Increased serum IgG and IgA in overweight children relate to a less favourable metabolic phenotype

BackgroundThe adaptive immune system has emerged as an unexpected modulator of insulin resistance. B lymphocytes accumulate in adipose tissue and produce pathogenic antibodies that cause insulin resistance. ObjectiveWe studied whether circulating immunoglobulins (IgG, IgA and IgM) were related to metabolic risk markers in pre-pubertal children with and without overweight. Design and methodsSubjects were 270 asymptomatic pre-pubertal Caucasian children (145 lean, 125 overweight) recruited in a primary care setting. Assessments included serum IgG, IgA and IgM concentrations (nephelometry), insulin resistance (HOMA-IR) and fasting lipids (triacylglycerol and high-density lipoprotein [HDL]-cholesterol). ResultsOverweight children had higher IgG and IgA serum levels than lean children (P0.01). Increasing serum IgG and IgA, but not IgM, were associated with a less favourable metabolic phenotype, consisting of higher HOMA-IR and triacylglycerol and lower HDL-cholesterol, particularly in obese children, in whom serum IgG and IgA were both independently associated with HOMA-IR (=0.308, P=0.017, r(2)=9.5% and =0.361, P=0.005, r(2)=13.0%, respectively) and triacylglycerol (=0.343, P=0.006, r(2)=11.1% and =0.354, P=0.003, r(2)=12.2%, respectively). ConclusionsIncreased circulating IgG and IgA in overweight children are associated with a less favourable metabolic phenotype, particularly in obese children. These results suggest a relationship between adaptive immunity and insulin resistance in childhood obesity.