Myokines & Muscle Signaling

topic

Myokines are peptides and proteins secreted by contracting skeletal muscle that function as endocrine and paracrine signaling molecules — with IL-6 (the first myokine discovered, produced during muscle contraction and having anti-inflammatory effects despite IL-6 from fat tissue being pro-inflammatory), irisin (stimulating BDNF in the brain and browning of white adipose tissue), SPARC (suppressing colon cancer cell proliferation), FGF21 (promoting fat metabolism), and meteorin-like (stimulating anti-inflammatory macrophage polarization) constituting a muscle-to-organ communication system that was unknown before 2003.

Role

Myokines represent the most significant recent paradigm shift in exercise physiology — establishing skeletal muscle not merely as a contractile mechanical tissue but as an endocrine organ that actively communicates protective signals to the brain, liver, adipose tissue, immune system, and cancer biology. The anti-cancer, anti-inflammatory, neuroprotective, and metabolic effects of myokines explain why muscle mass is associated with reduced cancer risk, reduced dementia risk, reduced inflammation, and reduced metabolic disease — providing the molecular mechanism linking muscle activity to systemic health benefits beyond the cardiovascular and metabolic effects of exercise itself. Most people exercise without any awareness that their contracting muscles are secreting protective peptides that are traveling to and influencing their brain, their fat tissue, and their cancer surveillance mechanisms.

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