The Effect of BMI, Age, Gender, and Pubertal Stage on Bone Turnover Markers in Chinese Children and Adolescents

Abstract

Objectives: To ascertain the associations of serum bone turnover markers (BTMs) levels with body mass index (BMI) in Chinese children and adolescents, and whether the influence of BMI, age, pubertal stage on BTMs varied by gender.

Methods: A total of 500 students (180 controls and 320 children and adolescents with overweight/obesity) aged 9-14 years were randomly selected from the Chinese National Survey on Students Constitution and Health Cohort. Serum levels of BTMs, including bone formation marker bone alkaline phosphatase (BAP), collagen type 1 C-terminal propeptide (CICP), and bone resorption markers C-terminal telopeptide of type-I collagen (CTX) were determined by commercial enzyme-linked immunosorbent assay kits. The associations among BMI, age, gender, pubertal stage, and BTMs were analyzed.

Results: Serum levels of CICP and CTX in overweight/obese children and adolescents were lower than those in controls (p<0.05). Moreover, after subgroup analysis stratified by gender, the decreased serum CICP and CTX levels in overweight/obese children and adolescents were observed only in boys (p<0.05). After adjustment of age and pubertal stage, there was a negative correlation between serum BAP and BMI in both boys and girls (p<0.05). However, the correlations between serum CICP, CTX levels, and BMI were significant in boys but not in girls. Serum BAP and CICP levels were independently correlated with BMI, age, gender, and pubertal stage, while CTX levels were independently correlated with BMI, age, and gender (p<0.05). BAP, CICP, and CTX levels showed a clear age, gender, and pubertal stage dependence with significantly higher values in boys (p<0.05).

Conclusions: Our findings support the associations between serum BTMs levels and BMI in Chinese children and adolescents, and suggest age, gender, and pubertal stage differences in this relationship that warrant future studies.

Keywords: age; body mass index (BMI); bone turnover markers (BTMs); children; gender; pubertal stage.

Figure 1

Scatter plot that showing the relationship between BAP (A), CICP (B), CTX (C), FGF23 (D) and BMI in boys and girls, respectively. Partial correlation analysis was performed after adjustment for age and pubertal stages. BAP, bone-specific alkaline phosphatase; CICP, C-propeptide of type I procollagen; CTX, collagen type 1 C-terminal propeptide; FGF23, fibroblast growth factor 23; BMI, body mass index.

Figure 2

Serum levels for BAP (A, B), CICP (C, D), CTX (E, F), FGF23 (G, H) by age and gender. BAP, bone-specific alkaline phosphatase; CICP, C-propeptide of type I procollagen; CTX, collagen type 1 C-terminal propeptide; FGF23, fibroblast growth factor 23. ^aP < 0.05 compared with children aged 9 years; ^bP < 0.05 compared with children aged 10 years; ^cP < 0.05 compared with children aged 11 years; ^dP < 0.05 compared with children aged 12 years; ^eP < 0.05 compared with children aged 13 years.

Figure 3

Serum levels for BAP (A, B), CICP (C, D), CTX (E, F), FGF23 (G, H) by developmental staging and gender. BAP, bone-specific alkaline phosphatase; CICP, C-propeptide of type I procollagen; CTX, collagen type 1 C-terminal propeptide; FGF23, fibroblast growth factor 23. ^aP < 0.05 compared with Tanner stage I; ^bP < 0.05 compared with Tanner stage II; ^cP < 0.05 compared with Tanner stage III; ^dP < 0.05 compared with Tanner stage IV.