Inflammation and insulin resistance according to body composition in European adolescents : the HELENA study

Introduction: Inflammation is related to insulin resistance in adults, especially on those individuals with high levels of body composition. Objectives: The aim of this study is to assess the relationship between a set of inflammatory biomarkers and insulin resistance by levels of body composition in a sample of European adolescents. Material and methods: Nine hundred and sixty-two adolescents (442 boys and 520 girls) from nine European countries met the inclusion criteria of having measurements for the homeostasis model assessment (HOMA) and a set of inflammation-related biomarkers: C-reactive protein (CRP), tumor necrosis factor alpha (TNF-alpha), interleukin (IL-6), complement factors C3 and C4 and selected cell adhesion molecules. Body mass index (BMI), fat mass index (FMI) and waist circumference (WC) were categorized using tertiles. To assess the associations stratifying by body composition indexes, ANOVA and linear regression models were performed. Results: Mean biomarkers' concentrations differed across BMI, FMI and WC tertiles (p < 0.05) by sex. In both sexes, insulin, HOMA, CRP, C3 and C4 were significantly different between categories (p < 0.001), always showing the highest mean concentration in the upper category of BMI, FMI and WC. The most consistent finding was an association between insulin resistance and C3 concentrations (p < 0.05), in the adolescents in the highest tertile of BMI, FMI and WC, except in the case of FMI in girls. Conclusion: Inflammatory and glucose metabolism markers differed by tertiles of body composition, being usually higher in the highest tertile. C3 complement factor was associated with insulin resistance in adolescents, especially those with high total and abdominal adiposity