Effects of Exercise on Circulating Muscle-related Cytokines in Adults with Type 2 Diabetes and/or Obesity

Abstract

Background: Skeletal muscle is an endocrine organ that plays an important role in metabolic health by secreting a variety of myokines. Recent studies have shown that exercise significantly decreases interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in patients with type 2 diabetes (T2D). This paper explores the effect of chronic exercise on myokines in patients with T2D and/or obesity. Methods: The author searched for relevant English-language articles in PubMed. A total of 14 randomized controlled studies were found to be eligible for this short review. Results: It has been observed that chronic exercise does not change brain-derived neurotrophic factor (BDNF), irisin, and secreted protein acidic and rich in cysteine levels, whereas it decreases TNF-α levels in patients with T2D. Combined aerobic exercise (AE) and resistance training (RT) or sprint interval training increase insulin-like growth factor 1 (IGF-1) levels and decrease IL-6 and IL-15 levels in patients with T2D. Combined AE and RT may also increase IL-15 levels in obese individuals. In addition, RT alone may increase BDNF, IGF-1, and IL-7 levels in overweight individuals. However, AE alone does not change circulating myokine levels in patients with T2D, while it may increase myonectin levels in obese individuals. Conclusion: This short review demonstrated that exercise appears to have favorable effects on some myokines in patients with T2D and/or obesity. However, it remains inconclusive due to the heterogeneity in subject characteristics and exercise modalities.