New cardiovascular risk factors: homocysteine and vitamins involved in homocysteine metabolism.

Among risk factors for vascular diseases, hyperhomocysteinemia has gained increased importance in recent years. The first description of a relationship between hyperhomocysteinemia and atherosclerosis dates back to 1964, when a rare recessive autosomal syndrome, due to a deficiency of the enzyme cystathionine betasynthase, was described. The disease was characterized by high urinary and plasma levels of homocysteine, and by a constellation of signs and symptoms including atherosclerosis, skeletal anomalies, as well as abnormalities of the central nervous system and the eye1. The relationship between severe hyperhomocysteinemia and atherosclerosis was first hypothesized, in a case-control study, by McCully2 in 1969. This relationship was recently confirmed by prospective and retrospective case-control studies, showing the existence of a graded relationship between plasma levels of homocysteine and the risk for cardiovascular disease. It has been estimated that the incidence of coronary artery disease increases by a factor of 1.6 to 1.8 for every 5 mol/l increase in fasting plasma homocysteine3. Slight-to-moderate hyperhomocysteinemia as a risk factor