Thermolabile methylenetetrahydrofolate reductase polymorphism (C677T) and total homocysteine concentration among African-American and white women

A polymorphism associated with a thermolabile variant (C677T) of the enzyme methylenetetrahydrofolate reductase has been associated with both elevated total homocysteine (tHcy) levels and risk for cardiovascular disease. Data from the Stroke Prevention in Young Women Study were used to determine the prevalence of the C677T genotype and to assess whether environmental factors modified the association between genotype and tHcy concentration. The C677T genotype prevalence was 80% -/-, 20% +/-, and 0% +/+ among 46 African-American women; and 39% -/-, 53% +/-, and 8% +/+ among 77 white women (P<0.01). There was a trend toward higher tHcy levels in African-American women with the +/- genotype when compared with the -/- genotype (6.9 μmol/L vs 5.3 μmol/L respectively, p=0.10); no association was found among the white women (6.0 μmol/L, -/-; 4.5 μmol/L, +/-; and 6.2 μmol/L, +/+; p=0.67). Among African American women, those who smoked and were +/- genotype had the highest tHcy levels (8.0 μmol/L); while among white women, those who smoked and were -/-had the highest tHcy levels (8.1 μmol/L). Despite being hampered by a limited sample size, the thermolabile allele is significantly less common among African-American than white women. The association between genotype and tHcy concentration is influenced by smoking and multivitamin use.