Study On The Improvement Effect Of Lactobacillus Reuteri SL001 On AD Model Mice

Alzheimer’s disease(AD)is a multifactorial neurodegenerative disease,which the pathological features are beta amyloid deposition and neurofibrillary tangles.There are no reported therapies that can reverse or cure AD without side effects so far.It is urgent to change research strategies and develop safe and effective drugs.More and more studies have revealed that Alzheimer’s disease,intestinal microorganisms and cholesterol have certain correlation.Therefore,in this study,we started with gut microbes,treated AD model mice with Lactobacillus reuteri SL001(NCBI accession number is KU255544.1,and the strain collection number is CCTCC M 2019122)for 150 days,then the toxicity of Lactobacillus reuteri SL001 was evaluated.Through RT-qPCR,Western blotting,immunohistochemistry and ELISA,we explored the following questions,①whether the intervention of Lactobacillus reuteri SL001 can adjust the cholesterol metabolism of the body,②whether it can improve the pathological in the brain of AD mice,and ③whether it can improve cognitive function of AD mice.The main results are listed below:1.Adding Lactobacillus reuteri SL001 had no toxic effect on miceAPP/PS1 double transgenic mice were gavaged with Lactobacillus reuteri SL001(2×10^11 CFU/mL)for 150 days,and C57BL/6 mice were used as negative controls.During the gavage,we measured the body weight once a week and observe whether the behavior and physical condition of the mice were abnormal.The blood glucose,liver index,blood biochemical indexes of mice were measured after gavage,and the changes of liver morphology were observed by HE staining and Masson staining.The results showed that AD model mice had a steady weight gain during feeding,no abnormal behavior,and no abnormal changes in their bodies.There were no significant differences between the four indexes of blood glucose,liver index,ALT,AST and blood lipids with wild-type mice.The liver tissue staining results showed that long-term intake of Lactobacillus reuteri SL001 had no significant effect on histomorphology and liver fibrosis.All these results confirmed that Lactobacillus reuteri SL001 is safe for mice.2.Adding Lactobacillus reuteri SL001 affected cholesterol metabolismAfter the end of the gavage cycle,we dissected and stored tissue samples,including liver,duodenum,jejunum,ileum,cortex,and thalamus.RT-qPCR and Western blotting were used to detect the expression of cholesterol metabolism related genes(Lxrα,Hmgcr,Ldlr,ApoE,Abcg1)in the above tissues.The results showed that in liver tissue,dietary supplementation with Lactobacillus reuteri SL001 in AD mice could reduce the expression of Lxrα,Hmgcr,Ldlr and ApoE genes,increased the expression of Abcg1 gene,thereby inhibiting the synthesis of cholesterol and lipoproteins,increasing the reverse transport and metabolism process of cholesterol.Throughout the small intestine,fed the Lactobacillus reuteri SL001 could down-regulate the expression of ApoE gene and reduce lipoprotein synthesis.In the duodenum,the expression of Lxra gene decreased,and the expression of Ldlr and Abcg1 increased,which accelerated the reverse cholesterol transport and the clearance process of low-density lipoprotein.At the same time,the addition of Lactobacillus reuteri SL001 reduced the expression of Lxr?α,Hmgcr,Ldlr,ApoE and Abcg1 genes in the ileum and the expression of the Ldlr gene in the jejunum.In the cortex tissue,the addition of Lactobacillus reuteri SL001 could up-regulate the expression of Lxra and ApoE genes,down-regulated the expression of Ldlr.In thalamus,all genes were up-regulated,indicated that the intervention of Lactobacillus reuteri SL001 could change the cholesterol metabolism in the brain3.Effects of adding Lactobacillus reuteri SL001 on brain pathology and cognitive functionTo study whether the intervention of Lactobacillus reuteri SL001 can reduce the pathological characteristics of AD,we used RT-qPCR and Western blotting to detect the expression of Bace1 gene that regulates β-secretase,used ELISA to detect the total content of Aβ in hippocampus and serum.The results showed that intake of Lactobacillus reuteri SL001 could reduce the expression of Bacel and content of Aβ in AD mice,the effect of adding 100 days was better than 150 days.This also indicated that Lactobacillus reuteri SL001 could alleviate the brain pathological changes in AD,but it couldn’t inhibit its development.We also tested the learning and memory ability of mice through Morris water maze.The results showed that there was no significant difference between the SL001 feeding group and AD positive group,indicating that long-term intake of Lactobacillus reuteri SL001 could not improve the learning and memory ability of AD mice.