Is Irisin Release A Function of Muscle Energy Demand?

Research Paper Title

Plasma Irisin Levels Progressively Increase in Response to Increasing Exercise Workloads in Young, Healthy, Active Subjects.

Background

Irisin, a recently discovered myokine, has been shown to induce white adipose tissue browning, enhancing energy expenditure and mediating some of the beneficial effects of exercise. The researchers aimed to estimate the time frame of changes in irisin levels after acute exercise and the effect of different exercise workloads and intensities on circulating irisin levels immediately post-exercise.

Methods

In a pilot study, four healthy subjects (22.5±1.7 years) underwent maximal workload exercise (maximal oxygen consumption, VO2max) and blood was drawn at pre-specified intervals to define the timeframe pre- and post-exercise irisin changes over a 24-hr period. In the main study, 35 healthy, non-smoking (23.0±3.3 years) men and women (n=20/15) underwent three exercise protocols ≥48-hr apart, in random order: 1-maximal workload (VO2max), 2-relative workload (70% of VO2max/10 minutes) and 3-absolute workload (75W/10 minutes). Blood was drawn immediately pre-, and 3 minutes post-exercise.

Results

In the pilot study, irisin levels increased by 35% 3 minutes post-exercise, then dropped and remained relatively constant. In the main study, irisin levels post-exercise were significantly higher than pre-exercise after all workloads (all, P<.001). Post- to pre-exercise differences in irisin levels were significantly different between workloads (P=.001), with the greatest increase by 34% following maximal workload (P=.004 vs. relative and absolute).

Conclusions

Circulating irisin levels were acutely elevated in response to exercise, with a greater increase after maximal workload. These findings suggest that irisin release could be a function of muscle energy demand. Future studies need to determine the underlying mechanisms of irisin release and explore irisin’s therapeutic potential.

Reference

Daskalopoulou, S.S., Cooke, A.B., Gomez, Y-H., Mutter, A.F., Filippaios, A., Mesfum, E.T. & Mantzoros, C.S. (2014) Plasma Irisin Levels Progressively Increase in Response to Increasing Exercise Workloads in Young, Healthy, Active Subjects. European Society of Endocrinology. Published online before print June 11, 2014, doi: 10.1530/EJE-14-0204.

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