Study On The Gut-brain Axis Mechanism Of Spatial Cognition Changes Caused By Olfactory Loss In Mic

In chronic neurodegenerative diseases,such as Alzheimer’s disease,the early clinical symptoms are olfactory dysfunction,resulting in reduced behavioral cognitive ability.However,whether smell can cause spatial cognitive changes and what the underlying gut-brain axis mechanism is remains to be investigated.In this study,mice were injected with Trition X-100 in the nasal cavity to study the behavioral cognition and spatial memory ability of C57/BL mice in the non-destructive and reversible anosmia group and the healthy control group.The changes of intestinal microflora structure were investigated by 16 S rRNA high-throughput amplicon sequencing.The effects of anosmia on the hippocampal proteomics of C57/BL mice were studied by TMT labeling and quantitative proteomics.The main research results are as follows:1.Behavioral test: the body weight and food intake of mice in anosmia group decreased significantly.Behavioral test results showed that mice in anosmia group entered the central area of the open field experiment system and spent less time in the central area than the healthy control group.The number of entering the central area,the time spent in the central area,the total distance moved in the open field,and the number of standing on the front feet in the open field were statistically significant compared with the healthy control group.In the Barnes Maze experiment,the time spent in the correct target hole in the anosmia group was different from that in the healthy control group.These results suggest that anosmia can lead to differences in behavioral cognitive ability in mice.2.Determination of intestinal flora of 16 S rRNA in model mice: In the intestinal flora of C57/BL mice,2805 ASVs were recorded in the anosmia group and 2642 ASVs were recorded in the healthy control group.Bacteroidetes and Firmicutes in the anosmia group were the dominant bacterias of C57/BL mice.The dominant bacteria classes were Bacteroidia and Clostridia.The dominant Bacteroidales were Bacteroidales and Lachnospirales.The dominant bacterial family in anosmia group was Muribaculaceae.Lactobacillus was the dominant bacterium in the anosmia group C57/BL mice.The α diversity of C57/BL mice was not affected by anosmia,but βdiversity was significantly affected,indicating that anosmia can change the structure and composition of intestinal flora in C57/BL mice.3.Hippocampal proteomic mass spectrometry analysis of hippocampal proteomic mass spectrometry of C57/BL mice showed that a total of 4259 quantifiable proteins were detected by specific peptide segments,with the difference ratio of greater than1.3 times significantly up-regulated and less than 1/1.3 times significantly downregulated as the standard.In the hippocampus of C57/BL mice,75 differentially expressed proteins,56 significantly up-regulated proteins and 19 significantly downregulated proteins were identified.Among them,Pvalb,Rps6ka1,Vat1 l and other proteins were significantly correlated with spatial memory.We conducted differential enrichment studies on the characteristics of these proteins and associated pathways from the aspects of cell process,cell component,molecular function,and KEGG pathway.Most of the proteins were associated with long-term enhancement,spinocerebellar combined disorders,and long-term depression.4.Determination of 16 S rRNA intestinal flora of fecal bacteria transplanted mice:After fecal bacteria transplantation,the intestinal flora structure of fecal bacteria transplanted mice with anosmia and healthy control group showed significant difference.A total of 819 ASVs were annotated in the cecum samples of the anosmia fecal bacteria transplantation group and 918 ASVs were annotated in the healthy control group.At the phylum level,Firmicutes were the common dominant phylum in both groups,and the abundance of firmicutes was lower in anosmia coprophytes transplantation group,while the abundance of Bacteroidetes was higher in anosmia coprophytes transplantation group.At the class level,Bacteroidia was the dominant class in both groups,and the abundance of Bacteroidia was higher in the anosmia fecal transplantation group.At the eye level,the relative abundance of Rickettsiales in the anosmia fecal bacteria transplantation group was significantly higher than that in the healthy control group.At the family level,the relative abundance of Anaplasmataceae in the anosmia fecal bacteria transplantation group was significantly higher than that in the healthy control group.At the genus level,the relative abundance of Wolbachia,Blautia and Incertae＿Sedis in anosmia fecal transplantation group was higher than that in healthy control fecal transplantation group,and there was a significant difference.According to KOG secondary functional cluster analysis,Amino acid metabolism,Biosynthesis of other secondary metabolites,carbohydrate metabolism in anosmia fecal bacteria transplantation group of mice metabolism,Drug resistance: Drug resistance: Antimicrobial,Energy metabolism,Environmental adaptation,Immune system,Lipid metabolism metabolism,Metabolism of other amino acids and other functions decreased,and had significant differences compared with healthy control fecal bacteria transplantation group.These results suggest that anosmia leads to changes in intestinal flora,hippocampal function,and cognitive function in mice,and that the microbial imbalance caused by anosmia leads to cognitive impairment.