IGF-1R mRNA expression is increased in obese children

Abstract Objectives Obese children are often taller than age-matched subjects. Reports on GH and IGF-I levels in obese individuals are controversial, with normal and reduced GH-IGF-I levels having been reported in this group of patients. Thus, the aim of this study was to analyse insulin-like growth factor type 1 receptor (IGF-IR) mRNA expression in obese children. Methods Forty-seven pre-pubertal children were included in this study: 29 were obese and taller than their target height, and 18 were normal eutrophic controls. Fasting blood samples were collected for IGF-IR mRNA expression in isolated lymphocytes and serum IGF-I, ALS, IGFBP-3, and IGFBP-1 concentration analysis. Results Relative IGF-IR gene expression (2 − ΔΔ C T ) was significantly ( P  = 0.025) higher in obese children (median 1.87) than in controls (1.15). Fourteen of the 29 obese subjects showed 2 − ΔΔ C T values greater than or equal to 2, while only 2 individuals in the control group showed values above 2 ( P  = 0.01). Obese children showed significantly ( P  = 0.01) higher IGF-I concentrations than the control group (237 ng/ml and 144 ng/ml, respectively). Among obese patients, 65.5% had IGF-I values above the 75 percentile of the control group ( P  = 0.02). ALS concentration was significantly ( P  = 0.04) higher in the obese group, while IGFBP-3 levels were similar in obese and control children. IGFBP-1 concentration was lower in obese children, while insulin levels and HOMA-IR index were higher than in controls. Conclusions The higher IGF-IR mRNA expression observed in obese children, associated with the higher IGF-I and ALS and the lower IGFBP-1 levels, suggest that the higher stature observed in these children may be due to increased IGF-I bioactivity.