Arginine and nitric oxide synthase: Regulatory mechanisms and cardiovascular aspects

Abstract

L-Arginine (L-Arg) is a conditionally essential amino acid in the human diet. The most common dietary sources of L-Arg are meat, poultry and fish. L-Arg is the precursor for the synthesis of nitric oxide (NO); a key signaling molecule via NO synthase (NOS). Endogenous NOS inhibitors such as asymmetric-dimethyl-L-Arg inhibit NO synthesis in vivo by competing with L-Arg at the active site of NOS. In addition, NOS possesses the ability to be "uncoupled" to produce superoxide anion instead of NO. Reduced NO bioavailability may play an essential role in cardiovascular pathologies and metabolic diseases. L-Arg deficiency syndromes in humans involve endothelial inflammation and immune dysfunctions. Exogenous administration of L-Arg restores NO bioavailability, but it has not been possible to demonstrate, that L-Arg supplementation improved endothelial function in cardiovascular disease such as heart failure or hypertension. L-Arg supplementation may be a novel therapy for obesity and metabolic syndrome. The utility of l-Arg supplementation in the treatment of L-Arg deficiency syndromes remains to be established. Clinical trials need to continue to determine the optimal concentrations and combinations of L-Arg, with other protective compounds such as tetrahydrobiopterin (BH4 ), and antioxidants to combat oxidative stress that drives down NO production in humans.

Apple as a Source of Dietary Phytonutrients: Bioavailability and Evidence of Protective Effects against Human Cardiovascular Disease

“…Nitric oxide (NO), which can be derived from both endogenous and exogenous sources, is a critical regulator of endothelial function [51]. Dietary components, such as particular flavonoids can augment NO status acutely and in so doing enhance endothelial function.…”

Effects of vegetarian diets on blood pressure

“…46 Lysine competes with arginine for transport into the cell, 47,48 and arginine deficiency is associated with endothelial inflammation and immune dysfunction in humans. 49 Therefore, the lysine/arginine ratio may be important in understanding the BP-lowering effect. Compared with animal protein, plant proteins contain lower lysine levels and a low lysine/arginine ratio.…”

Dynamics of structural, functional and vegetative changes of heart under the influence of combined therapy with the use of ursodeoxycholic acid and L-arginine in patients with coronary heart disease associated with nonalcoholic fatty liver disease

“…This amino acid has antioxidant, cytoprotective, anti-hypoxic, membrane stabilizing effects. Evidence available at present suggests that the administration of L-arginine improves the endothelial function in patients with angina, heart failure, hypercholesterolemia [10]. In experimental studies, the positive influence of L-arginine on the autonomic nervous system state [11] has been proven.…”