Biological activities of conjugated fatty acids: conjugated eicosadienoic (conj. 20:2Δc11,t13/t12,c14), eicosatrienoic (conj. 20:3Δc8,t12,c14), and heneicosadienoic (conj. 21:2Δc12,t14/c13,t15) acids and other metabolites of conjugated linoleic acid

The elongated form of conjugated linoleic acid (CLA), conjugated eicosadienoic acid (CEA, conj. 20:2Δc11,t13/t12,c14), was generated from CLA by liver microsomal fractions. Subsequent testing showed that dietary CEA significantly reduced body fat, and increased lean mass similar to CLA when compared to controls. CEA also decreased lipoprotein lipase activity and triacylglyceride, and increased glycerol release in 3T3-L1 adipocytes, correlated with the trans-12,cis-14 isomer, but CEA required a longer incubation period than cells treated with CLA. Based on the fact that CEA fed animals had CLA in tissue, we suggest that the effect of CEA is due to the CLA converted from CEA in the system. The delta-6 desaturated and elongated form of trans-10,cis-12 CLA (conjugated eicosatrienoic acid, CETA, conj. 20:3Δc8,t12,c14) inhibited LPL activity and increased glycerol release but was less active than trans-10,cis-12 CLA or CEA. The 21-carbon conjugated fatty acid, conjugated heneicosadienoic acid (CHDA, conj. 21:2Δc12,t14/c13,t15), was not active on LPL inhibition, triacylglyceride, or glycerol release in 3T3-L1 adipocytes. We also provide evidence that CLA was metabolized to conjugated dodecadienoic acid (conj. 12:2Δc3,t5/t4,c6). In addition, there were indications of the presence of conjugated tetradecadienoic acid (conj. 14:2Δc5,t7/t6,c8), suggesting that CLA can be metabolized through fatty acid β-oxidation. This is the first work to report the presence of conjugated 12 and 14 carbon fatty acids, originated from CLA, and the biological activities of CEA, CETA and CHDA.