The alterations of intestinal mechanical barrier in rat models of non-alcoholic fatty liver disease

Abstract

Objective To explore the alterations of intestinal mechanical barrier during the nonalcoholic fatty liver disease (NAFLD) progression. Methods To establish NAFLD rats' model,ninety male SD rats were divided into three groups equally: normal-diet group, high-sucrose diet group and high-fat diet group. At the 4th, 8th and 12th week each time point, ten rats were sacrificed in each group. Another twenty SD rats were randomly divided into carbon tetrachloride (CCl4) group and control group. The liver injured model of CCl4 group was induced by CCl4 ; all the rats of these two groups were killed at the 4th week. The degree of liver steatosis was observed through HE staining of liver paraffin sections. The lipopolysaccharide (LPS) level of portal vein blood was measured by limulus test. The occludin expression in intestinal mucosal was detected by immunofluorescent assay,and the fluorescence intensity was scored. The morphology change of intestinal mucosa tight junction was observed through electron microscopy. Results The liver histopathology suggested that NAFLD and liver injured rats' model was successfully established. There was no statistical significance of LPS level between high-sucrose diet group and normal diet group at all the time point (P＞0.05). At the 4th and 12th week, there was no statistical significance of LPS level between high-fat diet group and normal diet group (P＞0.05), while it was significantly higher in high-fat diet group than normal diet group at the 8th week (P＜0. 05). There was no statistical significance of LPS level between CCl4 group and control group (P＞0. 05). At the 8th week, the expression of occludin in normal-diet group, high-sucrose diet group and high-fat diet group was 1.80±0. 42, 1. 50 ± 0. 53 and 1.30±0.67, respectively, the expression was a little bit lower in high-sucrose diet group and high-fat diet group than in normal diet group, the difference was statistical significance (P＜0. 05). At the 12th week, the expression of occludin was significantly lower in high-sucrose diet group and high-fat diet group than normal diet group. The expression of occludin was significantly lower in CCl4 group (0.60±0.16) than in control group (1.80±0. 42) (P＜0. 05). No obvious morphology changes of tight junction was found in high-sucrose diet group, high-fat diet group and CCl4 group at each time point.Conclusion The expression of occludin decreased gradually during the non-alcoholic fatty liver disease progression. So in the NAFLD treatment, besides improving insulin resistance and protecting liver function,the protection of intestinal mucosa barrier as early as possible may slow down the progression of liver injury. Key words: Fatty liver; Intestinal mucosa; Tight junctions; Membrane proteins; Lipopolysacchariides