Bioactivity assessment of novel non-conjugated non-methylene interrupted dienoic acids isolated from beef fat
Citation
Vahmani, P., Meadus, W.J., Duff, P., Rolland, D.C. and Dugan, M.E.R. 2017 Bioactivity assessment of novel non-conjugated non-methylene interrupted dienoic acids isolated from beef fat. AOCS, April, Orlando.
Plain language summary
During ruminal biohydrogenation of α-linolenic acid, non-conjugated non-methylene interrupted dienoic acids are formed, namely trans(t)10,cis(c)15-18:2 and t11,c15-18:2. We have isolated these isomers from beef fat using a combination of silver ion solid phase extraction and high perfomance liquid chromatgraphy, and tested their effects on lipid metabolism in fat cells.
Fat cells were treated with t10,c15-18:2, t11,c15-18:2, t10,c12- conjugated linoleic acid (t10,c12-CLA; positive control), c9,c12-18:2 (linoleic acid; negative control) or bovine serum albumin control (BSA control). Treating cells with t10,c12-CLA substantially decreased triacylglycerol in fat cells. Trans10,cis12 also decreased expression of genes related to fatty acid synthesis, desaturation, elongation and uptake. Other fatty acid treatments did not affect the expression of any genes tested or cell triglyceride content. Culturing cells with t10,c15-18:2, t11,c15-18:2 resulted in detection of their novel chain shortening and elongation products. However, no desaturation of t10,c15-18:2 or t11,c15-18:2 was found.
Despite being a diene and having a t10 double bond, t10,c15-18:2 does not exert the same anti-adipogenic effects as t10,c12-CLA. Trans11,c15-18:2 is also likely not used for conjugated linolenic acid synthesis (c9,t11,c15-CLnA), the major conjugated linolenic acid isomers found in ruminant fats.
Abstract
During ruminal biohydrogenation of α-linolenic acid, non-conjugated non-methylene interrupted dienoic acids are formed, namely trans(t)10,cis(c)15-18:2 and t11,c15-18:2. We have isolated these isomers from beef fat using a combination of Ag+SPE and Ag+-HPLC, and sought to test their effects on lipid metabolism in in 3T3-L1 adipocytes.
Differentiated 3T3-L1 adipocytes were treated with 35µM or 70µM of t10,c15-18:2, t11,c15-18:2, t10,c12- conjugated linoleic acid (t10,c12-CLA; positive control), c9,c12-18:2 (linoleic acid; negative control) or bovine serum albumin control (BSA control). After a 5 day treatment period, cells were analyzed for fatty acid composition and gene expression using gas chromatography and quantitative PCR respectively. Cellular triacylglycerol and protein were quantified using commercial colorimetric kits. Treating cells with t10,c12-CLA substantially decreased (P < 0.05) adipocyte triacylglycerol (TAG) content which was mainly related to a reduction in 16:0, 15:0 and. c9-16:1 and c9-18:1. Trans10,cis12 also decreased (P < 0.05) the expression of genes related to fatty acid synthesis, Δ9desaturation, elongation and uptake. Other fatty acid treatments did not affect the expression of any genes tested or cell TAG and fatty acid content. Culturing cells with t10,c15-18:2, t11,c15-18:2 resulted in tentative detection of their novel chain shortening (t18,c13-16:2 and t9,c13-16:2), Δ6 desaturation (c6, t10,c15-18:2 and c6, t11,c15-18:2) and elongation products (c8,t12,c17-20:3 and c8,t13,c17-20:3 ). However, no Δ9 desaturation was found for t10,c15-18:2 or t11,c15-18:2.
Despite being a diene and having a t10 double bond, t10,c15-18:2 does not exert the same anti-adipogenic effects as t10,c12-CLA. Trans11,c15-18:2 is likely not the substrate for c9,t11,c15-conjugated linolenic acid (c9,t11,c15-CLnA), the major CLnA found in ruminant fats.