Zuogui pill regulates DKK1 in the prevention and treatment of glucocorticoid‐induced osteoporosis

BACKGROUND: Chinese medicine is effective for preventing and treating glucocorticoid-induced osteoporosis, however, the underlying mechanism remains unclear. DKK1, an inhibitor of Wnt/β-catenin signaling pathway, can be up-regulated by glucocorticoid. Thereafter, DKK1 is an important target in the prevention and treatment of osteoporosis. OBJECTIVE: To explore the regulatory effect of Zuogui pill on DKK1 in the prevention and treatment of glucocorticoid-induced osteoporosis. METHODS: Eighteen three-month-old female Sprague-Dawley rats were randomly divided into three groups: control group, model group and Zuogui pill group. Rats in the model and Zuogui pill groups received the subcutaneous injection of dexamethasone to establish the model of glucocorticoid-induced osteoporosis. The Zuogui pill group rats were administrated Zuogui pill extracts, and the control rats were given the same volume of normal saline. At 1 month after modeling, the lumbar vertebrae were removed to test the bone mass and microstructures by micro-CT scanning. The biomechanical properties were detected by compression test. The mRNA expression levels of DKK1, Runx2 and CTSK were determined by Qpcr. The serum alkaline phosphatase activity was tested. RESULTS AND CONCLUSION: Compared with the control group, in the model group, the volumetric bone mineral density, trabecular bone volume fraction, trabecular number, and trabecular thickness were significantly decreased (P < 0.05), the trabecular separation and structure model index were significantly increased (P < 0.05). The serum alkaline phosphatase activity was on a decline. The mRNA expression level of DKK1 showed a significant up-regulation (P < 0.05). The mRNA expression level of Runx2 showed a down-regulated trend while mRNA expression level of CTSK showed an up-regulated trend. Compared with the model group, the Zuogui pill group showed significantly enhanced volumetric bone mineral density, trabecular bone volume fraction, and trabecular number (P < 0.05); the structure model index was significantly decreased (P < 0.05); the trabecular separation was reduced; the serum alkaline phosphatase activity was enhanced; the mRNA expression level of DKK1 showed a significant down-regulation (P < 0.05); the mRNA expression level of Runx2 showed an up-regulated trend while mRNA expression level of CTSK showed a down-regulated trend. The vertebral compressive strength in the Zuogui pill group was significantly higher than that in the model group (P < 0.05). In summary, Zuogui pill prevents and treats glucocorticoid-induced osteoporosis possibly through the down-regulation of mRNA expression of DKK1. Subject headings: Drugs, Chinese Herbal; Bone Density; Alkaline Phosphatase; Osteoporosis; Tissue Engineering Funding: the Self-Financing Project of Science and Technology Department of Guangdong Province, No. 20140221; the National Natural Science Foundation of China, No.81503591, 81774338 and 81674000; the Natural Science Foundation of Guangdong Province, No. 2016A030313645; the Project of Science and Technology Department of Guangdong Province, No. 2016A020226006; the Excellent Doctoral Paper Training Project of the First Clinical Medical School of Guangzhou University of Chinese Medicine, No. YB201602; the Innovation and Strengthening Hospital Project of the First Affiliated Hospital of Guangzhou University of Chinese Medicine, No. 2015QN03