Screening And Degradation Mechanism Of Cholesterol-lowering Lactic Acid Bacteria In Traditional Fermented Foods In Northeast China

Cholesterol is an indispensable substance in human physiological activities,but its high content can cause harm to the human body.Epidemiological studies have shown that higher than normal levels of cholesterol in serum are closely related to the occurrence of cardiovascular disease.Although some drugs have been shown to have good cholesterol-lowering effects in the body,long-term use is expensive,and the side effects of the drug are irreversible.Including symptoms such as rhabdomyolysis,impaired renal,and etc.Therefore,it is very important to research and develop a product that is inexpensive,efficient and harmless.Lactic acid bacteria(LAB)are important bacteria in fermented foods,with a long-term and safe application and consumption history in the production of fermented foods and beverages.Lactobacillus is a common microorganism in the mammalian gastrointestinal tract(GIT)and is a potential probiotic beneficial to the health of the host.Probiotics are defined as "living microorganisms that,when consumed in sufficient quantities,have a health effect on the host ",with benefits of stimulating mucosal immunity,reducing pathological changes,and interacting with inflammatory mediators.In this paper,strains with high cholesterol scavenging ability were screened from lactic acid bacteria,and the mechanism of cholesterol-lowering was analyzed by in vitro and in vivo experiments.Main methods and results:(1)Screening ability of cholesterol-lowering ability in vitro: In the previous experiment,a strain H6 with the highest in vitro degradation ability was screened by phthalaldehyde chromogenic method.After 16 SrRNA sequencing,the results of the NCBI comparison showed Lactobacillus plantarum.The in vitro cholesterol clearance rate was 92.07%.(2)By measuring the adsorption of cholesterol on the cell membrane of lactic acid bacteria,co-precipitation,and the effect of lactic acid bacteria on the formation of cholesterol micelles,the mechanism of the possible removal of cholesterol by lactic acid bacteria in vitro was studied.(3)Bile salt hydrolase,bile salt hydrolase gene and gene expression were determined.The results showed that the different cholesterol-lowering strains in vitro were mainly reflected in the different activities of bile salt hydrolase and the difference in BSH1 gene expression.(4)C57BL/6 mice fed with high cholesterol diet were used as models to study the effects of lactic acid bacteria on the expression of lipids and lipid metabolism-related genes in mice.The results showed that Lactobacillus plantarum H6 could effectively reduce the increase of blood lipid levels caused by high cholesterol diet.It also reverses the abnormal expression of related genes due to the high cholesterol diet.(5)The mechanism of cholesterol lowering in lactic acid bacteria was analyzed mainly through the FXR pathway,aiming to increase the genes related to bile acid synthesis in CYP7A1,increase the synthesis of bile acids in the body;reduce the expression of HMGCR gene,reduce the synthesis of cholesterol in the body;and improve ABCG5 /8.The expression level of the gene limits the amount of cholesterol absorbed by the intestine.