Abstract:

Objective To discuss the protective effect of velvet antler peptide （VAP） in the osteoporosis （OP） model rats，and to clarify the possible mechanism. Methods Sixty 12-week-old SD rats were randomly divided into control group， model group， positive drug group （treated with 1 mg·kg^－1·d^－1 of alendronate sodium by gavage）， low dose of VAP group （treated with 100 mg·kg^－1·d^－1 VAP), medium dose of VAP group （treated with 200 mg·kg^－1·d^－1 VAP), and high dose of VAP group （treated with 300 mg·kg^－1·d^－1 VAP), and there were ten rats in each group. Except for control group，the rats in the other groups were injected with dexamethasone （2 mg·kg^－1) to replicate the OP rat model， while the rats in control group were injected with the equivalent volume of saline twice a week for 11 consecutive weeks. Dual-energy X-ray absorptiometry was used to detect the bone mineral density （BMD） of femur tissue of the rats in various groups；enzyme-linked immunosorbent assay （ELISA） method was used to detect the levels of serum calcium （Ca²⁺）， phosphate （P）， osteoprotegerin （OPG）， alkaline phosphatase （ALP）， and osteocalcin （OCN）in serum of the rats in various groups； biochemical method was used to detect the malondialdehyde （MDA） level and superoxide dismutase （SOD） activity in serum of the rats in various groups； HE staining was used to observe the pathomorphology of bone tissue of the rats in various groups； Western blotting method was used to detect the expression levels of silent information regulator 1 （SIRT1）， catalase （CAT）， Runt-related transcription factor 2 （RUNX2）， and forkhead box protein O1 （FOXO1） proteins in bone tissue of the rats in various groups. Results Compared with control group， the BMD of femoral tissue of the rats in model group was decreased （P<0.05）； compared with model group， the BMD of femur tissue of the rats in positive drug group， medium dose of VAP group， and high dose of VAP group were increased （P<0.05 or P<0.01）. Compared with control group， the levels of Ca²⁺， P， OPG， and SOD activities in serum of the rats in model group were decreased （P<0.05）， and the levels of ALP， OCN， and MDA were increased （P<0.05）； compared with model group， the level of OPG in serum of the rats in low dose of VAP group was significantly increased（P<0.05），the levels of Ca²⁺， P， OPG， and activities of SOD in serum of the rats in positive drug group， medium dose of VAP group， and high dose of VAP group were significantly increased （P<0.05 or P<0.01）， and the levels of ALP， OCN， and MDA in serum of the rats in positive drug group and different doses of VAP groups were decreased （P<0.05 or P<0.01）. The HE staining results showed that compared with control group， the rats in model group had fewer bone cells and disordered arrangements in the bone tissue， thinner bone trabeculae with large fractures， and an expanded marrow cavity； compared with model group， the rats in positive drug group， medium dose of VAP group， and high dose of VAP group had thicker bone trabeculae arranged more tightly. The Western blotting results showed that compared with control group， the expression levels of SIRT1， CAT， RUNX2， and FOXO1 proteins in bone tissue of the rats in model group were decreased （P<0.05）； compared with model group， the expression levels of SIRT1， CAT， RUNX2， and FOXO1 proteins in bone tissue of the rats in positive drug group， medium dose of VAP group， and high dose of VAP group were significantly increased （P<0.05 or P<0.01）. Conclusion VAP has the protective effect against OP in the rats， and its mechanism may be related to mediating the antioxidant stress action through the SIRT1/FOXO1 signaling pathway.

Key words: Osteoporosis, Dexamethasone, Velvet antler polypeptide, Oxidative stress, Silent information regulator 1, Forkhead box protein O1, Signaling pathway