FNDC5 and osteoporosis: Noteworthy, a potential therapeutic role of irisin has also been suggested in osteoporosis, as demonstrated by its ability to promote osteoblast differentiation, stimulate bone formation through regulation of the Wnt/β-catenin pathway, and promote mineralization through the expression of pentraxin 3 (PTX3), a novel biomarker of bone mineralization [9–11].