Quinapril treatment enhances vascular sensitivity to insulin

Insulin-mediated vasodilation has been shown to be impaired with hypertension and aggravated by dietary sodium restriction. Whether vascular insulin resistance in this setting could be improved by antihypertensive therapy was unknown. Therefore, we determined the effect of therapy with an angiotensin-converting enzyme inhibitor, on vascular sensitivity to insulin in hypertensive subjects fed a sodium-restricted diet.

The effects of 3 months of therapy with quinapril on vascular sensitivity to insulin was assessed in 11 hypertensive subjects using a randomized, placebo-controlled, double-blind design. Vascular sensitivity to insulin was assessed by determination of the insulin ED50 from dorsal hand vein linear variable differential transformer in phenylephrine-preconstricted vessels. Subjects were maintained on a 75 mmol/day sodium diet for 3 days prior to each study.

Quinapril therapy significantly improved vascular sensitivity to insulin, as assessed by a decrease in the ED50 for insulin (ED50 insulin: placebo = 501 +/- 189 [muU/ min; quinapril = 276 +/- 100 muU/min P < 0.05). Isoproterenol-mediated relaxation was also enhanced by quinapril treatment (maximal isoproterenol-mediated relaxation: Placebo = 92 +/- 15% of baseline distension; Quinapril = 151 +/- 31% P < 0.05).

The current study suggests the hypothesis that the ACE-inhibitor quinapril has beneficial effects on vascular function in general, and on insulin-mediated vascular responses, in particular.