Inhibitory effect of conjugated linoleic acid on linoleic acid elongation in transformed yeast with human elongase.

Conjugated linoleic acid (CLA; 18:2) refers to a group of positional and geometric isomers derived from linoleic acid (LA; delta9,12-18:2). Using a growing baker's yeast (Saccharomyces cerevisiae) transformed with human elongase gene, we examined the inhibitory effect of CLA at various concentrations (10, 25, 50, and 100 microM) on elongation of LA (25 microM) to eicosadienoic acid (EDA; delta11,14-20:2). Among four available individual CLA isomers, only c9,t11- and t10,c12-isomers inhibited elongation of LA to EDA. The extent of inhibition (ranging from 20 to 60%) was related to the concentration of CLA added to the medium. In the meantime, only these two isomers, when added at 50 microM to the media, were elongated to conjugated FDA (c11,t13- and t12,c14-20:2) by the same recombinant elongase at the rate of 28 and 24%, respectively. The inhibitory effect of CLA on LA elongation is possibly due to competition between CLA isomers and LA for the recombinant elongase. Thus, results from this study and a previous study suggest that the biological effect of CLA is exerted through its inhibitory effect on delta6-desaturation as well as elongation of LA which results in a decrease in long-chain n-6 fatty acids and consequently the eicosanoid synthesis.