Gut Microbial Metabolites Short-Chain Fatty Acids Partially Reverse Surgery And Anesthesia-Induced Behavior Damage In C57Bl/6J Mice

Objective: Perioperative neurocognitive disorder(PND)is one of the most common postoperative complications in elderly patients.It mainly manifests as inattention,memory impairment,learning ability and language understanding,and decreased expression ability.PND can lead to longer hospital stays,delayed rehabilitation,increased disability and death risk.However,the neurobiological basis of PND and the exact pathogenesis are not clear.Old age,multiple surgeries,and prolonged anesthesia are risk factors for PND.Increasing evidence suggests that gut microbiota can remotely regulate brain function and behavior through neuro-endocrine-immune pathways of the brain-gut-microbial axis.The abnormal composition of gut microbiota is closely related to the onset of various brain diseases such as Alzheimer's disease(AD),autism,schizophrenia and depression.Recent evidence suggests that metabolites of the gut microbiome,such as short-chain fatty acids(SCFAs),may affect the immune response and inhibit the development of inflammatory diseases.The main purpose of this study was to elucidate whether the gut microbiota plays a key role in the pathogenesis of PND.In addition,this study aimed to investigate whether supplementation with SCFAs could improve surgical trauma and anesthesia-induced behavioral defects in mice.Methods: A total of 150 healthy male C57 BL / 6J mice aged 8-10 weeks were randomly divided into 5 groups: control group(Control group),surgery group(Surgery group),short-chain fatty acid group(SCFAs group),short-chain fatty acid + surgery Group(SCFAs + Surgery group)and fecal microbiota transplantation group(Fecal Microbiota Transplantation,FMT group),30 animals / group.All mice were housed in cages with appropriate temperature and humidity.They were fed with standard feed,freely drinking water,following natural circadian light,keeping the mice's living environment ventilated and clean and hygienic.The experiment was started after one week.The SCFAs group and the SCFAs + surgery group were given oral SCFAs mixture for 4 weeks,with 3 times of gavage per week.Mice in the control group and the surgery group were intragastrically administered with saline for 4 weeks,and were administered intragastrically 3 times a week at the same time as the SCFAs and SCFAs + surgery groups.The surgical group and the SCFAs + surgical group underwent partial hepatectomy under general anesthesia within 24 hours after the last day of surgery.The surgical group collected the appropriate amount of fresh feces 3 days after surgery by gently pressing the abdomen of the mice or stimulating the perianal area to promote defecation.Mice in the FMT group received a broad-spectrum antibiotic(dissolved in normal saline)orally for 2 consecutive weeks before fecal microbiota transplantation,and were replaced every two days.The fecal filtrate of mice in the surgery group was transplanted into the mice in the FMT group by gavage for a total of 3 weeks,3 times per week.Each group was trained for a 4-day water maze experiment before surgery or before the last day of fecal microbiota transplantation.The training was performed for 4 days,4 times / day.After the training was completed,surgery and fecal microbiota transplantation were continued.Perform water maze space exploration experiments and open field experiments on the 3rd and 7th days after surgery or fecal microbiota transplantation to observe the behavioral changes of mice;Western blot was used to detect each group protein expression levels of interleukin(IL)-1?,IL-6 and brainderived neurotrophic factor(BDNF)in the hippocampus of mouse brain;Immunohistochemistry was used to detect the expression of microglial activation marker--Ionized calcium binding adaptor molecule-1(Iba-1)in the hippocampus of each group of mice;Metabolomics was used to detect the content of endogenous shortchain fatty acids in the feces of each group.Results: 1.The spatial learning and memory ability of mice was impaired due to surgical trauma and anesthesia,and the pretreatment of exogenous SCFAs could alleviate the behavioral damage;2.The hippocampal area of mice after anesthesia and surgery increased expression of inflammatory factors such as IL-1? and IL-6,SCFAs can reduce the expression of inflammatory factors;3.BDNF expression in mice after anesthesia and surgery is reduced,SCFAs increase BDNF expression;4.Increased expression of Iba-1,a microglial activation marker in hippocampus of mice after anesthesia and surgery,SCFAs can partially inhibit Iba-1 expression caused by surgical traumas;5.Fecal microbiota transplantation leads to impairment of behavioral performance in mice,increased expression of IL-1? and IL-6,decreased expression of BDNF,and increased microglial activation;6.Surgical trauma and anesthesia and fecal microbiota transplantation caused a decrease in SCFAs production in mice.Conclusion: The gut microbiota is involved in the impairment of spatial learning and memory in mice caused by anesthesia and surgery.and its metabolite SCFAs alleviates the postoperative spatial learning and memory impairment of mice by partially inhibiting the activation of microglia cells and controlling the release of related inflammatory factors.