Conjugated linoleic acid isomers have differential effects on triglyceride secretion in Hep G2 cells.
The effect of different conjugated linoleic acid (CLA) isomers (trans-10,cis-12 (t10,c12)-CLA and cis-9,trans-11 (c9,t11)-CLA), compared with oleic acid (OA) and linoleic acid (LA), on hepatic lipid synthesis and secretion were investigated in Hep G2 cells. The cells were incubated in a medium containing 1 mmol/l fatty acid-bovine serum albumin (BSA) complex for 5 h, with BSA alone as control. [(3)H]Glycerol and [(14)C]acetate were used to monitor lipid synthesis and secretion. The results show that cellular uptake rates of these fatty acids were similar. Incubation with OA, t10,c12-CLA, c9,t11-CLA and LA resulted in 6-, 4-, 2- and 1.8-fold increases in intracellular [(3)H]triglyceride ([(3)H]TG) compared with incubation with BSA alone. OA, LA and c9,t11-CLA increased [(3)H]TG secretion 3.6-, 2.5- and 1.2-fold above the control, whereas t10,c12-CLA markedly suppressed the secretion of [(3)H]TG. Hepatic secretion of TG mass increased 3.5-, 3.3-, 2.7- and 1.5-fold in the cells incubated with OA, LA, c9,t11-CLA and t10,c12-CLA, respectively. Since the secreted TG is mainly contained in very low density lipoproteins (VLDL), the decreased ([(3)H])TG secretion by t10,c12-CLA reflects a diminished secretion of VLDL. With respect to cholesterol synthesis OA was more effective in stimulating the incorporation of [(14)C]acetate into cellular total cholesterol followed in descending order by LA, c9,t11-CLA and t10,c12-CLA. In conclusion, the biological properties of 18-carbon fatty acids are clearly influenced by both the number and (geometric) positions of their double bonds. Furthermore t10,c12-CLA is more effective than c9,t11-CLA on suppressing hepatic TG secretion in vitro.
Lin
Y
Y
Unilever Research Vlaardingen, P.O. Box 114, 3130 AC, Vlaardingen, The Netherlands. yuguang.lin@unilever.com
Schuurbiers
E
E
Van der Veen
S
S
De Deckere
E A
EA
D019342:Acetic Acid / Q000378:metabolism; D002250:Carbon Radioisotopes; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002784:Cholesterol / Q000032:analysis / Q000096:biosynthesis; D015536:Down-Regulation; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D007536:Isomerism; D019787:Linoleic Acid / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D019301:Oleic Acid / Q000494:pharmacology; D014280:Triglycerides / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D005227:Fatty Acids; D014280:Triglycerides; D014316:Tritium; D019301:Oleic Acid; D002784:Cholesterol; D019787:Linoleic Acid; D005990:Glycerol; D019342:Acetic Acid