Gumi Bao decoction regulates bone metabolism-related mRNA expression in glucocorticoid-induced osteoporosis in rats.

Background: Gumi Bao decoction is effective for the treatment of osteoporosis, but the theoretical and scientific basis is unknown. This study aimed to observe the effect of Gumi Bao decoction on Dickkopf-related protein 1 (DKK1) mRNA, runt-related transcription factor 2 (Runx2) mRNA, and cathepsin K (CTSK) mRNA in glucocorticoid-induced osteoporosis (GIOP) in rats and to investigate the underlying mechanism.

Methods: Sixty Sprague-Dawley (SD) rats were weighed and randomly divided into six groups: the normal control group (NC group), the methylprednisolone group (Met group), the Fosamax group, the low-dose Gumi Bao Decoction group (GBDL group), the medium-dose Gumi Bao Decoction group (GBDM group), and the high-dose Gumi Bao Decoction group (GBDH group). The basic physiological conditions of the rats and the bone morphology of the fourth lumbar vertebra and the left femur of three rats in each group were observed, and the mRNA expressions of bone tissue-related genes were detected.

Results: After administration, DKK1 mRNA expression was significantly up-regulated in the Met group compared to the NC group (P<0.001). Meanwhile, DKK1 mRNA was significantly down-regulated in the Fosamax group compared with the Met group (P<0.001). There was a significant difference in the down-regulation of DKK1 mRNA between the GBDM and GBDH groups (P<0.001). Runx2 mRNA was considerably down-regulated in the Met group compared with the NC group (P<0.001). Runx2 mRNA was up-regulated in the GBDM group, and the GBDH group was significantly different compared to the Met group (P<0.001). CTSK mRNA was significantly up-regulated in the Met group compared to the NC group (P<0.001). Compared with the Met group, CTSK mRNA expression was significantly down-regulated in the Fosamax group (P<0.001), as well as in the GBDL, GBDM, and GBDH groups (P<0.001). At 200× and 400×, there were significantly fewer osteoblasts and osteoclasts in the Met group than in the Fosamax, GBDM, and GBDH groups.

Conclusions: The imbalance of bone homeostasis of GIOP is caused by an increase in bone resorption and decreased osteogenesis. Gumi Bao could regulate bone metabolism through the action of DKK1 via the Wnt/β-catenin signaling pathway, up-regulating Runx2 mRNA and down-regulating CTSK mRNA.