Major role of soybean oil in preventing decrease in CYP4A1 mRNA content relative to PPARα mRNA down-regulation in infant rats

Changes in the levels of CYP4A1, PPAR alpha, and RXR alpha mRNA expression in the liver following overdose of fat-free or fat-containing total parenteral nutrition (TPN) were studied in 3-week-old male Sprague-Dawley rats. The rats were divided into three groups: group 1, oral diet; group 2, fat-free TPN; and group 3, TPN with 20% of calories from soybean oil emulsion. Levels of CYN4A1, PPAR alpha and RXR alpha mRNA in the fat-free TPN group were significantly lower than those in the other groups. Levels of CYP4A1 and PPAR alpha mRNA were strongly correlated (r=0.849), and levels of CYP4A1 and RXR alpha mRNA were weakly correlated (r=0.618). This is the first report of a strong correlation between the levels of CYP4A1 and PPAR alpha mRNA following overdose of fat-free or fat-containing TPN in infant rats. Our results also indicate that it is important to include fat in TPN regimens in order to prevent CYP4A1 mRNA down-regulation, which may be related to changes in PPAR alpha mRNA levels in the liver.