Differentially expressed genes in mouse liver during development of fatty liver disease (FLD)

Abstract

FLD is considered as the hepatic manifestation of the metabolic syndrome but still poorly understood at the molecular level. To study differentially expressed genes during development of FDL in C57BL/6 mice upon challenge with a high fat diet for 1 and 5 weeks, respectively. Hepatic gene expression was determined in livers from 3 groups of four male mice. Total liver RNA was isolated, reverse transcribed and labelled with Cy5- or Cy3-dUTP, respectively. Labeled probes were hybridized to the same microarray spotted with more than 17,000 oligonucleotides. Slides were scanned with a GENE PIX 4000B array scanner and signals of fluorescence-tagged cDNA spots were quantitated. Genes were considered to be expressed differentially if there was a greater than 1.5-fold difference in abundance of mRNA when compared with controls. Following one and five weeks on the high fat diet, liver weight increased by 22% (p<0.05) and 76% (p<0.005), respectively and liver specimens demonstrated an increasing number of fatty vacuoles with an inflammatory infiltrate after 5 weeks. Following 1 week of the high fat diet, 51 genes were differentially expressed (47 overexpressed) whereas at 5 weeks the number of differentially genes decreased to 19 (13 overexpressed). Highly overexpressed genes included Septin 2 (Sept2), Zinc finger protein 239 (Zfp239), Nerve growth factor beta (Ngfb), Ankyrin repeat domain 6 (Ankrd6), proprotein convertase subtilisin/kexin type 2 (Pcsk2), all of which are important for cell growth and differentiation. In addition activation of the immune response was noted by overexpression of small inducible cytokine A3 (Scya3), Interleukin 10 (IL10) and Linker of T-cell receptor pathways (Lnk). Interestingly, stearoyl-CoA desaturase 1 (Scd1), a rate-limiting enzyme in the synthetic pathway of unsaturated fatty acids was overexpressed, too. Genes with a significant down-regulation included Opsin (Opn3), Major urinary protein 3 (Mup3) and 4 (Mup4) both of which are members of the lipocalin family, Forkhead box P2 (Foxp2) and Cytidine 5'-triphosphate synthase (Ctps). In conclusion, our study provides a framework to identify genes with relevance for the development of FLD.