AMINO ACIDS, ARGINASE AND NITRIC OXIDE IN VASCULAR HEALTH

SUMMARY 1 Nitric oxide (NO) plays a fundamental role in the vasculature because of its diverse influence in vascular protection, including its well‐reported antiproliferative, anti‐inflammatory, antithrombotic and vasodilator effects. In many vascular disease states, NO production is reduced as a result of endothelial dysfunction, in part caused by a decrease in substrate (l‐arginine) availability. 2 The role of l‐arginine and other amino acids important in nitrogen balance has been re‐examined in the context of their effects on vascular health. The metabolism of l‐arginine is complex because it is involved in a plethora of other pathways, such as urea, creatine and agmatine production. l‐Arginine supplementation in patients with vascular disease is well reported to benefit patients therapeutically because of its effect on both NO‐dependent and ‐independent mechanisms. 3 l‐Arginine availability depends on the flux of other amino acids in the body, including l‐glutamine, l‐glutamate, l‐ornithine, l‐citrulline and l‐lysine. The role of l‐methionine and homocystine and their effect on NO also play an influential role in the body. 4 Recent data suggest that the key enzyme involved in the l‐arginine–urea cycle, arginase, is coexpressed in NO‐producing cells in the vasculature. In the present review, we examine the potential role of arginase as a therapeutic target for vascular health.