HYPERINSULINEMIA, INSULIN RESISTANCE AND ESSENTIAL-HYPERTENSION

Glucose intolerance and noninsulin-dependent diabetes are commonly ass ociated with hypertension. Epidemiological data suggest that this asso ciation is independent of age and obesity. Much evidence indicates tha t the link between diabetes and essential hypertension is hyperinsulin emia. When hypertensive patients whether obese or of normal weight are compared with matched normotensive control subjects, an increased pla sma insulin response to a glucose challenge is consistently observed. Studies using insulin glucose clamp techniques in combination with tra cer glucose infusion and indirect calorimetry have demonstrated that t he insulin resistance in hypertensive subjects is located in muscles a nd restricted to glycogen synthesis. The relations between hyperinsuli nemia and blood pressure do not prove that the relationship is a causa l one. However, at least four mechanisms may link hyperinsulinemia wit h hypertension: Na+ retention, sympathetic nervous system overactivity , disturbed membrane ion transport and proliferation of vascular smoot h muscle cells. Diuretics and beta-blockers may enhance insulin resist ance, which is not affected by calcium antagonists, but decreased by t he ACE inhibitor captopril. Weight reduction and regular physical exer cise can improve insulin sensitivity and decrease blood pressure value s. These nonpharmacological interventions should be more strongly reco mmended to diabetic and nondiabetic hypertensive patients.