Hypertriglyceridemic Very Low Density Lipoproteins Induce Triglyceride Synthesis and Accumulation in Mouse Peritoneal Macrophages

Sandra H. Gianturco; William A. Bradley; Antonio M. Gotto; Joel D. Morrisett; Duane L. Peavy

doi:10.1172/JCI110590

Hypertriglyceridemic Very Low Density Lipoproteins Induce Triglyceride Synthesis and Accumulation in Mouse Peritoneal Macrophages

Sandra H. Gianturco, William A. Bradley, Antonio M. Gotto Jr., Joel D. Morrisett, and Duane L. Peavy

Published July 1, 1982 - More info

View PDF

Abstract

Triglyceride-rich lipoproteins may be responsible for the lipid accumulation in macrophages that can occur in hypertriglyceridemia. Chylomicrons and very low density lipoproteins (VLDL, total and with flotation constant [S_f] 100-400) from fasting hypertriglyceridemic subjects induced a massive accumulation of oil red O-positive inclusions in unstimulated peritoneal macrophages. Cell viability was not affected. The predominant lipid that accumulated in cells exposed to hypertriglyceridemic VLDL was triglyceride. Hypertriglyceridemic VLDL stimulated the incorporation of [¹⁴C]oleate into cellular triglyceride up to ninefold in 16 h, but not into cholesteryl esters. Mass increase in cellular triglyceride was 38-fold. The stimulation of cellular triglyceride formation was dependent on time, temperature, and concentration of hypertriglyceridemic VLDL. By contrast, VLDL, low density, and high density lipoproteins from fasting normolipemic subjects had no significant effect on oleate incorporation into neutral lipids or on visible lipid accumulation.

¹²⁵I-Hypertriglyceridemic VLDL (S_f 100-400) were degraded by macrophages in a dose-dependent manner, with 50 and 100% saturation observed at 3 and 24 μg protein/ml (2.5 and 20 nM), respectively. Hypertriglyceridemic VLDL inhibited the internalization and degradation of ¹²⁵I-hypertriglyceridemic VLDL (4 nM) by 50% at 3 nM. Cholesteryl ester-rich VLDL from cholesterol-fed rabbits gave 50% inhibition at 5 nM. Low density lipoproteins (LDL) inhibited by 10% at 5 nM and 40% at 47 nM. Acetyl LDL at 130 nM had no effect. We conclude that the massive triglyceride accumulation produced in macrophages by hypertriglyceridemic VLDL is a direct consequence of uptake via specific receptors that also recognize cholesteryl ester-rich VLDL and LDL but are distinct from the acetyl LDL receptor. Uptake of these triglyceride-rich lipoproteins by monocyte-macrophages in vivo may play a significant role in the pathophysiology of atherosclerosis.

Images.