Higher daily physical activity is associated with higher osteocalcin levels in adolescents

• We examined the influence of physical activity on OCN.
• Moderate physical activity is associated with higher levels of OCN.
• Obesity did not impact the positive association between physical activity and OCN.
• OCN may play a role in the insulin sensitizing effects of physical activity.

BackgroundExercise stimulates bone remodeling and improves insulin sensitivity (Si), even without associated weight loss. Osteocalcin (OCN), a bone-derived protein, is associated with improved Si.PurposeWe examined how daily physical activity is associated with OCN and Si.MethodsPhysical activity was measured through questionnaires completed in Minneapolis from 2010 to 2012. A physical activity score (PAQsum) was calculated to quantify physical activity (range 1–5). OCN and bone specific alkaline phosphatase (BAP) were measured by ELISA. Si was measured by the insulin modified frequently sampled IV glucose tolerance test.ResultsThe mean PAQsum value was 2.4 ± 0.8 in 47 participants (12–17.9 years old). PAQsum was positively associated with OCN (p = 0.006). Participants with PAQsum <  2 had significantly lower OCN levels compared to participants with PAQsum >  2 (p < 0.02). Obesity did not modify the association between PAQsum and OCN. There was no statistically significant association between PAQsum and Si or between OCN and Si, even after adjustment for percent body fat.ConclusionsOCN is higher in more physically active individuals. More research is needed to clarify the relationship between OCN, physical activity and Si.