Abstract
Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases worldwide with an unclear mechanism. Long non-coding RNAs (lncRNAs) have recently emerged as important regulatory molecules. To better understand NAFLD pathogenesis, lncRNA and messenger RNA (mRNA) microarrays were conducted in an NAFLD rodent model. Potential target genes of significantly changed lncRNA were predicted using cis/trans-regulatory algorithms. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were then performed to explore their function. In the current analysis, 89 upregulated and 177 downregulated mRNAs were identified, together with 291 deregulated lncRNAs. Bioinformatic analysis of these RNAs has categorized these RNAs into pathways including arachidonic acid metabolism, circadian rhythm, linoleic acid metabolism, peroxisome proliferator-activated receptor (PPAR) signaling pathway, sphingolipid metabolism, steroid biosynthesis, tryptophan metabolism and tyrosine metabolism were compromised. Quantitative polymerase chain reaction (qPCR) of representative nine mRNAs and eight lncRNAs (named fatty liver-related lncRNA, FLRL) was conducted and this verified previous microarray results. Several lncRNAs, such as FLRL1, FLRL6 and FLRL2 demonstrated to be involved in circadian rhythm targeting period circadian clock 3 (Per3), Per2 and aryl hydrocarbon receptor nuclear translocator-like (Arntl), respectively. While FLRL8, FLRL3 and FLRL7 showed a potential role in PPAR signaling pathway through interaction with fatty acid binding protein 5 (Fabp5), lipoprotein lipase (Lpl) and fatty acid desaturase 2 (Fads2). Functional experiments showed that interfering of lncRNA FLRL2 expression affected the expression of predicted target, circadian rhythm gene Arntl. Moreover, both FLRL2 and Arntl were downregulated in the NAFLD cellular model. The current study identified lncRNA and corresponding mRNA in NAFLD, providing new insight into the pathogenesis of NAFLD. Moreover, we identified a new lncRNA FLRL2, that might participate NAFLD pathogenesis mediated by Arntl.
Highlights
Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases worldwide, affecting approximately 20% of the general population and up to about 70% in patients with type 2 diabetes [1]
It is widely accepted that NAFLD consists of four histological stages, namely simple steatosis, non-alcoholic steatohepatitis (NASH), fibrosis and cirrhosis [2]
Simple steatosis is recognized as benign liver disease with slow exacerbation over decades, whereas NASH may progress into cirrhosis and even hepatocellular carcinoma in a short period of time [3]
Summary
Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases worldwide, affecting approximately 20% of the general population and up to about 70% in patients with type 2 diabetes [1]. It is widely accepted that NAFLD consists of four histological stages, namely simple steatosis, non-alcoholic steatohepatitis (NASH), fibrosis and cirrhosis [2]. Simple steatosis is recognized as benign liver disease with slow exacerbation over decades, whereas NASH may progress into cirrhosis and even hepatocellular carcinoma in a short period of time [3]. The first hit results from insulin resistant accompanied by fat accumulation and on this basis, oxidative stress induces varied inflammatory cytokines (tumor necrosis factor-α (TNF-α), interleukin (IL) 1, IL-6, etc.) as well as adipokines (leptin, adiponectin and resistin), resulting in hepatic inflammation and hepatocyte injury, known as the second hit. Medical intervention is necessary, such as insulin sensitizer, lipid lowering agents, and antioxidants, which incur a prolonged high cost [5]
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