Factors influencing Lp[a]- particle size as determined by gradient gel electrophoresis

This study examined factors influencing the particle diameter of Lp[a]-, the low density lipoprotein (LDL)-like moiety of Lp[a], in 26 subjects chosen to provide a range of Lp[a] and triglyceride levels. Lp[a] and LDL fractions were isolated by vertical density ultracentrifugation. Lp[a] was further purified using a lysine-Sepharose affinity column and Lp[a]- obtained by incubating Lp[a] with dithiothreitol. Lp[a], LDL, and Lp[a]- fractions were run on 3-13% gradient gels to determine particle diameter. Lp[a] size correlated positively with LDL size (r = 0.62; P < 0.001), but the association between Lp[a]- size and LDL size was stronger (r = 0.82; P < 0.0001). Log triglyceride level correlated inversely with Lp[a]- size (r = -0.72; P < 0.0001) and LDL size (r = 0.69; P < 0.0001). HDL cholesterol level correlated positively with Lp[a]- size (r = 0.67; P < 0.0005) and LDL size (r = 0.64; P < 0.0005). The strong correlation between LDL size and Lp[a]- size may be due to extracellular utilization of circulating LDL in the production of Lp[a] or may reflect the same metabolic processes influencing both these particles once Lp[a] has been formed.