Kawazoe Yusuke, Miyauchi Mutsumi, Nagasaki Atsuhiro, Furusho Hisako, Yanagisawa Syunryo, Chanbora Chea, Inubushi Toshihiro, Hyogo Hideyuki, Nakamoto Takashi, Suzuki Keiko, Moriwaki Sawako, Tazuma Susumu, Niida Shumpei, Takata Takashi
Department of Oral and Maxillofacial Pathobiology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
Department of Medicine and Molecular Science, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
PLoS One. 2015 Sep 29;10(9):e0139620. doi: 10.1371/journal.pone.0139620. eCollection 2015.
Cholestatic liver diseases exhibit higher levels of serum γ-glutamyl transpeptidase (GGT) and incidence of secondary osteoporosis. GGT has been identified as a novel bone-resorbing factor that stimulates osteoclast formation. The aim of this study was to elucidate the interaction of elevated GGT levels and cholestatic liver disease-induced bone loss.
Wistar rats were divided into three groups: sham-operated control (SO) rats, bile duct ligation (BDL) rats, and anti-GGT antibody-treated BDL rats (AGT). Serum GGT level was measured. Bone mineral density (BMD) was analyzed by dual-energy X-ray absorptiometry. Bone morphometric parameters and microarchitectural properties were determined by micro-computed tomography and histomorphometry of the distal metaphysis of femurs. Alterations of bone metabolism-related factors were evaluated by cytokine array. Effects of GGT on osteoblasts or stromal cells were evaluated by RT-PCR, enzyme activity, and mineralization ability.
Serum levels of GGT were significantly elevated in the BDL-group. In the BDL group, BMD, bone mass percentage, and osteoblast number were significantly decreased, whereas osteoclast number was significantly increased. These alterations were markedly attenuated in the AGT group. The mRNA levels of vascular endothelial growth factor-A, LPS-induced CXC chemokine, monocyte chemoattractant protein-1, tumor necrosis factor-α interleukin-1β and receptor activator of nuclear factor-kappa B ligand were upregulated, and those of interferon-γ and osteoprotegerin were downregulated in the GGT-treated stromal cells. Furthermore, GGT inhibited mineral nodule formation and expression of alkaline phosphatase and bone sialo-protein in osteoblastic cells.
Our results indicate that elevated GGT level is involved in hepatic osteodystrophy through secretion of bone resorbing factor from GGT-stimulated osteoblasts/bone marrow stromal cells. In addition, GGT also possesses suppressive effects on bone formation. Managing elevated GGT levels by anti-GGT antibody may become a novel therapeutic agent for hepatic osteodystrophy in chronic liver diseases.
胆汁淤积性肝病患者血清γ-谷氨酰转肽酶（GGT）水平较高，且继发性骨质疏松的发生率也较高。GGT已被确定为一种刺激破骨细胞形成的新型骨吸收因子。本研究的目的是阐明GGT水平升高与胆汁淤积性肝病所致骨质流失之间的相互作用。
将Wistar大鼠分为三组：假手术对照（SO）大鼠、胆管结扎（BDL）大鼠和抗GGT抗体处理的BDL大鼠（AGT）。检测血清GGT水平。采用双能X线吸收法分析骨密度（BMD）。通过微计算机断层扫描和股骨远端干骺端的组织形态计量学确定骨形态计量学参数和微观结构特性。通过细胞因子阵列评估骨代谢相关因子的变化。通过逆转录聚合酶链反应、酶活性和矿化能力评估GGT对成骨细胞或基质细胞的影响。
BDL组血清GGT水平显著升高。在BDL组中，BMD、骨量百分比和成骨细胞数量显著降低，而破骨细胞数量显著增加。这些改变在AGT组中明显减轻。在GGT处理的基质细胞中，血管内皮生长因子-A、LPS诱导的CXC趋化因子、单核细胞趋化蛋白-1、肿瘤坏死因子-α、白细胞介素-1β和核因子κB受体激活剂配体的mRNA水平上调，而干扰素-γ和骨保护素的mRNA水平下调。此外，GGT抑制成骨细胞中矿结节的形成以及碱性磷酸酶和骨唾液蛋白的表达。
我们的结果表明，GGT水平升高通过GGT刺激的成骨细胞/骨髓基质细胞分泌骨吸收因子参与肝性骨营养不良。此外，GGT对骨形成也具有抑制作用。通过抗GGT抗体控制升高的GGT水平可能成为慢性肝病肝性骨营养不良的一种新型治疗药物。
