Loss of Junctional Adhesion Molecule A Promotes Severe Steatohepatitis in Mice on a Diet High in Saturated Fat, Fructose, and Cholesterol

Abstract

Background & Aims There is evidence from clinical studies that compromised intestinal epithelial permeability contributes to the development of non-alcoholic steatohepatitis (NASH), but the exact mechanisms are not clear. Mice with disruption of the gene (F11r) encoding junctional adhesion molecule A (JAM-A) have defects in intestinal epithelial permeability. We used these mice to study how disruption of the intestinal epithelial barrier contributes to NASH. Methods Male C57BL/6 (control) or F11r−/− mice were fed a normal diet or a diet high in saturated fat, fructose and cholesterol (HFCD) for 8 weeks. Liver and intestinal tissues were collected and analyzed by histology, quantitative reverse transcription PCR and flow cytometry. Intestinal epithelial permeability was assessed in mice by measuring permeability to fluorescently labeled dextran. The intestinal microbiota were analyzed using 16S rRNA sequencing. We also analyzed biopsies from proximal colon of 30 patients with non-alcoholic fatty liver disease (NAFLD) and 19 subjects without NAFLD (controls) undergoing surveillance colonoscopy. Results F11r−/− mice fed a HFCD, but not a normal diet, developed histologic and pathologic features of severe NASH including steatosis, lobular inflammation, hepatocellular ballooning, and fibrosis, whereas control mice fed a HFCD developed only modest steatosis. Interestingly, there were no differences in body weight, ratio of liver weight:body weight, or glucose homeostasis between control and F11r−/− mice fed a HFCD. In these mice, liver injury was associated with significant increases in mucosal inflammation, tight junction disruption and intestinal epithelial permeability to bacterial endotoxins, compared with control mice or F11r−/− mice fed a normal diet. The HFCD led to a significant increase in inflammatory microbial taxa in F11r−/− mice, compared with control mice. Administration of oral antibiotics or sequestration of bacterial endotoxins with sevelamer hydrochloride reduced mucosal inflammation and restored normal liver histology in F11r−/− mice fed a HFCD. Protein and transcript levels of JAM-A were significantly lower in the intestinal mucosa of patients with NAFLD than without NAFLD; decreased expression of JAM-A correlated with increased mucosal inflammation. Conclusions Mice with defects in intestinal epithelial permeability develop more severe steatohepatitis following a HFCD than control mice; colon tissues from patients with NAFLD have lower levels of JAM-A and higher levels of inflammation than subjects without NAFLD. These findings indicate that intestinal epithelial barrier function and microbial dysbiosis contribute to development of NASH. Restoration of intestinal barrier integrity and manipulation of gut microbiota might be developed as therapeutic strategies for patients with NASH.

Non-alcoholic fatty liver disease and its relationship with cardiovascular disease and other extrahepatic diseases

“…Dietary fatty acids promote inflammation through several mechanisms, including direct effects on immune cells, activation of toll-like receptors and cytokine cascades,169 and affect intestinal permeability 170. Mice with a loss of junctional adhesion molecule A (JAM-A) have a defective intestinal epithelial barrier and exhibit more prominent NASH, and colonic tissue from patients with NAFLD have lower levels of JAM-A and higher levels of inflammation compared with healthy controls 171. In healthy individuals, a high-fat Western diet induces endotoxaemia and, therefore, might contribute to the observed chronic inflammation in NAFLD 172.…”

The role of the microbiome in NAFLD and NASH

“…A delicate crosstalk and balance among gut microbiota, intestinal epithelial cells, and gut mucosal system are important to maintain intestinal permeability and tissue homeostasis (Peterson & Artis, 2014). On the molecular level, NAFLD patients exhibit decreased expression of zonula occludens-1 (ZO-1) and junctional adhesion molecule A (JAM-A; Miele et al, 2009;Rahman et al, 2016). A meta-analysis based on five clinical studies shows that NAFLD and NASH patients are more likely to have altered gut permeability in comparison with healthy controls (Luther et al, 2015).…”

Emerging Role of the Gut Microbiome in Nonalcoholic Fatty Liver Disease: From Composition to Function

“…demonstrated that administering a high fat, fructose and cholesterol diet to knockout mice for the gene encoding junctional adhesion molecule A resulted in severe fibrotic steatohepatitis compared to only modest steatosis in control mice, and administration of oral antibiotics or sequestration of bacterial endotoxins resulted in improvement of liver histology. 42 While impairment in gut permeability appears to contribute to NAFLD pathogenesis, it remains unclear if patients with NAFLD are predisposed to altered gut barrier function, if dietary changes directly affect intestinal permeability, or if a Western diet leads to deleterious changes in the microbiota that mediate impairments in gut barrier function. 43 …”