Erythrocyte insulin binding in obese children and adolescents

Insulin binding studies in obese patients have been limited to adults due to the relative inaccessibility of tissues for study in the pediatric age group. Insulin binding to the erythrocytes (RBCs) of 9 obsese prepubertal children, 8 obese adolescents, and 10 obese adults was studied. There was a mean decrease of 15% in insulin binding in the obese patients (P < 0.02 vs. controls). Calculation of receptor concentrations by means of Scatchard plots showed a mean 30% reduction in insulin receptors on the RBCs of obese patients as a group (P < 0.001 vs. controls). The binding of insulin and receptor concentration were inversely proportional to the fasting plasma insulin concentration (r = —0.60 and —0.44, respectively). These correlations were significant (P < 0.001 and P < 0.05, respectively). The mean empty site receptor affinity (Ke) was significantly increased in obese patients, but only partially compensated for the loss of receptors with respect to total insulin bound over the physiological range of insulin concentrations. The results of binding studies in the obese adults were similar to those in the children and adolescents, and agreed with published reports of insulin binding in obese adults using adipocytes or monocytes as the source of insulin receptors. The observed decrease in insulin binding to the RBCs of obese children and adolescents correlated with fasting hyperinsulinemia and, therefore, may contribute to the etiology of the insulin resistance or glucose intolerance observed in these patients.