Journal of Clinical Endocrinology & Metabolism, Vol 60, 103-108, Copyright © 1985 by Endocrine Society

ARTICLES

Diminished in vitro responsiveness of circulating erythroid progenitor cells to insulin as an indicator of insulin resistance

ME Geffner, SA Kaplan, N Bersch, BM Lippe, ML Scott, RN Bergman and DW Golde

While insulin resistance is considered characteristic of extreme obesity, it may be more difficult to demonstrate in less severe forms of obesity. We studied five moderately obese individuals [mean body mass index (MBMI), 34.1 +/- 1.85 (+/- SE) kg/m2], one massively obese patient (BMI, 50.2 kg/m2), and seven age-matched normal subjects (MBMI, 22.4 +/- 0.93 kg/m2). While two of the obese patients had normal glucose tolerance, all had fasting hyperinsulinemia (P less than 0.02 vs. normal subjects) and exaggerated insulin responses after oral glucose challenge, as defined by area under the 3-h insulin response curve (P less than 0.01 vs. normal subjects). That this hyperinsulinemia represented in vivo insulin resistance was supported by the glucose and insulin responses in four individuals to an iv glucose bolus analyzed by the minimal modeling technique. Study of monocyte insulin receptors revealed no reduction in total insulin binding in the four obese patients tested. Since physiological concentrations of insulin stimulate the in vitro growth of normal human erythroid progenitor cells (EPC), we reasoned that this response might be blunted in cells from individuals with endogenous insulin resistance. The mean peak EPC proliferative response (26.7 +/- 9.11% above baseline) in the obese hyperinsulinemic group was significantly less than the corresponding mean value in the control group (92.6 +/- 5.24% above baseline, P less than 0.001). These results suggest that the minimal modeling technique is a sensitive method for the in vivo demonstration of insulin resistance in moderately obese individuals and that EPC responsiveness to physiological concentrations of insulin reflects in vivo insulin sensitivity and may be used as an in vitro indicator of insulin resistance.