2014 年 3 巻 2 号 p. 211-215
Growing evidence has shown that skeletal muscle secretes several bioactive proteins from muscle cells into extracellular fluid. The secretion of several proteins, whose levels increase in response to exercise, can regulate the functions of several organs via autocrine, paracrine, and endocrine actions, and mediate exercise-induced benefits such as metabolic improvement, muscle building, and anti-inflammation. This is known as the myokine theory. Recently, we found a novel myokine, secreted protein acidic and rich in cysteine (SPARC), a member of the matricellular protein family that essentially modulates cell-cell and cell-matrix interactions. The secreted SPARC has been shown to prevent colon tumorigenesis via an apoptotic effect in in vitro and in vivo studies. Therefore, the muscle-secreted protein SPARC can support underlying mechanisms of epidemiological studies that suggest that habitual exercise can prevent the incidence of colon cancer. Many different types of studies have suggested that many other factors including proteins, metabolites, and microRNAs secreted from muscle have yet to be identified. These secretory factors may be biomarkers that reflect muscular function and beneficial adaptation achieved by exercise, along with the underlying mechanisms of beneficial effects.