FNDC5 and type 2 diabetes mellitus: Researchers have investigated different exercise interventions in type 2 diabetic patients, measuring levels of fibroblast growth factor 21 (FGF21), irisin, myostatin (MSTN), and follistatin (FST) in blood samples, and identified the concurrent training that increased irisin and FST while decreasing MSTN as the optimal approach (Motahari Rad et al., 2023).