Hyperinsulinemia blunts sympathetic vasoconstriction: a possible role of beta-adrenergic activation

Herein we report in a sample of healthy young men (n = 14) and women (n = 12) that hyperinsulinemia induces time-dependent decreases in total peripheral resistance and its contribution to the maintenance of blood pressure. In the same participants, we observe profound vasodilatory effects of insulin in the lower limb despite concomitant activation of the sympathetic nervous sys-tem. We hypothesized that this prominent peripheral vasodilation is possibly due to the ability of the leg vasculature to escape sympathetic vasoconstriction during systemic insulin stimulation. Consistent with this notion, we demonstrate in a subset of healthy men (n = 9) and women (n = 7) that systemic infusion of insulin blunts sympathetically mediated leg vasoconstriction evoked by a cold pressor test, a well-established sympathoexcitatory stimulus. Further substantiating this observation, we show in mouse aortic rings that insulin exposure suppresses epinephrine and norepinephrine-induced vasoconstriction. Notably, we found that such insulin-suppressing effects on catecholamine-induced constriction are diminished following beta-adrenergic recep-tor blockade. In accordance, we also reveal that insulin augments beta-adrenergic-mediated vasorelaxation in isolated arteries. Collectively, these findings support the idea that sympathetic vasoconstriction can be attenuated during systemic hyperinsulin-emia in the leg vasculature of both men and women and that this phenomenon may be in part mediated by potentiation of beta-ad-renergic vasodilation neutralizing a-adrenergic vasoconstriction.