Initially, it was found that skeletal muscles release a type of hormone-like molecule that promotes white fat browning after extensive exercise (Jedrychowski et al., 2015; Colaianni et al., 2017); subsequent studies confirmed that this molecule is irisin (Zhang and Zhang, 2016), which is expressed in skeletal muscle, heart, brain, and other tissues, and is involved in macromolecular metabolism, certain mitochondrial functions (Colaianni et al., 2017), as well as glucose metabolism, immune regulation, and metabolic diseases (Polyzos et al., 2018; Yang and Leung, 2020). This evidence concerns the gene FNDC5 and metabolic disease.