Wnt signaling plays an important role in the bone development and remodeling. The Wnt antagonist Dkk-1 is a potent inhibitor of bone formation. The aims of this study were firstly to compare the serum Dkk-1 levels in postmenopausal osteoporosis patients with age-matched healthy controls, and secondly, to assess the possible relationship between Dkk-1 and β-catenin, sclerostin, or bone turnover markers [CTX, PINP, N-MID-OT and 25(OH)D] in the setting of postmenopausal osteoporosis. A total of 350 patients with postmenopausal osteoporosis and 150 age-matched healthy controls were enrolled, and the serum levels of Dkk-1, β-catenin, sclerostin, OPG, and RANKL were detected by ELISA, and bone turnover markers [CTX, PINP, N-MID-OT and 25(OH)D] were measured by Roche electrochemiluminescence system in two groups. Serum Dkk-1 levels were significantly higher in postmenopausal osteoporosis group than in control group (P<0.001). Univariate analyses revealed that serum Dkk-1 levels were weakly negatively correlated to β-catenin (r=-0.161, P=0.003) and OPG (r=-0.106, P=0.047), while multiple regression analysis showed a negative correlation between serum Dkk-1 levels with β-catenin (β=-0.165, P=0.009) and BMD (β=-0.139, P=0.027), and a positive correlation between serum Dkk-1 levels and CTX (β=0.122, P=0.040) in postmenopausal osteoporosis group. No similar correlations ware observed in control group. The results provided evidence for the role of Dkk-1 in bone metabolism and demonstrated the link of Dkk-1 and Wnt/β-catenin in some ways.

This study provides evidence that the role of local RAS is related to BMD in GIOP patients, and suggests that local RAS might influence RANKL/OPG signaling to modulate bone metabolism.

Purpose/ObjectivePrompted by preliminary findings, this study was conducted to investigate the impact of zoledronic acid on the cancellous bone microstructure and its effect on the level of β-catenin in a mouse model of postmenopausal osteoporosis.Methods and Materials96 8-week-old specific-pathogen-free C57BL/6 mice were randomly divided into 4 groups (24 per group): a sham group, an ovariectomized osteoporosis model group, an estradiol-treated group, and a zoledronic acid-treated group. Five months after surgery, the third lumbar vertebra and left femur of the animals were dissected and scanned using micro-computed tomography (micro-CT) to acquire three-dimensional imagery of their cancellous bone microstructure. The impact of ovariectomy, the effect of estradiol, and the effect of zoledronic acid intervention on cancellous bone microstructure, as well as on the expression of β-catenin, were evaluated.ResultsThe estradiol-treated and the zoledronic acid-treated group exhibited a significant increase in the bone volume fraction, trabecular number, trabecular thickness, bone surface to bone volume ratio (BS/BV), and β-catenin expression, when compared with those of the control group (P <0.01). In contrast, the structure model index, trabecular separation, and BS/BV were significantly lower compared with those of the model group (P <0.01). No differences were observed in the above parameters between animals of the zoledronic acid-treated and the estradiol-treated group.ConclusionThese results suggest that increased β-catenin expression may be the mechanism underlying zoledronic acid-related improvement in the cancellous bone microstructure in ovariectomized mice. Our findings provide a scientific rationale for using zoledronic acid as a therapeutic intervention to prevent bone loss in post-menopausal women.