Role of Myokines in Regulating Skeletal Muscle Mass and Function

Abstract

Loss of skeletal muscle mass and strength has recently become a hot research topic with the extension of life span and an increasingly sedentary lifestyle in modern society. Maintenance of skeletal muscle mass is considered an essential determinant of muscle strength and function. Myokines are cytokines synthesized and released by myocytes during muscular contractions. They are implicated in autocrine regulation of metabolism in the muscle as well as in the paracrine/endocrine regulation of other tissues and organs including adipose tissue, the liver, and the brain through their receptors. Till date, secretome analysis of human myocyte culture medium has revealed over 600 myokines. In this review article, we summarize our current knowledge of major identified and characterized myokines focusing on their biological activity and function, particularly in muscle mass and function.

Keywords: muscle strength; muscular contraction; myocytes; myokines; skeletal muscle mass.

FIGURE 1

The function of muscle contraction-induced myokines. The figure shows the selected the functions for each myokines released from muscle contraction (exercise) in muscle. BDNF, brain-derived neurotrophic factor; FGF21, fibroblast growth factor 21; SPARC, secreted protein acidic and rich in cysteine; IL, interleukin.

FIGURE 2

Signaling pathways of muscle contraction-induced myokines. The myokine-mediated signaling pathways lead to its target genes expression, which in turn regulate muscle cell proliferation, differentiation, and growth. It ultimately increases/decreases muscle mass. ALK, activin receptor-like kinase; ActRIIB, activin type IIB receptor; BDNF, brain-derived neurotrophic factor; TrKB, tropomyosin-related kinase receptor B; FGF21, fibroblast growth factor 21; SPARC, secreted protein acidic and rich in cysteine.