Objective To investigate the correlations of serum Apelin-13 and fatty acid binding protein 4 (FABP4) levels with metabolic and bone metabolic indicators in postmenopausal women with different bone mass.

Methods A total of 145 postmenopausal women were selected as subjects and divided into three groups based on bone mineral density (BMD) test results: normal bone mass group(49 cases), osteopenia (ON) group(51 cases), and osteoporosis (OP) group(45 cases). Serum Apelin-13, FABP4 levels, bone metabolic indicators, and biochemical indicators were measured and compared among the three groups. Spearman correlation analysis was used to analyze the correlations of Apelin-13, FABP4, and other indicators with BMD. Multivariate Logistic regression analysis was performed to analyze the risk factors for OP, and the receiver operating characteristic (ROC) curve was plotted to analyze the predictive value of serum Apelin-13 for postmenopausal osteoporosis (PMOP).

Results The serum Apelin-13 level in the OP group was lower than that in the ON group and the normal bone mass group (P < 0.05). No significant difference in serum FABP4 levels was found among the three groups (P>0.05). The levels of serum parathyroid hormone (PTH), alkaline phosphatase (ALP), type Ⅰ procollagen amino-terminal propeptide (PⅠNP), type Ⅰ collagen cross-linked C-terminal peptide (CTXⅠ), and bone-specific alkaline phosphatase (BALP) in the OP group were higher than those in the ON group and the normal bone mass group (P < 0.05). Lumbar post-menopause BMD was positively correlated with serum Apelin-13 levels (P < 0.05), but had no correlation with serum FABP4 levels (P>0.05). Lumbar BMD was negatively correlated with serum PTH, ALP, PⅠNP, CTXⅠ, BALP, and age (P < 0.05), but positively correlated with body weight, body mass index, T-score, fasting insulin, and insulin resistance index (P < 0.05). Multivariate Logistic regression analysis showed that serum Apelin-13, PTH, ALP, PⅠNP, CTXⅠ, and BALP levels were independent factors influencing the occurrence of OP in postmenopausal women (P < 0.05). ROC curve results showed that the optimal cut-off value of serum Apelin-13 for predicting PMOP was 18.51 pg/mL, with an area under the curve of 0.716, a sensitivity of 70.0%, and a specificity of 64.4%.

Conclusion Apelin-13 is lowly expressed in the serum of PMOP patients, and its expression level is closely related to lumbar BMD, which may serve as an early screening indicator and potential therapeutic target for PMOP.