ABSTRACT
Milk enriched in conjugated linoleic acid (CLA) was obtained from cows on pasture supplemented with full-fat rapeseeds (FFR; 2.26 g cis 9, trans 11 (c9,t11)-CLA/100 g fatty acid methyl esters) and full-fat soyabeans (1.83 g c9,t11-CLA100 g fatty acid methyl esters). A control milk fat (1.69 g c9,t11-CLA/100 g fatty acid methyl esters) was obtained from cows fed on pasture only. The present study assessed the potency of the CLA-enriched milk fats to modulate biomarkers that had previously been observed to respond to c9,t11-CLA in the MCF-7 and SW480 cell lines. Cell numbers decreased (P<0.05) by up to 61 and 58% following the incubation of MCF-7 and SW480 cells, respectively, for 4 d with milk fats (yielding CLA concentrations between 60.2 and 80.6 microM). The FFR milk fat, containing the highest CLA content, increased (P<0.05) [14C]arachidonic acid (AA) uptake into the monoacylglycerol fraction of MCF-7 and SW480 cells while it decreased (P<0.05) uptake into the phospholipid fraction of the latter. This milk fat also decreased (P<0.05) [14C]AA conversion to prostaglandin (PG) E2 while increasing conversion to PGF2alpha in both cell lines. All milk-fat samples increased (P<0.05) lipid peroxidation as measured by 8-epi-PGF2alpha in both cell lines. In SW480 cells the milk-fat samples decreased (P<0.05) bcl-2 and cytosolic glutathione levels while increasing (P<0.05) membrane-associated annexin V levels. All milk-fat samples decreased (P<0.05) the expression of ras in SW480 cells. These data suggest that milk-fat CLA was effective at modulating synthetic CLA-responsive biomarkers.
Subject(s)
Dietary Fats/metabolism , Dinoprost/analogs & derivatives , Linoleic Acids, Conjugated/metabolism , Milk/metabolism , Animals , Annexin A5/analysis , Apoptosis/physiology , Arachidonic Acid/metabolism , Biomarkers , Cell Count , Cell Division/physiology , Cell Line, Tumor , Dinoprost/biosynthesis , Eicosanoids/metabolism , Gene Expression/genetics , Genes, bcl-2/genetics , Genes, ras/genetics , Glutathione/analysis , Humans , Lipid Peroxidation/physiologyABSTRACT
The aims of this study were to determine whether vaccenic acid (VA; t11-18:1) is converted to c9,t11-CLA in human mammary (MCF-7) and colon (SW480) cancer cell lines and whether VA influences cell viability and other CLA-bioresponsive markers. When cells were incubated in the presence of VA at concentrations of 5 to 20 microg/mL, both VA and c9,t11-CLA increased in cellular lipids in a dose-dependent manner. After 4 d of incubation of SW480 and MCF-7 cells with VA (20 microg/mL), c9,t11-CLA increased from undetectable levels to 8.57 and 12.14 g/100 g FAME in cellular lipids, respectively. VA supplementation for 4 d at 5, 10, and 15 microg/mL had no effect on cell growth, whereas 20 microg/mL significantly (P < 0.05) reduced cell growth in both cell lines. VA (20 microg/mL) treatment induced DNA fragmentation and significantly (P < 0.05) depleted cytosolic GSH levels in the SW480 cell line after 4 d of incubation, suggesting that apoptosis was the mode of cell death induced by VA. Both VA and c9,t11-CLA reduced (P < 0.05) total ras expression in SW480 cells. 14C-Arachidonic acid uptake into the MG fraction was significantly increased (P < 0.05) in both cell lines while uptake into the phospholipid fraction decreased in response to VA. VA treatment significantly (P < 0.05) increased 8-epi-prostaglandin F2alpha in both cell lines. The data indicate that growth suppression and cellular responses of both cells lines are likely mediated by VA desaturation to c9,t11-CLA via delta9-desaturase.
Subject(s)
Fatty Acids/analysis , Linoleic Acids, Conjugated/metabolism , Oleic Acids/metabolism , Apoptosis/drug effects , Arachidonic Acid/metabolism , Biotransformation , Carbon Radioisotopes , Cell Line, Tumor , Chromatography, Thin Layer , Glycerides/metabolism , Humans , Linoleic Acids, Conjugated/chemistry , Oleic Acids/chemistry , Oleic Acids/pharmacology , Phospholipids/metabolism , Prostaglandins/metabolismABSTRACT
Dietary conjugated linoleic acid (CLA) has been shown to reduce colon tumor incidence in rodents by mechanisms probably involving apoptosis. The aim of this study was to evaluate the effects of three commercial CLA preparations (pure c9, t11-CLA, pure t10, c12-CLA and a CLA mixture, containing 29.5% c9, t11 and 29% t10, c12-CLA) on caspase-dependent apoptosis in colon SW480 tumor cells. After 4 days incubation, all CLA-treated cells displayed an increase in caspase 3 (27-34%) and caspase 9 activities (37-47%), cleavage of pro-caspase 3 (32 kDa) to 17 and 12 kDa subunits, increased membrane annexin V levels and reduced expression of bcl-2 compared with untreated controls. Cytosolic cytochrome c was increased (p < 0.05) by all CLA preparations, with the t10, c12-CLA isomer being the most potent. The data indicate that t10, c12-CLA may be the more biologically active isomer for inhibition of colon tumor cell proliferation in vitro.
