Effect of the methylenetetrahydrofolate reductase 677C-->T mutation on the relations among folate intake and plasma folate and homocysteine concentrations in a general population sample.
BACKGROUND
Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate and homocysteine metabolism. The common MTHFR 677C-->T polymorphism decreases the enzyme's activity.


OBJECTIVE
The objective of the study was to assess the effect of the polymorphism on the relations among folate intake, plasma folate concentration, and total plasma homocysteine (tHcy) concentration.


METHODS
The design was a cross-sectional analysis in a random sample (n = 2051) of a Dutch cohort (aged 20-65 y).


RESULTS
At a low folate intake (166 micro g/d), folate concentrations differed significantly among the genotypes (7.1, 6.2, and 5.4 nmol/L for the CC, CT, and TT genotypes, respectively; P for all comparisons < 0.05). At a high folate intake (250 microg/d), folate concentrations in CT and CC subjects did not differ significantly (8.3 and 8.6 nmol/L, respectively, but were significantly higher (P = 0.2) than those in TT subjects (7.3 nmol/L; P = 0.04). At a low folate concentration (4.6 nmol/L), TT subjects had a significantly higher (P = 0.0001) tHcy concentration than did CC and CT subjects (20.3 compared with 15.0 and 14.1 micromol/L, respectively), whereas at a high folate concentration (11.9 nmol/L), the tHcy concentration did not differ significantly between genotypes (P > 0.2; <13.1 for all genotypes). The relation between folate intake and tHcy concentration had a pattern similar to that of the relation between plasma folate and tHcy concentrations.


CONCLUSIONS
At any folate intake level, TT subjects have lower plasma folate concentrations than do CT and CC subjects. Yet, at high plasma folate concentrations, tHcy concentrations in TT subjects are as low as those in CT and CC subjects.
de Bree
Angelika
A
Department of Chronic Disease Epidemiology, National Institute of Public Health and the Environment, Bilthoven, Netherlands.
Verschuren
W M Monique
WM
Bjørke-Monsen
Anne-Lise
AL
van der Put
Nathalie M J
NM
Heil
Sandra G
SG
Trijbels
Frans J M
FJ
Blom
Henk J
HJ
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000097:blood*; D005838:Genotype; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D008875:Middle Aged; D009154:Mutation; D009426:Netherlands; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics* / Q000378:metabolism; D011110:Polymorphism, Genetic; D011795:Surveys and Questionnaires
D006710:Homocysteine; D005492:Folic Acid; D000587:Oxidoreductases Acting on CH-NH Group Donors; D042965:Methylenetetrahydrofolate Reductase (NADPH2)