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Background: Moderately elevated blood levels of homocysteine are weakly correlated with coronary heart disease (CHD) risk, but causality remains uncertain. When folate levels are low, the TT genotype of the common C677T polymorphism (rs1801133) of the methylene tetrahydrofolate reductase gene (MTHFR) appreciably increases homocysteine levels, so ''Mendelian randomization'' studies using this variant as an instrumental variable could help test causality. Methods and Findings: Nineteen unpublished datasets were obtained (total 48,175 CHD cases and 67,961 controls) in which multiple genetic variants had been measured, including MTHFR C677T. These datasets did not include measurements of blood homocysteine, but homocysteine levels would be expected to be about 20% higher with TT than with CC genotype in the populations studied. In meta-analyses of these unpublished datasets, the case-control CHD odds ratio (OR) and 95% CI comparing TT versus CC homozygotes was 1.02 (0.98-1.07; p = 0.28) overall, and 1.01 (0.95-1.07) in unsupplemented low-folate populations. By contrast, in a slightly updated meta-analysis of the 86 published studies (28,617 CHD cases and 41,857 controls), the OR was 1.15 (1.09-1.21), significantly discrepant (p = 0.001) with the OR in the unpublished datasets. Within the meta-analysis of published studies, the OR was 1.12 (1.04-1.21) in the 14 larger studies (those with variance of log OR,0.05; total 13,119 cases) and 1.18 (1.09-1.28) in the 72 smaller ones (total 15,498 cases). Conclusions: The CI for the overall result from large unpublished datasets shows lifelong moderate homocysteine elevation has little or no effect on CHD. The discrepant overall result from previously published studies reflects publication bias or methodological problems. [ABSTRACT FROM AUTHOR]

Myocardial infarction (MI) results from complex interactions of multiple genetic and environmental factors. To disclose genetic backgrounds of MI, we performed a large-scale, case-control association study using 52,608 gene-based single-nucleotide polymorphism (SNP) markers, and identified a candidate SNP located on chromosome 3p21.2–p21.1. Subsequent linkage–disequilibrium mapping indicated very significant association between MI and a SNP in exon 2 of the inter-alpha (globulin) inhibitor 3 gene ( ITIH3; χ 2 = 24.88, P = 6.1 × 10−7, 3,353 affected individuals versus 3,807 controls). In vitro functional analyses showed that this SNP enhanced the transcriptional level of the ITIH3 gene. Furthermore, we found expression of the ITIH3 protein in the vascular smooth muscle cells and macrophages in the human atherosclerotic lesions, suggesting ITIH3 SNP to be a novel genetic risk factor of MI. [ABSTRACT FROM AUTHOR]

Myocardial infarction (MI) is one of the common diseases whose pathogenesis includes genetic factors. To reveal genetic backgrounds of this clinically heterogeneous disorder, we started our case-control association study by examining large-scale gene-based single nucleotide polymorphism (SNP) sets for ∼1,000 patients and controls. As a core genotyping method, a combination of multiplex PCR and Invader method was used, and after genotyping ∼65,000 SNPs, we found two SNPs located within lymphotoxin-α ( LTA) gene showing significant association with MI. LTA is one of the cytokines produced in the early stages of vascular inflammatory processes. These SNPs seem to be involved in inflammation by both qualitatively and quantitatively modifying the function of LTA protein, thereby conferring a risk of MI. The genetic association was further confirmed by other researchers using white European trios. To further understand the roles of LTA protein in the pathogenesis of MI, we searched for proteins that interact directly with LTA protein and identified galectin-2 protein as a binding partner of LTA protein. It is a member of galactose-binding lectin family whose function has not been well characterized. Genetic association study again revealed that an SNP in LGALS2 encoding galectin-2 was also associated with susceptibility to MI. This genetic substitution seemed to affect the transcriptional level of galectin-2, which led to altered secretion of LTA, thereby affecting the degree of inflammation. Thus, our findings indicate the importance of inflammation, especially the LTA cascade, in the pathogenesis of MI. Also, combined strategy of genetic and molecular-cellular biological approaches may be useful for clarification of the pathogenesis of common diseases in general. [ABSTRACT FROM AUTHOR]

Galectins, a family of animal lectins that bind ß-galactoside sugar chains, are thought to have a variety of intra- and extracellular functions. Through a case-control study in the Japanese population and subsequent functional analyses, we previously showed that a functional single nucleotide polymorphism (SNP) in the gene encoding galectin-2 (lectin, galactoside-binding, soluble, 2;LGALS2) is associated with susceptibility to myocardial infarction. As an addition to the genetic information aboutLGALS2reported earlier, we provide here a map of polymorphic sites within an 11-kb region containing the gene encoding a closely related molecule, galectin-1 (lectin, galactoside-binding, soluble, 1;LGALS1). The map includes 14 SNPs and two genetic variations of other types detected in a Japanese population sample. Five of the 14 SNPs were not among those deposited in the dbSNP database in the US National Center for Biotechnology Information and appeared to be novel. We also analyzed linkage disequilibrium (LD) using the 12 SNPs in which minor-allele frequencies were>0.20. Investigation of haplotype structure within theLGALS1locus revealed five common haplotypes covering more than 95% of the test population. One, or a pair, of the SNPs described here might serve as a “tag” for detecting associations between complex diseases and genes in this local segment of chromosome 22q13.1. [ABSTRACT FROM AUTHOR]