Effect of Various Exercise Regimens on Selected Exercise-Induced Cytokines in Healthy People

Abstract

Different forms of physical activity-endurance, resistance or dynamic power-stimulate cytokine release from various tissues to the bloodstream. Receptors for exercise-induced cytokines are present in muscle tissue, adipose tissue, liver, brain, bones, cardiovascular system, immune system, pancreas, and skin. They have autocrine, paracrine and endocrine activities. Many of them regulate the myocyte growth and differentiation necessary for muscle hypertrophy and myogenesis. They also modify energy homeostasis, lipid, carbohydrate, and protein metabolism, regulate inflammation and exchange information (crosstalk) between remote organs. So far, interleukin 6 and irisin have been the best studied exercise-induced cytokines. However, many more can be grouped into myokines, hepatokines and adipomyokines. This review focuses on the less known exercise-induced cytokines such as myostatin, follistatin, decorin, brain-derived neurotrophic factor, fibroblast growth factor 21 and interleukin 15, and their relation to various forms of exercise, i.e., acute vs. chronic, regular training in healthy people.

Keywords: brain-derived neurotrophic factor; decorin; exercise; exercise-induced cytokines; fibroblast growth factor 21; follistatin; hepatokines; interleukin 15; myokines; myostatin.

Figure 1

Potential relations of exercise-induced cytokines with physical activity and accompanying phenomena. From the top in clockwise manner: Overall insulin resistance is related with increased levels of myostatin; IL-15 decreases lipid accumulation; muscle-contraction induced increase of brain-derived neurotrophic factor (BDNF) drives lipid oxygenation; increased levels of myostatin are related with higher content of type II fibers and lower content of type I fibers and probably are associated with muscle adaptation to exercise; interleukin 15 (IL-15) stimulates synthesis of myosin heavy chain proteins and increase glucose uptake in the muscle; decorin binds with myostatin and downregulates its activity; in the liver, myostatin suppresses growth hormone (GH)—induced insulin-like growth factor 1 (IGF-1) expression; increased glucagon/insulin ratio after exercise leads to increased production of follistatin in the liver, which suppress myostatin activity; fibroblast growth factor 21 (FGF21) is produced mainly by the liver; IL-15 improves insulin-sensitivity; follistatin promotes browning of white adipose tissue.