Basic Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jan 21, 2018; 24(3): 323-337
Published online Jan 21, 2018. doi: 10.3748/wjg.v24.i3.323
circRNA_0046366 inhibits hepatocellular steatosis by normalization of PPAR signaling
Xing-Ya Guo, Fang Sun, Jian-Neng Chen, Yu-Qin Wang, Qin Pan, Jian-Gao Fan
Xing-Ya Guo, Fang Sun, Yu-Qin Wang, Qin Pan, Jian-Gao Fan, Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China
Jian-Neng Chen, Department of Hepatology, Zhengxing Hospital, Zhangzhou 363000, Fujian Province, China
Jian-Gao Fan, Shanghai Key Laboratory of Children’s Digestion and Nutrition, Shanghai 200092, China
Author contributions: Pan Q and Fan JG should be as the co-corresponding authors; Guo XY, Sun F and Chen JN contributed equally to this paper; Pan Q and Fan JG conceived and designed the experiments; Guo XY and Sun F performed the experiments; Chen JN, Wang YQ and Pan Q analyzed the data; Pan Q wrote the paper.
Supported by National Key Research and Development Plan ‘Precision Medicine Research’, No. 2017YFSF090203; National Natural Science Foundation of China, No. 81070346, No. 81270492, No. 81470859, No. 81270491 and No. 81470840; State Key Development Program for Basic Research of China, No. 2012CB517501; 100 Talents Program, No. XBR2011007h; and Program of the Committee of Science and Technology, No. 09140903500.
Institutional review board statement: This paper was approved by the Xinhua Hospital Ethics Committee Affiliated to Shanghai Jiaotong University School of Medicine.
Conflict-of-interest statement: No conflict of interest is declared for each author of the manuscript.
Data sharing statement: Technical appendix, statistical code, and dataset available from the authors at fanjiangao@xinhuamed.com.cn or panqin@xinhuamed.com.cn. Participants gave informed consent for data sharing.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Qin Pan, MD, PhD, Professor, Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Kongjiang Road NO 1665, Yangpu District, Shanghai 200092, China. panqin@xinhuamed.com.cn
Telephone: +86-21-25078999 Fax: +86-21-25077340
Received: October 7, 2017
Peer-review started: October 9, 2017
First decision: October 25, 2017
Revised: November 15, 2017
Accepted: November 27, 2017
Article in press: November 27, 2017
Published online: January 21, 2018
Processing time: 104 Days and 2.5 Hours
ARTICLE HIGHLIGHTS
Research background

Hepatic steatosis reflects one of the most common chronic liver diseases with hepatocyte-specific lipid dysmetabolism and triglyceride (TG) accumulation. Its close association to steatohepatitis, metabolic syndrome, and extrahepatic diseases (i.e., cardiovascular events, cerebrovascular diseases, cancers) indicates an importance for clinical interference. Micro (mi)R-34a is now confirmed to underlie the hepatic steatosis. However, the ambiguity in miR-34a-specific antagonist keeps hepatic steatosis from effective therapy. Circular (circ)RNA has recently been determined to interact with miRNA, mainly on the basis of complementation between miRNA response element (MRE) of circRNA and ‘seed sequence’ of miRNA. This circRNA/miRNA interaction abolishes the inhibitory effect of miRNA on its targets. circRNA, therefore, is highlighted to function in a miRNA-antagonizing manner.

Research motivation

Because of its importance in hepatic steatosis, miR-34a represents a critical target of clinical intervention. miR-34a-targeting antagonist, therefore, is assessed in our experiments so as to cure hepatosteatotic degeneration on the basis of miR-34a inactivation.

Research objectives

Serving as the selective sponge of miRNA, circRNA is exposed to bioinformatical and functional analysis for a purpose of uncovering the antagonist specific to miR-34a.

Research methods

To shed light on the antagonistic effect of circRNA against miR-34a, investigation of miR-34a-targeting circRNA was carried out by MRE recognization and dual-luciferase reporter assay. The filtered circRNA was then subjected to functional study in HepG2-based experimental steatosis induced high-fat stimulation. In detail, rescue experiment, real-time quantitative PCR, and western blot demonstrated the impact of circRNA on miR-34a, peroxisome proliferator-activated receptor (PPAR)α, and transcriptional downstream genes. Both triglyceride (TG) quantification and cytopathologic assessment revealed the steatosis-related outcome of circRNA administration.

Research results

circRNA_0046366 loss reflects the epigenetic characteristics of high fat-induced hepatocellular steatosis. Both bioinformatical and functional proofs indicate a circRNA_0046366-dependent miR-34a inactivation by the complementary antagonism. Dramatically, circRNA_0046366 up-regulation abolishes the inhibitory effect of miR-34a on PPARα. PPARα restoration further promotes the transcriptional activity of downstream genes, which improves the steatosis-related TG metabolism. In conclusion, the circRNA_0046366 administration leads to a significant attenuation of TG accumulation, and finally alleviates the hepatosteatotic phenotype with decreased cytoplasmic lipid droplets.

Research conclusions

The present study identifies great importance of circRNA_0046366/miR-34a/PPARα signaling in hepatocellular steatosis. circRNA_0046366 may act as a potential agent in the clinical interference of hepatic steatosis.

Research perspectives

The role of circRNA_0046366 in hepatocellular steatosis qualifies it for further evaluation in experimental hepatic steatosis with different etiologies (i.e., high-fat high-cholesterol diet, high-fat high-fructose diet, methionine and choline-deficient diet). These results could provide substantial evidence for circRNA_0046366-related prevention and therapy of hepatic steatosis.