Effects of a Long-Term High-Fat Diet and Switching from a High-Fat to Low-Fat, Standard Diet on Hepatic Fat Accumulation in Sprague-Dawley Rats

To investigate the effects of a long-term high-fat diet and switching from high-fat to a low-fat diet on hepatic fat accumulation in Sprague-Dawley (SD) rats, 3-week-old male SD rats were fed a high-fat diet (HFD) containing 45% fat (kilocalories) for 43 weeks (HDHD group), an HFD for 23 weeks followed by a low-fat, standard diet (LFD) containing 10% fat for 20 weeks (HDLD group), and an LFD for 43 weeks (LDLD group). Histopathologically, steatosis and lobular inflammation was obvious in the HDLD and HDHD groups at 46 weeks of age, and ballooning hepatocytes and Mallory hyalines were seen in the HDHD group. Mild fibrosis was observed in 5 of 13 (38%) rats in the HDHD or HDLD groups. Our results demonstrate that a long-term high-fat diet can induce nonalcoholic steatohepatitis (NASH) in SD rats. Switching to a low-fat, standard diet prevented the progression of NASH, although steatosis was not improved.