Homocysteine, B12, plaque, and HD.
"Elevated plasma total homocysteine levels are a strong, graded independent risk factor for stroke and myocardial infarction. Mechanisms by which homocysteine may cause vascular disease include a propensity for thrombosis and impaired thrombolysis, increased production of hydrogen peroxide, endothelial dysfunction and increased oxidation of low-density lipoproteins and Lp(a) lipoproteins.
Folic acid fortification of enriched cereal grain products began in North America in March 1996 and was made mandatory in 1998. Fortification has reduced the number of neural tube defects by half,4 which is clearly a beneficial outcome, but so far it has had little impact on cardiovascular mortality.
Carotid plaque area is a strong predictor of cardiovascular events.6 High homocysteine levels, which are associated with plaque formation, can result from inadequate intake of folate and vitamin B12. Now that folic acid fortification is widespread, vitamin B12 has become an important determinant of homocysteine levels.7 We sought to determine the prevalence of low serum levels of vitamin B12, and their relation to homocysteine levels and carotid plaque area among patients referred for treatment of vascular disease since folic acid fortification of enriched grain products.
Methods
The subjects of this study were all consecutive new patients referred to 1 of us (JDS) for secondary vascular prevention in either the Premature Atherosclerosis Clinic or the Stroke prevention Clinic of the University Campus of the London Health Science Centre in London, Ont., between January 1998 (after folic acid fortification had begun) and January 2002 (coinciding with JR’s time in our research unit). During that time, 520 patients were referred.
A chart review showed that 421 patients had complete data, including measurement of carotid plaque areas, serum vitamin B12 levels, plasma total homocysteine levels, blood pressure, smoking (pack-years), serum cholesterol levels, triglyceride levels, high-density lipoprotein cholesterol levels and calculated lowdensity lipoprotein cholesterol levels. The data used for analysis were abstracted from the clinical records; except for the measurement of serum methylmalonic acid levels in a subgroup from the Stroke Prevention Clinic, all investigations were done as part of patient care." |
