Efficacy of L-arginine Treatment on Blood Pressure Control Patients With Stage 1 Hypertension

Scientific background

Essential Hypertension is characterized by endothelial dysfunction with impaired vasorelaxation.

Reduced nitric oxide bioavailability, which is considered a hallmark of endothelial dysfunction, plays an important role in mediating blood pressure elevation. Accumulating evidence demonstrates a critical role of nitric oxide in blood pressure regulation. Released from the endothelial cells, nitric oxide increases 30,50-cyclic-guanosine monophosphate (cGMP) production and subsequent cGMP-dependent protein kinase (PKG) activation in the underneath vascular smooth muscle cells (VSMCs), resulting in vasodilatation. The investigators and others have shown that inhibition of NO synthesis increase blood pressure in normal pregnant rats and different animal models. In vivo studies confirmed an essential role of nitric oxide in vasorelaxation of large human arteries. Impairment in nitric oxide-mediated vasodilatation in brachial, coronary, and renal arteries has been demonstrated in patients with essential hypertension.

Several mechanisms have been found responsible for nitric oxide deficiency in hypertension. One of them is deficit of the NO substrate, L-arginine. L-arginine transport is impaired in hypertensive and normotensive patients with a genetic background of essential hypertension, and the offspring of essential hypertensive patients are characterized by a reduced response to acetylcholine linked to a defect in the nitric oxide pathway. These data represent the link between L-arginine and the onset of essential hypertension. The Km of endothelial nitric oxide synthase for L-arginine is about 3mmol/l, but the concentration of plasma L-arginine rarely falls below 60mmol/l in pathological conditions. An elevation in asymmetric dimethylarginine (ADMA, an endogenous NO competitive inhibitor) levels may explain this 'L-arginine paradox'. The administration of excess exogenous L-arginine displaces the competitive inhibitor, improves intracellular transport of this amino acid, and restores NO production to physiological levels. In fact L-arginine supplementation improved endothelial dysfunction in hypertension.

Administration of L arginine in humans have not shown uniform blood pressure responses. A meta-analysis published in 2011 was able to find only 11 articles dealing with l-arginine administration and blood pressure. The population studies were heterogeneous. Compared with placebo, oral L-arginine intervention was associated with an average net change ranging from -23.0 to 2.8 mm Hg for SBP and from -11.0 to 1.0 mm Hg for diastolic BP. Most trials showed an intervention-related trend toward BP reductions, but only a few reached statistical significance.