A prospective study of the APOA1 XmnI and APOC3 SstI polymorphisms in the APOA1/C3/A4 gene cluster and risk of incident myocardial infarction in men.

BACKGROUND: Apolipoproteins AI/CIII/AIV play important roles in the metabolism of triglycerides (TG) and high-density lipoprotein (HDL) cholesterol. However, whether genetic variations in the APOA1/C3/A4 gene cluster are associated with the risk of myocardial infarction (MI) remains uncertain and prospective data are sparse. METHODS: In a prospective nested case-control study of 385 incident cases of MI and 373 age- and smoking-matched controls from the Physicians' Health Study, we examined the relationship between 2 common single nucleotide polymorphisms (APOA1 XmnI and APOC3 SstI) in the APOA1/C3/A4 gene cluster and haplotypes defined by these SNPs and risk of incident MI. RESULTS: No significant differences in allele or genotype frequency for the APOA1 XmnI and APOC3 SstI polymorphisms were detected between cases and controls. After adjusting for non-lipid coronary risk factors, the relative risks for incident MI were 1.00 (95% CI 0.68-1.47) for men carrying the X2 allele compared with those homozygous for the X1 allele in the APOA1 XmnI site and 1.07 (95% CI 0.69-1.64) for men carrying the S2 versus those homozygous for the S1 allele in the APOC3 SstI site. Moreover, we did not observe any effect modification by HDL or TG levels for the associations of these APOA1 and APOC3 genotypes with MI risk. There were significant differences in TG levels among men carrying different haplotypes (P=0.01) and men carrying the X1-S2 haplotype had higher levels of TG than those carrying the X2-S1 haplotype (202 mg/dl versus 157 mg/dl, P=0.03); however, haplotype frequencies defined by these two polymorphisms did not differ significantly between cases and controls. CONCLUSION: In this prospective study of apparently healthy middle-aged US men, carriers of the X1-S2 haplotype in the APOA1 XmnI and APOC3 SstI variants across the APOA1/C3/A4 gene cluster had higher TG levels, but there was no evidence for significant associations between these two common variants or haplotypes defined by them and risk of incident MI in this cohort.