Abstract:

Objective To discuss the protective effect of velvet antler peptide （VAP） on the postmenopausal osteoporosis （PMOP） model rats，and to clarify its possible mechanism. Methods A total of 60 twelve-week-old female SD rats were randomly divided into sham operation group， model group， alendronate sodium group （1 mg·kg?1·d?1 alendronate sodium administered via gavage）， low dose of VAP group （100 mg·kg?1·d?1 VAP administered via gavage）， medium dose of VAP group （200 mg·kg?1·d?1 VAP administered via gavage）， and high dose of VAP group （300 mg·kg?1·d?1 VAP administered via gavage）， and there were 10 rats in each group. Except for the sham operation group， the rats in the other groups underwent bilateral ovariectomy to establish the PMOP rat models. Dual-energy X-ray absorptiometry was used to detect the femur bone mineral density （BMD） of the rats in various groups；enzyme-linked immunosorbent assay （ELISA） was used to detect the levels of serum calcium （Ca²⁺）， serum phosphorus （P）， bone alkaline phosphatase （BALP）， and procollagen type Ⅰ N-terminal propeptide （PINP） of the rats in various groups； Kits were used to detect the activities of superoxide dismutase （SOD） and the levels of malondialdehyde （MDA） 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 phosphatidylinositol 3-kinase （PI3K）， phosphorylated PI3K （p-PI3K）， protein kinase B （AKT）， and phosphorylated AKT （p-AKT） proteins in bone tissue of the rats in various groups. Results Compared with sham operation group， the BMD in femur of the rats in model group was decreased （P<0.01）； compared with model group， the BMD in femur of the rats in alendronate sodium group， medium dose of VAP group， and high dose of VAP group was increased （P<0.05 or P<0.01）. Compared with sham operation group，the levels of Ca2?， P， BALP， PINP， and SOD activity in serum of the rats in model group were decreased （P<0.05 or P<0.01）， and the MDA level was increased （P<0.01）； compared with model group， the level of P in serum of the rats in medium dose of VAP group was increased （P<0.01）， and the levels of Ca2?， P， BALP， PINP and the activities of SOD in serum of the rats in alendronate sodium group and high dose of VAP group were increased （P<0.05 or P<0.01）， and the level of MDA in serum was decreased （P<0.05）. The HE staining results showed that compared with sham operation group， the bone trabeculae in bone tissue of the rats in model group were thin and fractured， and the medullary cavity was enlarged； compared with model group， the bone trabeculae in bone tissue of the rats in alendronate sodium group， medium dose of VAP group， and high dose of VAP group were thick and tightly arranged， and had more osteocytes. The Western blotting results showed that compared with sham operation group， the ratios of p-PI3K/PI3K and p-AKT/AKT in bone tissue of the rats in model group were decreased （P<0.01）； compared with model group， the ratios of p-PI3K/PI3K in bone tissue of rats in different doses of VAP groups were increased （P<0.05 or P<0.01）， and the ratios of p-AKT/AKT of the rats in alendronate sodium group and high dose of VAP group was increased （P<0.01）. Conclusion VAP can improve PMOP in the rats， and its mechanisms may be related to the regulation of the PI3K/AKT signaling pathway and the reduction of oxidative stress in bone tissue by VAP.

Key words: Osteoporosis, Velvet antler polypeptides, Oxidative stress, Phosphatidylinositol-3 kinase/protein kinase B signaling pathway