The search for exercise factors in humans

Area of Science:

• Exercise physiology
• Molecular biology
• Endocrinology

Background:

• Regular exercise confers protection against chronic diseases by inducing systemic adaptations beyond skeletal muscle.
• The precise mechanisms underlying these systemic changes are not fully understood, with exercise factors proposed as a key link.
• Exercise factors are a subclass of myokines, proteins secreted by skeletal muscle with signaling functions.

Purpose of the Study:

• To provide an overview of the current literature on myokines, focusing on their role as exercise factors.
• To highlight myokines with the highest potential to act as exercise factors based on evidence of increased plasma levels during exercise.
• To emphasize the need for further research into the functional roles of myokines in exercise and metabolic disease.

Main Methods:

• Literature review of studies identifying and characterizing myokines.
• Analysis of evidence for increased plasma levels of specific myokines during exercise.
• Synthesis of current understanding regarding the functional relevance of identified myokines.

Main Results:

• Numerous myokines have been identified, but their functional significance remains largely unclear.
• Few identified myokines are considered putative exercise factors.
• Interleukin-6 (IL-6), secreted protein acidic and rich in cysteine (SPARC), angiopoietin-like 4 (ANGPTL4), C-X3-C motif ligand 1 (CX3CL1), and C-C motif ligand 2 (CCL2) show the highest potential as exercise factors due to documented increases in circulation during exercise.

Conclusions:

• Further research should prioritize elucidating the functional roles of myokines in both acute and chronic exercise responses.
• Myokines represent a promising therapeutic target for managing metabolic diseases.
• Understanding myokine function is crucial for fully leveraging the systemic benefits of exercise.