Methylenetetrahydrofolate reductase mutation (677C → T) negatively influences plasma homocysteine response to marginal folate intake in elderly women

Individuals who are homozygous for the methylenetetrahydrofolate reductase (MTHFR) 677C → T mutation have depressed serum folate (SF) and elevated plasma total homocysteine (tHcy) concentrations, which may affect folate requirements and increase the risk for coronary artery disease. A controlled metabolic study (14 weeks) using a depletion/repletion protocol was performed in women (aged 60 to 85 years, N = 33) to provide age-specific data on the effects of the MTHFR mutation on SF and tHcy status. Subjects consumed a moderately folate-deplete diet (118 μg/d) for 7 weeks, followed by 7 weeks of folate repletion with 200 or 415 μg/d provided as two different treatments. Following folate depletion, the mean SF concentration was lower for homozygous (P = .017) versus heterozygous subjects. Homozygotes for the 677C → T mutation showed a higher (P = .015) percent increase in plasma tHcy (44%) than heterozygous (20%) or normal (15%) subjects. At week 7, the mean plasma tHcy concentration was higher in homozygous subjects (12.5 ± 5.3 μmol/L, mean ± SD) versus the heterozygous (10.8 ± 3.8 μmol/L, P = .008) or normal (11.3 ± 2.7 μmol/L, P = .001) genotype groups. Following folate repletion, plasma tHcy concentrations were not different between genotype groups, despite a higher (P < .016) SF concentration in subjects with the homozygous genotype. These data suggest that older women who are homozygous for the MTHFR 677C → T mutation may be at risk for greater elevations in plasma tHcy in response to moderately low folate intake as compared with individuals with the normal or heterozygous genotypes. Copyright (C) 2000 by W.B. Saunders Company.