About this Research Topic
A novel paradigm has recently emerged whereby individual striated muscle fibers communicate and are involved in vast crosstalk with other body cells and organs, such as the adipose tissue, the immune system, glands such as liver and pancreas, bones and even with the brain. This communication mostly relies on humoral factors that reach and depart from the striated muscles through the circulation; at the same time, it deeply affects and depends on muscle physiopathology.
Striated muscles show high biosynthetic activity, represent over 40% of the total body mass and are highly vascularized: these features, typical of secretory organs, have led to the conception of a new view of muscles as endocrine organs. Their secretory products are collectively known as myokines and consist of hundreds of secreted proteins and other products, including miRNA and exosomes. A particularity of striated muscles as secretory organs is that this activity is significantly affected by muscle major and most typical activity: contraction, i.e. physical exercise.
The traditional view of adipose tissue as a metabolic and storage center for fatty acids has also been challenged and now this tissue is also envisaged as a pivotal controller of inflammation. By this mean, adipocytes affect striated muscle homeostasis and a plethora of other tissues. Worth noting, fat pads are present in many organs and adipocytes are included in the perimysium, favoring paracrine interaction with muscles. Adipokynes, the adipose tissue secretome, are affected by the individual status and shift to a pro-inflammatory state in several pathological conditions. Furthermore, muscle physiology and contraction elicit humoral alterations that reach and affect the adipose tissue.
Immune cells secrete cytokines to regulate their own proliferation and activity, ultimately controlling immune response and inflammation following tissue damage. They also present the unique capacity to migrate and interact locally with different other cells, including adipocytes and muscle stem cells or fibers, in a cell-based/paracrine fashion.
The rational above poses the basis for a comprehensive view of the body where tissue cross-talk plays a major role in controlling whole-body metabolism and disease progression. Deepening the understanding of one such integrated view shall provide basis for the development of future multimodal therapies aimed at counteracting striated muscle diseases and hence contribute to minimize the effects of aging and chronic diseases.
This Research Topic welcomes original contributions and reviews dealing with the following aspects of muscle physiopathology:
- crosstalk between different striated muscles, such as heart and skeletal muscle, or a specific skeletal muscle and its neighboring tissues or, still, contralateral counterparts
- crosstalk between striated muscle and fat tissue
- crosstalk between striated muscle and the immune system
- identification and characterization of novel myokines, adipokynes or cytokines, or other secreted products
- physical exercise effects on the endocrinological bases of tissue crosstalk.
Keywords: Endocrine crosstalk, exercise training, striated muscle, wasting, adipocytes
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