THE INSULIN RECEPTOR IN NORMAL AND OBESE PERSONS
ABSTRACT Using [125I]insulin at 172 pmol/l (1 ng/ml) the binding of insulin to mononuclear leucocytes isolated from peripheral blood was studied. Our present study comprised 21 healthy subjects (22–33 years old, 90–110% of ideal weight) and a comparable group of 22 obese subjects (20–37 years old, minimum 150% of ideal weight). A significant difference in insulin binding was found between the two groups, the mean specific insulin binding fraction in normals being 1.92 ± 0.58 (s) × 10−2 and that for the obese 1.19 ± 0.41 (s) × 10−2 (P < 0.01). No correlation was found between body weight and the number of insulin receptors in the obese subjects. However, the number of insulin receptors was negatively correlated to fat cell size (P < 0.05). Insulin receptors in subjects were also negatively correlated to fasting plasma insulin (P < 0.05). Insulin receptors were studied in 11 obese subjects before and after 10 days of fasting. A significant increase in the number of insulin receptors was observed with a simultaneous decrease in plasma insulin to normal values. The results indicate that obesity complicated by hyperinsulinism is associated with a decrease in the number of insulin receptors compared with the normal. This finding may in part explain the decreased insulin sensitivity of the hyperinsulinaemic obese.