Proteomic identification of secreted proteins from human skeletal muscle cells and expression in response to strength training

Abstract

Regular physical activity protects against several types of diseases. This may involve altered secretion of signaling proteins from skeletal muscle. Our aim was to identify the most abundantly secreted proteins in cultures of human skeletal muscle cells and to monitor their expression in muscles of strength-training individuals. A total of 236 proteins were detected by proteome analysis in medium conditioned by cultured human myotubes, which was narrowed down to identification of 18 classically secreted proteins expressed in skeletal muscle, using the SignalP 3.0 and Human Genome Expression Profile databases together with a published mRNA-based reconstruction of the human skeletal muscle secretome. For 17 of the secreted proteins, expression was confirmed at the mRNA level in cultured human myotubes as well as in biopsies of human skeletal muscles. RT-PCR analyses showed that 15 of the secreted muscle proteins had significantly enhanced mRNA expression in m. vastus lateralis and/or m. trapezius after 11 wk of strength training among healthy volunteers. For example, secreted protein acidic and rich in cysteine, a secretory protein in the membrane fraction of skeletal muscle fibers, was increased 3- and 10-fold in m. vastus lateralis and m. trapezius, respectively. Identification of proteins secreted by skeletal muscle cells in vitro facilitated the discovery of novel responses in skeletal muscles of strength-training individuals.

Myokines in insulin resistance and type 2 diabetes

“…Nowadays, skeletal muscle is recognised as an endocrine organ, and proteins expressed by and released from skeletal muscle have been termed myokines [1]. In three studies using primary human myotubes and proteomic approaches, hundreds of myokines have been identified, including more than 50 novel myokines [2][3][4].…”

Exercise Proteomics: Review

“…Exercise proteomics was used to study protein alterations in humans (Malm et al2012;Egan et al 2011;Norheim et al 2011;Hody et al 2011;Moriggi et al 2010;Holloway et al 2009) and animal models of physical activity Magherini et al 2012;Macedo et al 2012;Yamaguchi et al 2010;Bouwman et al 2010;Burniston 2008;Donoghue et al 2007;Guelfi et al 2006;Donoghue et al 2005). The neuromuscular system has a vast capacity to become accustomed to a great variety of physical demands and differing training conditions by muscle remodelling involving changes in contractile properties, metabolic pathways and tissue mass (Bassel and Olson 2006).…”

“…The global effects of high-intensity training during strenuous interval training or strength training have also been analysed by proteomics Norheim et al 2011;Yamaguchi et al 2010;Holloway et al 2009;Guelfi et al 2006). Human vastus lateralis muscle showed increased expression levels of the mitochondrial enzymes succinate dehydrogenase and ATP synthase in response to interval training, as well as post-translational modulations of troponin TnT and muscle creatine kinase (Holloway et al 2009).…”

“…Changes in these muscle-associated proteins appear to represent distinct alterations in the fibre proteome following the stimulation of the AMP-activated protein kinase AMPK and elevation of sarcoplasmic Ca2+ levels during muscle contraction. Norheim and co-workers (Norheim et al 2011) have initiated the proteomic identification of potential alterations in the secretion of signalling proteins from human skeletal muscle cells in response to strength training. Initial studies suggest that several types of myokines with paracrine or endocrine functions may be synthesized in myofibres and then being secreted for interactions with other tissues (Norheim et al 2011).…”

“…Norheim and co-workers (Norheim et al 2011) have initiated the proteomic identification of potential alterations in the secretion of signalling proteins from human skeletal muscle cells in response to strength training. Initial studies suggest that several types of myokines with paracrine or endocrine functions may be synthesized in myofibres and then being secreted for interactions with other tissues (Norheim et al 2011). The exact activation process, release mechanisms and non-muscle targets of these novel protein factors remain to be determined.…”