Effects Of Phytosterol Esters On Gut Microbiota Of NAFLD Rats

In recent years,changes of people’s dietary patterns have resulted in the increasing prevalence of nonalcoholic fatty liver disease(NAFLD).Lacking timely intervention would probably lead this chronic liver damage progress to nonalcoholic steatohepatitis,liver fibrosis,cirrhosis and even liver cancer.Therefore,the prevention of NAFLD by dietary intervention is of great importance.Phytosterol esters(PSE)is the esterified form of phytosterol(PS).PSE can be hydrolyzed into PS by esterase in vivo,and exhibit the same physiological activities such as cholesterol lowering effect,antioxidant,and anti-inflammatory activity.In present study,a high fat diet was used to establish NAFLD models,and the two PSE intervention groups were orally administered low(0.05 g/100 g BW)or high(0.10 g/100 gBW)doses of PSE fortified milk respectively.The preventive effects of PSE on NAFLD rats were explored via the determination of the serum biochemical parameters,levels of short chain fatty acids in colon content and feces,changes of gut microbiota,and the mRNA expression of tight junction protein in hepatic and colon tissues.The results are as follows:(1)Compared to the model group,two doses of PSE treatment could both significantly reduce the serum TC,LDL-C and AST levels,and increase HDL-C levels(p<0.05).Besides,high dose of PSE treatment could also significantly decrease the serum ALT levels(p<0.05).Futhermore,both low and high doses of PSE intervention could significantly reduce the abdominal fat index and liver index of NAFLD rats(p<0.05).The HE stainning results showed that both low and high dose of PSE treatment could obviously attenuate hepatic steatosis in rats.(2)RT-qPCR results showed that low dose of PSE treatment could increase the relative quantity of Lactobacillus,Enterobacter,Enterococcus,and Bacteroides,and decrease the relative quantity of Bifidobacterium in the rats gut bacteria(p>0.05).High dose of PSE treatment could increase the relative quantity of Lactobacillus,but present no obvious effect on the relative quantity of other four bacteria(p>0.05).Results of 16 S rDNA sequencing showed that the diversity and abundance in gut microbiota of NAFLD rats were markedly different from those of normal control group.The high dose PSE treatment group showed the similar results to the normal control group in Chao1 index,Shannon index,and taxonomic classification and distribution.The results of functional community distribution showed that high dose of PSE treatment could also increase the abundance of cell motility,the translation,replication and repair of genetic information,and regulate the distribution of glycan biosynthesis and metabolism,lipid metabolism,and nucleotide metabolism abundance,which were similar to the normal control group.(3)Both high and low dose of PSE treatment could reduce the levels of SCFAs in colon contents in varying degrees.Different results were observed in fecal samples of rats,in which low dose of PSE treatment could increase the levels of isobutyric acid(98.99%),valeric acid(44.89%),and isovaleric acid(60.10%)(p>0.05),while high dose of PSE treatment could increase levels of valeric acid(44.86%)(p>0.05),and significantly increase levels of isobutyric acid(188.14%),and isovaleric acid(118.92%)(p<0.05).(4)Compared with model group,both low and high doses of PSE treatments could reduce the plasma endotoxin levels of NAFLD rats.Low dose of PSE treatment could extremely significantly up-regulate the mRNA expression of claudin-1 in colon tissues(p<0.01),and high dose of PSE treatment could significantly up-regulate the mRNA expression of occludin(p<0.05).In addition,both low and high doses of PSE treatment could extremely significantly down-regulate the mRNA expression of claudin-2 in hepatic tissues(p<0.01),besides,high dose of PSE treatment could also significantly up-regulate the mRNA expression of claudin-3 and occludin(p<0.05).Conclusion: PSE could correct the intestinal microflora disturbance in NFALD rats caused by a high fat diet,regulate the distribution of functional community of intestinal microbes,meanwhile correcting the levels of short chain fatty acids in colon and feces,and maintaining liver and colon permeability,thus prevent the occurrence and progression of NAFLD.