Low density lipoprotein-cholesteryl ester-derived linoleic acid is mainly incorporated into the phospholipid...

The cellular metabolism of the cholesterol in the low density lipoprotein cholesteryl ester (LDL-CE) moiety is well characterized, whereas the cellular fate of the fatty acid (mainly linoleic acid) in the LDL-CE has not been studied in detail. The distribution of the LDL-CE-derived linoleic acid among cellular lipids was studied in J-774 A.1 macrophages, using LDL that was radiolabeled in the linoleic acid of its CE moiety. Macrophages were incubated with radiolabeled LDL for 4 h at 4 degrees C, washed and further incubated for up to 24 h at 37 degrees C in a fresh medium (without LDL). The distribution of the linoleic acid among cellular lipids was then analyzed. After 20 min of incubation, most of the linoleic acid was found in the CE fraction as a constituent of the internalized LDL, and the CE-associated linoleate was progressively decreased. In parallel, the linoleic acid was found to be esterified into the macrophage phospholipids (mostly in the macrophage phosphatidyl choline fraction), accounting for up to 62% of the total cellular labeled linoleic acid after 24 h of incubation. We conclude that the fatty acid derived from the hydrolysis of the LDL-CE moiety in macrophages is mainly incorporated into the cellular phospholipids where it can serve for various cellular metabolic processes.