Relationship between Serum Folate and Plasma Nitrate Concentrations: Possible Clinical Implications

Endothelial-cell–derived nitric oxide (NO) relaxes vascular smooth muscle cells, causes vasodilation, and inhibits platelet aggregation. It has been demonstrated that NO3 is the predominant and stable form of NO present in plasma and represents the bioavailability of NO (1)(2). NO generation is depressed in blood vessels affected by atherosclerosis, and a loss of NO activity is associated with impaired vasoreactivity, enhanced platelet aggregation, and increased endothelial cell–leukocyte interactions (3). Recently, evidence has accumulated that suggests that increased concentrations of the amino acid homocysteine (Hcy) also increase the risk for cardiovascular disease (CVD) (4). Hcy concentrations can be lowered by supplementation with folate, vitamin B6, vitamin B2, and vitamin B12 (5)(6). In particular, folate may also contribute in the prevention of CVD because folate seems to restore impaired NO metabolism (7). In the present investigation, we included apparently healthy persons. Individuals on all types of medications were excluded from this cross-sectional study. Blood samples were collected from participants who had been fasting for 12 h. The blood samples were centrifuged at 4 °C within 1 h and stored at −80 °C until analysis. Informed written consent was obtained from all participants. The study was approved by the Regional Ethics committee, University of Bergen, Norway. Total homocysteine (tHcy) concentrations in plasma were measured by an HPLC method (8). Plasma …