Expression of interleukin-15 in human skeletal muscle effect of exercise and muscle fibre type composition.
The cytokine interleukin-15 (IL-15) has been demonstrated to have anabolic effects in cell culture systems. We tested the hypothesis that IL-15 is predominantly expressed by type 2 skeletal muscle fibres, and that resistance exercise regulates IL-15 expression in muscle. Triceps brachii, vastus lateralis quadriceps and soleus muscle biopsies were obtained from normally physically active, healthy, young male volunteers (n = 14), because these muscles are characterized by having different fibre-type compositions. In addition, healthy, normally physically active male subjects (n = 8) not involved in any kind of resistance exercise underwent a heavy resistance exercise protocol that stimulated the vastus lateralis muscle and biopsies were obtained from this muscle pre-exercise as well as 6, 24 and 48 h post-exercise. IL-15 mRNA levels were twofold higher in the triceps (type 2 fibre dominance) compared with the soleus muscle (type 1 fibre dominance), but Western blotting and immunohistochemistry revealed that muscle IL-15 protein content did not differ between triceps brachii, quadriceps and soleus muscles. Following resistance exercise, IL-15 mRNA levels were up-regulated twofold at 24 h of recovery without any changes in muscle IL-15 protein content or plasma IL-15 at any of the investigated time points. In conclusion, IL-15 mRNA level is enhanced in skeletal muscles dominated by type 2 fibres and resistance exercise induces increased muscular IL-15 mRNA levels. IL-15 mRNA levels in skeletal muscle were not paralleled by similar changes in muscular IL-15 protein expression suggesting that muscle IL-15 may exist in a translationally inactive pool.
Nielsen
Anders Rinnov
AR
Department of Infectious Diseases Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
Mounier
Remi
R
Plomgaard
Peter
P
Mortensen
Ole Hartvig
OH
Penkowa
Milena
M
Speerschneider
Tobias
T
Pilegaard
Henriette
H
Pedersen
Bente Klarlund
BK
D000328:Adult; D015444:Exercise / Q000502:physiology*; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D019409:Interleukin-15 / Q000097:blood / Q000378:metabolism*; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D052097:Quadriceps Muscle / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D019409:Interleukin-15; D012333:RNA, Messenger
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