Insulin binding substances, autoimmunity and type I diabetes in Kuwaiti patients and their kindred

Insulin autoantibodies (IAAs) are associated with type I diabetes mellitus (DM) and have been suggested as predictive markers of the disease. Using an ELISA assay, we have studied the prevalence of binding to human insulin in sera from an Arab type I DM population and compared it with the prevalence in the family members (FMs) of the probands, in type II DM patients from the same population, and in Arab control subjects. Significant levels of binding occurred in 11/16 (69%) of type I DM patients and in 21/34 (62%) of their FMs, but in only 5/31 (16%) of type II DM patients and in 1/25 (4%) of control subjects. Within families, there was homogeneity with regard to the level of insulin binding and the mean family levels correlated with those of the proband (r = 0.68, df = 7, p = 0.05). HLA-DR3 or -DR4 antigens occurred in 55/63 (87%) of type I DM patients and in 95/118 (81%) of their FMs. This was significantly higher (p less than 0.001) than in either type II DM patients (39/75, 52%) or in control subjects (34/93, 37%). ICAs were present in significantly more (25/43, 58%) of type I DM patients than their FMs (3/82, 3%) (p less than 0.001). They did not occur in either type II DM patients or in the control group. In conclusion, insulin binding occurred in sera from both type I diabetic patients and their kindred, and hence did not appear to be specifically associated with the development of clinical diabetes.