CLAs, nature, origin and some metabolic aspects

¹ Inra, Unité de nutrition lipidique, 17, rue Sully, BP 86510, 21065 Dijon Cedex
² Inra-Université d’Auvergne, Unité du métabolisme protéino-énergétique, Clermont-Ferrand

^* chardign@dijon.inra.fr

Abstract

CLA (conjugated linoleic acid) is a generic term for several isomers of linoleic acid with conjugated double bonds. They have been reported since 1935 in butter fat, but the major natural isomer (9cis,11trans-18 :2) was identified in 1977 and further named « rumenic acid ». This fatty acid is formed in the rumen as a product of biohydrogenation. Tissues may also produce rumenic acid from vaccenic acid, which is a further intermediate of ruminal biohydrogenation. Interest for CLAs started with a report on beneficial effects of CLA from grilled beef on skin tumours. CLA was produced as mixtures of isomers from chemically modified vegetable oil. As a metabolic point of view, it has been shown that rumenic acid is bioconverted like linoleic acid and beta-oxidised. CLA isomers may also interfere with the metabolism of other fatty acids. Other targets than skin tumours have also been identified. These aspects will be developed in other sections of the present issue.