Muscle–Organ Crosstalk: The Emerging Roles of Myokine

cookwithkathy

Feb 28

Mai Charlotte, Krogh Severinsen and Bente Klarlund Pedersen wrote . . . . . . . . .

Abstract

Physical activity decreases the risk of a network of diseases, and exercise may be prescribed as medicine for lifestyle-related disorders such as type 2 diabetes, dementia, cardiovascular diseases, and cancer. During the past couple of decades, it has been apparent that skeletal muscle works as an endocrine organ, which can produce and secrete hundreds of myokines that exert their effects in either autocrine, paracrine, or endocrine manners. Recent advances show that skeletal muscle produces myokines in response to exercise, which allow for crosstalk between the muscle and other organs, including brain, adipose tissue, bone, liver, gut, pancreas, vascular bed, and skin, as well as communication within the muscle itself. Although only few myokines have been allocated to a specific function in humans, it has been identified that the biological roles of myokines include effects on, for example, cognition, lipid and glucose metabolism, browning of white fat, bone formation, endothelial cell function, hypertrophy, skin structure, and tumor growth. This suggests that myokines may be useful biomarkers for monitoring exercise prescription for people with, for example, cancer, diabetes, or neurodegenerative diseases.

Essential Points

Myokines are defined as cytokines and other peptides that are produced, expressed and released by muscle fibers and exert either autocrine, paracrine, or endocrine effects
Myokines mediate communication between muscle and other organs, including brain, adipose tissue, bone, liver, gut, pancreas, vascular bed, and skin, as well as within the muscle itself
Myokines exert their effects on, for example, cognition, lipid and glucose metabolism, browning of white fat, bone formation, endothelial cell function, hypertrophy, skin structure, and tumor growth
The myokine IL-6 mediates the exercise-associated anti-inflammatory effects both acutely with each bout of exercise and as a consequence of training adaptation, including reduction in abdominal adiposity.
The identification of new myokines and their specific roles may lead to novel therapeutic targets
Myokines can be useful biomarkers for monitoring the type and amount of exercise that are required for the prescription of exercise for people with, for example, cancer, diabetes, or neurodegenerative diseases
[ . . . . . . ]

Muscle–Cancer Crosstalk

Epidemiological studies suggest that physical activity in leisure time reduces the risk of at least 13 different cancer types. People who are physically active after a diagnosis of prostate cancer, colorectal cancer, and breast cancer have a higher survival rate than physically inactive people suffering from the same cancer types.

It is obvious, that many cancers are accompanied by systemic low-grade chronic inflammation and that such inflammation may drive tumor progression. Therefore, the anti-inflammatory effects of physical training may mediate some of the protective effects of exercise on cancer development.

Pernille Hojman and her team explored the effect of exercise on tumor growth in preclinical models. She first established a B16F10 melanoma model and randomized tumor-bearing mice to voluntary wheel running or control. Running mice demonstrated a marked reduction in tumor volume and incidence across 6 different tumor models. The effects of exercise on cancer growth were mediated via a direct regulation of natural killer cells by a mechanism that involved epinephrine-dependent mobilization of natural killer cells to the circulation and an IL-6-dependent redistribution to tumors. Blocking IL-6 signaling during exercise abolished the exercise-induced inhibition of tumor growth. The findings in mice indicate that IL-6 may have a role in mediating anti-cancer effects.

A few mechanistic studies have demonstrated a potential role of other myokines, including Oncostatin M, irisin, and SPARC in the suppression of breast and colon cancer growth.

[ . . . . . . . ]

Source: NIH (Full text)

Read also:

Myostatin Decreases with Aerobic Exercise and Associates with Insulin Resistance . . . . .