Development of Fibrosis in Nonalcoholic Steatosis through Combination of a Synthetic Diet Rich in Disaccharide and Low-Dose Lipopolysaccharides in the Livers of Zucker (fa/fa) Rats

Nonalcoholic steatohepatitis (NASH) can develop into end-stage disease such as cryptogenic cirrhosis and hepatocellular carcinoma. Hence, it is important to understand the pathogenesis of NASH. In general, the “two-hit theory” has prevailed as a pathogenic mechanism of NASH. According to this theory, lipopolysaccharides (LPS) contained in normal portal blood are the “second hit,” but their role is not completely understood. Based on this theory, we evaluated the role of LPS in NASH pathogenesis. For the first hit to develop metabolic abnormalities, a synthetic diet rich in disaccharide (synthetic diet: 12.1 cal% disaccharide) was fed to Zucker (fa/fa) rats for 12 weeks. For the second hit, 100 µg/kg LPS was injected intraperitoneally once daily for 2 weeks. Synthetic diet-fed rats treated with LPS showed an increase in the triglyceride content and higher expression of profibrogenic mRNAs in the liver. Plasma alanine aminotransferase levels were significantly elevated using this protocol. Furthermore, histological examination demonstrated that this protocol induced mild hepatic fibrosis and focal necrosis in the livers of all rats. Synthetic diet-fed Zucker (fa/fa) rats treated with LPS could be useful for understanding the development of hepatic fibrosis in the two-hit theory.