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International Journal of Endocrinology
Volume 2014 (2014), Article ID 902186, 8 pages
http://dx.doi.org/10.1155/2014/902186
Research Article

Irisin Enhances Osteoblast Differentiation In Vitro

1Department of Basic Medical Science, Neuroscience and Sense Organs, University of Bari, 70124 Bari, Italy
2Department of Clinical and Experimental Medicine, University of Foggia, 71100 Foggia, Italy
3Department of Experimental and Clinical Medicine, Center of Obesity, United Hospitals—University of Ancona, 60020 Ancona, Italy

Received 19 December 2013; Accepted 13 January 2014; Published 4 March 2014

Academic Editor: Nicola Napoli

Copyright © 2014 Graziana Colaianni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

It has been recently demonstrated that exercise activity increases the expression of the myokine Irisin in skeletal muscle, which is able to drive the transition of white to brown adipocytes, likely following a phenomenon of transdifferentiation. This new evidence supports the idea that muscle can be considered an endocrine organ, given its ability to target adipose tissue by promoting energy expenditure. In accordance with these new findings, we hypothesized that Irisin is directly involved in bone metabolism, demonstrating its ability to increase the differentiation of bone marrow stromal cells into mature osteoblasts. Firstly, we confirmed that myoblasts from mice subjected to 3 weeks of free wheel running increased Irisin expression compared to nonexercised state. The conditioned media (CM) collected from myoblasts of exercised mice induced osteoblast differentiation in vitro to a greater extent than those of mice housed in resting conditions. Furthermore, the differentiated osteoblasts increased alkaline phosphatase and collagen I expression by an Irisin-dependent mechanism. Our results show, for the first time, that Irisin directly targets osteoblasts, enhancing their differentiation. This finding advances notable perspectives in future studies which could satisfy the ongoing research of exercise-mimetic therapies with anabolic action on the skeleton.