Lipoprotein (a) phenotype distribution in a population of bypass patients and its influence on lipoprotein (a) concentration.

A case control study was undertaken to compare the distribution of apolipoprotein (a) phenotypes in patients suffering from atherosclerosis and undergoing coronary bypass surgery with the distribution observed in adequately selected controls. Cases differed from controls for triglycerides (1.90 +/- 0.88 mmol l-1 and 1.16 +/- 0.79 mmol l-1, P < 0.0001, respectively), HDL cholesterol (1.15 +/- 0.34 mmol l-1 and 1.69 +/- 0.42 mmol l-1, P < 0.0001, respectively), apolipoprotein AI (1.31 +/- 0.24 g l-1 and 1.70 +/- 0.29 g l-1, P < 0.0001, respectively) and lipoprotein a (Lp(a)) (0.32 +/- 0.30 g l-1 and 0.19 +/- 0.20 g l-1, P < 0.0001, respectively). The apolipoprotein (a) phenotypes were distributed differently in cases and controls (chi 2 = 25.26, P < 0.0001) with a lower percentage of isoforms of larger size and a higher percentage of isoforms of smaller size in patients. The Lp(a) concentration remained significantly higher in patients than in controls for most of the phenotypes, suggesting that both a high Lp(a) concentration and a different apolipoprotein (a) size distribution could be involved in the development of atherosclerosis in this population. In addition, patients exhibiting the highest Lp(a) concentrations had higher levels of LDL cholesterol and apolipoprotein B than patients exhibiting the lowest Lp(a) concentrations. This feature was not observed in controls. By contrast, controls with the highest Lp(a) concentration had significantly higher triglyceride levels than controls with the lowest Lp(a) concentration. This feature was not observed in patients. Our results indicate that patients undergoing bypass surgery have higher Lp(a) concentrations than controls, this increase being not completely explained by the difference in apolipoprotein (a) phenotype distribution. The high Lp(a) concentration seems to be associated with different lipid profiles in patients than in controls.