Polymorphisms in 33 inflammatory genes and risk of myocardial infarction--a system genetics approach.

The hypothesis of a causal link between inflammation and atherosclerosis would be strengthened if variants of inflammatory genes were associated with disease. Polymorphisms of 33 genes encoding inflammatory molecules were tested for association with myocardial infarction (MI). Patients with MI and a parental history of MI (n = 312) and controls from the UK (n = 317) were genotyped for 162 polymorphisms. Thirteen polymorphisms were associated with MI (P values ranging from 0.003 to 0.041). For three genes, ITGB1, SELP, and TNFRSF1B haplotype frequencies differed between patients and controls (P values < 0.01). We further assessed the simultaneous contribution of all polymorphisms and relevant covariates to MI using a two-step strategy of data mining relying on Random Forest and DICE algorithms. In a replication study involving two independent samples from the UK (n = 649) and France (n = 706), one interaction between the ITGA4/R898Q polymorphism and current smoking status was replicated. This study illustrates a strategy for assessing the joint effect of a large number of polymorphisms on a phenotype that may provide information that single locus or single gene analysis may fail to uncover. Overall, there was weak evidence for an implication of inflammatory polymorphisms on susceptibility to MI.

Genetic evidence that nitric oxide modulates homocysteine: the NOS3 894TT genotype is a risk factor for hyperhomocystenemia.

OBJECTIVE: Mild hyperhomocystenemia is an independent, graded risk factor for cardiovascular disease. Genetic determinants of hyperhomocystenemia include functional polymorphisms in several folate/homocysteine metabolic enzymes. Nitric oxide may also modulate plasma homocysteine (tHcy) concentrations, either by direct inhibition of methionine synthase or via an indirect effect on folate catabolism. METHODS AND RESULTS: The hypothesis that the endothelial nitric oxide synthase (NOS3) G894T polymorphism is a genetic determinant of tHcy concentrations was tested in 2 independent healthy adult populations. In both populations, NOS3 genotype was significantly associated with tHcy concentrations in nonsmokers with low folate (P=0.03 for each). Models were constructed to adjust for known determinants of tHcy concentrations and test for interactions between NOS3 genotype and these determinants in nonsmokers from each population. NOS3 genotype remained a significant determinant of tHcy concentrations after adjustment. Interactions between NOS3 genotype and serum folate were significant in both populations, and the interaction between NOS3 genotype and MTHFR C677T genotype was significant in the larger population. CONCLUSIONS: These data indicate that the NOS3 894TT genotype is a risk factor for elevated tHcy in healthy nonsmoking adults with low serum folate and supports the hypothesis that nitric oxide modulates homocysteine through an effect on folate catabolism.

Family-based investigation of the C677T polymorphism of the methylenetetrahydrofolate reductase gene in ischaemic heart disease.

BACKGROUND: Elevated homocysteine is associated with ischaemic heart disease (IHD). The C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene results in reduced MTHFR enzyme activity and reduced methylation of homocysteine to methionine resulting in mild hyperhomocysteinaemia. Case-control association studies of the role of the C677T MTHFR polymorphism in IHD have produced conflicting results. We therefore used newly described family-based association tests to investigate the role of this polymorphism in IHD, in a well-defined population. METHODS: A total of 352 individuals from 129 families (discordant sibships and parent-child trios) were recruited. Linkage disequilibrium between the polymorphism and IHD was tested for using the combined transmission disequilibrium test (TDT)/sib-TDT and pedigree disequilibrium test (PDT). Homocysteine levels were measured. RESULTS: Both the TDT/sib-TDT and PDT analyses found a significantly reduced transmission of the T allele to affected individuals (P=0.016 and P=0.021). There was no significant difference in homocysteine levels between affected and unaffected siblings. TT homozygotes had mean homocysteine levels significantly higher than those of TC heterozygotes (P<0.001) and CC homozygotes (P<0.001). CONCLUSIONS: These data suggest that in contrast to the conventional hypothesis the T allele may be protective against IHD, independent of homocysteine levels.

Endothelial nitric oxide synthase gene polymorphism and ischemic heart disease.

BACKGROUND: Ischemic heart disease (IHD), the leading cause of death worldwide, is a multifactorial disease arising from the complex interplay of genetic and environmental factors. There is considerable evidence that nitric oxide (NO) plays an important role in protecting against atherosclerosis, the process underlying IHD. Endothelial NO is synthesized from the amino acid l-arginine by the endothelial isoform of NO synthase (eNOS). Thus, polymorphisms of the eNOS gene, by altering production of NO within the vascular endothelium, are potential risk factors for IHD. Several groups have investigated the role of the G894T polymorphism of the eNOS gene in IHD by using case-control association studies; however, its role is unclear because of contradictory results from these studies. We applied family-based association tests to investigate the role of this polymorphism in IHD in a well-defined Irish population. METHODS: A total of 1023 individuals from 388 families (discordant sibships and parent-offspring trios) were recruited. Linkage disequilibrium between the polymorphism and IHD was tested for by using the combined transmission disequilibrium test/sib-transmission disequilibrium test and pedigree disequilibrium test. RESULTS: Both the combined transmission disequilibrium test/sib-transmission disequilibrium test and pedigree disequilibrium test analyses found no statistically significant excess transmission of either allele to affected individuals (P = .57 and P = .38, respectively). CONCLUSIONS: Using robust family-based association tests specifically designed for the study of complex diseases, we found no evidence that the G894T polymorphism of the eNOS gene has a significant role in the development of IHD in our population.