Response Of Il-4 And Il-4r Of Human Skeletal Muscle To Strength Training

Abstract

Interleukin-4 (IL-4) is involved in the regulation of the myoblast fusion and IL-4 receptor (IL-4R) has significance for skeletal muscle growth in vitro and in mice. Taking into account that strength training can lead to muscle hypertrophy and/or regeneration and/or fiber type transformation, we hypothesized that IL-4 and IL-4R may play a role in these processes. PURPOSE To investigate the effects of strength training on IL-4R and IL-4 expression in skeletal muscle in humans. METHODS Twelve volunteers received a 6-week strength training with maximum contractions. Muscle samples were taken from triceps brachii before and after the total course of training. Total RNA was extracted from the muscle samples and Oligo primed synthesis of cDNA was performed using MuLV reverse transcriptase. MRNA levels of IL-4R and IL-4 expression were determined by quantitative real-time PCR and IL-4 protein expression by ELISA. RESULTS The expression of IL-4R was significantly increased after training from 0,19±0,10 to 1,38±0,36 mRNA copy number (p=0.004). There was a slight increase in IL-4 mRNA level of skeletal muscle after training from 654±268 to 1054±757 mRNA copy number (p=0,623) and a slight decrease in IL-4 protein expression from 0,35±0,06 to 0,26±0,04 OD (p=0,263). CONCLUSIONS We demonstrate for the first time that IL-4R is upregulated after strength training in human skeletal muscle. There were only slight effects on IL-4 protein and mRNA expression in skeletal muscle after strenght training. In conclusion, a possible role of IL-4 and IL-4R could be postulated for the adaptation of skeletal muscle in response to strength training in humans. This is supported by the established mitogenic effects of IL-4 and IL-4R in some cell types and tissues. The relevance of this findings has to be determined in further studies.