Expression of Intestinal Tight Junction Proteins in Patients with Non-alcoholic Fatty Liver Disease

Background/aims: To investigate the expression of tight junction (TJ) proteins including Zonula occludens-1 (ZO-1), occludin and claudin-1 in intestinal epithelial cells in patients with non-alcoholic fatty liver disease (NAFLD) and study its potential association with the pathogenesis of NAFLD.

Methodology: Twenty-eight NAFLD patients with elevated transaminase, 30 NAFLD patients with normal transaminase and 34 healthy volunteers were enrolled. Their biochemical characters were measured and the expression of ZO-1, occludin and claudin-1 proteins in intestinal epithelial cells was assessed by immunohistochemical analysis and its relationship with transaminase levels was also discussed.

Results: Significant differences were observed on the levels of BMI, TC, TG, FPG, ALT, and AST among the three groups. The levels in NAFLD patients with elevated transaminase were significantly higher than NAFLD patients with normal transaminase and the latter had higher levels than the volunteers. The expression of ZO-1 and occludin were significantly different among the three groups (chi2 = 14.210, p < 0.01; chi2 = 20.543, p < 0.01). The expression of ZO-1 and occludin decreased gradually from NAFLD with elevated transaminase to healthy volunteers (r = 0.386, p <0.01; r = 0.449, p < 0.01). In NAFLD patients, the levels of the expression of ZO-1 and occludin were negatively correlated with the transaminase level (r = -0.426, p < 0.01; r = -0.597, p < 0.01). The expression of claudin-1 was found among all the three groups but no statistical significance was observed among three groups (chi2 = 0.686, p = 0.953).

Conclusions: The expression of TJ proteins in intestinal epithelial cells are closely related with the occurrence and development of NAFLD. The contribution of different TJ protein varies in maintaining barrier function.