Insulin as a vascular and sympathoexcitatory hormone: implications for blood pressure regulation, insulin sensitivity, and cardiovascular morbidity.

The past several years have witnessed a major surge of interest in the cardiovascular actions of insulin. This interest has stemmed on the one hand from epidemiological studies that demonstrated an association between obesity, insulin resistance, and hypertension, leading to the so-called insulin hypothesis of hypertension. On the other hand, this interest has been stimulated by experimental evidence suggesting that the vascular actions of insulin may play a role in its main action, namely the promotion of glucose uptake in skeletal muscle tissue. Two tenets have emerged about how insulin may exert its cardiovascular actions. First, it is now firmly established that acute insulin administration stimulates sympathetic nerve activity in both animals and humans. Second, there is increasing evidence that insulin stimulates muscle blood flow, an effect that appears to be mediated at least in part by an endothelium-dependent mechanism. This review summarizes the current understanding and gaps in knowledge on cardiovascular actions of insulin in humans and pathophysiological consequences of derangements of such actions.