Low-Grade Inflammation, Obesity, and Insulin Resistance in Adolescents

CONTEXT: Low-grade inflammation is associated with insulin resistance and precedes the onset of type 2 diabetes mellitus in adults, but there are no comparable data in youth. OBJECTIVE: The objective of the study was to characterize the pattern of subclinical immune activation that is associated with indices of obesity and insulin resistance in youth and analyze whether this association is explained by obesity. DESIGN: This was a cross-sectional study. SETTING: Medical check-up of schoolchildren was conducted by the Public Health Office in Düsseldorf (Germany). PARTICIPANTS: Participants included 519 adolescents (mean age 15.5 +/- 0.8 yr). MAIN OUTCOME MEASURES: Measures included body mass index (BMI) and waist circumference (WC) as indices of obesity; fasting glucose, insulin, and homeostasis model assessment of insulin resistance; serum concentrations of TNFalpha, IL-6, IL-8, IL-18, monocyte chemoattractant protein-1, interferon-gamma-inducible protein (IP)-10 and adiponectin as immunological variables. RESULTS: In age-, sex-, and lipid-adjusted analyses, IL-6, IL-18, IP-10, and adiponectin (inversely) were associated with both BMI and WC (all P <or= 0.002). None of the immune markers was related to glucose, but IL-6, IL-18, and adiponectin (inversely) were associated with insulin and homeostasis model assessment of insulin resistance in age- and sex-adjusted models. Adjustment for BMI or WC indicated that a considerable proportion of these associations may be mediated by obesity. CONCLUSIONS: We found that a differential low-grade immune activation is associated with parameters of obesity in adolescents. Moreover, there is evidence that IL-6, IL-18, IP-10, and adiponectin (inversely) are associated with insulin resistance and that these associations can mainly be attributed to obesity.