The association of fasting insulin, glucose, and lipids with bone mass in adolescents: findings from a cross-sectional study.

CONTEXT

It is unclear whether variation in insulin resistance mediates the positive association of fat mass with bone mass in children/adolescents.

OBJECTIVE

Our objective was to examine whether markers linked to insulin resistance [fasting insulin, glucose, triglycerides, and high-density lipoprotein cholesterol (HDLc)] are associated with bone mass in adolescents, and if they are, to examine whether they mediate the fat mass-bone mass association.

DESIGN AND SETTING

We conducted a cross-sectional analysis in participants from the Avon Longitudinal Study of Parents and Children.

PARTICIPANTS

Participants included 2305 (1100 male) individuals of mean age 15.5 yr.

OUTCOME MEASURES

We evaluated total body less head bone mineral content (BMC) (grams), bone area (BA) (square centimeters), and bone mineral density (BMD) (grams per square centimeter) from a dual-energy x-ray absorptiometry scan.

RESULTS

Fat mass, fasting insulin, and triglycerides were positively associated with BMD, BMC, and BA; HDLc was inversely associated with these outcomes. For example, the adjusted mean difference in BMC per 1 sd fasting insulin was 45 g (95% confidence interval = 17-73 g) in males and 50 g (95% confidence interval = 28-72 g) in females. When the associations of fat mass with outcomes were adjusted for markers of insulin resistance, they were largely unchanged. Associations of triglycerides and HDLc with outcomes were attenuated to the null when they were adjusted for fat mass, whereas those of insulin changed direction; i.e. with adjustment for fat mass, higher fasting insulin was associated with lower BMD, BMC, and BA.

CONCLUSIONS

Fasting insulin, glucose, and lipids do not appear to mediate the positive association of fat mass with bone mass in children/adolescents. The inverse association of fasting insulin with BMD, BMC, and BA once fat mass has been controlled for needs further study.