Department of Basic Medical Science, Neuroscience and Sense Organs, University of Bari, 70124 Bari, Italy.
Department of Clinical and Experimental Medicine, University of Foggia, 71100 Foggia, Italy.
Int J Endocrinol. 2014;2014:902186. doi: 10.1155/2014/902186. Epub 2014 Mar 4.
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.
最近的研究表明，运动可以增加肌肉细胞分泌的肌肉因子鸢尾素的表达，这种蛋白可以促使白色脂肪细胞向棕色脂肪细胞转化，可能是通过一种转分化的过程。这一新发现支持了肌肉可以被视为一种内分泌器官的观点，因为它能够通过促进能量消耗来靶向脂肪组织。基于这些新发现，我们假设鸢尾素直接参与骨代谢，证明其能够促进骨髓基质细胞向成熟成骨细胞分化。首先，我们证实了经过 3 周自由转轮运动的小鼠成肌细胞中鸢尾素的表达增加，与非运动状态相比。来自运动小鼠成肌细胞的条件培养基（CM）在体外诱导成骨细胞分化的程度大于在休息状态下饲养的小鼠。此外，分化的成骨细胞通过鸢尾素依赖的机制增加碱性磷酸酶和胶原 I 的表达。我们的研究结果首次表明，鸢尾素可以直接靶向成骨细胞，促进其分化。这一发现为未来的研究提供了重要的视角，这些研究可能会满足对具有骨骼合成代谢作用的运动模拟疗法的持续研究需求。
