In:
Journal of Applied Physiology, American Physiological Society, Vol. 118, No. 4 ( 2015-02-15), p. 437-448
Abstract:
Interleukin-15 (IL-15) is a putative myokine hypothesized to induce an oxidative skeletal muscle phenotype. The specific IL-15 receptor alpha subunit (IL-15Rα) has also been implicated in specifying this contractile phenotype. The purposes of this study were to determine the muscle-specific effects of IL-15Rα functional deficiency on skeletal muscle isometric contractile properties, fatigue characteristics, spontaneous cage activity, and circulating IL-15 levels in male and female mice. Muscle creatine kinase (MCK)-driven IL-15Rα knockout mice ( mIl15ra fl/fl /Cre + ) were generated using the Cre-loxP system. We tested the hypothesis that IL-15Rα functional deficiency in skeletal muscle would increase resistance to contraction-induced fatigue, cage activity, and circulating IL-15 levels. There was a significant effect of genotype on the fatigue curves obtained in extensor digitorum longus (EDL) muscles from female mIl15ra fl/fl /Cre + mice, such that force output was greater during the repeated contraction protocol compared with mIl15ra fl/fl /Cre − control mice. Muscles from female mIl15ra fl/fl /Cre + mice also had a twofold greater amount of the mitochondrial genome-specific COXII gene compared with muscles from mIl15ra fl/fl /Cre − control mice, indicating a greater mitochondrial density in these skeletal muscles. There was a significant effect of genotype on the twitch:tetanus ratio in EDL and soleus muscles from mIl15ra fl/fl /Cre + mice, such that the ratio was lower in these muscles compared with mIl15ra fl/fl /Cre − control mice, indicating a pro-oxidative shift in muscle phenotype. However, spontaneous cage activity was not different and IL-15 protein levels were lower in male and female mIl15ra fl/fl /Cre + mice compared with control. Collectively, these data support a direct effect of muscle IL-15Rα deficiency in altering contractile properties and fatigue characteristics in skeletal muscles.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.00704.2014
Language:
English
Publisher:
American Physiological Society
Publication Date:
2015
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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