AJTR Copyright © 2009-All rights reserved. Published by e-Century Publishing Corporation, Madison, WI 53711
Am J Translational Res 2010;2(1):95-104

Original Article
Quantification and mechanisms of oleic acid-induced steatosis in
HepG2 cells

Wei Cui, Stephen L Chen, Ke-Qin Hu

Division of Gastroenterology and Hepatology, Dept. of Medicine, University of California, Irvine, CA

Received November 2, 2009; accepted November 3, 2009; available online January 1, 2010

Abstract: Developing a quantifiable in vitro model of steatosis is critical in understanding the pathogenesis of
non-alcoholic fatty liver disease (NAFLD) and searching for effective therapies. Using an ORO-based colorimetric
measurement, we developed a convenient assay to qualify the degree of OA-induced steatosis in HepG2 cells.
We demonstrated that in the absence of exogenous inflammatory mediators, OA-induced steatosis was
associated with increased production and secretion of tumor necrosis factor alpha and decreased expression of
peroxisome proliferators-activated receptor α in HepG2 cells. OA-induced steatosis was also associated with
increased lipid peroxidation, apoptosis, but decreased proliferation in these cells. The increased lipid peroxiation
was related to decreased SOD-1, a free radical scavenger enzyme; while increased apoptosis was related to
increased active caspase-9. The decreased proliferation mediated by OA-induced steatosis was associated with
increased production of p27 with unchanged alanine transaminase (ALT) level in the culture medium, indicating
OA-induced steatosis alters cell cycle progression without direct toxicity to these cells. In conclusion, the present
study developed a colorimetric assay that accurately quantifies OA-induced steatosis in HepG2 cells. In the
absence of exogenous inflammatory mediators, OA-induced steatosis results in a series of pathophysilogical
changes in HepG2 cells, indicating direct pathogenic roles of hepatocytes in NAFLD. (AJTR910003).

Key words: Steatosis, tumor necrosis factor α, peroxisome proliferators-activated receptor α, apoptosis, lipid
peroxidation, cell proliferation

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Address all correspondence to:
Ke-Qin Hu, MD
Division of GI/Hepatology
University of California, Irvine
101 The City Drive
Building 53, Rm. 113
Orange, CA 92868
Phone: (714) 456-6926
FAX: (714) 456-3283
Email: kqhu@uci.edu