Simultaneous Study of Mechanical Stretch-Induced Cell Proliferation and Apoptosis on C2C12 Myoblasts.

Mechanical stretch may cause myoblasts to either proliferate or undergo apoptosis. Identifying the molecular events that switch the fate of a stretched cell from proliferation to apoptosis is practically important in the field of regenerative medicine. A recent study on vascular smooth muscle cells illustrated that identification of these events may be achieved by addressing the stretch-induced opposite cellular outcomes simultaneously within a single investigation. To define conditions or a model in which both proliferation and apoptosis can be studied at the same time, we exposed in vitro cultured C2C12 myoblasts to a cyclic mechanical stretch regimen of 15% elongation at a stretching frequency of 1 Hz for 0, 2, 4, 6, or 8 h every day, consecutively, for 3 days. Both proliferation and apoptosis were observed. Moreover, as the duration of the stretch was prolonged, cell proliferation increased until it peaked at the optimal stretching duration. Afterwards, apoptosis gradually prevailed. Therefore, we established a model in which stretch-induced cell proliferation and apoptosis can be studied simultaneously.

[Effects of laser stimulation with different power on oxygen consumption rate of C2C12 myoblasts in mice].

OBJECTIVE: To investigate the effects of 650 nm laser irradiation on cell oxygen consumption rate in C2C12 myoblasts following different doses. METHODS: C2C12 cells were irradiated with 650 nm laser(λ=650 nm, p=5 mW) with energy densities of 0, 0.4, and 0.8 J/cm2. Cell oxidative function was measured by oxygen consumption rate kit. Protein expression of myogenic determination factor (MyoD), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), mammalian target of rapamycin (mTOR) and its phosphorylation were detected by Western blot. RESULTS: Compared to the control group, the expression levels of MyoD, PGC-1α protein were increased and cell oxygen consumption rate was promoted in the low dose group(P<0.05). MyoD and PGC-1α protein expressions were also increased(P<0.05), the ratio of mTOR and its phosphorylationwere decreased significantly in the high dose group(P<0.05). CONCLUSIONS: 650 nm laser irradiation that dose is 0.4 J/cm2 enhances cell oxidative function, it related to that proper dose laser irradiation promoted the expression of PGC-1a protein.

[Effects of dietary corn peptide and exercise on hepatic ATGL and TNF-α in obese rats].

OBJECTIVE: To determine whether dietary corn peptides supplementation with or without exercise on body composition and fac-tors related to hepatic lipid metabolism in obese rats induced by a high fat diet. METHODS: Male SD rats were fed a high-fat diet (40% calorie as fat) for 8 weeks as a dietary induced obesity model (DIO, n=32). They were then randomly divided into four groups, control, corn pip-tide(CP) group, exercise group and CP + exercise group (n=8). Supplement (CP:200 g/kg) and exercise(tread mill Ex was performed 15 m/min for 60 min/d, 5 days a week) protocol for 4 weeks. Body weight and dietary levels of rats were monitored during the experimental peri-od. At the end of the 4th weeks, rats of all groups were sacrificed. Perirenal fat and liver were harvested, and hepatic adipose triglyceride li-pase(ATGL) and TNF-α were analyzed via Western blot. RESULTS: After 4 weeks, compared with DIO control group, body weight and perire-nal fat mass index in CP + exercise group were significantly decreased (P < 0.05). Hepatic ATGL was significantly higher in corn peptides supplementation, especially in combination with exercise (P < 0.05). At the same time, the values of TNF-α expression were decreased signif-icantly in exercise groups compared with DIO group (P < 0.05). CONCLUSIONS: Corn peptides combined with aerobic exercise has a weight re-duction by lowering adipose tissue in experimental animals, it may be related to the expression of ATGL and TNF-α in the liver, and promote lipid metabolism.

[Swimming training enhances muscle growth and potentiates p70s6k, rpS6 protein expression in rat skeletal muscle].

OBJECTIVE: To illustrate the molecular mechanism of skeletal muscle growth by examining the effect of swimming training on skeletal muscle growth and p70s6k, rpS6 protein expression. METHODS: Twenty four male SD rats were used to establish swimming training models with a 15% body mass load. The training protocol adopted interval swimming training (every other day with 8 weeks). The gastrocnemius and soleus muscle were collected and weighed after training, and the protein expression of p70s6k, rpS6 and their phosphorylated forms were examined. RESULTS: After 8 weeks treatment, no significant change was observed in skeletal muscle mass between training group (T) and control group (C) (P > 0.05), but muscle mass in training rapamycin (TR) group has a significantly decrease compared with that in T and C groups (P < 0.05). Soleus and gastrocnemius muscle mass index in T group increased significantly compared with C group (P < 0.05). Compared with the C group, the ratio of P-p70s6k/p70s6k in T group increased with significant difference (P < 0.05), but the ratio in TR group was significantly reduced (P < 0.05). The ratio of P-rpS6/rpS6 had a significant difference between TR and T group (P < 0.05). CONCLUSION: These results suggest that the interval training protocol is helpful to increase the relative muscle hypertrophy, and has a role in promoting the expression of p70s6k and rpS6.