Research Article
Possible Involvement of Leptin in the Elevated Osteoblastic Activity Observed in High Turnover Type Osteoporosis of Ovariectomized Mice
| Mitsuki Tezuka, Seiko Tatehara, Takahiro Imamura, Ryusuke Tachibana, Yusuke Takebe, Reiko Tokuyama and Kazuhito Satomura* | ||
| Department of Oral Medicine and Stomatology, Second Department of Oral and Maxillofacial Surgery, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-5801, Japan | ||
| Corresponding Author : | Kazuhito Satomura, DDS, PhD Department of Oral Medicine and Stomatology Second Department of Oral and Maxillofacial Surgery Tsurumi University School of Dental Medicine 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan Tel: +81-45-580-8326 E-mail: satomura-k@tsurumi-u.ac.jp |
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| Received July 25, 2014; Accepted October 30, 2014; Published November 04, 2014 | ||
| Citation: Tezuka M, Tatehara S, Imamura T, Tachibana R, Takebe Y, et al. (2014) Possible Involvement of Leptin in the Elevated Osteoblastic Activity Observed in High Turnover Type Osteoporosis of Ovariectomized Mice. J Autacoids 3:105. doi: 10.4172/2161-0479.1000105 | ||
| Copyright: © 2014 Tezuka M et al., This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. | ||
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Abstract
Postmenopausal osteoporosis is a high turnover type of osteoporosis induced by estrogen deficiency following menopause. In this type of osteoporosis, the osteoblastic activity is known to be elevated even though bone resorption by osteoclasts eventually exceeds bone formation by osteoblasts, resulting in the deterioration of the bone structure. Although the mechanisms underlying the progression of bone resorption in this disease are relatively well understood, the mechanisms underlying the elevated osteoblastic activity are yet to be elucidated. The purpose of this study is to investigate the possibility that leptin, a 16 kDa circulating hormone secreted mainly by white adipose tissue, is involved in the development and/or progression of the high turnover type of osteoporosis. Immunohistochemical analysis and ELISA were used to examine the expression of leptin in bones of ovariectomized mice. To investigate the effect of leptin on proliferation and osteoblastic differentiation of bone marrow stromal cells, cell proliferation assay and real-time RT-PCR analysis were performed using a mouse bone marrow stromal cell line, MMSC3. Immunohistochemistry and ELISA revealed enhanced expression of leptin in bone marrows of ovariectomized mice. A cell proliferation assay detected no significant effect of leptin on the proliferation of MMSC3 cells. In contrast, real-time RT-PCR revealed that leptin promoted the osteoblastic differentiation of this cell line. Estrogen depletion caused by ovariectomy induces the pregulation of leptin expression in the bone marrow cavity,which leads to the elevated osteoblastic activity observed in the early phase of high turnover type osteoporosis of ovariectomized mice.
