Effect And Mechanism Of Probiotics And Oligosaccharides In Improving NAFLD

With the development of the social economy and changes in diet,metabolic diseases like obesity,nonalcoholic fatty liver disease(NAFLD)and others have been epidemic around the world.The essence of NAFLD development is the energy entering the liver higher than the consumption.The high-energy gain not only comes from food but also from the alteration of intestinal function affected by microbiota.Regulation of gut microbiota by prebiotics and probiotics is an expected way to alleviate NAFLD-related metabolic diseases.Here,this study uses a systematic way to explore the effect of FOS’ and XOS’ intake dosage and pattern in intestinal function,gut microbiota and their metabolites,and studied the mechanism of using probiotics in collaboration with oligosaccharide to improve intestinal microflora and alleviate NAFLD.The main contents are listed as follows:(1)Dose effect of FOS/XOS and intervention effect of probiotic supplementation.The intake dose of oligosaccharides may affect their efficacy.Two kinds of oligosaccharides(FOS and XOS)were used to study the improvement effects of different doses of oligosaccharides on NAFLD model mice.The result showed that low and medium doses of oligosaccharides could improve the gut microbiota of NAFLD mice,but excessive oligosaccharides led to intestinal flatulence and diarrhea,microflora disorder,mucus barrier destruction,and cause intestinal inflammation.To investigate whether the intestinal injury was caused by diarrhea,the twice gavage in the morning and afternoon was used to eliminate diarrhea.It was found that the intestinal mucous layer was still damaged,which proved that it had nothing to do with diarrhea.Two probiotics,L.paracasei and P.pentosaceus,that could degrade fructooligosaccharides(FOS)effectively,were screened by in vitro experiments.Supplementation of two strains can relieve FOS-induced mucous layer injury,intestinal microflora disorder and improve intestinal inflammation in NAFLD mice.(2)Influence mechanism of FOS/XOS in food on NAFLD.Unlike the acute effects of gavaged oligosaccharides,oligosaccharides in food ferments slowly in the gut and play their role.Thus,a diet containing oligosaccharides without changing food calories was designed in this study.The result showed that moderate FOS/XOS can affect NAFLD developing by regulating food intake.Hypothalamus and serum associated hormone test showed that oligosaccharide intake led to restraint of food intake at 0-8 h,but later increased food intake.SCFAs supplement showed that SCFAs produced by gut microbiota’s metabolism of oligosaccharides was one of the main reasons for food intake increased in the later period of oligosaccharide intake.SCFAs supplementation in drinking water suggests that butyrate,but not acetate,regulates the fat synthesis and influences NAFLD improving.ACCase activity in vitro demonstrated that butyryl-Co A inhibited the synthesis of malonyl-Co A.Molecular docking showed butyrylCo A or acts as an analogue of acetyl-Co A to impede hepatic DNL.(3)Effects of environmental factors on XOS improvement of NAFLD.Mice in wildness and standard conditions were treated with XOS and C.butyricum(high butyrate yield);the result showed that wild conditions had better improve.The difference of efficacy induced by the environment was related to the intestinal microbiota,and the intestinal microbiota changed to different degrees after adaptive feeding and diet change.The stable intestinal flora would resist the colonization of exogenous bacteria,and the strength of the resistance was related to the shaped microbiota.In vitro co-culture suggests that P.acidilactici can inhibit the growth of C.bifermentans and C.butyricum,and reduce the butyrate production,while C.butyricum can inhibit the growth of P.acidilactici by enriching butyrate.Based on the interaction of intestinal bacteria and their metabolites,study showed that combination of XOS,C.bifermentans and C.butyricum can resist the difference of gut microbiota caused by environment,enriched intestinal butyrate and alleviate NAFLD.(4)Effects of host gut microbiotca on the FOS alleviating NAFLD.The response of different populations to oligosaccharides is different.Using a questionnaire survey to collect the dietary habits of college students and collect their feces.Compared with the obese group,the lean group had higher defecation frequency,fecal relative Bifidobacterium and Lactobacillus abundance and SCFAs content.Microorganisms were isolated from the feces of lean individual and supplemented with FOS or XOS in NAFLD mice,respectively.The results showed that L.fermentium from lean individual could colonize the intestines of mice and relieve NAFLD,but its colonization depended on FOS supplementation.The acetate and fructose produced by FOS supplementation are beneficial to the growth of L.fermentium and its metabolism to produce EPS.EPS can reduce intestinal erosion from harmful microorganisms and intestinal energy absorption by improving constipation.In conclusion,the above conclusions confirm that excessive FOS/XOS are harmful to improving gut microbiota and liver fat accumulation in NAFLD mice,and probiotics combined with two prebiotics can alleviate the adverse symptoms.