Effect And Mechanism Of Lactobacillus Casei On Intestinal Flora And Lipid Metabolism Of High-fat Diet Hamsters

High blood lipid levels are an important cause of cardiovascular disease.Studies have shown that reducing serum lipid levels can significantly reduce the risk of cardiovascular disease and reduce its mortality.At present,chemical drugs are the main way to treat cardiovascular diseases.The effects of chemical drugs are obvious,but there are still some shortcomings,such as higher treatment costs and long-term use of drugs that have greater side effects on the human body.Certain bacteria of the genus Lactobacillus,as an important probiotic in the human intestine,have been proven to have the ability to improve blood lipid levels and can cause long-term and beneficial changes in the intestinal micro-ecosystem.However,the mechanism of how Lactobacillus improves serum lipid levels in the serum by affecting the intestinal microecology is not clear.In this paper,telve strains of lactic acid bacteria from traditional fermented dairy products,baby feces and silage corn feed were selected as the research objects.Three strains of lactic acid bacteria with potential lipid-lowering function were obtained by in vitro cholesterol removal and bile salt hydrolase activity screening.Three strains of lactic acid bacteria were fed to hamsters,while using second-generation high-throughput sequencing technology,NMR-based metabolomics technology and multivariate statistical analysis to explore the effects of probiotics on hamster intestinal microflora,metabolites and blood lipid indexes,to reveal how probiotics can regulate blood lipid in hamsters through the adjustment of micro-ecological flora.The main results are as follows:(1)Three excellent strains(Lactobaillus casei AST18,Lactobaillus casei SY13 and Lactobaillus casei CAAS36)were selected to reduce cholesterol in vitro.The three strains have the ability to remove cholesterol above 28%,have bile salt hydrolyzing enzyme activity,and their activities are above 0.91 U/mg protein,have good acid resistance,bile salt resistance,intestinal colonization ability and exert regulation The potential of lipid metabolism.(2)L.casei AST18,L.casei SY13,and L.casei CAAS36 were fed to high-fat diet hamsters,respectively.It was found that these three strains can reduce the levels of TC,TG and LDL-C in the serum of high-fat diet hamsters to different degrees,liver TC,TG levels,liver index,liver fat accumulation,and has a certain ability to regulate liver tissue damage recovery.At the same time,L.casei AST18,L.casei SY13,L.casei CAAS36 significantly increased the serum GSH-Px activity and reduced MDA levels of hamsters in a high-fat diet,and had a certain antioxidant capacity.In addition,they can increase the amount of total bile acid excretion in the stool of high-fat diet hamsters,promote the conversion of cholesterol to bile acids,and have a certain ability to regulate hamster lipid metabolism.(3)This study found that a high-fat diet led to a more fragile and unstable hamster intestinal flora structure,while reducing the diversity of hamster intestinal flora.After feeding L.casei AST18,L.casei SY13,L.casei CAAS36 three kinds of probiotics,the diversity of hamster intestinal flora has been restored to varying degrees,of which L.casei CAAS36 has the most obvious effect.Both L.casei AST18 and L.casei CAAS36 can restore the structure of intestinal flora of hamsters in high-fat diet,and L.casei CAAS36 has a certain dose-effect relationship when adjusting the intestinal flora of hamsters in high-fat diet..The study also found that low-dose CAAS36 has the potential to reduce the incidence of diarrhea and intestinal stress syndrome in hamsters.(4)Based on metabolomics technology to explore the mechanism of L.casei lipid-lowering function,it was found that high-fat diet will cause hamster fatty acid metabolism,amino acid metabolism,glucose metabolism,choline metabolism,ketone body metabolism,purine metabolism and other multiple metabolic pathways disorder,L.casei AST18 and L.casei CAAS36 can effectively regulate and restore fatty acid metabolism and glucose metabolism disorder caused by high-fat diet,and have the ability to regulate lipid metabolism.(5)Finally,the use of high-throughput sequencing technology and metabolomics technology correlation analysis to explore the previous experiments proved that the best regulation of blood lipid performance L.casei CAAS36 improves the interaction mechanism between hamster intestinal microflora structure and regulates metabolic pathways.L.casei CAAS36 plays an important role in regulating and stabilizing the intestinal flora.The treatment of L.casei CAAS36 reversed the ratio of Pachyphyta and Bacteroidetes increased by the high-fat diet,and in particular increased the abundance of Muribaculaceae producing propionic acid.L.casei CAAS36 can reverse the metabolic disorder caused by imbalance of lipid metabolism to a certain extent.By regulating the intestinal flora,more important metabolites such as propionic acid and succinic acid are produced.These metabolites play an important role in preventing and treating hyperlipidemia and its complications.In summary,L.casei CAAS36 is a probiotic that can regulate the intestinal flora and lipid metabolism of high-fat diet hosts.