Diminished Insulin Receptors on Erythrocyte Ghosts in Nonobese Patients with Essential Hypertension Independent of Hyperinsulinemia

Hypertension is associated with insulin resistance and dyslipidemia in a syndrome named X. Epidemiologic evidence also supports a link between hyperinsulinemia and blood pressure (BP), independent of obesity and non-insulin-dependent diabetes mellitus. To assess the possible role of insulin receptors in this syndrome, we studied insulin binding by erythrocyte ghosts in patients with moderate essential hypertension with or without fasting or postglucose hyperinsulinemia. We measured plasma glucose and insulin before and at 30, 60, and 120 min after administration of 75 g glucose in 62 hypertensive patients and 20 matched normotensive controls. Both groups had comparable age (mean 45 years) and waist/hip ratios (mean 0.88). Patients undergoing antihypertensive treatment did not receive antihypertensive medication for 3 weeks. Patients with fasting or postglucose hyperglycemia were excluded from the study. Insulin binding to erythrocyte ghosts was significantly decreased (p < 0.001) to almost half the values of controls (6.5% specific binding) in both patients with hyperinsulinemic (3.2% specific binding) and those with normoinsulinemic (3.9% specific binding) hypertension. Scatchard analysis demonstrated that this was due to a lesser number of insulin receptors. These data indicate that patients with essential hypertension can show decreased erythrocyte insulin receptors without detectable hyperinsulinemia.