title: Contractile C2C12 myotube model for studying exercise-inducible responses in skeletal muscle.
abstract: Adequate exercise leads to a vast variety of physiological changes in skeletal muscle as well as other tissues/organs and is also responsible for maintaining healthy muscle displaying enhanced insulin-responsive glucose uptake via GLUT4 translocation. We generated highly developed contractile C(2)C(12) myotubes by manipulating intracellular Ca(2+) transients with electric pulse stimulation (EPS) that is endowed with properties similar to those of in vivo skeletal muscle in terms of 1) excitation-induced contractile activity as a result of de novo sarcomere formation, 2) activation of both the AMP kinase and stress-activated MAP kinase cascades, and 3) improved insulin responsiveness as assessed by GLUT4 recycling. Tbc1d1, a Rab-GAP implicated in exercise-induced GLUT4 translocation in skeletal muscle, also appeared to be phosphorylated on Ser(231) after EPS-induced contraction. In addition, a switch in myosin heavy-chain (MHC) expression from "fast type" to "slow type" was observed in the C(2)C(12) myotubes endowed with EPS-induced repetitive contractility. Taking advantage of these highly developed contractile C(2)C(12) myotubes, we identified myotube-derived factors responsive to EPS-evoked contraction, including the CXC chemokines CXCL1/KC and CXCL5/LIX, as well as IL-6, previously reported to be upregulated in contracting muscles in vivo. Importantly, animal treadmill experiments revealed that exercise significantly increased systemic levels of CXCL1/KC, perhaps derived from contracting muscle. Taken together, these results confirm that we have established a specialized muscle cell culture model allowing contraction-inducible cellular responses to be explored. Utilizing this model, we identified contraction-inducible myokines potentially linked to the metabolic alterations, immune responses, and angiogenesis induced by exercise.
authors.affiliation: Center for Research Strategy and Support, Tohoku University Biomedical Engineering Research Organization, Sendai, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Nedachi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Fujita
authors.forename: Makoto
authors.initials: M
authors.lastname: Kanzaki
mesh_terms: D000263:Adenylate Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D018925:Chemokines / Q000097:blood / Q000235:genetics / Q000378:metabolism; D004558:Electric Stimulation; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D007328:Insulin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D010805:Physical Conditioning, Animal / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D023063:Receptors, Interleukin-8B / Q000037:antagonists & inhibitors; D012518:Sarcomeres / Q000378:metabolism
chemical_list: D018925:Chemokines; D051275:Glucose Transporter Type 4; D007328:Insulin; D009124:Muscle Proteins; D047428:Protein Kinase Inhibitors; D023063:Receptors, Interleukin-8B; C495693:Slc2a4 protein, mouse; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; D000263:Adenylate Kinase; D005947:Glucose