L-Arginine is involved in numerous areas of human physiology – protein production, wound healing, erectile function and fertility. Arginine also effects cardiovascular function because of arginine-induced production of nitric oxide (NO) which is a key messenger molecule involved in endocrine function, vascular regulation and immune activity.
However, in the body about 50-percent of ingested L-arginine is rapidly metabolized by the enzyme arginase to L-ornithine which is a central part of the urea cycle.1 Hence, only half of L-arginine can be processed by four other enzymes, including endothelial nitric oxide synthase (eNOS) which converts it into nitric oxide.2
However, this process can be further complicated by asymmetrical dimethylarginine (ADMA) – a naturally occurring component of human blood plasma – which also competes with L-arginine for binding with endothelial nitric oxide synthase (eNOS), subsequently down-regulating activity of this vital enzyme. Hence, ADMA interferes with L-arginine in the production of nitric oxide, a key chemical involved in normal endothelial function and, by extension, cardiovascular health.
Increased plasma ADMA has been shown to be an independent risk factor for cardiovascular disease because of its inhibitory activity on eNOS.3 As it was observed, oral L-arginine supplementation overrides the inhibitory effect of ADMA on eNOS and improves vascular function in those with high ADMA levels.4-6 Direct alteration of ADMA levels with supplements of L-arginine have been suggested.7-8
Bearing in mind all processes L-arginine is involved in, there is no other way to maintain sufficient NO production in the body but taking daily l-arginine supplementation.
2. Meijer AJ, Lamers WH, Chamuleau RA. Nitrogen metabolism and ornithine cycle function. Physiol Rev 1990;70:701-748.
3.Determination of asymmetric dimethylarginine (ADMA) using a novel ELISA assay by Walter de Gruyter,Clin Chem Lab Med 2004;42(12):1377–1383 2004
4.Boger RH, Vallance P, Cooke JP. Asymmetric dimethylarginine (ADMA): a key regulator of nitric oxide synthase. Atherosclerosis Suppl 2003;4:1-3.
5.Boger RH. Asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, explains the “Larginine paradox” and acts as a novel cardiovascular risk factor. J Nutr 2004;134:2842S-2847S.
6.Boger RH, Ron ES. L-Arginine improves vascular function by overcoming deleterious effects of ADMA, a novel cardiovascular risk factor. Altern Med Rev 2005;10:14-23.
7. Bode-Boger SM, Muke J, Surdacki A, Brabant G, Boger RH, Frolich JC (2003). “Oral L-arginine improves endothelial function in healthy individuals older than 70 years”. Vasc Med 8 (2): 77–81. doi:10.1191/1358863x03vm474oa. PMID 14518608.
8.John P. Cooke (2002). The Cardiovascular Cure. Random House. ISBN 0-7679-0881-3.