title: CTRP3 acts as a negative regulator of osteoclastogenesis through AMPK-c-Fos-NFATc1 signaling in vitro and RANKL-induced calvarial bone destruction in vivo.
abstract: Adipokines derived from adipocytes are important factors that act as circulating regulators of bone metabolism. C1q/tumor necrosis factor (TNF)-related Protein-3 (CTRP3) is a novel adipokine with multiple effects such as lowering glucose levels, inhibiting gluconeogenesis in the liver, and increasing angiogenesis and anti-inflammation. However, the effects and the mechanisms of CTRP3 on bone metabolism, which is regulated by osteoblasts and osteoclasts, have not been investigated. Here, we found that CTRP3 inhibited osteoclast differentiation induced by osteoclastogenic factors in bone marrow cell-osteoblast co-cultures, but did not affect the ratio of receptor activator of nuclear factor κB (NF-κB) ligand (RANKL) to osteoprotegerin (OPG) induced by osteoclastogenic factors in osteoblasts. We also found that CTRP3 inhibited osteoclast differentiation from mouse bone marrow macrophages (BMMs) induced by RANKL in a dose-dependent manner without cytotoxicity. Functionally, CTRP3 inhibited the F-actin formation and bone resorbing activity of mature osteoclasts. Pretreatment with CTRP3 significantly inhibited RANKL-induced expression of c-Fos and nuclear factor of activated T-cells (NFATc1), essential transcription factors for osteoclast development. Surprisingly, the activation of AMP-activated protein kinase (AMPK) was considerably increased by pretreatment with CTRP3 for 1h. The CTRP3-stimulated AMPK activation was also maintained during RANKL-induced osteoclastogenesis. CTRP3 did not affect RANKL-induced p38, ERK, JNK, Akt, IκB, CREB, and calcium signaling (Btk and PLCγ2). These results suggest that CTRP3 plays an important role as a negative regulator of RANKL-mediated osteoclast differentiation by acting as an inhibitor of NFATc1 activation through the AMPK signaling pathway. Furthermore, CTRP3 treatment reduced RANKL-induced osteoclast formation and bone destruction in mouse calvarial bone in vivo based on micro-CT and histologic analysis. In conclusion, these findings strongly suggest that CTRP3 deserves new evaluation as a potential treatment target in various bone diseases associated with excessive osteoclast differentiation and bone destruction.
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Ju-Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Jung-Youl
authors.initials: JY
authors.lastname: Min
authors.affiliation: Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Baek
authors.affiliation: Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Sung-Jun
authors.initials: SJ
authors.lastname: Ahn
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Hong Young
authors.initials: HY
authors.lastname: Jun
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Department of Radiology, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Kwon-Ha
authors.initials: KH
authors.lastname: Yoon
authors.affiliation: Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Institute for Environmental Science, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Min Kyu
authors.initials: MK
authors.lastname: Choi
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Division of Rheumatology, Department of Internal Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Institute for Skeletal Disease, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea. Electronic address: ckhlms@wku.ac.kr.
authors.forename: Myeung Su
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Institute for Skeletal Disease, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea. Electronic address: jmoh@wku.ac.kr.
authors.forename: Jaemin
authors.initials: J
authors.lastname: Oh
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D054392:Adipokines / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D050778:NFATC Transcription Factors / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D055114:X-Ray Microtomography
chemical_list: D054392:Adipokines; C428135:CORS26 protein, mouse; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D016760:Proto-Oncogene Proteins c-fos; D053245:RANK Ligand; D034741:RNA, Small Interfering; C505689:Tnfsf11 protein, mouse; D055372:AMP-Activated Protein Kinases
keywords: AMPK; Adipokine; Bone resorption; CTRP3; Osteoclast differentiation