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Expression and Regulation of FNDC5/irisin in Periodontium and Dental Pulp

Irisin, which is secreted as a product of fibronectin type III domain-containing protein 5 (FNDC5) from muscle in response to exercise [2], is regarded as a crucial bridge linking exercise and overall health [3]. Irisin regulates multi-organ metabolism through autocrine, paracrine and endocrine signalling [3]. It plays an important role in the musculoskeletal system. Effect on bone is delivered via αV/β5 integrin receptors [4], and it has been shown that irisin improves bone mineral density and strength in vivo [5,6] as well as enhances osteoblast proliferation [7,8] and differentiation [7-9] in vitro. Effect on muscle is modulated via AMP-activated protein kinase [10], and it has been shown that irisin increases muscle growth and strength both in vitro and in vivo [11,12], and that its expression could be increased by autocrine manner [5]. However, the relationship between irisin and oral health is not elucidated. Similarly, to musculoskeletal system, irisin might also affect dynamic and biomechanically adaptive periodontium and dental pulp.