Associations of GHR, IGF-1 and IGFBP-3 expression in adipose tissue cells with obesity-related alterations in corresponding circulating levels and adipose tissue function in children

Abstract

Components of the growth hormone (GH) axis, such as insulin-like growth factor-1 (IGF-1), IGF-1 binding protein-3 (IGFBP-3), GH receptor (GHR) and GH-binding protein (GHBP) regulate growth and metabolic pathways. Using our Leipzig Adipose Tissue (AT) Childhood Cohort and Leipzig Atherobesity Childhood Cohort (n=306), we asked if serum levels of these factors are altered with overweight/obesity and if this is related to gene expression of these factors in AT cells and/or increased fat mass in childhood obesity. Furthermore, we hypothesized that gene expression of GHR, IGF-1 and IGFBP-3 in AT is associated with overweight/obesity and AT function in children. Serum GHBP levels were increased in children with overweight/obesity throughout childhood, while for IGF-1 levels and the IGF-1/IGFBP-3 molar ratio this obesity-related elevation was only detectable until early puberty. Circulating levels did not correlate with gene expression of these factors in AT cells, which was decreased with overweight/obesity. Independent from body mass index, gene expression of GHR, IGF-1 and IGFBP-3 in AT cells was related to parameters of AT dysfunction, such as adipocyte hypertrophy, and increased insulin levels. Serum GHBP was associated with the percentage of liver fat and transaminase levels. We conclude that the obesity-related elevations in serum GHBP and IGF-1 are unlikely to be caused by increased subcutaneous AT mass and elevations in serum GHBP are more closely related to liver status in children. The diminished gene expression of these factors in AT cells with childhood obesity may contribute to early AT dysfunction and a deterioration of the metabolic state.