title: The 677C-->T mutation in the methylenetetrahydrofolate reductase gene: associations with plasma total homocysteine levels and risk of coronary atherosclerotic disease.
abstract: Homozygosity for a 677C-->T mutation at the locus that codes for 5,10-methylenetetrahydrofolate reductase (MTHFR), a folate-dependent crucial enzyme in homocysteine metabolism, may render the enzyme thermolabile and less active and has been associated with increased levels of plasma total homocysteine (tHcy). We assessed whether this mutation was associated with increased risk of coronary atherosclerosis and plasma levels of tHcy and furthermore studied whether folate status would modify the associations. Data were collected from subjects with substantial coronary atherosclerosis (> or = 90% occlusion in one and > or = 40% occlusion in a second coronary artery, referred to as cases, n = 131) or virtually no coronary narrowing (referred to as coronary controls, n = 87) and from a population-based control group (n = 100), all residing in the Rotterdam area, The Netherlands. Both males and females, aged 25-65 years were studied. The frequency of homozygosity for the mutation (+/+) in cases (10.0%) did not significantly differ statistically from that observed in coronary controls (11.5%, P = 0.71), population-based controls (7.0%, P = 0.43), or combined control groups (9.1%, P = 0.80). In the overall group (as well as in the three subgroups), plasma tHcy levels, fasting and to a lesser extent after a methionine-loading test, were higher in +/+ subjects than in homozygous normal subjects (-/-), whereas heterozygous subjects (+/-) had intermediate levels (Ptrend = 0.001). The +/+ subjects with erythrocyte folate levels < 790 nmol/l (population median) had a 77%, (95% CI, 27-144%) higher geometric mean fasting tHcy (21.4, micromol/l) than those with higher erythrocyte folate (12.1 micromol/l). The odds ratio (OR) of coronary atherosclerosis for +/+ subjects, with +/- and -/- subjects as the reference group, in analyses with combined control groups, was 1.1 (95% CI, 0.5-2.4). The ORs were 2.2 (95% CI, 0.7-6.8) and 0.6 (95% CI, 0.2-1.7) among subjects with low and high folate levels, respectively. Our study indicates that homozygosity for the 677C-->T MTHFR mutation, especially in combination with low folate status, predisposes to high plasma levels of fasting tHcy. However, homozygosity for this mutation, whether or not in combination with low folate status, was not associated with increased risk of coronary artery disease.
authors.affiliation: Department of Epidemiology and Public Health, Agricultural University, Wageningen, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Verhoef
authors.forename: F J
authors.initials: FJ
authors.lastname: Kok
authors.forename: L A
authors.initials: LA
authors.lastname: Kluijtmans
authors.forename: H J
authors.initials: HJ
authors.lastname: Blom
authors.forename: H
authors.initials: H
authors.lastname: Refsum
authors.forename: P M
authors.initials: PM
authors.lastname: Ueland
authors.forename: D A
authors.initials: DA
authors.lastname: Kruyssen
mesh_terms: D000328:Adult; D000368:Aged; D000428:Alcohol Drinking / Q000453:epidemiology; D016022:Case-Control Studies; D015897:Comorbidity; D003324:Coronary Artery Disease / Q000097:blood / Q000453:epidemiology* / Q000235:genetics; D004198:Disease Susceptibility; D004912:Erythrocytes / Q000737:chemistry; D005215:Fasting / Q000097:blood; D005260:Female; D005492:Folic Acid / Q000097:blood; D005796:Genes; D005838:Genotype; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D006949:Hyperlipidemias / Q000453:epidemiology; D006973:Hypertension / Q000453:epidemiology; D008297:Male; D008715:Methionine; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics*; D017354:Point Mutation; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology
chemical_list: D006710:Homocysteine; D005492:Folic Acid; D008715:Methionine; D000587:Oxidoreductases Acting on CH-NH Group Donors; D042965:Methylenetetrahydrofolate Reductase (NADPH2)