Table 1.
PCR Primer set sequences.
Table 2.
Typology, mean fiber cross-sectional area and fiber area/nucleus ratio of FDP muscle after 2, 4 and 10 weeks of resistance training (TR2, TR4 and TR10 respectively).
Figure 1.
STAT3 activity in rat skeletal muscle following acute resistance exercise.
(1a) Representative western blot from FDP muscle protein samples taken at REST, 2 hours (E2H), 6 hours (E6H) post-exercise and after 10 weeks of training (CTL10, TR10), with anti-phospho-STAT3 (Tyr705) (pSTAT3), anti-total STAT3 (tSTAT3) and anti-α-tubulin. The arrow indicates the pSTAT3 band at 79 kDa and α-tubulin at 55 kDa. Graph shows arbitrary units of pSTAT3 normalized to tSTAT3 representing the mean ± SEM of 4–6 rats * significantly different from REST (p<0.05); † significantly different from CTL10 (p<0.01). (1b) Representative merged image of E2H at 40× magnification with inset box showing (b-i) nuclei (Hoestch = blue), (b-ii) satellite cells (red = Pax7+ indicated by arrow), (b-iii) pSTAT3 protein (green = pSTAT3 indicated by arrowhead), (b-iiii) Pax7+/pSTAT3+ cell at 2 h (E2H). Note: No Pax7+/pSTAT3+ staining found at REST, E6H, CTL10 or TR10 (not shown).
Figure 2.
STAT1 activity in rat skeletal muscle following acute resistance exercise.
A: representative western blot of protein extracted from FDP muscle samples taken at REST, 2 hours (E2H), 6 hours (E6H) post-exercise and after 10 weeks of training (CTL10, TR10), with anti-phospho-STAT1 (Tyr701) (pSTAT1), anti-total STAT1 (tSTAT1) and anti-α-tubulin. The arrow indicates the pSTAT1 band at 91 kDa. and α-tubulin at 55 kDa. B: The graph shows arbitrary units of pSTAT1 normalized to tSTAT1 representing the mean ± SEM of 4–6 rats. * Significantly different from resting value (REST; p<0.05). † Significantly different from E2H (p<0.01). ‡ Significantly different from E6H (p<0.01).
Figure 3.
Erk1/2 activity in rat skeletal muscle following acute resistance exercise.
A: representative western blots of protein extracted from FDP muscle samples taken at REST, 2 hours (E2H) and 6 hours (E6H) after acute resistance exercise or after 10 weeks of resistance training (TR10) or rest (CTL10), with anti-phospho-Erk1/2 (Tyr202/204) (pErk1/2), anti-total Erk1/2 (tErk1/2) and α-tubulin. The arrow indicates the pErk1/2 bands at 42/44 kDa and α-tubulin at 55 kDa. B: The graph shows arbitrary units of pErk1/2 normalized to tErk1/2 representing the mean ± SEM of 4–6 rats. * Significantly different from resting value (p<0.05).
Figure 4.
Satellite cell proliferation following acute resistance exercise.
A–C: Representative merged image (×20 magnification) of laminin staining (green) and BrdU-positive cells (red) of FDP muscle taken at REST (A), E2H (B), and E6H (C). b–c: Inset box (×40 magnification) of (i) laminin (green), (ii) BrdU (red), (iii) BrdU-positive satellite cells (merged image). D: The graph shows the mean ±SEM of BrdU-positive satellite cells (%) expressed per 2000 fibers of 4 rats. * Significantly different from REST (p<0.05). † Significantly different from E2H (p<0.05).
Figure 5.
IL-6 (A), LIF (B), SOCS3 (C), CyclinD1 (D), c-Myc (E), Myf5 (F), MyoD (G), Myogenin (H), Pax7 (I), Pax7/MyoD (J) gene expressions.
mRNA expressions 2 hours (E2H) and 6 hours (E6H) after a single bout of resistance exercise and 72 hours after 10 weeks of strength training program (CTL10, TR10) in FDP skeletal muscle of rats. Values are means of mRNA-fold change from REST or CTL10 ±SEM, n = 4–6 rats. * Significantly different from Rest (p<0.05). † Significantly different from E2H (p<0.05). ‡ Significantly different from CTL10 (p<0.05).
Figure 6.
Involvement of IL-6/JAK/STAT pathway upon satellite cells behavior after resistance exercise and training.
1. In response to increase workload, the SRF mediated IL-6 increasing production leads to satellite cells proliferation and first preferentially activate the JAK1/STAT1/STAT3 pathway leading to the rebuilt of the Pax7(+)/MyoD(−) pool. Like the Notch activity for the maintenance of the Pax7(+) SCs, the mitogen activated protein kinase Erk1/2 cooperates with the JAK1/STAT1/STAT3 pathway to repress early myogenic differentiation. 2. Later, the decreased Notch activity, the activation of the JAK2/STAT2/STAT3 together with multiple pro-differentiating factors (p38, Calcineurin, IGF-1…) activate SCs which loose the Pax7 expression (Pax7(−)/MyoD(+)) and start to differentiate. At this stage, SCs express late MRFs (Myf5, Myogenin) and then fuse to existing myocytes leading to hypertrophy.