Study On The Activity And Mechanism Of GOS In The Treatment Of Non-alcoholic Fatty Liver Disease In Mice

Non-alcoholic fatty liver disease(NAFLD)is a lipotoxic disease,in which liver steatosis and oxidative stress are the key pathogenic characteristics.In recent years,the prevalence of NAFLD in China has risen rapidly,which is related to obesity in epidemiology and pathogenesis.Up to now,the treatment of NAFLD is still a basic treatment based on improving lifestyle,and there is no specific drug approved for the treatment of NAFLD.Therefore,exploring the pathogenesis of NAFLD will provide new enlightenment for clinical practice and have significant practical significance.As a functional oligosaccharide with natural properties,galactooligosaccharides(GOS)have been added as prebiotics in infant milk powder,bread and other foods,bringing many benefits to human health.GOS will be used as the subject of this study,through in vivo and in vitro experiments,the therapeutic effect of GOS on NAFLD will be studied.In order to provide theoretical basis and experimental basis for the development of health food and drugs with the function of GOS for the treatment of NAFLD,the mechanism of action of GOS to improve liver lipid metabolism and inflammation was discussed.The NAFLD mice was established through high-fat and high-sugar diet(HFHSD),and the effects of GOS on lipid metabolism,liver function,insulin resistance(IR)and liver steatosis in mice were studied.(1)After 20 weeks of HFHSD,the levels of blood lipids TG,TC,FFA,LDL-C and liver TG,TC and LDL-C in the Model group were significantly higher than those in the Control group,while the levels of HDL-C were significantly lower,indicating that HFHSD can cause dyslipidemia and hepatic lipid deposition.The administration group could significantly reduce the levels of TG,TC and LDLC in NAFLD mice,and increase the level of HDL-C,suggesting that GOS could regulate lipid metabolism,improve lipid deposition in the liver,reduce potential threats to the liver during the disease process,and reduce the chance of "a second blow" to the liver.(2)HFHSD-induced NAFLD mice ALT and AST levels increased significantly,indicating that lipid deposition could cause liver cell damage to a certain extent.The administration group could reduce the levels of ALT and AST in mice,indicating that GOS could protect liver cells and improve liver function in the early stage of liver lipid deposition induced hepatocyte damage.(3)IR is an important characteristic of metabolic syndrome.The results showed that GOS can improve IR,reduce fasting blood glucose,improve the body’s sensitivity to insulin response,and does not lead to hypoglycemia,thus improving the glucose tolerance of mice.From another side,the hypoglycemic effect of GOS is safe and reliable.(4)Long-term HFHSD can cause oxidative stress in mice,resulting in the production of liver inflammatory cells and cytokines.GOS can alleviate oxidative stress in mice and reduce the expression of inflammatory cytokines TNF-α and IL-6.The study of mouse liver lipid omics showed that:(1)The PCA and OPLSDA models established by the multivariate statistical analysis were effectively distinguished between the Control group and the Model group,and the model quality was good.Compared with the normal diet mice,the metabolite abundance in the liver of HFHSD-fed mice was significantly changed.(2)The metabolites of HFHSD in mice were mainly concentrated in vitamin digestion and absorption,thermogenic effect,regulation of lipid decomposition in adipocytes,insulin resistance,metabolism of glycine and cholesterol,etc.(3)GOS can promote the body heat production,regulate lipid decomposition of adipocytes,accelerate the metabolism of glycine and cholesterol in HFHSDinduced NAFLD mice.In vitro culture of human liver cell Hep G2,through free fatty acids(FFA)stimulus mode,the study found that:(1)By measuring the levels of ALT and AST in cell medium,it was found that ALT and AST in FFA group were significantly increased,indicating that Hep G2 hepatocyte was damaged.Under the joint action of GOS,high dose of GOS could significantly reduce the content of ALT and AST in cell medium.(2)By determining the contents of intracellular TC and TG,and using oil red O staining to observe the formation of intracellular lipid droplets.Compared with the Control group,the contents of intracellular TC and TG were significantly increased in the FFA group,and a large number of red lipid droplets were gathered in the cells,and the cell boundaries were fuzzy,and the morphology was irregular.Compared with FFA group,GOS could reduce intracellular TC and TG content,and reduce intracellular lipid droplet aggregation,and the effect was more obvious with the increase of GOS concentration.In vitro and in vivo PCR results showed that:(1)GOS could inhibit the expression of SREBP-1c,FAS and ACC1,thereby inhibiting the de initio lipid synthesis pathway.It can down-regulate the expression of PPARγ1 and PPARγ2,and reduce lipid synthesis in liver.GOS can also increase the expression of PPARα and increase lipid oxidation in liver.(2)GOS can inhibit the expression of inflammatory genes TNF-α,IL-6 and IL-1β,thus exerting its antiinflammatory effect.In conclusion,GOS can improve liver lipid deposition,improve liver function,relieve IR and oxidative stress,and reduce fasting blood glucose in mice.GOS inhibited SREBP-1c,FAS and ACC1,thus inhibiting the de novo lipid synthesis pathway.PPARγ1 and PPARγ2 were downregulated to reduce lipid synthesis in liver.The expression of PPARα increased liver lipid oxidation.GOS can inhibit the expression of inflammatory genes TNF-α,IL-6 and IL-1β,thus exerting its anti-inflammatory effect.