Triglycerides-Total Cholesterol-Body Weight Index, bone metabolism indicators and bone mineral density in Chinese children: a mediation analysis

Purpose: This study aimed to investigate the correlation between the Triglycerides × Total Cholesterol × Body Weight Index (TCBI) and bone mineral density (BMD) in children and whether bone-specific alkaline phosphatase (B-ALP), and insulin-like growth factor 1 (IGF-1) mediate the relationship between TCBI and BMD. Methods: This study included 411 preschool children from 2 township kindergartens in a rural area of Gansu Province, China, who were surveyed at baseline in September 2021 and followed up in September 2022. The independent variable is the mean value of TCBI at baseline and follow-up. The dependent variable was the raw value of BMD during the follow-up period, measured by dual-energy X-ray absorptiometry. Multiple linear regression was used to analyze the relationship between TCBI and BMD in the nondominant forearm and heel bone. Results: The results showed that TCBI in preschoolers was significantly and positively correlated with BMD (P < 0.001). In the fully adjusted model, for each unit increase in log-transformed TCBI, the BMD of the nondominant forearm and heel bone increased by 0.042 g/cm² (95% CI: 0.024, 0.059), and 0.034 g/cm² (95% CI: 0.015, 0.054), respectively. Mediation analyses showed that IGF-1 mediated TCBI and BMD of the forearm bone and heel bone with mediation proportions of 12.50% and 32.35%, respectively, whereas B-ALP mediated TCBI and BMD of the forearm bone and heel bone with mediation proportions of 10.00% and 11.76%, respectively. Conclusion: TCBI is positively correlated with nondominant forearm and heel BMD in preschoolers, and IGF-1 and B-ALP partially mediate the positive association between TCBI and BMD.