title: The role of myokines in muscle health and disease.
abstract: OBJECTIVE
  This article updates on the concept that muscle-derived cytokines (myokines) play important roles in muscle health and disease.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Myokines appear to exert diverse beneficial effects, though their mechanistic roles in myositis and other myopathologies remain poorly understood.
authors.affiliation: MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing, Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Lightfoot
authors.forename: Robert G
authors.initials: RG
authors.lastname: Cooper
mesh_terms: D016207:Cytokines / Q000378:metabolism / Q000502:physiology*; D058575:Decorin / Q000378:metabolism; D015444:Exercise / Q000502:physiology; D006801:Humans; D015850:Interleukin-6 / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009135:Muscular Diseases / Q000378:metabolism*; D055435:Myostatin / Q000378:metabolism; D019947:Receptors, Interleukin-6 / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology
chemical_list: D016207:Cytokines; C546878:DCN protein, human; D058575:Decorin; C508600:IL6 protein, human; D015850:Interleukin-6; C525911:MSTN protein, human; D055435:Myostatin; D019947:Receptors, Interleukin-6