FNDC5 and chronic kidney disease: Concerning the kidney, irisin inhibits the epithelial–mesenchymal transition (EMT) to lessen fibrosis.35 Moderate exercise in patients with chronic kidney disease significantly increases serum irisin levels and delays CKD progression.28 Furthermore, preventive administration of irisin before AKI in mice can have a protective effect, and its mechanism may be related to uncoupling protein 2 (UCP-2).36 Irisin seems affected by sex since higher plasma irisin levels are observed in men than women.37,38 However, the present study shows no such difference in either group (Figure 1).