The effects of aerobic exercise training on serum osteocalcin, adipocytokines and insulin resistance on obese young males

Abstract

Osteocalcin has been proposed to be a novel link between bone and energy metabolism. Previous studies showed its relations to exercise, body fat and glucose metabolism, but their interrelationship remains inconslusive. We evaluated the changes in osteocalcin level following 8-week exercise programme and assessed how they are related to concomitant changes in body fat composition, insulin resistance and various adipocytokines in a single centre, randomized and prospective design. A total of 39 young obese, otherwise healthy males were randomly assigned to control (n = 10) and exercise (n = 29) groups. Subjects in Exercise group were on 8-week supervised exercise training programme of four sessions per week. Body fat compositions were analysed using whole body bone mineral density, various metabolic parameters, osteocalcin and adipocytokines were assessed from fasting blood samples before and after 8-week exercise programme. Body fat reduction following exercise significantly increased serum total (1·51 ± 0·36 vs 1·69 ± 0·39 mmol/l, P = 0·01, baseline vs postexercise) and undercarboxylated osteocalcin level (0·44 ± 0·14 vs 0·64 ± 0·26 mmol/l, P < 0·01), and the increase in osteocalcin was in negative correlations with changes in body weight, BMI and body fat percentage as well as HOMA-IR and leptin (all P < 0·05). The changes in osteocalcin and leptin were not independent predictors of changes in insulin resistance and osteocalcin, respectively. In a physiological axis of bone-fat-energy metabolism, exercise-induced body fat reduction and improved insulin sensitivity were accompanied by an increase in serum osteocalcin and leptin levels, but other factors also seem to be involved in this interrelationship.