Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 7, 2015; 21(25): 7754-7763
Published online Jul 7, 2015. doi: 10.3748/wjg.v21.i25.7754
Ezetimibe improves hepatic steatosis in relation to autophagy in obese and diabetic rats
Eugene Chang, Lisa Kim, Se Eun Park, Eun-Jung Rhee, Won-Young Lee, Ki-Won Oh, Sung-Woo Park, Cheol-Young Park
Eugene Chang, Department of Nutritional Science and Food Management, Ewha Womans University, Seoul 120-750, South Korea
Lisa Kim, Diabetes Research Institute, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 110-746, South Korea
Se Eun Park, Eun-Jung Rhee, Won-Young Lee, Ki-Won Oh, Sung-Woo Park, Cheol-Young Park, Division of Endocrinology and Metabolism, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 110-746, South Korea
Cheol-Young Park, Diabetes Research Institute, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, 110-746, South Korea
Author contributions: Chang E conceived and designed the experimental study, conducted the experiments, performed the data analysis, and wrote the manuscript; Kim L conducted the experiments; Park SE, Rhee EJ, Lee WY, Oh KW and Park SW contributed to the discussion; and Park CY directed the study and revised the manuscript.
Supported by Samsung Biomedical Research Institute, Grant No. SBRI C-B1-111-3; National Research Foundation of Korea, No. 2012R1A1A2009143/2013027171; and Korean Diabetes Association (to Park CY, 2014S-1)
Institutional animal care and use committee: All procedures involving animals were reviewed and approved by the Institutional Animal Care and Use Committee of Kangbuk Samsung Hospital, Sungkyunkwan University (IACUC protocol number: 201010014).
Conflict-of-interest statement: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Data sharing statement: No additional data are available.
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: Cheol-Young Park, MD, PhD, Division of Endocrinology and Metabolism, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, No. 108, Pyung-Dong, Jongno-Ku, Seoul 110-746, South Korea. cydoctor@chol.com
Telephone: +82-2-20011869 Fax: +82-2-20011588
Received: August 31, 2014
Peer-review started: September 1, 2014
First decision: September 27, 2014
Revised: November 18, 2014
Accepted: January 8, 2015
Article in press: January 8, 2015
Published online: July 7, 2015
Abstract

AIM: To investigate whether ezetimibe ameliorates hepatic steatosis and induces autophagy in a rat model of obesity and type 2 diabetes.

METHODS: Male age-matched lean control LETO and obese and diabetic OLETF rats were administered either PBS or ezetimibe (10 mg/kg per day) via stomach gavage for 20 wk. Changes in weight gain and energy intake were regularly monitored. Blood and liver tissue were harvested after overnight fasting at the end of study. Histological assessment was performed in liver tissue. The concentrations of glucose, insulin, triglycerides (TG), free fatty acids (FFA), and total cholesterol (TC) in blood and TG, FFA, and TG in liver tissue were measured. mRNA and protein abundance involved in autophagy was analyzed in the liver. To investigate the effect of ezetimibe on autophagy and reduction in hepatic fat accumulation, human Huh7 hepatocytes were incubated with ezetimibe (10 μmol/L) together with or without palmitic acid (PA, 0.5 mmol/L, 24 h). Transmission electron microscopy (TEM) was employed to demonstrate effect of ezetimibe on autophagy formation. Autophagic flux was measured with bafilomycin A1, an inhibitor of autophagy and following immunoblotting for autophagy-related protein expression.

RESULTS: In the OLETF rats that received ezetimibe (10 mg/kg per day), liver weight were significantly decreased by 20% compared to OLETF control rats without changes in food intake and body weight (P < 0.05). Lipid parameters including TG, FFA, and TC in liver tissue of ezetimibe-administrated OLETF rats were dramatically decreased at least by 30% compared to OLETF controls (P < 0.01). The serum glucose, insulin, HOMA-IR, and lipid profiles were also improved by ezetimibe (P < 0.05). In addition, autophagy-related mRNA expression including ATG5, ATG6, and ATG7 and the protein level of microtubule-associated protein light chain 3 (LC3) were significantly increased in the liver in rats that received ezetimibe (P < 0.05). Likewise, for hepatocytes cultured in vitro, ezetimibe treatment significantly decreased PA-induced fat accumulation and increased PA-reduced mRNA and protein expression involved in autophagy (P < 0.05). Ezetimibe-increased autophagosomes was observed in TEM analysis. Immunoblotting analysis of autophagy formation with an inhibitor of autophagy demonstrated that ezetimibe-increased autophagy resulted from increased autophagic flux.

CONCLUSION: The present study demonstrates that ezetimibe-mediated improvement in hepatic steatosis might involve the induction of autophagy.

Keywords: Autophagy, Ezetimibe, Hepatic steatosis, Nonalcoholic fatty liver disease

Core tip: As an anti-hypercholesterolemia drug, ezetimibe is reported to improve metabolic disorders. Moreover, the hepatic expression of Niemann-Pick C1-like 1 protein, the target of ezetimibe, has led to increased interest in the effects, which have not been fully delineated, of ezetimibe on the liver. In the current study, ezetimibe treatment improved hepatic fat accumulation, which was accompanied by the induction of hepatic autophagy in obese and diabetic rats. In addition, in vitro hepatocytes treated with an inhibitor of autophagy showed that ezetimibe-induced autophagy resulted from an increase in autophagic flux. Therefore, ezetimibe-increased autophagy flux may play an important role in the improvement of hepatic steatosis.