Turnover of Lipoprotein (a) in Man

Abstract

A B S T R A C T An elevated concentration of lipoprotein (a) [Lp(a)] in the serum has been considered a risk factor for coronary heart disease by various investigators. In the present study, the turnover of Lp(a) was investigated in nine individuals with serum Lp(a) levels ranging from 1 to 68 mg/100 ml. After intravenous injection of radioiodinated Lp(a), the radioactivity time-curve of the serum and the specific activitity time-curves of the isolated Lp(a) and Lp(a) apolipoproteins were measured for 14 d. More than 97% of the label was found in the protein moiety of Lp(a). During the entire study period, the serum radioactivity remained with Lp(a), only insignificant amounts of radioactivity were detectable in other lipoprotein fractions. The serum radioactivity timecurves and the specific activity time-curves of the isolated Lp(a) and Lp(a) apolipoproteins were identical.The kinetic parameters of Lp(a) turnover were calculated in terms of a two-compartment model.

The assembly of lipoprotein Lp(a)

“…These studies revealed that Lp(a) is not a direct metabolic product of VLDL, which led us to conclude that Lp(a) might be independently synthesized from triglyceride-rich lipoproteins and probably secreted directly from the liver. Extending these studies, turnover experiments in humans demonstrated a highly significant correlation between plasma Lp(a) levels and the rate of synthesis; the fractional catabolic rate of Lp(a) was not correlated with plasma concentrations [19]. As pointed out above, plasma Lp(a) levels show a strong negative correlation with apo(a) size (i.e.…”

Binding of LP(a) to the low density lipoprotein receptor of human fibroblasts

“…It has been postulated that Lp(a) is not a metabolic product of other apo B-containing lipoproteins (chylomicrons, VLDL or LDL) and thus Lp(a) should be synthesized as a separate lipoprotein [5]. Furthermore Lp(a) is not converted into other lipoproteins [6]. At present, the site(s) of Lp(a) synthesis and catabolism are unknown.…”

Lp(a) phenotyping by immunoblotting with polyclonal and monoclonal antibodies.

“…The Lp(a) standard serum (83.7 mg/100 ml) from Immuno (Austria) and its serial dilutions were used as standards in this assay. This standard was prepared in the manner described by Krempler et al 20 …”