Dietary fat, cholesterol, and cholic acid affect the histopathologic severity of nonalcoholic steatohepatitis in Sprague-Dawley rats

Understanding of the pathogenesis of nonalcoholic steatohepatitis (NASH)-associated fibrosis has been hampered by the lack of a comprehensive and physiological small animal model of NASH with fibrosis. Feeding a high-fat and high-cholesterol (HFC) diet supplemented with cholic acid to rats is known to replicate human NASH pathology, and it induces fibrosis earlier than with an HFC diet alone. In the present study, physiological and histopathological observations from 65 Sprague-Dawley (SD) rats fed an HFC diet with or without cholic acid for 9 or 18 weeks in our laboratory between January 2013 and February 2018 were retrospectively reviewed. The liver weight/body weight ratio at the end of the rearing period was higher in rats fed an HFC diet than in rats fed a normal diet in a cholesterol dose-, cholic acid dose-, or rearing period dependent manner. Dietary fat, cholesterol and/or cholic acid and rearing period affected the histopathologic severity of NASH. Overall, 56 (86.2%) of 65 SD rats fed an HFC diet for 9 or 18 weeks developed histopathologically proven NASH. It is noted that the SD rats fed an HFC diet supplemented with 2% (w/w) cholic acid for 18 weeks frequently developed advanced fibrosis, including cirrhosis. Thus, this diet-induced NASH rat model is likely to be a highly reproducible.