Conjugated linoleic acids and inflammation: isomer- and tissue-specific responses

Abstract

Conjugated linoleic acids (CLAs) are a series of geometric and positional isomers of linoleic acid that have been studied for their effects against diabetes, cancer and atherosclerosis, all conditions with an inflammatory component. Despite the continued interest in CLA, there are many controversies surrounding the health benefits of these fatty acids owing to isomer- and tissue-specific responses. Dietary CLA, found mainly in dairy products and ruminant meat, consists of mainly the 9cis(Z), 11trans(E) isomer, while dietary supplements consist of equal amounts of 9Z,11E- and 10E,12Z-CLA. Other CLA isomers exist, and there is increasing realization that modest alterations in fatty acid structure have profound effects on the biological response observed. In this article, the effects of CLA on inflammation will be discussed with an emphasis on the mechanisms of action and the isomer-specific effects. The primary focus is the macrophage, a classical mediator of inflammatory responses that impact atherogenesis, as well as adipocytes, cells with inflammatory capacity that influence metabolism in distant tissues. These cell types highlight the dramatically different inflammatory responses to specific isomers of CLA. By understanding the effects of the individual CLA isomers on specific cell types, in particular, the dichotomous effects of 10E,12Z-CLA in the macrophage and adipocyte, health claims for the dietary consumption or supplementation of CLA may be more adequately evaluated.

Keywords:

• adipogenesis
• atherogenesis
• conjugated linoleic acid
• eicosanoid
• endoplasmic reticulum stress
• fatty acid metabolism
• inflammation
• lipid raft
• PGF_2α
• transcription