Decreased plasma levels of lipoprotein(a) in patients with hypertriglyceridemia.

Lipoprotein(a) (Lp(a)) is an atherogenic lipoprotein which is similar in structure to, but metabolically distinct from, LDL. Factors modulating plasma Lp(a) concentrations are poorly understood. To investigate the possible interaction of Lp(a) with triglycerides, we determined the apo(a) phenotype, Lp(a) concentration, and distribution of Lp(a) in a group of patients with triglycerides > 400 mg/dl (n = 60) compared with a control group (n = 128). Lp(a) concentrations were significantly lower in hypertriglyceridemic patients (mean +/- S.E., 13 +/- 4 mg/dl; median, 6 mg/dl; 25/75 percentile, 2-13 mg/dl) as compared with the controls (mean, 22 +/- 2 mg/dl; median, 10 mg/dl; 25/75 percentile, 7-30 mg/dl). Plasma Lp(a) concentrations in the hypertriglyceridemic patients correlated negatively with triglyceride levels (r = -0.69, P = 0.03). The difference in Lp(a) levels between patients and controls was maintained when subjects were stratified by apo(a) phenotype and type of hyperlipidemia. After subdividing the hypertriglyceridemic patients into one group with apo(a) isoforms < or = S2 and one group with apo(a) isoforms > or = S3, we found that the differences in plasma Lp(a) concentrations between patients and controls were more pronounced in the group with the lower molecular weight apo(a) isoforms. These data indicate that hypertriglyceridemia is associated with lower plasma Lp(a) concentrations and suggest that increased levels of triglyceride-rich lipoproteins may influence the metabolism of Lp(a).