Individual trans Monounsaturated Fatty Acids Have Distinct Effects on Lipogenesis in 3T3-L1 Adipocytes
The objective of this research was to determine the isomer specific effects of trans 18:1 isomers on lipogenic gene expression and fatty acid composition in adipocytes. Differentiated 3T3-L1 adipocytes were treated with 200 µM of either trans-9 18:1, trans-11 18:1, trans-13 18:1, or cis-9 18:1 (control) for 120 h. Cells were then analyzed for changes in gene expression and fatty acid composition using real-time PCR and gas liquid chromatography respectively. The experiment was repeated three times and data were analyzed using the MIXED Procedure of SAS. The trans-9 18:1 treatment increased the expression of acetyl-CoA carboxylase (1.6 fold, P = 0.08), fatty acid synthase (1.5 fold, P = 0.03) and stearoyl-CoA desaturase-1 (1.7 fold, P = 0.03) compared to the control, whereas trans-11 18:1 and trans-13 18:1 did not affect (P > 0.10) the expression of these genes. Consistent with the gene expression results, the content of cis-9 16:1(P = 0.01; SEM = 8.63), total monounsaturated fatty acids (P = 0.002; SEM = 31.5) and total fatty acids (P = 0.04; SEM = 41.7 ) were higher in trans-9 18:1 (191, 986 and 1502 µg/well respectively) compared with cis-9 18:1 (144, 783 and 1272 µg/well respectively), trans-11 18:1 (141, 716 and 1370 µg/well respectively) or trans-13 18:1 (128, 659 and 1349 µg/well respectively ). The trans-9 18:1 treatment also increased the cis-9 16:1/16:0 ratio (P < 0.01; SEM = 0.016) compared to the cis-9 18:1, trans-11 18:1 or trans-13 18:1 treatments (0.61, 0.52, 0.41 and 0.42 respectively). The amount of treatment fatty acid deposited in cells was highest (P = 0.01; SEM = 31.5) for trans-9 18:1 (585 µg/well) followed by cis-9 18:1 (493 µg/well), trans-11 18:1 (382 µg/well) and trans-13 18:1 (339 µg/well). About 32% of trans-13 18:1 was desaturated to cis-9, trans-13 18:2, whereas 19% of trans-11 18:1 was desaturated to cis-9, trans-11 18:2. Our results suggest that trans-9 18:1, the most abundant industrial trans fatty acid, is more lipogenic than trans-11 18:1 or trans-13 18:1. We also found that trans-13 18:1 is used as a preferred substrate for delta-9 desaturation. Our results demonstrate that trans-13 18:1, the second most abundant trans-18:1 isomer in beef when feeding forage based diets, is metabolized differently and may have differing bioactivity than major industrially produced trans fatty acids. Consequently, potential bioactivities of trans-13 18:1 and its delta-9 desaturation product deserve further investigation.
adipocytes, mouse, trans monounsaturated fatty acids