BACKGROUND: Different intensities of exercises make different effects on human body,
and the changes of skeletal muscle after
exercise remain unclear. Physical change of human body during exercise is a
hotspot.
OBJECTIVE: To investigate the effect of
different intensities of exercises on the mass of rat skeletal muscle, and the
role of BNIP3-mediated mitophagy in maintaining skeletal muscle mass.
METHODS: The study was approved by the
Laboratory Animal Ethical Committee of Beijing Sport University. Twenty-four
healthy male Sprague-Dawley rats aged 8 weeks were randomly divided into three
groups: control, moderate-intensity exercise (5°, 15 m/min, 1 hour, 60% VO2max)
and high-intensity exercise (5°, 35 m/min, 20 minutes, 85% VO2max)
groups (n=8/group), 6 times weekly.
The rat soleus and gastrocnemius were removed to measure the wet weights. The
cross-sectional area of muscle fiber was detected by immunofluorescence. The
protein expression levels of BNIP3, p62 and LC3 in the soleus and gastrocnemius
were detected by western blot assay.
RESULTS AND
CONCLUSION: (1) The wet weight of
gastrocnemius in the exercise groups was significantly lower than that in the
control group (
P < 0.01). (2) The
cross-sectional area of gastrocnemius fiber in the exercise groups was
significantly less than that in the control group (
P < 0.01), and the cross-sectional area of soleus fiber in the
exercise groups was significantly more than that in the control group (
P < 0.01). (3) The moderate-intensity
exercise induced increased mitophagy, and the expression level of BNIP3 and
LC3-II/LC3-I were up-regulated (
P < 0.05), while p62 was down-regulated (
P < 0.05) compared with the control group. The expression level of
LC3-II/LC3-I in the high-intensity
exercise group was higher (
P <
0.05), but the expression level of p62 was lower than that in the
moderate-intensity exercise group and the expression of BNIP3 was decreased (
P < 0.05). (4) To conclude, 4-week
moderate-intensity exercise can promote the removal of damaged mitochondria and
maintain skeletal muscle function by increasing BNIP3-regulated mitophagy in
skeletal muscle. In high-intensity exercise, the level of autophagy is higher,
but will cause harmful effect on skeletal muscle.