Effect of Bacillus licheniformis preparation on hepatic steatosis and intestinal mucosal barrier function in a rat model of nonalcoholic fatty liver disease
Objective To investigate the effects of Bacillus licheniformis on liver histopathology and intestinal mucosal barrier function in rats with nonalcoholic fatty liver disease(NAFLD).Methods A total of 30 male Sprague-Dawley rats were randomly divided into normal control group(Control group with 5 rats),model group(Mod group with 15 rats),low-dose Bacillus licheniformis group(BLL group with 5 rats),and high-dose Bacillus licheniformis group(BLH group with 5 rats).The rats in the Control group were fed with normal diet,and those in the Mod,BLL,and BLH groups were fed with high-fat diet for 16 weeks;after 8 weeks of feeding with high-fat diet,the rats in the BLL and BLH groups were given Bacillus licheniformis preparation by gavage once a day for 8 consecutive weeks at a dose of 2.5×107 CFU/kg and 5.0×107 CFU/kg,respectively.The serum levels of alanine aminotransferase(ALT),aspartate aminotransferase(AST),total cholesterol(TC),triglyceride(TG),fasting plasma glucose(FPG),superoxide dismutase(SOD),catalase(CAT),malondialdehyde(MDA),interleukin-6(IL-6),interleukin-1β(IL-1β),and tumor necrosis factor-α(TNF-α)were measured after the 8 weeks of intervention;HE staining was used to observe the histopathological changes of rat liver,and NAFLD activity score(NAS)was used for scoring;transmission electron microscopy was used to observe the tight junction of the intestinal mucosa;immunohistochemical staining was used to measure the expression of myosin light chain kinase(MLCK)in intestinal mucosa,and quantitative real-time PCR was used to measure the mRNA expressional level of MLCK in intestinal mucosa;high-throughput 16S rRNA sequencing was used to analyze the composition of intestinal microbiota.A one-way analysis of variance was used for comparison between groups,and the Bonferroni method was used for multiple comparisons.Results Compared with the Mod group,the BLH and BLL groups had significant reductions in the serum levels of ALT,AST,TC,TG,FPG,IL-1β,and TNF-α,a significant increase in the level of SOD,significant alleviation of hepatocyte steatosis,a significant reduction in NAS score,recovery of the tight junction of intestinal mucosa,and significant reductions in the protein and mRNA expression levels of MLCK(all P＜0.05).In addition,compared with the Mod group,the BLH group had a significant increase in CAT and significant reductions in MDA and IL-6(all P＜0.05).Compared with the BLL group,the BLH group had significant reductions in the serum levels of MDA,IL-6,and TNF-α and a significant increase in CAT,as well as significant reductions in the protein and mRNA expression levels of MLCK(all P＜0.05).The analysis of intestinal microbiota showed that compared with the Mod group,the BLH and BLL groups had recovery of the relative abundances of Firmicutes and Bacteroidetes,and the relative abundances of Firmicutes and Bacteroidetes in the BLH group were closer to those in the Control group.Conclusion Bacillus licheniformis preparation can effectively alleviate hepatic steatosis in NAFLD rats,possibly by downregulating the expression level of MLCK and improving the tight junction structure of intestinal mucosa.
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