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
Abstract
AIM

To investigate micro (mi)R-34a-antagonizing circular (circ)RNA that underlies hepatocellular steatosis.

METHODS

The effect of circRNA on miR-34a was recognized by the miRNA response element (MRE), and validated by the dual-luciferase reporter assay. Its association with hepatocellular steatosis was investigated in HepG2-based hepatocellular steatosis induced by free fatty acids (FFAs; 2:1 oleate:palmitate) stimulation. After normalization of the steatosis-related circRNA by expression vector, analysis of miR-34a activity, peroxisome proliferator-activated receptor (PPAR)α level, and expression of downstream genes were carried out so as to reveal its impact on the miR-34a/PPARα regulatory system. Both triglyceride (TG) assessment and cytopathological manifestations uncovered the role of circRNA in miR-34a-dependent hepatosteatogenesis.

RESULTS

Bioinformatic and functional analysis verified circRNA_0046366 to antagonize the activity of miR-34a via MRE-based complementation. In contrast to its lowered level during FFA-induced hepatocellular steatosis, circRNA_0046366 up-regulation abolished the miR-34a-dependent inhibition of PPARα that played a critical role in metabolic signaling pathways. PPARα restoration exerted transcriptional improvement to multiple genes responsible for lipid metabolism. TG-specific lipolytic genes [carnitine palmitoyltransferase 1A (CPT1A) and solute-carrier family 27A (SLC27A)] among these showed significant increase in their expression levels. The circRNA_0046366-related rebalancing of lipid homeostasis led to dramatic reduction of TG content, and resulted in the ameliorated phenotype of hepatocellular steatosis.

CONCLUSION

Dysregulation of circRNA_0046366/miR-34a/PPARα signaling may be a novel epigenetic mechanism underlying hepatocellular steatosis. circRNA_0046366 serves as a potential target for the treatment of hepatic steatosis.

Keywords: Hepatocytes; Steatosis; circRNA_0046366; miR-34a; Peroxisome proliferator-activated receptor α

Core tip: circRNA_0046366, which demonstrated expression loss in HepG2-based hepatocellular steatosis, exerts antagonistic effect on miR-34a activity. miR-34a inactivation abrogates its inhibitory role against peroxisome proliferator-activated receptor (PPAR)α, and then rescues the PPARα level. PPARα restoration further improves the expression of downstream genes [i.e. carnitine palmitoyltransferase 1A (CPT1A) and solute-carrier family 27A (SLC27A)], at both transcriptional and translational levels, which are associated to triglyceride metabolism. In conclusion, the rebalancing of lipid homeostasis down-regulates triglyceride content, and attenuates the hepatocellular steatosis.