Circular RNA Profiling and Bioinformatic Modeling Identify Its Regulatory Role in Hepatic Steatosis.

Qing Su,Xing-Ya Guo,Chong-Xin He,Guang-Ming Li,Yu-Qin Wang,Jian-Gao Fan,Chao Sun,Qin Pan

doi:10.1155/2017/5936171

Abstract

Circular RNAs (circRNAs) exhibit a wide range of physiological and pathological activities. To uncover their role in hepatic steatosis, we investigated the expression profile of circRNAs in HepG2-based hepatic steatosis induced by high-fat stimulation. Differentially expressed circRNAs were subjected to validation using QPCR and functional analyses using principal component analysis, hierarchical clustering, target prediction, gene ontology (GO), and pathway annotation, respectively. Bioinformatic integration established the circRNA-miRNA-mRNA regulatory network so as to identify the mechanisms underlying circRNAs' metabolic effect. Here we reported that hepatic steatosis was associated with a total of 357 circRNAs. Enrichment of transcription-related GOs, especially GO: 0006355, GO: 004589, GO: 0045944, GO: 0045892, and GO: 0000122, demonstrated their specific actions in transcriptional regulation. Lipin 1 (LPIN1) was recognized to mediate the transcriptional regulatory effect of circRNAs on metabolic pathways. circRNA-miRNA-mRNA network further identified the signaling cascade of circRNA_021412/miR-1972/LPIN1, which was characterized by decreased level of circRNA_021412 and miR-1972-based inhibition of LPIN1. LPIN1-induced downregulation of long chain acyl-CoA synthetases (ACSLs) expression finally resulted in the hepatosteatosis. These findings identify circRNAs to be important regulators of hepatic steatosis. Transcription-dependent modulation of metabolic pathways may underlie their effects, partially by the circRNA_021412/miR-1972/LPIN1 signaling.

Highlights

Hepatic steatosis reflects a pathological disorder characterized by excess triglyceride (TG) accumulation (≥5% of volume or weight) in the liver and demonstrates close association with obesity, type 2 diabetes, hyperlipidemia, and other components of metabolic syndrome with limited exceptions [1,2,3]
Mimicking high-fat diet that induces nonalcoholic fatty liver disease (NAFLD), HepG2 cells were administrated using the mixture of saturated and unsaturated fatty acids at a ratio of 1 : 2 [37]. Both the lipid droplets positive to Oil Red-O staining and the significant increase in TG content indicated the establishment of hepatic steatosis
Joint analysis of largescale profiling coupled with computational prediction represents a powerful approach to elucidate the possible biological roles of Circular RNA (circRNA)

Summary

Introduction

Hepatic steatosis reflects a pathological disorder characterized by excess triglyceride (TG) accumulation (≥5% of volume or weight) in the liver and demonstrates close association with obesity, type 2 diabetes, hyperlipidemia, and other components of metabolic syndrome with limited exceptions (i.e., alcohol abuse, chronic hepatitis C) [1,2,3]. High incidence of extrahepatic death and disability (i.e., cardiovascular events, cerebral apoplexy, and cancers) takes place in the population with hepatic steatosis [5,6,7]. For the sake of our limited understanding in its mechanisms, hepatic steatosis is still beyond the reach, to a large extent, of clinical interference. Circular RNA (circRNA), a class of noncoding RNAs with the linking of 3󸀠 and 5󸀠 ends, used to be regarded as the nonfunctional byproducts of mRNA splicing [12]. Characteristics of circRNA, including tissue- and development-specific expression, enrichment of miRNA response element (MRE), and resistance to both RNase R

Methods

Results

Conclusion