Mechanism For In Vivo Cholesterol-lowering Effect By Lactobacillus Plantarum KLDS1.0386

Cardiovascular diseases?CVD?,such as atherosclerosis and coronary heart disease are the main causes of human mortality.There are various methods for treating cardiovascular diseases.Lactobacilli play important roles in the dairy industry and are utilized to the production of yogurt and cheese.Studies have reported that Lactobacilli play important roles in the treatment of coronary heart disease and can reduce cholesterol levels in the body,but its mechanism is not yet known.The purpose of this study was to investigate the mechanism of cholesterol-lowering ability of Lactobacillus plantarum to provide a theoretical basis for the development of strains with cholesterol-lowering efficacy.Firstly,the gastrointestinal tolerance of Lactobacillus plantarum KLDS 1.0386 was evaluated under simulated gastrointestinal tract conditions;secondly,a high-cholesterol mice model was constructed to evaluate the effect of KLDS 1.0386 on cholesterol metabolism in mice,and further studies were performed to detect the effect of KLDS 1.0386 on the expression of liver cholesterol-related genes.Finally,the contents of the intestinal tract were collected to analyze the changes of gut microbiota.Safety status and antioxidant capacity of KLDS 1.0386 were preliminarily studied,respectively.The results obtained by above experiments were as follows:In the simulated gastric environment of pH 3,the survival rate of KLDS 1.0386 was 92.62%after 3 h of incubation.In the simulated intestinal environment,the survival rate of this strain was83.91%after 3 h of incubation.These results indicate that KLDS 1.0386 could enter into the intestine along with its activity.KLDS 1.0386 can significantly decrease the levels of serum index including triglyceride,total cholesterol and LDL-C,and hepatic index including triglyceride and cholesterol,it can also increase the excretion of fecal bile acid and cholesterol in high-cholesterol mice.In addition,regarding the expression of gene related with liver cholesterol metabolism,the expression of gene HMGCR was down-regulated to inhibit cholesterol synthesis after KLDS 1.0386 administration,whilst the expression of gene FXR and gene CYP7A1 were up-regulated to promote the decomposition of cholesterol.The diversity of gut microbiota abundance,the taxonomic composition and the OTU distribution were analyzed.The diversity of gut microbiota diversity and the number of OTU were not changed by high cholesterol diet and KLDS 1.0386.At the phylum level,the Firmicutes abundance four groups of mice treated with high-cholesterol diet was significantly higher than that of the control group;the Proteobacterial abundance of the model group was significantly lower than that of the control group.Among the Venn chart of five groups,the highest number of OTU was observed in the high-diet group and the pravastrain group.Hypercholesterolemia also leads to a decrease in the antioxidant capacity of the body.Therefore,the antioxidant ability of KLDS 1.0386 was further studied.The antioxidant capacity of KLDS 1.0386 was carried out in vitro by seven indicators including survival efficacy under oxidative stress,DPPH radical-scavenging activity,hydroxyl radical-scavenging activity,lipid peroxidation inhibition capacity,reducing activity,superoxide anion radical-scavenging activity and Fe²⁺-chelating ability.The results showed that the higher the concentration of hydrogen peroxide,the longer the growth adjustment period and the more serious the oxidative damage to the strain.In the remaining 6 indicators,the antioxidant capabilities of cell suspension were higher than the cell-free extracts and fermented supernatant.Although Lactobacillus is usually a safe strain,it is essential to assess the safety of Lactobacillus isolated from nature before their routine use in clinical practice.The preliminary safety evaluation of strains was evaluated by nitroreductase activity,indole experiment,biogenic amine production,haemolysis activity and antibiotics susceptibility.The results showed that KLDS 1.0386 nitroreductase,indole and haemolysis were negative,and could not produce biogenic amines such as tyramine,histamine,cadaverine and putrescine.KLDS 1.0386 was sensitive to ampicillin,penicillin,imipenem,gentamicin,erythromycin and tetracycline,but it was resistant to vancomycin,kanamycin,clindamycin and chloramphenicol.The results showed that KLDS 1.0386 can be considered as a safe probiotic bacterium,and it also possesses high cholesterol-lowering ability and potential antioxidant capability.This strain can be used as a cholesterol removal with potential business development value.