ESPE Abstracts

Background: Obese children are often taller than non-obese ones before puberty. Reports on the GH/IGF system in obese children are not consistent and do not explain the increased height observed. Changes in IGF1 bioavailability/bioactivity have been claimed as a possible explanation, however, no data is available regarding the expression of the IGF type 1 receptor (IGF1R) gene.

Objective and hypotheses: To study the expression of IGF1R gene in obese children.

Method: Twenty-nine obese children (BMI >2 SDS) with height >+1SDS (15 males) and 18 non-obese (−2<BMI<+2 SDS) age-matched controls with height between −2 and +2 SDS were studied (nine males). All were prepubertal and none had any metabolic, endocrine, or genetic disease. Fasting blood samples were collected to analyze IGF1R gene expression in peripheral lymphocytes and determine the serum concentrations of IGF1 and IGFBP3. Lymphocytes were isolated from other blood cells using Fycoll–Hypaque and the RNA extracted. The IGF1R mRNA expression was analyzed by quantitative real-time PCR. IGF1 and IGFBP3 were determined by Immulite 2000 Kits. Data were compared by Mann-Whitney and Fisher tests.

Results: The expression of IGF1R mRNA, expressed as 2^−ΔΔCT, was higher in obese children than in non-obese controls (1.9 vs 1.15) (P=0.02). IGF1 levels were also higher in obese children (237 vs 143 ng/ml) (P=0.02). However, no difference was found on IGFBP3 levels.

Conclusion: Obese children showed higher IGF1R mRNA expression and higher serum IGF1 levels than non-obese children. This higher expression of IGF1R and the higher IGF1 levels may contribute to the increased height observed in many obese children. Differently from obese adults, in which GH secretion is decreased, the role of GH in the growth promotion of obese children is still unclear as IGFBP3 levels do not follow the increase in IGF1 levels.