Plasma Concentrations of Orexins in Children

Abstract

BACKGROUND: According to experiments done on animals and adult humans, orexins are involved in homeostasis of energy balance, feeding and arousal. The purpose of this study was to evaluate plasma orexins concentrations in children in relation to body mass index (BMI), energy demand and duration of sleep. MATERIAL AND METHODS: Studied children were grouped as follows: newborns (n = 7), infants (n = 15), prepubertal children (2-9 years, n = 12), pubertal children (10-15 years, n = 8) and postpubertal adolescents (16-18 years, n = 8). Plasma orexins concentrations were determined by EIA after extraction of samples on Sep-Pak columns. RESULTS: The plasma concentration of orexin A was higher than the concentration of orexin B in all children studied. The concentrations of these two peptides were correlated (r = 0.45, p < 0.03). The highest mean plasma levels of orexin A and B were found in neonates and in children during puberty (orexin A: 1.02 +/- 0.17 ng/ml and 1.01 +/- 0.12 ng/ml, orexin B: 0.67 +/- 0.18 and 0.65 +/- 0.09 ng/ml, respectively) while in other groups the results were significantly lower. A significant negative correlation was found between BMI and the concentrations of orexin A (r = -0.51, p < 0.01) and orexin B (r = -0.45, p < 0.03). A positive correlation was found between the concentrations of both orexins and caloric demand (orexin A: r = 0.43, p < 0.05, orexin B: r = 0.48, p < 0.02). No correlation was found between the concentrations of orexins and the duration of sleep. CONCLUSION: Orexins play a significant role in children's growth as a long-term satiety factor and may coordinate energy homeostasis with sexual maturation.