The effect of acute exercise on undercarboxylated osteocalcin in obese men

Summary The purpose of this study was to examine if the reduction in glucose post-exercise is mediated by undercarboxylated osteocalcin (unOC). Obese men were randomly assigned to do aerobic or power exercises. The change in unOC levels was correlated with the change in glucose levels post-exercise. The reduction in glucose postacute exercise may be partly related to increased unOC. Introduction Osteocalcin (OC) in its undercarboxylated (unOC) form may contribute to the regulation of glucose homeostasis. As exercise reduces serum glucose and improves insulin sensitivity in obese individuals and individuals with type 2 diabetes (T2DM), we hypothesised that this benefit was partly mediated by unOC. Methods Twenty-eight middle-aged (52.4±1.2 years, mean ± SEM), obese (BMI=32.1±0.9 kg m-2) men were randomly assigned to do either 45 min of aerobic (cycling at 75% of VO2peak) or power (leg press at 75% of one repetition maximum plus jumping sequence) exercises. Blood samples were taken at baseline and up to 2 h post-exercise. Results At baseline, unOC was negatively correlated with glucose levels (r=-0.53, p=0.003) and glycosylated haemoglobin (HbA1c) (r=-0.37, p=0.035). Both aerobic and power exercises reduced serum glucose (from 7.4±1.2 to 5.1±0.5 mmol L-1, p=0.01 and 8.5±1.2 to 6.0± 0.6 mmol L-1, p=0.01, respectively). Aerobic exercise significantly increased OC, unOC and high-molecularweight adiponectin, while power exercise had a limited effect on OC and unOC. Overall, those with higher baseline glucose and HbA1c had greater reductions in glucose levels after exercise (r=-0.46, p=0.013 and r=-0.43, p=0.019, respectively). In a sub-group of obese people with T2DM, the percentage change in unOC levels was correlated with the percentage change in glucose levels post-exercise (r=-0.51, p=0.038). Conclusions This study reports that the reduction in serum glucose post-acute exercise (especially aerobic exercise) may be partly related to increased unOC.