Effects of Zhuang Gu Zhi Tong Formula on Wnt/β-catenin Osteoporosis Pathway Antagonist SOST in Osteoporosis

Objective: To observe the effects of Zhuang Gu Zhi Tong Formula (ZGZTF) on antagonist SOST in canonical Wnt/β-catenin signaling pathway in osteoporosis. Methods: We analyzed the differential genes of patients with osteoporosis and normal subjects from the GEO database and then found SOST with specific expression. We analyzed SOST as an antagonist of the Wnt signaling pathway by the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. Then we studied the effect of ZGZTF on SOST in Wnt signaling pathway. Osteoporosis model was induced by ovariectomy (OVX) in 8-week-old female Sprague–Dawley (SD) rats. After 12 weeks of treatment with ZGZTF by intragastric administration, the rats were put to death in batch. The changes of alkaline phosphatase (ALP), bone gla protein (BGP) and estradiol (E2) in serum were determined, and bone mineral density (BMD) and histomorphology of right femur were observed. Biomechanics of lumbar vertebra were measured, and the expression of SOST, Wnt3a, β-catenin, LRP5, Runx2, Osx and their mRNA involving the canonical Wnt/β-catenin signaling pathway were detected by Western blot, RT-PCR and Immunohistochemical analysis. All data were analyzed by SPSS 22.0. Results: Twelve weeks of treatment with ZGZTF could significantly decrease the level of ALP and BGP in serum, increase the BMD of femurs, and improve the biomechanical capability of vertebral body in maximum loading and elastic modulus. Concerning histomorphology, we found ordered arrangement of trabeculae, slightly thinning of trabeculae and none obvious slight fractures in femurs after 12 weeks of treatment with ZGZTF. The expression of LRP5, β-catenin, Runx2 and Osx involved in the canonical Wnt/β-catenin signaling pathway was significantly up-regulated in the presence of ZGZTF, and the expression of SOST in this pathway was down-regulated. Conclusions: These results suggest that ZGZTF may be anti- osteoporosis by down-regulating SOST protein to promote Wnt/β-catenin signaling pathway. Keywords: Zhuang Gu Zhi Tong Formula (ZGZTF), Osteoporosis, SOST, Wnt, LRP5, β-catenin, Runx2, Osx