Effect of dietary cholesterol on gene expression in the liver of apoE-KO mice. Mus musculus

Apolipoprotein E-knock out (apoE-KO) mouse is known as a model animal for atherosclerosis accompanied by spontaneous hypercholesterolemia. When apoE-KO mice were fed a chow supplemented with 1.25% cholesterol (high-Chol diet), cholesterol and bile acids were highly increased in the liver within a week. However, the amount of triacylglycerol (TG) in very low-density lipoprotein (VLDL), but not in the liver, was reduced by 78%. The epididymal adipose tissue was almost diminished in the long term. Cholesterol metabolism is tightly regulated by both cholesterol and its metabolites in the mammalian liver, but the regulatory mechanism of TG synthesis remains to be elucidated. To evaluate the impact of high-Chol diet for 1 week on gene expression in the liver of apoE-KO mice, DNA microarray analysis was performed with comparison to apoE-KO mice fed a normal chow. We found that mRNA expression related to lipid metabolism was suppressed by the high-Chol diet in the liver of apoE-KO mice, which includes beta-oxidation and glycerol-3-phosphate (G3P) pathway for TG synthesis. In particular, the mRNA and protein expression of lipin-1 and lipin-2 was markedly decreased. PGC-1α, which up-regulates the transcription of lipin-1, was also suppressed. Lipin is reported to function as a coactivator of PGC-1α and is an inducible amplifier of PPARα, indicating that the suppression of genes involved in beta-oxidation could be induced by suppression of the lipins. These data using apoE-KO mice indicate that cholesterol and its metabolites are involved in regulating TG metabolism through a suppression of lipin-1 and lipin-2 in the liver. This research provides evidence for the mechanism of lipin expression in the liver. Overall design: Apo E-KO mice at 10 weeks of age were fed normal chow (control) or high-Chol diet containing 1.25% cholesterol for 1 week. Three independent experiments were performed at each diet.