Lipoprotein (a) and its immune complexes in dyslipidemic subjects

Objectives: To investigate plasma levels of lipoprotein (a) [Lp(a)] and low-density lipoprotein (LDL)-circulating immune complexes (IC) in subjects with various dyslipidemias. Methods: Plasma Lp(a), Lp(a)-IC, and LDL-IC levels were determined by enzyme-linked immunosorbent assays (ELISAs) in 198 subjects with various dyslipidemias and 34 control subjects. Results: Hypertriglyceridemic subjects exhibited the lowest plasma Lp(a) levels, while hypercholesterolemic subjects exhibited the highest levels. Subjects with mixed hyperlipidemia had intermediate plasma Lp(a) concentrations, which were significantly lower than those of subjects with normal lipid levels. Interestingly, we also found that hypertriglyceridemic subjects had the lowest plasma Lp(a)-IC and LDL-IC levels, while hypercholesterolemic subjects exhibited the highest levels. Triglyceride (TG) levels were negatively correlated with Lp(a) (r = −0.15, P< 0.05), Lp(a)-IC (r = −0.20, P< 0.01), and LDL-IC (r = −0.214, P< 0.01) concentrations. Furthermore, significantly positive relationships were found between Lp(a)-IC and Lp(a) levels (r = 0.65, P< 0.001) and between LDL-IC and LDL-C levels (r = 0.43, P< 0.001). Conclusions: The results argue for a regulatory role of TG on plasma Lp(a) and its circulating immune complexes in subjects with various dyslipidemias. The circulating levels of these immune complexes levels are likely to change with different concentrations of Lp(a) and LDL.