APO(a) variants and lipoprotein(a) in men with or without myocardial infarction

The lipoprotein Lp(a) with high plasma concentration is an independent genetic determinant for cardiovascular diseases. It was investigated as a quantitative factor of risk for myocardial infarction. A total of 345 Italian subjects, 127 Cases and 218 Controls, were studied. Lipids and lipoproteins were compared. Cases had atherogenic traits, such as lower HDL cholesterol and higher triglycerides than Controls. In particular, they had Lp(a) concentrations over the risk threshold, (median, 27 mg/dl in Cases vs 17 mg/dl in Controls; P = 0.0075, Mann-Whitney test) which confirmed the association of this parameter with the disease. Two main functional variants of the apo(a) gene, KringleIV and penta-nucleotide repeat, (PNR) were analyzed. Allele and genotype frequency distributions differed between Cases and Controls. Lp(a) concentrations differed according to PNR genotypes in Controls: subjects having alleles >8 showed lower Lp(a). This was not found in Cases. They had a higher prevalence of the smaller KringleIV alleles, the high Lp(a)-expressing ones. In Cases, genotypes consisting of two small KringleIV alleles were prevalently associated to PNR 8/9 and 8/10, thus preventing Lp(a) lowering. The putative apo(a) enhancer within LINE1 in the apo(a)-plasminogen intergenic region was investigated for functional polymorphisms. No variants that could be associated to the Lp(a) variability were found.