Electrically stimulated contractile activity-induced transcriptomic responses and metabolic remodeling in C₂C₁₂ myotubes: twitch vs. tetanic contractions

Abstract

The contraction of myotubes using electrical pulse stimulation is a research tool used to mimic muscle contractile activity and exercise in rodents and humans. Most protocols employed in previous work used low-frequency twitch contractions. However, high-frequency tetanus contractions that are more physiologically relevant to muscle contractions in vivo are poorly characterized. In this report, the similarities and differences in acute responses and chronic adaptations with different contractile modes using twitches (2 Hz, continuous, 3 h) and tetanus (66 Hz, on: 5 s/off: 5 s, 3 h) were investigated. RNA-seq-based transcriptome analysis and subsequent bioinformatics analysis suggest that tetanus may promote bioenergetic remodeling rather than twitch. Based on in silico analyses, metabolic remodeling after three contractile sessions of twitch and tetanus were investigated. Although twitch and tetanus had no significant effect on glycolysis, both types of contraction upregulated glucose oxidation capacity. Both twitch and tetanus qualitatively caused mitochondrial adaptations (increased content, respiratory chain enzyme activity and respiratory function). The magnitude of adaptation was much greater under tetanus conditions. Our findings indicate that the contraction of myotubes by tetanus may be a useful experimental model, especially when studying metabolic adaptations in C2C12 myotubes.

Skeletal muscle-derived extracellular vesicles are altered with chronic contractile activity

“…Increased mitochrondrial content/function is an important adaptation of habitual endurance exercise. Our results showed that mitochondrial biogenesis as measured by MitoTracker staining, COX activity and Cyt C (a critical protein in oxidatve phosphorylation) was increased in chronically stimulated myotubes, in line with reporter results by other groups [31], [32], [45], [46]. In general, our results validated that the chronic stimulation protocol was effective in mimicing the effects of chronic contractile activity in vitro , and we subsequently used it to interrogate the effects of contractile activity on Skm-EVs.…”

Investigation of Brain Function-Related Myokine Secretion by Using Contractile 3D-Engineered Muscle

“…Lactate [ 7 , 8 , 9 ], fibronectin type III domain-containing protein 5 (FNDC5)/irisin [ 10 ], and cathepsin B (CTSB) [ 11 ] are myokines associated with brain function. Specifically, lactate is secreted from skeletal muscle by mechanical muscle contractile stimulation in both in vitro [ 12 , 13 ] and in vivo [ 8 , 14 ] studies. Secreted lactate is delivered into the brain through blood vessels by crossing the blood-brain barrier (BBB) [ 15 , 16 ], which increases BDNF expression in the brain [ 7 ].…”

Transcriptome Analyses of In Vitro Exercise Models by Clenbuterol Supplementation or Electrical Pulse Stimulation

“…EPS induces calcium release from the sarcoplasmic reticulum, therefore EPS enables analysis of calcium signaling in vitro. Global transcriptional analyses of EPS have recently been published by two different groups [21,22]. Both experiments focused on relatively short-term EPS treatments.…”