Circulating Apelin-13, β-catenin and bone mineral density in postmenopausal women

To investigate associations of circulating Apelin-13, β-catenin, Exendin-4, and Nesfatin-1 with site-specific bone mineral density (BMD) in postmenopausal women, representing adipose-endocrine, Wnt/β-catenin, incretin-related, and energy-homeostasis pathways. A total of 315 postmenopausal women were classified as normal bone mass, osteopenia, or osteoporosis according to World Health Organization criteria using dual-energy X-ray absorptiometry. Serum biomarkers were measured by enzyme-linked immunosorbent assay. Lumbar spine BMD and hip BMD were analyzed separately using group comparisons, Spearman correlation, fully adjusted multivariable linear regression, and exploratory receiver operating characteristic (ROC) analyses. Lumbar spine BMD was 0.936 ± 0.084, 0.935 ± 0.121, and 0.741 ± 0.105 g/cm2 in the normal bone mass, osteopenia, and osteoporosis groups, respectively; hip BMD was 0.942 ± 0.045, 0.878 ± 0.073, and 0.702 ± 0.084 g/cm2. Apelin-13 decreased across groups from 702.09 ± 56.42 to 624.98 ± 43.99 and 334.37 ± 91.49 pg/mL, and β-catenin from 100.23 ± 11.34 to 76.21 ± 14.65 and 54.33 ± 8.25 ng/mL. In fully adjusted models, Apelin-13 was independently associated with lumbar spine BMD (β = 0.547, P < 0.001) and hip BMD (β = 0.524, P < 0.001), while β-catenin was associated with hip BMD (β = 0.272, P < 0.001). Exploratory ROC analyses suggested apparent discriminatory performance for Apelin-13, β-catenin, Nesfatin-1, Exendin-4, and the combined model, with AUCs of 1.000, 0.944, 0.680, 0.613, and 1.000, respectively; these findings should be interpreted cautiously and require external validation. Apelin-13 and β-catenin may serve as circulating biomarkers related to site-specific bone mass status, requiring external validation.