Uptake and metabolism of trans and conjugated fatty acids at the intestinal level : different pathways to produce c9t11 CLA

(eng) There is an increasing interest regarding the health effects of dietary fatty acids, which are indeed suspected to be either beneficial or harmful. Among them, a special focus has been put on the ω-3 or ω-6 fatty acids, on the saturated ones and also on conjugated or trans fatty acids (TFA). All are consumed by humans, in different amounts depending on the type of food and eating habits. All are absorbed by intestinal cells, distributed, processed and accumulated by various tissues. This work was focused on the metabolism of fatty acids owning conjugated and/or trans double bonds, i.e. TFA, conjugated linoleic acids (CLA) and conjugated linolenic acids (CLnA), which have all been reported to impact animal or human health. We have shown that C18:1 TFA isomers could be processed differently in intestinal cells and that c9t11 CLA, either directly added to cells or converted from trans-vaccenic acid (TVA), undergoes the same metabolic processing as the ω-3 or ω-6 C18 fatty acids. Caco-2 cells are also able to reduce some conjugated triene fatty acids such as -9,-11,-13 CLnA, present in high amounts in certain oils, into CLA containing the c9t11 or t9t11 structure. This could be an interesting approach to increase the CLA intake, which generally represent less than 1% of the total lipids of dairy products and are known to exert some beneficial health effects. Finally, we showed that the t11t13 CLA isomer might also be a source of c9t11 CLA. This work highlights that Caco-2 cells cultivated in serum-free conditions are able to absorb, accumulate and metabolize TFA, CLA and CLnA, sometimes very efficiently, and underlines that c9t11 CLA could be produced from different pathways and fatty acid precursors. We have indeed shown that Caco-2 cells are able to convert as well TVA as conjugated triene fatty acids like -9,-11,-13 CLnA or even another isomer of CLA such as t11t13 CLA into c9t11 CLA.