Resistance training increases fibroblast growth factor-21 and irisin levels in the skeletal muscle of Zucker diabetic fatty rats

[PURPOSE]: Although the fibroblast growth factor-21 (FGF-21) and irisin roles are well demonstrated in metabolic disease, there have been no reports investigating the effect of resistance exercise on FGF-21 and irisin levels in diabetic skeletal muscles. Therefore, this study aimed to investigate the change of FGF-21 and irisin levels in various skeletal muscles, and their association with muscle strength, following 8 weeks of resistance training using Zucker diabetic fatty rats (type 2 diabetic animal models). [METHODS]: Twenty-four male lean (Zucker lean control, ZLC) and diabetic (Zucker diabetic fatty, ZDF) rats (age, 8 weeks old) were separated into 3 groups, lean control (ZLC-Con, n=8), diabetic control (ZDF-Con, n=8), and diabetic exercise-trained groups (ZDF-Ex, n=8). The rats in ZDF-Ex were trained to climb a 1-m vertical (85 degrees inclined) ladder with weights. Resistance training was performed with 10 repetitions/day for 12 weeks (3 days/week). The skeletal muscle levels of FGF-21 and irisin were measured using enzyme-linked immunosorbent assays. [RESULTS]: The levels of FGF-21 in the soleus (SOL) and extensor digitorum longus muscles of ZDF-Ex were higher (p<0.05) compared to levels in ZDF-Con. Additionally, we found a significantly higher irisin level in the SOL muscles of ZDF-Ex compared to that in ZDF-Con. Moreover, we found that the levels of FGF-21 (R=0.532, p=0.02) and irisin (R=0.498, p=0.03) had significant correlations with grip strength. [CONCLUSION]: Based on these results, resistance training may be an efficient intervention for increasing FGF-21 and irisin levels in type 2 diabetic (T2DM) skeletal muscles.