Higher Serum Insulin Concentrations Positively Influence the Bone Mineral Density in African American Adolescents

BACKGROUND: Puberty is a developmental stage of increased insulin resistance that also is a critical period for bone mass accrual. Historically, African Americans (AA) have lesser risk for osteoporotic fractures compared to European Americans (EA). AA also have higher incidence of insulin resistance. The possibility that bone health and insulin secretion or concentrations are linked has not been investigated. AIMS: We aimed to examine the associations of bone mineral density (BMD) and bone mineral apparent density (BMAD) with insulin sensitivity and secretion in healthy adolescent girls and healthy female adults and to evaluate ethnic differences in these associations. STUDY DESIGN: Observational cohort design. PLACE AND DURATION OF THE STUDY: University of Alabama at Birmingham, between January 2010 and September 2011. METHODOLOGY: Healthy, female, non-smoking adolescents and young adults (14–55 years) were enrolled in this observational cohort study. RESULTS: Adolescents had significantly higher fasting insulin (P=0.0002), insulin area under the curve [AUC] (P= 0.0004) and lower insulin sensitivity (P=0.0005) compared to adults. Among adolescents, AA race was significantly associated with BMD (β=0.086, P=0.01) and BMAD (β=0.0075, P=0.002); however, adjusting for insulin AUC explained this difference. Insulin AUC (β=0.0006, P=0.029) and fasting insulin (β=0.0005, P=0.01) were positively associated with BMAD only in AA adolescents. Insulin AUC and fasting insulin were not significant predictors of BMD for adults. CONCLUSION: The higher insulin concentration among AA adolescents is associated with increased BMD and higher BMAD.