High-fat diets affect the expression of nuclear retinoic acid receptor in rat liver

The purpose of this study was to differentiate between the effects of the a mount and the type of dietary lipids on the expression of the retinoic acid receptor (RAR), but also the peroxisome proliferator-activated receptor (P PAR) and the receptor of the 9-cis retinoic acid (retinoid X receptor (RXR) ) in rat liver. Six groups of eight rats (5-weeks old) were fed during 4 we eks on the following diets: control 50 g vegetable oil/kg, high-fat diet 25 0 g vegetable oil/kg. These oils were either coconut oil (rich in saturated fatty acids) or olive oil (rich in monounsaturated fatty acids) or safflow er oil (rich in polyunsaturated fatty acids, mainly as n-6). The three high -fat diets induced a significant decrease of the maximal binding capacity o f RAR and of the abundance of RAR beta mRNA. Simultaneously, an increased e xpression of PPAR alpha mRNA was observed while no significant difference o n abundance of RXR alpha mRNA was observed. The mechanisms involved are pro bably multiple, but one hypothesis is that a modification of the equilibriu m between the nuclear receptors, resulting from an increased expression of PPAR, induces a decreased expression of RAR in rat liver.