Acute and Chronic Effects of High Frequency Electric Pulse Stimulation on the Akt/mTOR Pathway in Human Primary Myotubes

Mayalen Valero-Breton; Geoffrey Warnier; Mauricio Castro-Sepulveda; Louise Deldicque; Hermann Zbinden-Foncea

doi:10.3389/fbioe.2020.565679

Acute and Chronic Effects of High Frequency Electric Pulse Stimulation on the Akt/mTOR Pathway in Human Primary Myotubes

Front Bioeng Biotechnol. 2020 Nov 5:8:565679. doi: 10.3389/fbioe.2020.565679. eCollection 2020.

Authors

Mayalen Valero-Breton¹, Geoffrey Warnier², Mauricio Castro-Sepulveda¹, Louise Deldicque², Hermann Zbinden-Foncea^{1

2

3}

Affiliations

¹ Exercise Physiology Laboratory, School of Kinesiology, Universidad Finis Terrae, Santiago, Chile.
² Institute of Neuroscience, UCLouvain, Louvain-la-Neuve, Belgium.
³ Centro de Salud Deportiva, Clínica Santa María, Santiago, Chile.

Abstract

Electrical pulse stimulation (EPS) has been suggested to be a useful method to investigate the mechanisms underlying the adaptations of human skeletal muscle to both endurance and resistance exercise. Although different myotube stimulation protocols mimicking acute and chronic endurance exercise have been developed, no convincing protocol mimicking resistance exercise exists. Adaptations to resistance exercise mainly ensue via the Akt/mTOR pathway. Therefore, the aim of this study was to develop a high frequency EPS protocol mimicking resistance exercise both acutely (100 Hz, 15 V, 0.4 ms with 4 s rest between each contraction for 30 min) and chronically (acute EPS protocol repeated on three consecutive days) on human myotubes. Compared to control conditions, the acute EPS protocol increased the phosphorylation of Akt^Ser473 at 0 h (+91%, p = 0.02) and 3 h (+95%, p = 0.01), and mTOR^Ser2448 at 0 h (+93%, p = 0.03), 1 h (+129%, p = 0.01), and 3 h (+104%, p = 0.0250) post-stimulation. The phosphorylation of ERK1/2^{Thr202/Tyr204} was increased at 0 h (+69%, p = 0.02) and 3 h (+117%, p = 0.003) post-stimulation compared to control conditions. In addition, both S6K1^Thr389 (+157%, p = 0.009) and S6^Ser240/244 (+153%, p = 0.003) phosphorylation increased 1 h after EPS compared to control conditions. Chronic EPS protocol increased the phosphorylation of S6K1^Thr389 1 h (+105%, p = 0.03) and 3 h (+126%, p = 0.02) and the phosphorylation of S6^Ser240/244 1 h (+32%, p = 0.02) after the end of the last stimulation. In conclusion, the present work shows that human muscle cells subjected to EPS can be used as an in vitro model of acute and chronic resistance exercise.

Keywords: Akt; ERK1/2; cell culture; high frequency; mTOR.