Background: Hyperhomocyteinemia (HHcy) is a risk factor for coronary artery disease (CAD), and methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), and methionine synthase reductase (MTRR) polymorphisms may contribute to plasma total homocysteine (tHcy) variation. We investigated the association of polymorphisms 1298A→C in the MTHFR gene, 2756A→G in the MTR gene, and 66A→G in the MTRR gene with tHcy levels and with CAD in patients undergoing coronary angiography. Methods: CAD patients (n = 151) and control subjects (n = 79) were compared regarding the prevalence of the polymorphisms, risk factors, and biochemical parameters. Results: The mean tHcy concentration was significantly higher in CAD patients than in control subjects (P < 0.001). HHcy (tHcy ≥ 15 μmol/l) conferred an OR of CAD of 4.1 (95% CI 2.2-7.5, P < 0.001). In both cases and controls, smokers had a higher tHcy level than non-smokers and demonstrated a markedly increased risk for CAD (OR = 2.5, 95% CI 1.7-3.3, P < 0.001). The allele frequencies of the MTHFR 1298A→C, MTR 2756A→G, and MTRR 66A→G mutations were 36.7%, 15.7%, and 36.6%, respectively. The 1298C allele frequency was significantly higher in the CAD group than in controls (P < 0.05) and showed a significant association with CAD in heterozygote carriers. There was no statistically significant difference between cases and controls in the frequencies of the A2756G alleles/genotypes in the MTR gene and of the A66G alleles/genotypes in the MTRR gene. The contributions to tHcy levels of the three common mutations were statistically significant. The heterozygosity of the MTHFR 1298AC genotype, MTR 2756G allele, and MTRR 66G allele yielded an OR of 3.4, 2.0, and 2.1, respectively, for having HHcy. Conclusion: We suggest that HHcy confers a risk for CAD, and smokers with tHcy are at a greatly increased risk. Our finding supports an important role of the MTHFR gene in CAD and provides evidence of polygenic regulation of tHcy. © 2007 European Federation of Internal Medicine.
