The relationship between serum FGF-23 concentration and insulin resistance, prediabetes and dyslipidemia in obese children and adolescents.

Background Obesity is known to cause metabolic disturbances including insulin resistance, dyslipidemia and alters bone mineralization. The effects of obesity on fibroblast growth factor 23 (FGF-23), which is important in bone mineralization, have not yet been clarified. Our aim was to investigate the association between FGF-23 concentration and obesity-associated dysmetabolism. Methods Subjects comprised 46 obese children and adolescents. The same number of age-matched, healthy controls were recruited. Markers of bone mineralization and glucose metabolism were measured. Thyroid function and insulin resistance were investigated in both groups. In obese subjects; an oral glucose tolerance test (OGTT) was performed and hemoglobin A1c and lipid fractions were measured. Bone mineral density and hepatic steatosis were investigated. Results Serum FGF-23, α-klotho and 1,25(OH)2D3 concentrations were significantly lower while fasting insulin, fasting glucose, C-peptide and alkaline phosphatase (ALP) concentrations and homeostasis model assessment of insulin resistance (HOMA-IR) were significantly higher in the obese group compared to controls. A significant negative correlation was observed between free tri-iodothyronine (fT3) and both FGF-23 and α-klotho in the obese group. Significant negative correlation was found between FGF-23 and C-peptide and a positive correlation was found between FGF-23 and high density lipoprotein-cholesterol (HDL-c) in the obese subjects with impaired glucose tolerance (IGT). Significant negative correlations were found between FGF-23 and both fasting insulin levels and C-peptide levels in the obese subjects with hepatic steatosis. Conclusions In our study, insulin resistance-associated hyperinsulinism and/or lower 1,25(OH)2D3 levels, both present in obese children and adolescents, may lead to decreased serum FGF-23 concentrations in obese subjects.