Insulin and blood pressure: possible role of hemodynamics.

The association between hypertension and hyperinsulinemia/insulin resistance is well established but presently unexplained. Among several possible explanations, a connection between the two abnormalities can be envisioned at the level of the microvasculature in skeletal muscle. In fact, the insulin resistance of essential hypertension has been localized in skeletal muscle; in this tissue, on the other hand, rarefaction of the smaller arterioles can generate a rise in blood pressure. Thus, it is theoretically possible that structural changes in small vessels (caused by hypertension) may limit the diffusion of insulin and substrates from the intravascular space to the target cell surface. Alternatively, chronic hyperinsulinemia (caused by primary insulin resistance) could induce changes in small vessel walls (or their reactivity to pressor stimuli) capable of raising blood pressure. The details of these potential mechanisms are laid out within the framework of the hemodynamic phase of in vivo insulin action, and the available evidence bearing on them is discussed.