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CONTEXT: Fibroblast growth factor 21 (FGF-21), a potent activator of glucose uptake, has been proposed to be related to insulin resistance, metabolic syndrome (MetS), nonalcoholic fatty liver disease (NAFLD), and weight status. OBJECTIVE: Our objective was to study the relationships between FGF-21, parameters of MetS, and NAFLD before and after weight loss in obese children. DESIGN AND SETTING: This was a cross-sectional comparison between obese and normal-weight children and longitudinal 1-yr follow-up study in obese children participating in a lifestyle intervention in a primary care setting. PATIENTS: Patients included 60 obese and 40 lean children of same age, gender, and pubertal stage. INTERVENTION: The outpatient 1-yr intervention program was based on exercise, behavior, and nutrition therapy. MAIN OUTCOMES MEASURES: We evaluated fasting serum FGF-21, weight status body mass index (BMI) expressed as sd score (SDS), body fat, insulin resistance index (homeostasis model assessment), leptin, transaminases, free fatty acids (FFA), waist circumference, blood pressure, and lipids. RESULTS: Compared with the normal-weight children, obese children demonstrated significantly (P < 0.001) increased FGF-21, leptin, and homeostasis model assessment levels. FGF-21 was significantly (P < 0.05) correlated to BMI, SDS-BMI, FFA, and leptin both in cross-sectional and longitudinal analyses but not to any additional analyzed parameter. Children with and without MetS or NAFLD did not differ significantly with respect to their FGF-21 concentrations. A decrease of SDS-BMI was associated with a significant (P = 0.038) decrease of FGF-21 levels (mean -34%). CONCLUSIONS: FGF-21 concentrations are reversibly increased in obese children and are related to leptin and FFA. However, our data do not support a significant relationship between FGF-21, insulin resistance, and features of MetS or NAFLD in children.
Reinehr et al. (Fri,) studied this question.