| Purpose:Skeletal muscle is a highly malleable organization. Exercise training can make muscle fiber thickening, increase the number of muscle fibers. It can also cause the movement of skeletal muscle hypertrophy and increase the muscle contraction strength. Skeletal Muscle growth is a complex regulatory process. It is affected by various factors. Muscle mass is maintained by the balance of protein synthesis and metabolism of protein degradation. The Studies have shown that low-frequency pulsed electromagnetic fields can promote skeletal muscle blood circulation, relieve muscle spasticity. It can also relieve delayed onset muscle soreness. In this research, which is rat gastrocnemius for the study, rats which are after exercising were given PEMFs motion to intervene. Observe the changes in skeletal muscle morphology and the changes in skeletal muscle metabolism. Investigate the effects of electromagnetic fields combined with exercise training on skeletal muscle hypertrophy process of protein synthesis and breakdown of proteins associated signaling pathway. Mainly are PI3K/Akt signaling pathways related to upstream and downstream signaling molec and MSTN and its receptor.Method:In this study,30 adult female SD rats for the study were randomly divided into three groups:normal control group (Normal control group, NC), treadmill exercise group (Treadmill Exercise, TE), treadmill exercise and electromagnetic fields in the intervention group (Treadmill Exercise+electromagnetic fields, TE+EMF),10 rats in each group. Normal group without training; high-intensity exercise group rats have the slope treadmill training, each training time was 60min,28m/min, the experimental time are 8 weeks of training, every week the rats trading 6 days and 1 day of rest; the programs of training electromagnetic field in the intervention group are as same as the exercise group, as each additional 30min PEMFs after training. During the training, every four days weighed weight and grip. After the last training, the rats fasting 12 hours, accurately weighed and the weight on both sides of rat gastrocnemius, quadriceps, soleus muscle and other tissues. Kit for measuring rat gastrocnemius muscle tissue homogenates succinate dehydrogenase and malate dehydrogenase; Then doing gastrocnemius muscle tissue sections, HE staining method of analysis in each group of rats muscle fiber cross-sectional area; Coomassie brilliant blue method is used for rats gastrocnemius muscle protein concentration in each group. Using Western Blotting and RT-qPCR detected in skeletal muscle PI3K/Akt signaling pathway the key signaling molecule which are PI3K, Akt, mTOR, FoxO, Glut4 and MSTN and its receptor expression.Results:1.Through the 8 weeks slope treadmill training, (NC group, TE group, TE+EMF group) the body weight of each group and grip strength were significant changes (P<0.05). NC group, the body weight TE group and TE+EMF group were all increased compared with that before the training, NC group has the biggest weight change rate. Compared with NC group, the body weight TE group is decreased but there was no significant difference, TE+EMF group weight loss was significant difference (P<0.05). Grip results showed that compared with the NC group grip, TE group and TE+EMF group holding power were very significant improvement (P<0.01, P<0.01), TE+EMF group compared with TE grip is also improved, it was significantly (P<0.05).2. Compared with NC group, the TE gastrocnemius weight of rats increased significantly (P<0.05), TE+EMF group was significant than the NC group (P<0.01), but with respect to the TE group was not significant. Gastrocnemius calculations relative weight of the display, TE group and TE+EMF group gastrocnemius relative weight values were higher than NC group, TE group was significantly different (P <0.05), TE+EMF group has a very significant difference (P<0.01). Quadriceps rat soleus and heart weight were significantly increased, the increase is more obvious for TE+EMF group. TE group and TE+EMF group gastrocnemius relative weight value is smaller than the quiet group, and there was a significant difference (P<0.01).3. The SDH activity of TE group and TE+EMF group were higher than NC group, there is significant difference (P<0.05); compared with group TE, SDH activity of TE+ EMF group also improved, but no significant difference. TE group compared with NC group, MDH activity was significantly improved (P<0.05), compared TE+EMF group with the NC group, the MDH activity has a very significant increase (P<0.01); compared with group TE, TE+EMF group's MDH activity also improved which has the significant differences (P<0.05).4. Each rat gastrocnemius muscle tissue sections performed, and the results obtained by HE staining, the average area of the NC group TE group of muscle fibers contrast very significant increase (P<0.01), TE+EMF group's average area of muscle fiber is also very increased significantly (P<0.01), and compared with the TE group,TE +EMF group's average increased muscle fiber area has a significant difference (PO.01)5. Rat gastrocnemius RT-qPCR and Western Blotting's results showed that PEMF intervention and treadmill exercise on rat gastrocnemius hypertrophy significant role in promoting both the expression of PI3K/Akt signaling pathway key signaling molecule PI3K and Akt on or expression of mTOR, Glut4 downstream signaling molecules, have shown different degrees increased, while a negative regulator of the downstream expression of FoxO1 significantly decreased; in addition, TE+EMF group and the group of rat gastrocnemius TE MSTN's expression was significantly lower than NC group, on the other hand on rat gastrocnemius PI3K/Akt signaling pathway plays a certain role.Conclusion:1. PEMFs intervention makes the relative weight of gastrocnemius increased, muscle fiber cross-sectional area to further increase and with significant differences. Indicating that the low-frequency pulsed electromagnetic fields can promote exercise-induced skeletal muscle hypertrophy.2. PEMF can increase the activity of key enzymes in the TCA cycle, increase the rate of aerobic metabolism,so that the energy metabolism of skeletal muscle enhancement, provide a metabolic basis for skeletal muscle hypertrophy.3. PEMFs and exercise intervention can significantly inhibit the MSTN mRNA expression of gastrocnemius, promote muscle cell proliferation and growth. Electromagnetic field interference increases the expression of mTOR,decreased the expression of FoxO1.Low-frequency pluse electromagnetic field can promote protein synthesis and inhibit protein degradation, promoting exercise-induced skeletal muscle hypertrophy. At the same time, low frequency electromagnetic field promote an increase of Glut4 mRNA expression in intracellular.increasing Glut4 transport capacity of glucose. |
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