The role of myokines in muscle health and disease.

Lightfoot, AP and Cooper, RG (2016) The role of myokines in muscle health and disease. Current Opinion in Rheumatology, 28 (6). pp. 661-666. ISSN 1040-8711

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Abstract

This article updates on the concept that muscle-derived cytokines (myokines) play important roles in muscle health and disease.Interleukin-6 (IL-6) is released from normal skeletal muscle in response to exercise, mediating both anti-inflammatory responses and metabolic adaptations, actions contradictory to the prevailing view that IL-6 is a proinflammatory cytokine that is inducing and propagating disease. The anti-inflammatory effects of IL-6 result from its trans-membrane signalling capability, via membrane-bound receptors, whereas its proinflammatory effects result instead from signalling via the soluble IL-6 receptor and gp130. IL-15 is elevated following exercise, promoting muscle fibre hypertrophy in some circumstances, while inducing fibre apoptosis in others. This functional divergence appears because of variations in expression of IL-15 receptor isoforms. Decorin, a recently described myokine, is also elevated following exercise in normal muscle, and promotes muscle fibre hypertrophy by competitively binding to, and thus inhibiting, myostatin, a negative regulator of muscle protein synthesis. Exercise-induced myostatin downregulation thus promotes muscle fibre growth, prompting recent trials of a biological myostatin inhibitor in inclusion body myositis.Myokines appear to exert diverse beneficial effects, though their mechanistic roles in myositis and other myopathologies remain poorly understood.