The independent correlation of the impact of lipoprotein(a) levels and apolipoprotein E polymorphism on carotid artery intima thickness

Background. Apolipoprotein E (apoE) plays a key role in lipoprotein metabol ism. It occurs in three isoforms E2, E3 and E4. These isoforms have differe nt impacts on plasma lipoprotein levels. The allele, or gene, coding apoE4 is considered a candidate for premature atherosclerosis development while t he apoE2 gene is assumed to be protective. Lipoprotein(a) is also atherogen ic and its increased plasma concentration is presumed to be an independent risk factor for premature atherosclerosis. Lipoprotein(a) is a protein depo siting directly into the atheromatous plaques, enhancing cholesterol oxidat ion, competitively inhibiting plasminogen formation and thus having a proth rombogenic effect. The aim of our study was to establish a relationship bet ween common carotid artery intima thickness and two independent risk factor s, apoE polymorphism and elevation of plasma lipoprotein(a) levels. Methods. A cross-sectional study was performed on 114 patients who were ref erred to the lipid clinic for primary hyperlipoproteinaemia The patients re ceived no treatment prior to examination. Plasma levels of total cholestero l, triglycerides, HDL-cholesterol, LDL-cholesterol, apoA, apoB, lipoprotein (a) and the apoE genotype were determined and the carotid artery intima thi ckness was measured using ultrasonography. Results. The relative frequencies of apoE2, E3 and E4 were 0.049, 0.830 and 0.121. The equality of carotid intima thickness was tested using the Krusk al-Wallis test. Medians of intima thickness in a subgroup with the allele E 2 were 0.72 mm, in a subgroup with the E3/E3 genotype 0.70 mm and in a subg roup with the E4 allele 0.80 mm. The relationship between carotid intima th ickness and lipoprotein(a) levels was tested using Spearman's correlation c oefficient. Conclusions. No statistically significant differences of carotid intima thi ckness among subgroups divided according to their apoE genotype were found. No relationship between carotid intima thickness and lipoprotein(a) levels was found. On the contrary a close relationship between carotid intima thi ckness and age and also some of the plasma lipid Variables was recorded usi ng the method of multivariate linear regression.