Klotho, fibroblast growth factors 19 and 21 serum concentrations in children and adolescents with normal body weight and obesity – and their associations with metabolic parameters

Background: Fibroblast growth factor 19 (FGF19), Fibroblast growth factor 21 (FGF21) and Klotho are regulators of energy homeostasis. However, in the paediatric population the relationship between obesity, metabolic disorders and mentioned factors has not been clearly investigated. We analysed serum concentrations of FGF19, FGF21 and Klotho in children and adolescents with normal body weight as well as in overweight and obese subjects – and their associations with components of metabolic syndrome and insulin resistance (IR).Methods: The cross-sectional study conducted in the group of hospitalised children and adolescents. Laboratory investigation included serum ELISA tests for FGF19, FGF21, Klotho as well as lipid profile and oral glucose tolerance test for calculation of the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) index. The clinical analysis included blood pressure measurement, body fat percentage estimation and assessing the prevalence of metabolic syndrome (MS) and its components. Results: The study was conducted on 174 children/adolescents aged 6-17 years divided into the following groups: with normal body weight (N=48), with obesity (N=92) and overweight subjects (N=34). Klotho levels were significantly higher in the group of subjects with obesity [median 168.6 pg/ml]) than those with overweight [131.3 pg/ml] and normal body weight [116.6 pg/ml] (p=0.0334). Median serum FGF21 level was elevated in the group of patients with MS in comparison to other subjects [136.2 pg/ml vs 82.6 pg/ml, p=0.0285]. Increased Klotho concentrations were noted in patients affected by IR compared with subjects with normal insulin sensitivity [185.3 pg/ml vs 132.6 pg/ml, p=0.0282]. Multivariable model for HOMA-IR showed FGF19 as an independent predictor for IR after adjusting for the pubertal stage and BMI Z-score.Conclusions: Klotho levels were associated with body weight status in children and adolescents. Moreover, Klotho, FGF19 and FGF21 concentrations correlated with IR status and traits of MS.