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Insulin-receptor activity in nondiabetic and diabetic urbanized South African black women
V R Panz1, B I Joffe, J R Wing
1Carbohydrate and Lipid Metabolism Research Group, University of the Witwatersrand Medical School, Johannesburg, South Africa.
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 (NIDDM).
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, middle-aged (40-60 yr) nonobese nondiabetic women; group C, middle-aged obese (BMI greater than 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-peptide, and nonesterified 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 beta-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.