Nitric oxide (NO) is a chemical which functions in nearly every cellular activity of the body. NO in the walls of small blood vessels determines the tone of the blood vessels and controls blood flow. Abnormally low NO levels cause “endothelial dysfunction”*, with inability of blood vessel walls to relax. Low NO levels play a part in diabetes mellitus, high blood cholesterol, and hypertension.
Most NO is produced by the enzyme NO synthase (NOS) from arginine, and the production of NO is dependent on the presence of adequate arginine. BH4 (tetrahydrobiopterin) is a chemical necessary for NOS to function. The half-life of NO is short, and it is quickly converted to nitrates and nitrites.
The dietary presence of arginine, as well as the continued production of arginine from citrulline, are needed for NO production. While NOS produces arginine, arginase enzyme competes to break down arginine.
NO production is reduced in severe infections, trauma, undernutrition, blood vessel diseases, etc. Arginine and citrulline supplementation are believed to be therapeutic, while glutamine interferes with the ability of citrulline to substitute for arginine therapy. Homocysteine levels are inversely related to NO levels.
CONCLUSION: Supplementation and dietary treatment with arginine and citrulline can be used to treat endothelial dysfunction.
NOTE: *Endothelial dysfunction is a pathological state of the inner lining of blood vessels, with an imbalance in constricting and dilating elements. This results in loss of normal function.
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