Ricerc@Sapienza

Background: Obesity in youth is associated with increased risk of metabolic disorders. Adipose
tissue hormones are involved in body-weight regulation. Among these, apelin is recognized as an
insulin-sensitizer adipokine. Data on apelin levels in obese children and its relation to insulinsensitivity
are limited.
Objective: We aimed to evaluate apelin levels in relation to obesity and insulin sensitivity in a large
cohort of overweight/obese children and adolescents. Furthermore, these youths were reevaluated
after a median 6.5 years of follow-up, thus allowing assessing changes in apelin levels in relation to
increasing age and weight changes.
Methods: Clinical data in 909 children and adolescents were collected between 2007 and 2010.
Two hundred and one were reexamined at a median 6.5 years of follow-up. All subjects at baseline
and at follow-up underwent an OGTT. Apelin levels were measured on sera by ELISA method.
Results: At baseline, lower apelin levels were associated with increasing age and puberty (Tanner
≥II 0.67 ± 0.96 ng/mL vs. Tanner I 0.89 ± 1.13 ng/mL, p < .002), but not with body-weight. At followup,
apelin levels in the 201 subjects reexamined were significantly lower than at baseline
(0.45 ± 0.77 ng/mL at follow-up, 0.68 ± 0.95 ng/mL baseline, p < .001), confirming the effects of
age and puberty. Body-weight did not affect apelin levels. Multiple regression analysis confirmed
that sex and puberty were associated with lower apelin levels, independently from age and insulinsensitivity.
Conclusions: Apelin levels decrease significantly with pubertal development, whilst body-weight in
children and adolescents did not determine changes in apelin. Reduced levels of apelin in children
and adolescents may therefore represent a necessary response to maintain the “physiological”
insulin resistance of puberty.