Improvement of liver steatosis in CDAHFD-fed mice upon CDDO-Me treatment
To examine the hepatoprotective effects of CDDO-Me, it was orally administered to CDAHFD-fed mice, once daily for 8 weeks from 6 weeks of age, and serum and liver samples were collected at the end of the experiment (Figure 2a). No loss of body weight was observed upon daily administration of CDDO-Me below 10 mg・kg-1 for 8 weeks (Figure S1). HE staining of the liver from CDAHFD-fed mice showed marked features of NASH, accompanied by large lipid droplets and inflammation, in addition to leukocyte infiltration (Figure 2b). The NAFLD activity score (NAS) calculated with steatosis, lobular inflammation, and ballooning in HE staining was greater than 5 (Figure S2 and Table S2), indicating that NASH occurred in the liver after 8 weeks of CDAHFD feeding. Administration of CDDO-Me to NASH model mice improved the NAS in a dose-dependent manner (Figure 2c). Consistent with NAS, the increased biochemical parameters including aspartate aminotransferase and alanine aminotransferase were significantly decreased in the mice injected 10 mg・kg-1 of CDDO-Me (Table 1). The hepatic expression levels of the inflammatory cytokines Tnfa, Ifng, IL-6 , and IL-1b , which were upregulated in CDAHFD-fed mice, were significantly reduced according to the administered dose of CDDO-Me (Figure 2d,e and Figure S3a,b). The expression of Abcg5 , a transporter involved in the excretion of cholesterol into bile (Berge et al., 2000; Tian, Gao, Zhang, Hackfort, & Zucker, 2019), andCes2c and Ces1g , which are inhibitory enzymes of lipogenesis (Lian, Nelson, & Lehner, 2018), were significantly upregulated by administering CDDO-Me (Figure 2f,g, and Figure S3c). These observations revealed that CDDO-ME improved the symptoms of NASH in the livers of CDAHFD-fed mice.