Endocrine Abstracts

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of disease spanning from simple steatosis to non-alcoholic steatohepatitis (NASH) with risk of progression to fibrosis and eventually cirrhosis. Dysfunction of the gut-liver axis plays a role the progression to NASH. Intestinal damage and increased permeability can increase the delivery of pathogen-associated molecular patterns (PAMPs), such as LPS and intact bacteria, to the liver where they can activate the TLR4 signalling pathway, and drive hepatic inflammation. Previously, we have shown that the ALIOS diet (high fat/high fructose) causes hepatic steatosis, inflammation and fibrosis in both female and male mice. Here, we examine whether intestinal damage and increased permeability contribute to hepatic inflammation in ALIOS female and male mice. Female and male C57BL/6 mice were fed either normal chow (NC) or ALIOS (45% fat [30% trans-fat], 55% fructose: 45% glucose in H2O; n = 10 - 17 in each group) until 52-weeks of age. The TLR4 signalling pathway was upregulated in the ALIOS mice. In detail, hepatic protein levels of TLR4, total and phosphorylated NF-κB were increased, as was mRNA expression of the NF-κB target genes Tnfa, Il-1β and Ccl2. Marker of macrophage infiltration, F4/80, was also increased at mRNA and protein level. Increased intestinal permeability can be caused by loss of intestinal integrity and failure of antimicrobial response of the epithelial barrier. Consistent with intestinal damage, ALIOS diet altered the structure of the intestinal mucosa. Crypt depth was decreased in the ileum and, in females only, in the colon. Villus length was unchanged in both sexes. Suggesting increased permeability, expression of key tight junction genes occludin and ZO-1 were decreased in the colon of female, but not male, ALIOS fed mice. In addition, the antimicrobial and immune supporting genes Reg3g, Defa5 and Muc2 were decreased in the ileum of the female mice and colonic Reg3g and Muc2 were decreased in both sexes. Suggesting increased bacterial translocation and reduced barrier function, the amount of hepatic bacterial DNA was increased in both female and male ALIOS fed mice, although LPS levels were comparable to controls. Collectively, ALIOS diet represents a robust model for investigating the pathogenesis of NAFLD and its progression to NASH as it recapitulates the majority of the molecular features of NASH, with increased intestinal permeability, increased bacterial translocation and increased hepatic TLR4 pathway activation.