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This Article Full Text Full Text (PDF) All Versions of this Article: 295/6/E1510    most recent 90549.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lteif, A. A. Articles by Mather, K. J. Search for Related Content PubMed PubMed Citation Articles by Lteif, A. A. Articles by Mather, K. J.

Hyperinsulinemia fails to augment ET-1 action in the skeletal muscle vascular bed in vivo in humans

¹Division of Endocrinology and Metabolism, Indiana University School of Medicine, Indianapolis, Indiana; and ²Amylin Pharmaceuticals, Inc., San Diego, California

Submitted 30 June 2008 ; accepted in final form 18 October 2008

Endogenous endothelin action is augmented in human obesity and type 2 diabetes and contributes to endothelial dysfunction and impairs insulin-mediated vasodilation in humans. We hypothesized that insulin resistance-associated hyperinsulinemia could preferentially drive endothelin-mediated vasoconstriction. We applied hyperinsulinemic-euglycemic clamps with higher insulin dosing in obese subjects than lean subjects (30 vs. 10 mU·m^–2·min^–1, respectively), with the goal of matching insulin's nitric oxide (NO)-mediated vascular effects. We predicted that, under these circumstances, insulin-stimulated endothelin-1 (ET-1) action (assessed with the type A endothelin receptor antagonist BQ-123) would be augmented in proportion to hyperinsulinemia. NO bioactivity was assessed using the nitric oxide synthase inhibitor N^G-monomethyl-L-arginine. Insulin-mediated vasodilation and insulin-stimulated NO bioavailability were well matched across groups by this approach. As expected, steady-state insulin levels were approximately threefold higher in obese than lean subjects (109.2 ± 10.2 pmol/l vs. 518.4 ± 84.0, P = 0.03). Despite this, the augmentation of insulin-mediated vasodilation by BQ-123 was not different between groups. ET-1 flux across the leg was not augmented by insulin alone but was increased with the addition of BQ-123 to insulin (P = 0.01 BQ-123 effect, P = not significant comparing groups). Endothelin antagonism augmented insulin-stimulated NO bioavailability and NOx flux, but not differently between groups and not proportional to hyperinsulinemia. These findings do not support the hypothesis that insulin resistance-associated hyperinsulinemia preferentially drives endothelin-mediated vasoconstriction.

endothelin-1; insulin; obesity