The Effects Of Long-term High Fat Diet On Cognitive And Emotional Function In C57BL/6J Mice And Related Mechanisms

BackgroundThe rapid spread of cognitive and emotional dysfunctions(CEDs)in modern society has become a huge burden of mental health in the world.The lack of effective treatment is mainly due to our current lack of understanding of the pathogenic factors and related pathogenic mechanisms of these diseases.Epidemiological data show that the outbreak of cognitive affective disorder is consistent with the globalization of high-fat diet in time.Some researchers have proposed that cognitive affective disorder may be closely related to high-fat diet,but the essence and mechanism of the association are still unclear.In view of the current social cognitive emotional disorders of multiple and refractory,high fat diet of the epidemic,especially teenagers the universality of a high-fat diet,by chronic animal experiment analyzes long-term high fat diet(HFD),and HFD Initial age(IA)on the effect of cognitive emotional behavior and mechanism clearly has significant practical significance.HFD has been proven to cause increased levels of peripheral inflammation and central inflammation.Microglia,as the innate immune cells of the central nervous system,play an important role in the regulation of homeostasis and neuroplasticity of the central nervous system.There is considerable evidence linking cognitive affective disorder to abnormalities in the neuroplasticity of the hippocampus and amygdala in the limbic system.MethodsIn this study,healthy male C57BL/6J mice were randomly assigned after 1 week of adaptive feeding to control diet(CDj,CDa)or 60% fat high fat diet(HFDj,HFDa)at 4 weeks(juvenile group,Juvenial)and 8 weeks(Adult group,Adult).After 23 W/37 W respectively measuring body weight,fasting glucose,fasting blood glucose(FBG),such as metabolic index,and insulin tolerance test(ITT),evaluation long-term HFD and IA effects on the body metabolism;The effects of long-term HFD and IA on the cognitive behavior of mice were evaluated by Morris water maze(MWM)and nesting test(NT).The effects of long-term HFD and IA on the emotional behavior of mice were evaluated by open field test(OFT),elevated zero maze(EZM),forced swim test(FST),sucrose preference test(SPT),and three chamber social test(TCST).After the end of the behavioral experiment,samples were collected under animal anesthesia.According to the different subsequent experiments,the animals were divided into three groups:1.Skeletal muscle and hippocampus samples were performed for western blotting(WB),to analyze the levels of inflammatory factors were analyzed with IL-1βand TNF-α as the target proteins,and analyze synaptic plasticity with synptophysin and PSD95 as the target proteins.2.Frozen sections on the sagittal surface of the brain were prepared.By Immunofluorescence (IF)of the specific marker ionized calcium binding adapter molecule 1(Iba1)and the activation marker cluster of differentiation 68(CD68),the effects of long-term HFD and IA on hippocampal and amygdala microglial function were analyzed at the histology level. The effects of long-term HFD and IA on hippocampal synaptic plasticity were analyzed by immunofluorescence labeling of synptophysin and postsynaptic density protein.3.Serum was detected by ELISA,and levels of inflammatory factors were analyzed with IL- 1β as the target protein.Sagittal plane vibration sections of the brain were prepared,the effects of long-term HFD and IA on neuronal complexity were analyzed by golgi staining.Results1.The effects of long-term high-fat diet and initial age on metabolic indexes of the body:1.1 HFDj mice developed impaired insulin tolerance and abnormal epididymal fat deposition;1.2 HFDa mice developed impaired insulin tolerance and abnormal epididymal fat deposition.2.The effects of long-term HFD and IA on cognitive/emotional behavior:2.1 HFDj mice showed abnormal behavior in reverse water maze experiment and nesting experiment,and HFDa mice showed abnormal behavior in nesting test;2.2 HFDj and HFDa mice showed significant behavioral abnormalities in the OFT、EZM、FST、SPT.Only HFDj mice showed abnormal behavior in TCST.3.The effect of long-term HFD and IA on inflammatory level:3.1 HFDj mice showed significantly higher levels of IL-1-1β and/or TNF-α in skeletal muscle,serum and hippocampus;3.2 HFDj mice showed significantly increased IL-1β levels in skeletal muscle,serum and hippocampal tissue.4.Effects of long-term HFD and IA on the phenotype of hippocampal and amygdala microglia:4.1 HFDj mice CD68+ increased significantly in the dorsal 、ventral hippocampus and amygdala of,and the length and number of branches of microglia cells decreased significantly;4.2 HFDa mice the CD68+ of microglia in the ventral hippocampus and amygdala increased significantly,the length and number of branches of cell processes decreased significantly,and the cell coverage area decreased significantly,the body area size of microglia cells in several subregions of the ventral hippocampus of HFDa mice decreased significantly.5.Effects of long-term HFD and IA on hippocampal neuroplasticity:5.1 HFDj mice PSD95 and SYP proteins increased significantly in the hippocampal,while the co-labeling of PSD95/SYP significantly decreased,the dendritic branches of neurons were significantly reduced in the ventral DG region,the ventral CA1 region and the dorsal ventral CA3 region;5.2 HFDa mice PSD95 and SYP proteins and the co-standard density of PSD95/SYP were significantly reduced in the hippocampus.The dendritic branches of neurons in the dorsal CA3 region were significantly reduced.6.Correlation analysis between microglia and behavior:6.1 HFDj mice the proportion of CD68+ in hippocampus and amygdala microglial cells in was significantly correlated with the number of times the animals entered the central area in OFT;6.2 HFDa mice the proportion of CD68+ in the ventral hippocampal and amygdala microglial cells in was significantly correlated with the immobilized time of the animals in FST.Conclusion1.Long-term HFD causes abnormal glucose and lipid metabolism in animals;IA may be one of the factors affecting the metabolic damage effect.2.Long-term HFD mice showed anxiety-depression-like behaviors;Only HFDj animals showed decreased cognitive plasticity and social novelty,suggesting that adolescence may be a vulnerable period for HFD to cognitive and emotional functions.3.Long-term HFD caused the increase of peripheral and hippocampal inflammatory factors.4.Abnormal phenotypes of hippocampal and amygdala microglia in long-term HFD mice;The effect of long-term HFD on dorsal ventral microglia of hippocampus may be related to IA.5.Long-term HFD mice showed abnormal hippocampal synaptic plasticity and decreased hippocampal multisubregion neuron complexity.The effect of long-term HFD on neurostructural plasticity may be related to IA.6.Functional abnormalities of hippocampal and amygdala glial cells may be involved in mediating the long-term emotional damage effect of HFD.The results of this study provide new ideas and abundant animal experimental basis for the in-depth understanding of the pathogenesis of cognitive affective disorders,the optimization of prevention strategies and the development of therapeutic targets.