LEPTIN SERUM LEVELS IN NORMAL-WEIGHT AND OBESE CHILDREN AND ADOLESCENTS - RELATIONSHIP WITH AGE, SEX, PUBERTAL DEVELOPMENT, BODY-MASS INDEXAND INSULIN

OBJECTIVE: Leptin, the product of the ob gene, is present in higher co ncentrations in blood of obese subjects than of lean subjects. There i s scarce information on the role of leptin in the pathogenesis of huma n obesity and little is known about leptin serum levels in obese child ren. DESIGN, SUBJECTS AND MEASUREMENTS: To evaluate the influences of age, sex, pubertal development and weight excess on serum leptin level s, we have studied 390 obese subjects (OS) and 320 normal weight subje cts (NWS) aged 5-16 y. Easting insulin concentrations were assayed in NWS, and an oral glucose tolerance test was carried out in OS and tota l insulin area under the curve (TIA) was calculated. RESULTS: Log-tran sformed values of leptin serum concentrations appeared to be distribut ed according to an acceptable Gaussian pattern. As observed in adults, serum leptin concentrations in children and adolescents were also inc reased (4-5 times) in OS as compared to NWS. In both males and females , subdivided according to pubertal stages, serum leptin varied signifi cantly in stage IV-V as compared to the lower stages, with a reduction in males and an increase in females. On comparing the two sexes, grea ter serum leptin concentrations were observed in females of both NWS a nd OS. A significant linear correlation was found in both groups, subd ivided according to sex and pubertal stage, between log values of seru m leptin and standard deviation scores (SDS) of body mass index (BMI), and log-transformed relative body weight (RBW). Using partial correla tion analysis in subjects subdivided according to sex and pubertal sta ges, log values of serum leptin and fasting insulin values, adjusted b y age and SDS of BMI, correlated significantly with a weaker correlati on in males than in females. In OS, the leptin concentrations correlat ed better with TIA than with fasting insulin. A weight reduction progr am (WRP) was carried out in 141 OS and significant reductions of serum leptin and fasting insulin were observed, showing a reduction of RBW. There was a correlation between the reduction of RBW and of serum lep tin, but not of fasting insulin. No variation was found in non-respons ive OS. RBW reduction correlated with leptin, but not with insulin (fa sting and TIA), evaluated before the therapeutic program started. CONC LUSION: As observed in adults, obese children and adolescents have hig her serum leptin concentrations. However, several conditions should be taken into account when evaluating leptin concentrations in children. There are differences, independent of BMI, relative to pubertal stage and sex, females having greater leptin concentrations than males. The re is evidence of a possible role for leptin in the effectiveness of a weight reduction program in OS.