Aims: Aliskiren is a new oral non-peptide renin inhibitor. Its effects on vascular function in human hypertension are unknown. We assessed whether aliskiren may improve peripheral endothelial function and arterial stiffness in essential hypertensive patients (EH), when compared with the angiotensin-converting enzyme-inhibitor ramipril.
Methods and results: Fifty EH received treatment with aliskiren (150-300 mg/daily) or ramipril (5-10 mg/daily) for 12 weeks, according to a randomized, open with blind endpoints, parallel group design. We studied the forearm blood flow (straingauge plethysmography) response to intrabrachial acetylcholine, repeated under the nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (l-NMMA) (4 μmol/min), or the antioxidant ascorbic acid (8 mg/100 mL/min). Carotid-to-femoral pulse wave velocity (PWV), central blood pressure and augmentation index (AIx) were obtained by applanation tonometry. Brachial blood pressure was similarly normalized by aliskiren (from 149/94 to 136/86 mmHg) and ramipril (from 148/92 to 135/85 mmHg), as well as central blood pressure. Aliskiren increased (P < 0.001) the vasodilation to acetylcholine and restored the inhibitory effect of l-NMMA on acetylcholine. Ascorbic acid, which at baseline potentiated the response to acetylcholine, no longer improved endothelium-dependent relaxation after aliskiren treatment. In contrast, ramipril failed to affect the response to acetylcholine, the lacking inhibitory effect of l-NMMA, or the potentiating effect of ascorbic acid. Pulse wave velocity was significantly (P < 0.05) and similarly reduced by both drugs. Aliskiren induced a significantly (P < 0.05) greater AIx reduction than ramipril.
Conclusion: Aliskiren increased nitric oxide availability in the forearm resistance arterioles of EH, an effect probably determined by an antioxidant activity, which can also contribute to improved peripheral wave reflection.