Original Article Expression of fatty acid synthase in nonalcoholic fatty liver disease
Christoph Dorn, Marc-Oliver Riener, Georgi Kirovski, Michael Saugspier, Kathrin Steib, Thomas S. Weiss, Erwin Gäbele, Glen Kristiansen, Arndt Hartmann, Claus Hellerbrand
Department of Internal Medicine I, University Hospital Regensburg, Germany; Institute of Pathology, University Hospital Erlangen, Germany; Department of Surgery, University Hospital Regensburg, Germany; Department of Pathology, University Hospital Zurich, Switzerland.
Received May 14, 2010, accepted May 21, 2010, available online: March 25, 2010
Abstract: Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation which starts with simple hepatic steatosis and may progress toward inflammation (nonalcoholic steatohepatitis [NASH]). Fatty acid synthase (FASN) catalyzes the last step in fatty acid biosynthesis, and thus, it is believed to be a major determinant of the maximal hepatic capacity to generate fatty acids by de novo lipogenesis. The aim of this study was to analyze the correlation between hepatic steatosis and inflammation with FASN expression. In vitro incubation of primary human hepatocytes with fatty acids dose-dependently induced cellular fatty acidaccumulation and FASN expression, while stimulation with TNF did not affect FASN levels. Further, hepatic FASN expression was significantly increased in vivo in a murine model of hepatic steatosis without significant inflammation but not in a murine NASH model as compared to control mice. Also, FASN expression was not increased in mice subjected to bile duct ligation, an experimental model characterized by severe hepatocellular damage and inflammation. Furthermore, FASN expression was analyzed in 102 human control or NAFLD livers applying tissue micro array technology and immunohistochemistry, and correlated significantly with the degree of hepatic steatosis, but not with inflammation or ballooning of hepatocytes. Quantification of FASN mRNA expression in human liver samples confirmed significantly higher FASN levels in hepatic steatosis but not in NASH, and expression of SREBP1, which is the main transcriptional regulator of FASN, paralleled FASN expression levels in human and experimental NAFLD. In conclusion, the transcriptional induction of FASN expression in hepatic steatosis is impaired in NASH, while hepatic inflammation in the absence of steatosis does not affect FASN expression, suggesting that FASN may serve as a new diagnostic marker or therapeutic target for the progression of NAFLD. (IJCEP1005005).
Address all correspondence to: Claus Hellerbrand, MD University Hospital Regensburg Department of Internal Medicine I D-93042 Regensburg Germany Tel: +49-941-944-7155 Fax: +49-941-944-7154 E-mail: email@example.com