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Abstract
<p class="first" id="d1561638e115">Exercise induces the expression of peroxisome proliferator-activated
receptor gamma
co-activator 1-α (PGC-1α) in skeletal muscle, which promotes the cleavage of fibronectin
type III domain-containing protein 5 (FNDC5) to irisin. To explore the relationship
between irisin and its regulators, we analyzed the plasma irisin levels and the muscle
levels of FNDC5 and PGC-1α after exercise. Male C57BL/6J mice underwent a treadmill
exercise (60% of VO2max) for 30 min or one hour (h), and blood and gastrocnemius samples
were collected before exercise (pre-exercise), immediately after exercise, and during
24-h recovery after 1-h exercise. We found that plasma irisin levels were significantly
increased during exercise (P < 0.05), while FNDC5 protein levels were not significantly
increased. Moreover, PGC-1α mRNA and protein levels were significantly increased during
30-min exercise, but were decreased during 1-h exercise. After 1-h exercise, the irisin
levels peaked at 6 h (20.71 ± 0.25 ng/ml) and decreased to pre-exercise levels by
24 h (15.45 ± 0.27 ng/ml). Likewise, PGC-1α mRNA and protein levels were increased
at 1 h and maintained at elevated levels for 6 h; thereafter, the expression levels
of PGC1-α protein were decreased to pre-exercise levels at 12 h. Thus, the restoration
of PGC-1α expression to the pre-exercise levels was followed by the decrease in plasma
irisin levels. By contrast, during 24-h recovery, the expression levels of FNDC5 mRNA
and protein were maintained at elevated levels. These results suggest that the coordinated
expression of FNDC5 and PGC-1α may contribute to the increased levels of plasma irisin
after exercise.
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