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Contracting muscle releases hundreds of hormones
What Myokines Do
Myokines carry signals between muscle and the brain, the pancreas, and the liver. They help with lipid oxidation and carbohydrate metabolism beyond the fuel muscle burns during the workout itself. Both strength training and endurance work raise the amount and kinds of myokines released.
Interleukin 6
The most common is interleukin 6. In illness it is known as a cytokine in a cytokine storm, but interleukin 6 released from muscle has a different, pleiotropic effect. The field took shape through a group in Copenhagen led by an immunologist who is also an exercise physiologist.
Immune Role And Testing
Myokines also come from macrophages, which is one reason muscle matters for immune function: it balances inflammatory cytokines. Levels vary widely from person to person, and measuring them before and after a workout is happening only in research. Within about five years, that kind of test could show whether a given workout is working.
How were myokines discovered?
In 2000, researchers in Copenhagen showed that interleukin 6 in the blood rises during exercise and comes from the contracting muscle itself. Bente Klarlund Pedersen, an immunologist and exercise physiologist, and her group proposed the name myokine for such muscle-derived signals in 2003. Their work reframed muscle as an endocrine organ, one that sends chemical messages to distant tissues.
Why is interleukin 6 helpful from muscle?
Interleukin 6 from muscle can climb many-fold during prolonged exercise, according to reviews from Pedersen's group. Unlike in infection, it does not arrive with a surge of tumor necrosis factor. Instead it prompts anti-inflammatory signals such as interleukin 10 and interleukin 1 receptor antagonist. It also raises fat breakdown and glucose uptake in other tissues.
Why do we know so little about myokines?
Proteomic studies on cultured muscle cells have cataloged hundreds of secreted proteins, but most have never been tied to a function. Each circulates at tiny concentrations, and the blood also holds versions released by fat, liver, and immune cells. That makes it hard to trace a given molecule back to muscle. Much of what is known comes from cell and animal experiments.
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