Insulin-Receptor Activity in Nondiabetic and Diabetic Urbanized South African Black Women

Abstract

Objective To evaluate insulin receptor binding characteristics of urbanized South African black women with normal glucose tolerance and of patients with newly diagnosed untreated non-insulin-dependent diabetes mellitus (N1DDM). Research Design and Methods Four groups of 10 subjects each were selected by the following criteria: group A, young (20-39 yr) nonobese (body mass index [BMI] 19.0-24.9 kg/m2) nondiabetic women; group B, middleaged (40–60 yr) nonobese nondiabetic women; group C, middle-aged obese (BMI>30.0 kg/m2) nondiabetic women; and group D, middle-aged obese newly diagnosed but untreated female patients with NIDDM. Insulin binding to monocyte receptors was determined by radioreceptor assay. Fasting plasma samples were analyzed for glucose, insulin, C-pep tide, and nones terified fatty acids. Results In the four groups studied, maximum specific binding and receptor concentration were highest in group A, with a progressive and significant decrease in values through groups B and C to group D. Significant inverse correlations were obtained between maximum specific binding, 50% inhibition dose, and total receptor concentration on the one hand and glucose, insulin, and NEFA on the other. Conclusions Our study of urban South African black women showed decreasing insulin-receptor activity with obesity and glucose intolerance. In patients with NIDDM, hyperglycemia and (β-cell dysfunction were associated with a reduction in receptor concentration. In this regard, our findings in South African blacks are consistent with results of similar studies of NIDDM in other communities.