Quantification of lipoprotein(a) and apolipoprotein(a) in plasma and lipoprotein fractions in the hypertriglyceridemic state.

Lipoprotein(a) [Lp(a)] is a risk factor for coronary heart disease (CHD) in particular in association with high low density lipoprotein (LDL) cholesterol concentrations. Hypertriglyceridemia on the other hand has been found to be associated with low Lp(a) values. This observation could be confirmed in 851 patients of the outpatient lipid clinic. Lp(a) median levels were 2.7-fold higher in patients with triglycerides below 200 mg/dl as compared with patients expressing triglyceride levels above 200 mg/dl (19 vs 7 mg/dl, P < 0.0001). In contrast to these data apolipoprotein(a) [apo(a)] has been detected in triglyceride-rich lipoproteins (TRL). To find out whether the presence of apo(a) in TRL is determined by the concentration of these particles, apo(a) concentrations were measured in TRL in fasting plasma of ten hypertriglyceridemic patients and ten normal controls with Lp(a) serum levels above 25 mg/dl. The apo(a) concentration in TRL did not show statistically significant differences between controls and patients (2.0+/-0.9 vs 1.8+/-1.6 mg/dl). In the second part of the study apo(a) levels in TRL were measured before and after fat feeding in eight healthy volunteers. Again no significant differences were observed in the apo(a) concentrations of the d < 1.006 a ml fraction before and after fat feeding (1.03+/-1.06 vs 0.81+/-0.63 mg/dl). In summary, this study fails to show an association of apo(a) with TRL for different states of hypertriglyceridemia. This negative finding is shown for constant particle numbers but might not be true if the particle number in TRL increases.