Background: The APO B gene is characterised by numerous polymorphic sites, three of which (XbaI, EcoRI, SpIns/Del) are related to levels of total cholesterol (TC), low-density lipoproteins, apo B and tryglicerides, and to coronary artery disease (CAD) and/or myocardial infarction (MI). Moreover, conflicting results emerge from literature. To assess how each polymorphism of the APO B gene was associated with CAD and MI risk, we carried out a meta-analysis of all published studies.
Methods and results: Thirty case-control studies were considered, for a total of 6077, 3870 and 11616 individuals, respectively, for XbaI, EcoRI and SpIns/Del polymorphisms. For each polymorphism we calculated the risk of CAD/MI on the overall sample and for large and small studies separately. No evidence of increased risk emerged for XbaI polymorphism. Whereas, positive associations were detected for EcoRI, SpIns/Del and risk of CAD and MI, with odds ratio (OR) of 1.73 (95% CI, 1.19-2.50) and 1.19 (95% CI, 1.05-1.35) for carriers of AA and DD, respectively.
Conclusions: Despite the small size of most studies and the incomplete understanding of the effects of these polymorphisms on lipid metabolism and on final clinical implications, the findings suggest that EcoRI and SpIns/Del polymorphisms significantly increase the risk of CAD and MI. Despite the rarity of the allelic variant of EcoRI polymorphism, its presence is strongly related to the occurrence of CAD/MI. Moreover, there is a high consistency between small and large studies. The results on SpIns/Del polymorphism seem the most interesting and reliable, considering both the number of subjects analysed and the consistency of the evidence of its effect on lipid levels. These results need to be confirmed by larger and appropriately powered studies.