Effect And Mechanism Of Lactobacillus Reuteri Fn041 In Preventing Hypercholesterolemia In Mice

ObjectiveLactobacillus reuteri Fn041(Fn041),a probiotic strain isolated from breast milk in this area,has a low incidence of hypercholesterolemia in Gannan area of Gansu Province,and has the ability to produce indole-3-aldehyde(IALd,an aryl hydrocarbon receptor ligand).This study aimed to investigate the role and mechanism of Fn041 in preventing hypercholesterolemia in mice by activating aryl hydrocarbon receptors.MethodsEighty-four 6-week-old male C57BL/6N mice were randomly divided into 7 groups(n=12/group).LF,low-fat diet-fed mice,LF+Fn041,low-fat diet-fed mice treated with Fn041 by gavage,HF(60%of energy from fat),high-fat diet-fed mice,HF+Fn041,high-fat diet-fed mice treated with Fn041 by gavage,HF+LGG,high-fat diet-fed mice treated with Lactobacillus rhamnosus GG(LGG)by gavage,HF+IALd,high-fat diet-fed mice treated with IALd by gavage,HF+Lova,high-fat diet-fed mice treated with lovastatin(Lova)by gavage.The gavage dose was 1×10~9CFU/mouse·day,the doses of IALd and Lova were 18 mg/kg·day and 10 mg/kg·day,respectively,and the control group was gavaged with the same volume(100μL)of saline.The animals were continuously treated for 8 weeks and then executed,blood was collected,liver,intestine and fat were collected and stored at-80℃in the refrigerator,and liver and adipose tissue sections were prepared.ResultsThe body weight,plasma total cholesterol,low density lipoprotein cholesterol,epididymal fat and perirenal fat of mice in HF group were significantly higher than those in LF group,and all treatments significantly decreased their levels(P<0.05).LGG,Fn041and Lova treatments significantly reduced high-fat-induced excess weight gain compared to the HF group(P<0.05).Fn041,IALd and Lova treatments significantly inhibited the accumulation of peritesticular fat(P<0.05).All treatments reduced the percentage of lipid droplet area in liver sections and the area of adipocytes in adipose tissue sections(P<0.05),significantly increased the m RNA expressions of Occludin and Claudin-1 in ileum(P<0.05),and decreased plasma IL-6,TNF-α,lipopolysaccharide-binding protein and lipopolysaccharide content(P<0.05),relieve endotoxemia and chronic inflammation caused by high-fat diet.Compared with the HF group,Fn041,IALd and Lova treatments increased the cecal microbiota Chao1 and ACE index(P<0.05)and restored the reduced diversity of gut microbiota induced by a high-fat diet.Fn041 treatment significantly increased the cecal acetic acid content(P<0.05),and the other treatments significantly increased the cecal butyric acid content(P<0.05).All treatments significantly increased fecal total cholesterol and total bile acid excretion compared to the HF group(P<0.05).The m RNA expressions of Cyp7a1,Cyp7b1 and Cyp27a1 were significantly down-regulated in the liver of Fn041,LGG and IALd treatment groups(P<0.05),and the m RNA expressions of Ahr was significantly up-regulated in the liver of Fn041 and IALd treatment groups(P<0.05).The m RNA expression of Ahr,Slc10a2,and Npc1L1 were significantly up-regulated(P<0.05),and the m RNA expression of Abcg5 and Abcg8 in ileum treated with Fn041 and LGG were significantly up-regulated(P<0.05).Untargeted metabolomic analysis revealed that Fn041 treatment significantly increased indole,indole-3-aldehyde,indole acetic acid,phytosphingosine,L-isoleucine content and significantly decreased deoxycholic acid,choline,eicosapentaenoic acid,N-The content of acetylneuraminic acid,etc.,significantly increased the content of phytosphingosine,L-isoleucine,myristic acid,etc.in plasma,and significantly decreased the content of plasma thymidine(P<0.05).ConclusionFn041 and LGG can prevent hypercholesterolemia and fat accumulation in the liver and peritestis,and alleviate intestinal mucosal barrier damage,endotoxemia,chronic inflammation,and intestinal dysbiosis caused by high-fat diet.Fn041 may activate the expression of gene of intestinal aryl hydrocarbon receptor pathway through the produced indole-3-aldehyde,and promote the intestinal excretion of cholesterol and bile acids to play a cholesterol-lowering effect.