Favorable Vascular Actions of Angiotensin-(1–7) in Human Obesity

Abstract

Obese patients have vascular dysfunction related to impaired insulin-stimulated vasodilation and increased endothelin-1–mediated vasoconstriction. In contrast to the harmful vascular actions of angiotensin (Ang) II, the angiotensin-converting enzyme 2 product Ang-(1–7) has shown to exert cardiovascular and metabolic benefits in experimental models through stimulation of the Mas receptor. We, therefore, examined the effects of exogenous Ang-(1–7) on vasodilator tone and endothelin-1–dependent vasoconstriction in obese patients. Intra-arterial infusion of Ang-(1–7) (10 nmol/min) resulted in significant increase in unstimulated forearm flow ( P =0.03), an effect that was not affected by the Mas receptor antagonist A779 (10 nmol/min; P >0.05). In the absence of hyperinsulinemia, however, forearm flow responses to graded doses of acetylcholine and sodium nitroprusside were not different during Ang-(1–7) administration compared with saline (both P >0.05). During infusion of regular insulin (0.15 mU/kg per minute), by contrast, endothelium-dependent vasodilator response to acetylcholine was significantly enhanced by Ang-(1–7) ( P =0.04 versus saline), whereas endothelium-independent response to sodium nitroprusside was not modified ( P =0.91). Finally, Ang-(1–7) decreased the vasodilator response to endothelin A receptor blockade (BQ-123; 10 nmol/min) compared with saline (6±1% versus 93±17%; P <0.001); nitric oxide inhibition by l - N -monomethylarginine (4 µmol/min) during concurrent endothelin A antagonism resulted in similar vasoconstriction in the absence or presence of Ang-(1–7 Ang-(1–7) ( P =0.69). Our findings indicate that in obese patients Ang-(1–7) has favorable effects not only to improve insulin-stimulated endothelium-dependent vasodilation but also to blunt endothelin-1–dependent vasoconstrictor tone. These findings provide support for targeting Ang-(1–7) to counteract the hemodynamic abnormalities of human obesity.