Studies on an additional pre-beta-lipoprotein, sinking pre-beta (SPB). II. Fatty acid composition of lipid moieties.

The appearance of additional lipoprotein fractions with pre-beta-mobility on cellulose acetate and agarose gel electrophoresis has recently been linked with the early occurrence of ischemic heart disease (IHD). One of these fractions, designated sinking pre-beta-lipoprotein (SPB) has been isolated, purified, and identififed as synonymous with LP(a). In the present study, the lipid moieties of this lipoprotein fraction were further characterized as to their fatty acid composition. These were almost identical to those of low-density lipoprotein (LDL) lipid moieties. The acute influence on fatty acid composition of SPB lipid moieties, 5 hr after a linoleic acid-rich test meal, was a 40% increase in triglyceride linoleic acid content and only minor changes in phosphoglyceride fatty acids. Data speak against an actual conversion of chylomicron remnants into SPB but would allow a certain exchange of lipid moiety among chylomicrons, SPB, and LDL. It is therefore suggested that the origin of the SPB presumably synonymous with LP(a) is the same as for LDL: the liver.