| Abstract: | Objective: To examine the effects of ursolic acid (UA) on mitigating retinoic acid (RA)-induced osteoporosis in rats. Methods: Fifty female Sprague-Dawley rats were randomly divided into the control group (n=10) and the osteoporosis group (n=40). The 40 osteoporosis rats were induced by 75 mg/(kg?d) RA once daily for 2 weeks, and then were randomly assigned to vehicle control (model), low-, middle-, and high-dose UA (UA-L, UA-M, UA-H; 30, 60, 120 mg/(kg?d), respectively] groups (10 rats each). UA were administered once daily to the rats from the 3rd weeks for up to 4 weeks by gavage. Bone turnover markers serum alkaline phosphatase (ALP), osteocalcin (OCN), urine deoxypyridinoline (DPD)] and other parameters, including serum calcium (S-Ca), serum phosphorus (S-P), urine calcium (U-Ca), urine phosphorus (U-P), and bone mineral density (BMD) of the femur, 4th lumbar vertebra and tibia, bone biomechanical properties and trabecular microarchitecture, were measured. Results: The osteoporosis in rats was successfully induced by RA. Compared with the model group, UA-M and UA-H significantly reversed the RA-induced changes in S-P, U-Ca, U-P, ALP, OCN and urine DPD ratio and markedly enhanced the BMD of right femur, 4th lumbar vertebra and tibia (P<0.05 or P<0.01). Further, biomechanical test and microcomputed tomography evaluation also showed that UA-H drastically improved biomechanical properties and trabecular microarchitecture (P<0.05 or P<0.01). Conclusion: UA could promote bone formation, increase osteoblastic activity and reduce osteoclastic activity in rats, indicating that UA might be a potential therapeutic of RA-induced acute osteoporosis. |
