Abstract:

Objective To study the relationship between bone metabolism and intestinal flora imbalance in elderly patients with postmenopausal osteoporosis based on RANKL/RANK/OPG pathway.

Methods A total of 177 elderly female patients with postmenopausal osteoporosis were selected as the research subjects. The patients were divided into a research group and a control group based on the ratio of bifidobacteria to enterobacteria. Enzyme-linked immunosorbent assay(ELISA) was used to detect the serum inflammatory factors interleukin-6(IL-6), tumor necrosis factor-α(TNF-α), transforming growth factor-β1(TGF-β1) and bone metabolism indexes osteocalcin(OC), bone-specific alkaline phosphatase(BALP), 25-hydroxyvitamin D［25(OH)D］, and tartrate resistant acid phosphatase-5b(TRACP-5b) levels. Western blot method was used to detect relative expression of receptor activator of nuclear factor-κB ligand(RANKL), receptor activator of nuclear factor-κB(RANK), osteoprotegerin(OPG) protein in the synovial fluid of patients.

Results Serum IL-6,TNF-α, TGF-β1, OC, BALP, and TRACP-5b levels were significantly higher in the research group than in the control group, while serum 25(OH)D levels were significantly lower than those in the control group(P＜0.05). The relative expressions of RANKL and RANK proteins in the synovial fluid were higher in the research group than in the control group, and the relative expression of OPG protein was lower than that of the control group(P＜0.05). Correlation analysis showed that there was a positive correlation between bifidobacteria and 25(OH)D levels(r=0.332， P＜0.05) , and negatively correlated with OC, BALP, and TRACP-5b levels(r=-0.318, -0.408, -0.371, P＜0.05). Enterobacteria were negatively correlated with serum 25(OH)D levels(r=-0.378， P＜0.05), and positively correlated with OC, BALP, and TRACP-5b levels(r=0.356, 0.343, 0.364, P＜0.05).

Conclusion Intestinal flora imbalance may affect bone metabolism through the RANKL/RANK/OPG pathway, leading to abnormal bone metabolism and increased levels of inflammatory factors in elderly postmenopausal women.

Key words: osteoporosis, postmenopausal, bone metabolism, gastrointestinal microbiome