Livers were dissected from 18 mice after 21 weeks of diet intervention. Based in liver histology, mice were divided in 4 groups. Liver RNA samples from all mice were used for microarray analysis.
Growth protocol
Eight week old male wildtype C57Bl/6 mice were fed LFD (D12450B, Research Diets Inc.) for 3 weeks. Thereafter, mice were either kept on LFD for 21 weeks or put on HFD (D12451, research Diets Inc.) for 21 weeks. Lard in the HFD was replaced by palm oil. Mice were divided into 4 groups based on liver histology. LF-low (LFL) responders displaying normal liver morphology, LF-high (LFH) responders showing benign hepatic steatosis, HF-low (HFL) responders displaying pre-NASH with macrovesicular lipid droplets, and HF-high (HFH) responders exhibiting overt NASH characterized by ballooning of hepatocytes, presence of Mallory bodies, and activated inflammatory cells.
Extracted molecule
total RNA
Extraction protocol
Total RNA was prepared from mouse livers using TRIzol reagent, followed by purification of total RNA using Qiagen RNEasy columns. RNA integrity was checked on chip analysis (Agilent 2100 bioanalyzer, Agilent Technologies, Amsterdam, the Netherlands) according to the manufacturer's instructions. RNA was judged as suitable for array hybridization only if samples exhibited intact bands corresponding to the 18S and 28S ribosomal RNA subunits, and displayed no chromosomal peaks or RNA degradation products (RNA Integrity Number > 8.0).
Label
biotin
Label protocol
The Affymetrix GeneChip RNA One cycle Amplification Kit was used to prepare labelled cRNA from 5 μg of total RNA. The protocol was conducted using the reagents provided by Affymetrix in the One-Cycle cDNA synthesis kit (P/N 900431), One-Cycle IVT labelling kit (P/N 90449) and GeneChip Sample Cleanup Module (P/N 900371). A detailed description can be found in the Genechip Expression Analysis Technical Manual, section 2 (Eukaryotic Sample and Array Processing), chapter 1 (Eukaryotic Target Preparation) (P/N 701025, revision 6).
Hybridization protocol
Hybridisation of 10ug cRNA was done overnight for 16 hours at 45ºC in a Hybridisation Oven 640 (Affymetrix). The protocol is conducted as described in the Genechip Expression Analysis Technical Manual, section 2 (Eukaryotic Sample and Array Processing), chapter 2 (Eukaryotic Target Hybridization) (P/N 701027, revision 5).
Scan protocol
Arrays were scanned on an Affymetrix 3000 7G scanner, as described in the Genechip Expression Analysis Technical Manual, section 2 (Eukaryotic Sample and Array Processing), chapter 2 (Eukaryotic Arrays: Washing, Staining and Scanning (P/N 701028, revision 5).
Data processing
Expression estimates were calculated using GCRMA (v2.2.0) in Bioconductor, applying the emperical Bayes (EB) model for background estimation.
