Screening Of Cholesterol-lowering Probiotics And Its Mechanism Of Lipid Metabolism In Mice Fed A High-fat Diet

Hyperlipidemia is a major cause of cardiovascular disease(CVD)and arteriosclerosis.The WHO predicted that up to 40% of deaths will be related to CVD by 2030,affecting approximately 30 million people worldwide.Long-term intake of high-fat diets will lead to the occurrence of metabolic diseases such as hyperlipidemia.To date,the most widespread treatment of hyperlipidemia is drug therapy.However,long-term use of drugs is expensive and have toxic side effect.Therefore,the development of functional and nutritious foods will be of great significance for improving hyperlipidemia.Research have confirmed that probiotics have the function of modulating blood lipids.However,there are few studies on the mechanism of probiotics to prevent or relieve hyperlipidemia and its regulation of lipid metabolism.The present study aimed to screen probiotic strains with cholesterol-lowering ability,to explore the hypolipidemic effect of screening strains on high-fat diet mice and the mechanism of regulating lipid metabolism.A probiotic strain was isolated with bile salt hydrolase activity and high cholesterol-lowering ability from Kimchi.The antioxidant capacity,acid-resistance and bile salt-resistance,antibiotic sensitivity and antimicrobial activity of the strains in vitro were measured.C57BL/6N mice were randomly divided into 3 groups: the normal diet group(Control group),the high-fat diet group(HFD group)and the high-fat diet with screened strain group(screening strain intervention group).After feeding for 8 weeks,the determination of mice body weight,abdominal and perirenal fat coefficient,serum and liver related lipid levels,observation of liver histopathological changes,and research on hypolipidemic effect of screening strains.Through the changes of lipid metabolism related factors and intestinal flora,discussing the mechanism of screening strains to regulate lipid metabolism.Results: 1.The lactic acid bacteria strain LP104 with highly efficient cholesterol-lowering ability was screened in vitro and identified as Lactobacillus plantarum.The probiotic characteristics studies found that the strain could tolerate the acid and bile salt,gastrointestinal fluid,pathogenic bacteria and antibiotic resistance.L.plantarum LP104 also showed a good antioxidant capacity in vitro.2.L.plantarum LP104 intervention in a high-fat diet mouse model showed that this strain can significantly reduce the body weight,Lee's index,abdominal and perirenal fat index to alleviate obesity in mice;L.plantarum LP104 also significantly regulated the variations of TC,TG,LDL and HDL levels in the serum and liver of mice induced by a high-fat diet and achieve the goal of reducing blood lipid.Moreover,L.plantarum LP104 could significantly reduce the levels of ALT,AST,LPS and TNF-? in serum or liver.Effectively relieve the occurrence of hyperlipidemia in mice caused by high-fat diet alleviate the occurrence of inflammation or liver injury caused by high-fat diet.3.Western blotting analyzed the protein levels of CYP2E1 and Nrf2 in the liver of mice,L.plantarum LP104 could down-regulate the expression of CYP2E1 and up-regulate Nrf2 protein levels.L.plantarum LP104 activated the CYP2E1 / Nrf2 signaling pathway,increased the level of antioxidant enzyme GSH-Px in mice to reduce the occurrence of oxidative stress in the body caused by a high-fat diet,relieve the liver oxidative stress injury,and prevent the occurrence of metabolic syndrome.4.The protein level analysis of p-AMPK,SREBP-1,SCD1,p-ACC,PPARa,MTP and ACOX in mouse liver showed that L.plantarum LP104 could up-regulate the expression of pAMPK,PPARa,MTP,ACOX and down-regulate the protein levels of SREBP-1,SCD1 and pACC.It indicated that L.plantarum LP104 reduced adipogenesis by activating the AMPK signaling pathway and inhibiting the expression of lipogenesis-related genes SREBP-1 and SCD1;At the same time,it inhibits the expression of p-ACC,enhances the expression of PPARa,MTP and ACOX proteins,and promotes fatty acid oxidation to achieve the purpose of lipid reduction.5.High-throughput sequencing analysis of cecal flora composition in mice revealed that a high-fat diet caused a significant decrease in the abundance of S24-7 and a significant increase in the abundance of Proteobacteria and Desulfovibrio in the cecum of mice.L.plantarum LP104 could significantly inhance the abundance of Bifidobacterium,Lachnospiraceae,Butyricicoccus,Ruminococcus,Roseburia,Enterococcus,Clostridium and Staphylococcus abundance and significantly reduced the abundance of Oscillospira,Gemella,and Biotia to alter the composition of intestinal microorganisms.L.plantarum LP104 could prevent obesity by reducing the ratio of Firmicutes to Bacteroidetes,increases the abundance of the beneficial bacteria Bifidobacterium in the cecum,and make the intestinal microbiota disorder induced by high-fat diet tend to normal.L.plantarum LP104 regulates lipid metabolism by improving the composition of intestinal microorganisms.Conclusion: L.plantarum LP104 was a potential probiotic strain and had a positive effect on lowering blood lipid and regulating lipid metabolism.The mechanism of L.plantarum LP104 regulating lipid metabolism was mainly achieved by activating AMPK / Nrf2 / CYP2E1 signaling pathway and improving the composition of intestinal microbiota.