Identification of human exercise-induced myokines using secretome analysis

Abstract

Endurance exercise is associated with significant improvements in cardio-metabolic risk parameters. A role for myokines has been hypothesized, yet limited information is available about myokines induced by acute endurance exercise in humans. Therefore, the aim of the study was to identify novel exercise-induced myokines in humans. To this end, we carried out a 1 h one-legged acute endurance exercise intervention in 12 male subjects and a 12 wk exercise training intervention in 18 male subjects. Muscle biopsies were taken before and after acute exercise or exercise training and were subjected to microarray-based analysis of secreted proteins (secretome). For acute exercise, secretome analysis resulted in a list of 86 putative myokines, which was reduced to 29 by applying a fold-change cut-off of 1.5. Based on that shortlist, a selection of putative myokines was measured in the plasma by ELISA or multiplex assay. From that selection, CX3CL1 (fractalkine) and CCL2 (MCP-1) increased at both mRNA and plasma levels. From the known myokines, only IL-6 and FGF 21 changed at the mRNA level, whereas none of the known myokines changed at the plasma level. Secretome analysis of exercise training intervention resulted in a list of 69 putative myokines. Comparing putative myokines altered by acute exercise and exercise training revealed a limited overlap of only 13 genes. In conclusion, this study identified CX3CL1 and CCL2 as myokines that were induced by acute exercise at the gene expression and plasma level and that may be involved in communication between skeletal muscle and other organs.

Heat therapy promotes the expression of angiogenic regulators in human skeletal muscle

“…In agreement with our findings, prior studies have demonstrated that the mRNA expression of CX3CL1 tends to decrease slightly over time in resting/nonexercising skeletal muscle (6,70). Intriguingly, however, the expression of CCL2 has been reported to increase, albeit not significantly, in resting muscle 2-4 h following a baseline biopsy (6,70,78). These changes in the expression of key myokines illustrate the critical importance of incorporating a control group in long experiments to account for time-dependent variations in skeletal muscle gene expression in humans.…”

“…This response might be potentially explained by circadian oscillations in gene expression (56), changes in metabolic status (79), or forced physical inactivity for a long period of time. In agreement with our findings, prior studies have demonstrated that the mRNA expression of CX3CL1 tends to decrease slightly over time in resting/nonexercising skeletal muscle (6,70). Intriguingly, however, the expression of CCL2 has been reported to increase, albeit not significantly, in resting muscle 2-4 h following a baseline biopsy (6,70,78).…”

“…Recently, Strömberg et al (70) demonstrated that CX3CL1 stimulation of primary human myoblasts and myotubes promoted marked increases in the expression of proangiogenic factors and chemotactic mediators. These observations, coupled with the notion that the expression of both factors increases markedly in skeletal muscle following an acute bout of exercise in humans (6), indicate that these chemoattractants promote a microenvironment that facilitates angiogenesis and muscle repair (70).…”

Exercise Improves Insulin Sensitivity in the Absence of Changes in Cytokines

“…Fractalkine is secreted in both adipose tissue and skeletal muscle, (5,36) and plays a role in the regulation of pancreatic islet β cell function. In humans, fractalkine has been proven to modulate monocyte adhesion in adipose tissue, thereby influencing chronic inflammation processes,(36) and is independently associated with markers of insulin resistance (HOMA-IR).…”

Omics and Exercise: Global Approaches for Mapping Exercise Biological Networks

“…Early myokinome profiling efforts in human muscle involved translating secreted proteins in cultured human muscle cells to expression of candidate myokines in human muscle biopsies following strength training (Norheim et al 2011). More recently, global microarray (Catoire et al 2014) and MSbased ) approaches have uncovered novel components of the human muscle secretome in response to acute exercise and exercise training. Proteomics-based discovery of the adipokinome has expanded our understanding of secreted proteins from human adipocytes (Lehr et al 2012).…”