mice in the DHR groups performed an acute bout of DHR to exhaustion on a rodent treadmill at 17 m•min-1 and negative 20o decline. After completion of the DHR bout and recovery, mice received an oral gavage treatment of either 50 mg•kg-1 body mass (BM) of 20E (DHR + 20E) or vehicle (DHR + vehicle), and then treated daily for the next one (2-day post DHR) or four consecutive days (5-day post DHR). Groups that did not perform DHR, but were treated for two or five consecutive days with either 50 mg•kg-1 BM of 20E (No DHR + 20E) or vehicle (No DHR + vehicle), were used as controls. On the second or fifth day post-DHR, mice were not treated with 20E or vehicle; however, an IP injection of puromycin (0.040 µmol•g-1 BM) was administered 30 min prior to sacrifice to assess protein synthesis. Skeletal muscles were harvested and activation of protein synthesis was assessed using the SUnSET method and Western blot and Akt/mTOR signaling activation was measured via Western blot. At the 2-day time point, puromycin incorporation was significantly higher in 20E-treated mice, compared to vehicle-treated mice when no DHR was performed (p=0.011). Also, mice that were treated with 20E for two days, but did not perform DHR, had significantly higher puromycin incorporation, compared to the 2-day No DHR + vehicle mice (p<0.001). At the 5-day time point, no significant interaction was found with DHR and treatment (p=0.965). No significant interactions were found in the states of signaling proteins at either time point: phospho-Akt 2-day (p=0.283), 5-day (p=0.767); phospho-p70S6K 2-day (p=0.060); phospho-4EBP1 2-day (p=0.202), 5-day (p=0.080); phospho-rpS6 2-day (p=0.104), 5-day (p=0.962). It appears that 20E was unable to enhance puromycin incorporation or activation of the Akt/mTOR signaling pathway after an acute bout of DHR. Limitations of this study include the possibility of low bioavailability and rapid metabolic half-life of 20E, and that 20E was not administered on the day of sacrifice.

Additional Information

Honors Project
Goslen, K. (2017). "Effect Of Phytoecdysteroids On Protein Synthesis And Akt/Mtor Signaling After Downhill Running In Skeletal Muscle Of Mice." Unpublished Honors Thesis. Appalachian State University, Boone, NC.
Language: English
Date: 2017
Sarcopenia, Eccentric muscle damage, Phytoecdysteroids Protein synthesis, Akt/mTOR

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