Insulin resistance in essential hypertension: A psychophysiological approach to the "chicken and egg" question

Aims: High levels of plasma insulin have frequently been found in patients with high blood pressure. The causal role of insulin resistance in essentia l hypertension, however, is still debated. Epidemiological and clinical stu dies have not provided complete responses to the original pathophysiologica l speculations, while the suggestion that enhanced sympathetic tone may ind uce both insulin resistance and hypertension is gaining ground. Data synthesis: Many studies indicate that the high sympathetic drive in hy pertensive patients originates within the brain, while other studies show t hat insulin resistance is associated with reduced vasodilatory capacity and increased vasoconstrictive functional responses ascribed to endothelial im pairment. The sympathetic overdrive and enhanced cardiovascular reactivity, detectable since the earliest stages of hypertension lead to endothelial d amage anti, hence, impair the vasodilatory response, peripheral blood flow and flow-dependent metabolism. Thus, the link between hyperinsulinemia and high blood pressure might lie in the vascular abnormalities secondary to el evated sympathetic tone and exaggerated hemodynamic stress response. Conclusions: Examination of the literature and the results of recent pilot studies of the stress systemic and regional hemodynamic reactivity in the p resent paper suggests that behavioral characteristics and cardiovascular st ress responses play a pivotal role in determining the hyperinsulinemic stat e in hypertensive patients. High sympathetic tone, with consequent vascular impairment and altered functional responses, may be the primary event caus ing hyperinsulinemia and start very early in patients with high blood press ure. In turn, hyperinsulinemia further contributes to vascular damage and a ggravates the metabolic and hypertensive disease. (C) 2000, Medikal Press.