MicroRNA expression profile in non-alcoholic fatty liver disease

Simple steatosis (SS) and non-alcoholic steatohepatitis (NASH) are subtypes of non-alcoholic fatty liver disease. The difference in pathogenesis between SS and NASH is still not clear. MicroRNAs (miRNAs) are endogenous, non-coding short RNAs that regulate gene expression. The aim of this study was to examine the relationship of miRNA expression profiles with SS and NASH in animal models and humans. Animal models DD Shionogi (DS), Fatty Liver Shionogi (FLS Wild; W), and FLS ob/ob mice were subjected as the normal control, SS model and NASH model, respectively. Male DS mice (Riken BRC No. 03706) were provided by Riken bio-resource center through the national bio-resource project of Japan. Male FLS W and male FLS-ob/ob mice were obtained from Shionogi research laboratories (Shiga, Japan). Animals were housed in a room maintained at a controlled temperature of 24 ± 2 ˚C under a 12-h light-dark cycle. Animals were provided ad libitum access to water and standard pellet feed. Five male mice of every strain (24 weeks old; mean body weight of DS, FLS W and FLS-ob/ob were 31.1 ± 1.1g, 38.4 ± 3.4g and 56.0 ± 5.0g, respectively) were sacrificed under pentobarbital anesthesia by whole blood collection from the right ventricle. The livers were cut into about 200 mg pieces and fixed in 10% formalin for histological analysis or fresh-frozen in liquid nitrogen and stored at -80 °C in a freezer until use. miRNA expression analysis Total RNAs in mouse liver were isolated using TrizolReagent (Life Technologies, California, USA) as described the manufacturer’s protocol. The quality of total RNA samples was checked by applying the RNA Integrity Number (RIN) which is calculated by a proprietary algorithm of the Agilent 2100 Bioanalyzer expert software (Agilent technologies, CA, USA). Only high quality RNA, with RNA integrity number (RIN) greater than 8 and A260/280 and A260/230 greater than 1.8, will be considered for microarray analysis. TaqMan® Array Rodent MicroRNA A Card v2.0 (Thermo Fisher Scientific, MA, USA) was used to assess 375 miRNA expression profiles in mouse liver tissue.