Associations of serum leptin, ghrelin and peptide YY levels with physical activity and cardiorespiratory fitness in adolescent boys with different BMI values.

The aim of this study was to investigate the differences in associations of serum acylated and des-acylated ghrelin, peptide YY (PYY) and leptin levels with physical activity (PA) and cardiorespiratory fitness (CReF) in adolescent boys (mean age of 14.0 years) with overweight (OWB; n = 55) and with normal weight (NWB; n = 154). Methods: Total PA was measured by 7-day accelerometry (counts/min) and CReF by peak oxygen consumption (VO(2)peak/kg). Results: No differences were found in serum PYY, acylated ghrelin or des-acyl ghrelin levels, whereas mean leptin (11.6 +/- 10.6 vs. 2.0 +/- 2.7 ng/ml; p<0.05) and insulin (18.1 +/- 8.7 vs. 11.0 +/- 6.2 mU/l; p<0.05) levels were significantly higher in OWB compared to NWB. Mean CReF was significantly lower in OWB compared to NWB (39.7 +/- 8.7 vs. 50.5 +/- 6.8 ml/min/kg; p<0.05). Leptin was negatively correlated with CReF in both groups (r = -0.43; p<0.05), des-acylated ghrelin with CReF only in OWB (r = -0.36; p<0.05). In OWB leptin was negatively correlated with total PA (r = -0.32; p<0.05) and positively with sedentary time of PA (r = 0.35; p<0.05). In NWB 28.1% of the variability of CReF was determined by leptin and insulin resistance index (HOMA-IR), whereas in OWB 71.9% was determined by trunk FM and BMI. Conclusions: Leptin concentration was inversely associated with CReF in adolescent boys independently of BMI in both groups, while des-acylated ghrelin was associated with CReF only in OWB. Low PA in OWB was associated with high serum leptin level.