Circulating endothelin-1 levels in lean non-insulin-dependent diabetic patients: Influence of ACE inhibition

To evaluate the effect of captopril on plasma endothelin-1 (ET-1) levels and insulin sensitivity, 15 lean normotensive men (51.6 ± 3.8 years) affected by non-insulin-dependent diabetes mellitus (NIDDM) underwent 2-h euglycemic hyperinsulinemic clamp. Each patient was then assigned to receive either captopril (25 mg twice daily for 1 week) or placebo, in a double-blind randomized fashion, before repeating clamp. At baseline, plasma ET-1 levels were 0.77 ± 0.25 pg/mL in captopril (n = 10) and 0.83 ± 0.3 pg/mL in placebo patients (n = 5). A twofold increase in plasma ET-1 levels occurred during the 2-h insulin infusion in both groups (P< .05 after 60 and 120 min), with a rapid return to baseline after 30 min from insulin withdrawal. After 1 week of therapy, total glucose uptake significantly increased in captopril (from 3.71 ± 1.70 mg/kg/min to 4.24 ± 1.72 mg/kg/min, P< .03) but not in placebo patients. Plasma ET-1 levels significantly decreased after captopril therapy (0.48 ± 0.25 pg/mL at time 0, P< .03 v pretreatment levels), but were unaffected by placebo. Moreover, captopril slightly reduced the magnitude of ET-1 increment during insulin infusion (0.65 ± 0.28 pg/mL and 0.88 ± 0.48 pg/mL at 60 and 120 min, respectively, P< .05 v time 0). As a consequence, during the second insulin infusion circulating ET-1 levels were significantly lower in captopril- than in placebo-treated patients at time 0 (P< .02), 60 (P< .002), 120 (P< .004), and 150 min (P< .001). In conclusion, our data show that captopril treatment significantly reduces circulating ET-1 concentrations in patients with NIDDM. The decrease of plasma peptide levels is accompanied by a significant improvement in insulin sensitivity, suggesting the captopril-related ET-1 decrement as a potential contributor to the beneficial effects exerted by converting enzyme inhibition on glucose metabolism