Differential expressions of lipid metabolism related genes in the liver of young apoE knockout mice

The work was aimed to investigate the differential expressions of lipid metabolism related genes in the early stage of atherosclerosis in the young apolipoprotein E deficient (apoE-/-) mice at different ages with normal chow diet. The genotypes of mice were identified by using multiplex polymerase chain reaction (multi-PCR) analysis. The semi-quantitative reverse transcription- polymerase chain reaction (RT-PCR) and real-time quantitative RT-PCR were used to analyze the expressions of lipid metabolism related genes in the liver of apoE-/- and age-matched wild type (WT) mice of 14-day old, 1-month old, 2-month old, 3-month old. The serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) contents were assayed using COD-PAP and GPO-PAP methods. The serum apolipoprotein B100 (apoB100) content was quantitated by immune turbidimetry. The hearts were perfusion-fixed in 4% formaldehyde, infiltrated with 30% gum sucrose for 24 h at 4 oC, and embedded in OCT compound. The aortic sinus tissues were serially sectioned at -15 oC, stained with Sudan IV, and counterstained with light green. The results were shown as follows. Compared with that in WT mice, the mRNA levels of apoA I and apoA IV in apoE-/- mice aged from 14-day old to 3-month old changed prominently (P0.05), with apoA I up-regulated and apoA IV down-regulated. At the age of 1 month, the expression of apoB100 in apoE-/- mice was higher than that in WT mice (P0.05). The expression of apoA V was up-regulated (P0.05) and there was obvious lipid deposition in the aortic intima in apoE-/- mice at the ageof 2 months. The expressions of fatty acid translocase (Fat/CD36) and angiopoietin-like protein 3 (Angptl 3) in apoE-/- mice were higher than those in WT mice at the age of 3 months (P0.05), while the expressions of peroxisome proliferator-activated receptor α (PPARα), liver X receptor α (LXRα), carnitine palmitoyl transferase I (CPT I) and acyl coenzyme A oxidase 1 (ACOX1) showed no significant changes. The serum TC, TG, LDL-C and HDL-C contents in apoE-/- mice aged from 14-day old to 3-month old were higher than those in age-matched WT mice. apoE-/- mice showed a marked increase in serum apoB100 content, consistent with the trend of serum LDL-C content and apoB100 mRNA content in the liver. The results suggest that the mRNA expressions of apoA I, apoA IV, apoA V, apoB100 and Angptl 3 in apoE-/- mice change significantly compared with those in WT mice, and these genes might be relevant to the complicated lipid metabolism network, and involved in the early stage of atherogenesis.