title: ApoB-100 secretion by HepG2 cells is regulated by the rate of triglyceride biosynthesis but not by intracellular lipid pools.
abstract: Triglycerides (TGs), cholesteryl esters (CEs), cholesterol, and phosphatidylcholine have been independently proposed as playing regulatory roles in apoB-100 secretion; the results depended on the cellular model used. In this study, we reinvestigate the role of lipids in apoB-100 production in HepG2 cells and in particular, we clarify the respective roles of intracellular mass and the biosynthesis of lipids in the regulation of apoB-100 production. In a first set of experiments, the pool size of cholesterol, CEs, and TGs was modulated by a 3-day treatment with either lipid precursors or inhibitors of enzymes involved in lipid synthesis. We used simvastatin (a hydroxymethylglutaryl coenzyme A reductase inhibitor), 58-035 (an acyl coenzyme A cholesterol acyltransferase inhibitor), 5-tetradecyloxy-2-furancarboxylic acid (TOFA, an inhibitor of fatty acid synthesis), and oleic acid. The secretion rate of apoB-100 was not affected by the large modulation of lipid mass induced by these various pre-treatments. In a second set of experiments, the same lipid modulators were added during a 4-hour labeling period. Simvastatin and 58-035 inhibited cholesterol and CE synthesis without affecting apoB-100 secretion. By contrast, treatment of HepG2 cells with TOFA resulted in the inhibition of TG synthesis and apoB-100 secretion. This effect was highly specific for apoB-100 and was reversed by adding oleic acid, which stimulated both TG synthesis and apoB-100 secretion. Moreover, a combination of oleic acid and 58-035 inhibited CE biosynthesis and increased both TG synthesis and apoB-100 secretion. These results show that in HepG2 cells TG biosynthesis regulates apoB-100 secretion, whereas the rate of cholesterol or CE biosynthesis has no effect.
authors.affiliation: Laboratoire Glaxo Wellcome, Centre de Recherche, Les Ulis, France.
authors.forename: F
authors.initials: F
authors.lastname: Benoist
authors.forename: T
authors.initials: T
authors.lastname: Grand-Perret
mesh_terms: D001055:Apolipoproteins B / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005663:Furans / Q000494:pharmacology; D006801:Humans; D000960:Hypolipidemic Agents / Q000494:pharmacology; D050356:Lipid Metabolism; D008148:Lovastatin / Q000031:analogs & derivatives / Q000494:pharmacology; D019821:Simvastatin; D014280:Triglycerides / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
chemical_list: D001055:Apolipoproteins B; D004791:Enzyme Inhibitors; D005663:Furans; D000960:Hypolipidemic Agents; D014280:Triglycerides; C014289:5-(tetradecyloxy)-2-furancarboxylic acid; D008148:Lovastatin; D019821:Simvastatin