MTHFR C677T genotype and cardiovascular risk in a general population without mandatory folic acid fortification.
OBJECTIVE
Meta-analyses have suggested an effect of MTHFR C677T genotype (rs1801133), a proxy for blood total homocysteine, on cardiovascular disease (CVD) in populations with low population dietary folate. The aim was to examine the association and effect modification by serum folate and vitamin B12 levels between MTHFR and CVD-related outcomes in a general population with no mandatory folic acid fortification policy.


METHODS
The study population included 13,748 adults retrieved from pooling of four population-based studies conducted in Denmark. MTHFR genotype, serum folate (measured in approximately 9,356 individuals), and serum vitamin B12 (9,215 individuals), hypertension, and dyslipidemia were measured at baseline, and participants were followed for a mean of 10.5-11.7 years in central registries for diagnoses of stroke (623 incidents), ischaemic heart disease (IHD) (835 incidents), and all-cause mortality (1,272 incidents).


RESULTS
The MTHFR genotype (TT vs. CC/CT) was not associated with hypertension [OR (95% CI) 1.09 (0.95-1.25)], dyslipidemia [OR (95% CI) 0.97 (0.84-1.11)], stroke [HR (95% CI) 0.92 (0.69-1.23)], and all-cause mortality [HR (95% CI) 0.94 (0.77-1.14)], either overall, or in participants with low serum folate or B12 status (P values for interactions 0.15-0.94). Individuals with the MTHFR TT genotype had a higher risk of IHD (HR (95% CI) 1.38 (1.11-1.71)), but this association was not modified by folate status (P value for interaction 0.45).


CONCLUSIONS
Our results do not support a causal relationship between homocysteine and CVD. However, we cannot exclude a direct causal effect of MTHFR C677T genotype on IHD.
Research Centre for Prevention and Health, Glostrup University Hospital, The Capital Region of Denmark, Nordre Ringvej 57, 2600, Glostrup, Denmark, lloh@regionh.dk.
Lise Lotte N
LL
Husemoen
Tea
T
Skaaby
Torben
T
Jørgensen
Betina H
BH
Thuesen
Mogens
M
Fenger
Niels
N
Grarup
Camilla H
CH
Sandholt
Torben
T
Hansen
Oluf
O
Pedersen
Allan
A
Linneberg
D000293:Adolescent; D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000235:genetics*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D015331:Cohort Studies; D003718:Denmark; D050171:Dyslipidemias / Q000097:blood / Q000235:genetics; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000097:blood*; D005500:Follow-Up Studies; D005838:Genotype; D060005:Genotyping Techniques; D006710:Homocysteine / Q000097:blood; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000235:genetics; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D011110:Polymorphism, Genetic; D012307:Risk Factors; D020521:Stroke / Q000097:blood / Q000235:genetics; D014280:Triglycerides / Q000097:blood; D014805:Vitamin B 12 / Q000008:administration & dosage / Q000097:blood; D055815:Young Adult
D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D014280:Triglycerides; D006710:Homocysteine; D005492:Folic Acid; C573423:MTHFR protein, human; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D014805:Vitamin B 12