Abstract: BACKGROUND: Oxidative stress is considered to be one of the most important initiating factors for osteoporosis. In addition to directly activating classic mitochondrial and endoplasmic reticulum apoptosis pathways, oxidative stress can also activate an autophagy signaling pathway. The regulatory mechanism underlying the antioxidant function of osteoblasts in osteoporosis has not been clearly clarified.
OBJECTIVE: To explore the effect and mechanism of Bushen Jianpi Huoxue Recipe on phosphatidylinositol 3-kinase, protein kinase B, and mammalian target of rapamycin in osteoporotic rats by improving oxidative stress and autophagy.
METHODS: Seventy-two 6-month-old female Sprague-Dawley rats were randomly divided into a sham operation group (n=24) and an operation group (n=48), in which the rat ovaries were removed to make an ovariectomized model. After 3 months, 12 rats were taken from each group for detecting bone mineral density and serum osteocalcin, bone-specific alkaline phosphatase, type I procollagen N-terminal propeptide, and osteoprotegerin levels. The remaining 36 rats in the operation group were divided into model group, Bushen Jianpi Huoxue Recipe group, alendronate vitamin D3 (II) group, with 12 rats in each group. Drug groups were given intragastric administration of corresponding drugs. Sham operation and model groups were given an equal volume of normal saline. After 12 weeks, the rats in each group were sacrificed, and the bone mineral density of the lumbar spine and femur of the rats was detected by dual energy X-ray method. ELISA method was used to measure serum bone metabolism indexes and oxidative stress indexes. Real-time fluorescence quantitative PCR was used to detect the mRNA expression of LC3, Beclin1, ATG5, and mammalian target of rapamycin in femoral tissue. Western blot assay was used to detect the protein expression of phosphatidylinositol 3-kinase, phosphorylated protein kinase B, and mammalian target of rapamycin.
RESULTS AND CONCLUSION: Three months after modeling and drug treatment, compared with the sham operation group, the bone mineral density and osteoprotegerin of the model group were significantly reduced (P < 0.05), and the expression of osteocalcin, bone specific alkaline phosphatase, and type I procollagen N-terminal propeptide were significantly increased (P < 0.05). After 3 months of drug intervention, compared with the sham operation group, the expression levels of malondialdehyde and reactive oxygen species were significantly increased in the model group (P < 0.05), the mRNA expression of LC3, Beclin1 and ATG5 was significantly increased (P < 0.05), the mRNA levels of catalase, superoxide dismutase and mammalian target of rapamycin as well as the protein expression of phosphatidylinositol 3-kinase, phosphorylated protein kinase B, and mammalian target of rapamycin were significantly reduced (P < 0.05). After 3 months of drug interventions, compared with the model group, these indicators were all improved in the Bushen Jianpi Huoxue Recipe group and alendronate vitamin D3 (II) group (P < 0.05). To conclude, Bushen Jianpi Huoxue Recipe can improve postmenopausal osteoporotic bone metabolism, oxidative stress levels and inhibit autophagy, and its mechanism may be involved in the regulation of phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway.

Key words: Bushen Jianpi Huoxue Recipe, oxidative stress, autophagy, bone metabolism, PI3K/AKT/mTOR signaling pathway