Reduced Insulin Sensitivity in Nondiabetic, HLA-Identical Siblings of Insulin-dependent Diabetic Subjects

Nondiabetic, HLA-identical siblings of insulin-dependent diabetic subjects have an increased risk of developing diabetes. Since insulin resistance is present in newly diagnosed diabetic subjects, we studied 12 HLA-identical siblings to determine whether they have impaired insulin sensitivity. Each sibling was carefully matched for age, sex, and body weight to a control from a nondiabetic family. The insulin sensitivity index (S₁,) was determined after an intravenous glucose tolerance test (IVGTT) using the minimal model of insulin kinetics. The insulin sensitivity index was significantly lower in the HLA-identical siblings compared with their matched controls.