Abstract
Nonalcoholic steatohepatitis (NASH) is strongly associated with obesity and type 2 diabetes. The molecular factors underlying the development of inflammation and severe fibrosis in NASH remain largely unknown. The purpose of this study was to identify gene expression patterns related to obesity-related NASH inflammation and fibrosis. We performed sequencing-based mRNA profiling analysis of liver samples from individuals with normal histology (n = 24), lobular inflammation (n = 53), or bridging fibrosis, incomplete cirrhosis, or cirrhosis (n = 65). Hepatic expression of a subset of mRNAs was validated using an orthogonal method, analyzed in a hepatic stellate cell line, and used to identify transcriptional patterns shared by other forms of cirrhosis. We observed evidence for differential levels of 3820 and 2980 transcripts in lobular inflammation and advanced fibrosis, respectively, compared with normal histology (false discovery rate ≤0.05), including 176 genes specific to fibrosis. Functional enrichment analysis of these genes revealed participation in pathways involving cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, focal adhesion, and extracellular matrix-receptor interaction. We identified 34 differentially expressed transcripts in comparisons of lobular inflammation and fibrosis, a proportion of which were also upregulated during activation of hepatic stellate cells. A set of 16 genes from a previous independent study of NASH bridging fibrosis/cirrhosis were replicated, several of which have also been associated with advanced fibrosis/cirrhosis due to hepatitis viruses or alcohol in human patients. Dysregulated mRNA expression is associated with inflammation and fibrosis in NASH. Advanced NASH fibrosis is characterized by distinct set of molecular changes that are shared with other causes of cirrhosis.