Department of Food and Nutrition, Hallym University, Chuncheon, Kangwon-do 200-702, Republic of Korea.
Exp Biol Med (Maywood). 2012 Apr;237(4):417-28. doi: 10.1258/ebm.2011.011376. Epub 2012 Apr 10.
Bone-remodeling imbalance induced by increased bone resorption and osteoclast formation is known to cause skeletal diseases such as osteoporosis. There has been growing interest in the anabolic natural agents that enhance bone formation. Silymarin is flavonolignans extracted from blessed milk thistle. Several studies suggest that silymarin possesses antihepatotoxic properties and anticancer effects against carcinoma cells. This study investigated promoting effects of silymarin on differentiation and mineralization of osteoblastic MC3T3-E1 mouse cells and on bone mineral density (BMD) by in vivo fracture experiments. Osteoblasts were treated with 1-20 μmol/L silymarin for 15 days in a differentiating medium. In addition, this study explored signaling pathways implicated in the osteoblastogenesis of silymarin. It was found that silymarin stimulated alkaline phosphatase (ALP) activity and calcium nodule formation in a dose-dependent manner with a substantial effect on osteoblast proliferation. Silymarin treatment enhanced collagen secretion, osteocalcin transcription and bone morphogenetic protein (BMP) expression. The BMP inhibitor noggin suppressed the silymarin-promoted ALP activity in differentiated osteoblasts, suggesting that its osteoblastogenic actions entail the BMP pathway. This was proved by increased SMAD1/5/8 phosphorylation and runt-related transcription factor 2 (Runx2) expression in the presence of silymarin. In 21-day fracture-healing experiments, fractured and silymarin (10 mg/kg)-treated C57BL/6 mice showed better bone healing than fractured mice. Silymarin supplementation improved tibial bone strength with elevated BMD and serum levels of osteogenic ALP and osteocalcin. Taken together, these results demonstrate, for the first time, that silymarin has a potential to enhance osteoblastogenesis through accelerating BMP/SMAD/Runx2 signal pathways and to improve fracture healing and bone strength in mouse tibiae.
骨吸收增加和破骨细胞形成导致的骨重建失衡已知会引起骨质疏松症等骨骼疾病。人们对增强骨形成的合成代谢天然剂越来越感兴趣。水飞蓟素是从乳蓟中提取的类黄酮木脂素。多项研究表明，水飞蓟素具有抗肝毒性和抗癌作用，可抑制癌细胞。本研究通过体内骨折实验，研究了水飞蓟素对成骨细胞 MC3T3-E1 小鼠细胞分化和矿化以及骨密度（BMD）的促进作用。将成骨细胞在分化培养基中用 1-20μmol/L 的水飞蓟素处理 15 天。此外，本研究还探讨了水飞蓟素在成骨细胞形成过程中涉及的信号通路。结果发现，水飞蓟素以剂量依赖的方式刺激碱性磷酸酶（ALP）活性和钙结节形成，对成骨细胞增殖有显著影响。水飞蓟素处理增强了胶原蛋白分泌、骨钙素转录和骨形态发生蛋白（BMP）表达。BMP 抑制剂 noggin 抑制分化成骨细胞中水飞蓟素促进的 ALP 活性，表明其成骨作用涉及 BMP 途径。这一点在存在水飞蓟素的情况下，SMAD1/5/8 磷酸化和 Runt 相关转录因子 2（Runx2）表达增加得到了证明。在 21 天骨折愈合实验中，骨折和水飞蓟素（10mg/kg）治疗的 C57BL/6 小鼠的骨折愈合情况好于骨折小鼠。水飞蓟素补充提高了胫骨骨强度，增加了 BMD 和血清中成骨 ALP 和骨钙素水平。总之，这些结果首次表明，水飞蓟素通过加速 BMP/SMAD/Runx2 信号通路增强成骨作用，并改善小鼠胫骨骨折愈合和骨强度。
