Hepatic gene expression profile characterizes high levels of liver regeneration related genes in nonalcoholic fatty liver disease

Abstract

Nonalcoholic fatty liver disease (NAFLD) is a chronic hepatic disease caused by abnormal or excessive accumulation of fat in hepatocytes. NAFLD covers a spectrum of liver disorders ranging from simple steatosis (S) to nonalcoholic steatohepatitis (NASH) and cirrhosis, and is associated with changes in gene expression profiles. Tissue gene expression profiling has been precious for developing diagnostic and predictive biomarkers as well as for improving therapeutical strategies in many diseases. Therefore, the aim of this study was to use microarray analysis to characterize a liver gene expression profile that differentiates individuals diagnosed with steatosis or steatohepatitis. The discovery cohort (n = 22) including well-characterized human liver samples, categorized as normal (n = 7), steatosis (n = 7), and nonalcoholic steatohepatitis (n = 8), was analyzed by Affymetrix GeneChip and qRT-PCR. A gene set enrichment analysis was performed to identify processes that distinguish between steatosis/NASH and normal groups and hence, might be novel biomarkers or treatment targets. Among 1624 genes, Gene Ontology (GO) analysis identified six genes, involved in tissue repair/regeneration, which were differentially expressed and significantly upregulated in patients with NASH. This subset of the top-regulated liver regeneration-related genes includes amphiregulin (AREG), plasminogen activator receptor urokinase-type (PLAUR), thrombospondin 1 (THBS1), chemokine CC ligand 20 (CCL20), aldo-keto reductase family 1 member B10 (AKR1B10) and interleukin 32 (IL-32). These findings were validated in a second, independent and large cohort (n = 112) and confirmed by quantitative real-time PCR (qRT-PCR). Patients with NASH (n = 43) had significantly higher levels of AREG, PLAUR, THBS1, CCL20, AKR1B10 and IL-32 expression compared to steatotic (n = 37) and/or normal (n = 32) liver tissue. Subsequently, in this study we aim to correlate the mRNA expression of these genes with steatosis grade, NASH activity score, fibrosis, adipositas, BMI, Diabetes Mellitus and hypercholesterolemia.