Heterogeneity in the prevalence of methylenetetrahydrofolate reductase gene polymorphisms in women of different ethnic groups

Objective To determine the prevalence of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms in women of different ethnic groups and to relate these common mutations to plasma homocysteine, red cell folate, and serum folate. Design A one-time fasting blood sample was obtained for MTHFR genotype (C677T and A1298C) determinations (n=433). Serum folate, red cell folate, and homocysteine analyses were performed in nonfolic acid supplement users (n=215). Subjects/setting This study involved 433 women from four ethnic groups, including 193 Hispanic women of Mexican descent, 139 white women, 53 Asian women of mixed descent, and 48 African American women. Statistical Analyses Performed chi(2), t Test, and analysis of variance were used. Results Mexican women (18.1%) had a higher frequency of the 677 TT genotype compared with white (7.2%), Asian (3.8%), and African American (0%) women. White women (7.9%) had a higher frequency of the 1298 CC genotype than the other ethnic groups (range=1.9% to 2.6%). The frequency of compound heterozygosity (677 CT + 1298 AC) was higher in Mexican (17.6%) and white (15.1%) women than Asian and African American (similar to4% to 6%) women. In the era of folic acid fortification, neither genotype, independently or together, was associated with homocysteine or blood folate concentrations when ethnic groups were combined. In Mexican women, however, a linear trend (P less than or equal to .05) was detected for the C677T variants with the lowest red cell folate in the TT genotype. Applications/conclusions These data demonstrate ethnic differences in genetic polymorphisms that are diet responsive and may be useful when investigating ethnic variations in chronic disease, developmental anomalies, and folate requirements.