L-arginine improves endothelial function and reduces LDL oxidation in patients with stable coronary artery disease

Background: We investigated the effects of oral l-arginine on endothelial function, intravascular oxidative stress, and circulating inflammatory markers in patients with stable coronary artery disease (CAD). Methods: Thirty-one stable CAD patients were randomly assigned to oral l-arginine (10 g) or vitamin C (500 mg, an antioxidant, as active control) daily for 4 weeks, with crossover to the alternate therapy after 2 weeks off therapy, in this study. Brachial artery endothelial function studies were performed and serum concentrations of lipids and inflammatory markers were measured at baseline, at the end of each 4-week treatment period and at the 2-week wash-out period. Susceptibility of low-density lipoprotein (LDL) particles to oxidation, a marker of oxidative stress, was determined in 11 patients at random before and after 4-week treatment of oral l-arginine. Results: We demonstrates that consumption of either l-arginine or vitamin C significantly increased brachial artery flow-mediated dilatation (mean diameter change from baseline of 4.87%, P < 0.0001 and of 3.17%, P = 0.0003, respectively). Neither oral l-arginine nor vitamin C affected lipid profiles and circulating levels of inflammatory markers. However, in the 11 patients whose LDL susceptibility to oxidation was determined, lag time significantly increased by 27.1% (P = 0.045) after consumption of l-arginine for 4 weeks. Conclusions: Oral l-arginine supplement improved endothelial function and reduced LDL oxidation in stable CAD patients.