A diet rich in coconut oil decreases the expression of retinoic acid and triiodothyronine nuclear receptors in rat liver

A considerable part of the total energy consumed by western populations is accounted for by lipids and particularly by lipids containing saturated fatty acids. A high level of dietary fat induces a lipid status characterized by a changing fatty acid profil which, in turn, could affect several hormonal actions. Thus, the aim of this study was to explore the effect of a high fat diet rich in saturated fatty acids on the expression of nuclear receptors of retinoic acid (RAR) and triiodothyronine (TR) in rat liver. This expression was mainly evaluated as binding properties of RAR and TR (evaluated by an isotopic displacement analysis), and quantitation of mRNAs of these receptors (using a semi-quantitative RT-PCR method). Following seven weeks of a diet containing 30% coconut oil and 5% olive oil, the maximum binding capacity of RAR and TR was decreased by 36% and 23%, respectively (the apparent affinity of the receptors was not affected). The abundance of mRNAs of these receptors was also lowered (by approximately 37-40%), suggesting that the decreased number of receptors results from a mechanism occuring, at least in part, at a transcriptional level. (C) 1998 Elsevier Science Inc.