Lycium Barbarum Polysaccharide Exerts Antidepressant Effect By Regulating Gut Microbiota

ObjectiveDepression,also known as depressive disorder,is a mood disorder characterized by significant and persistent feelings of low mood caused by various factors.However,current medications have a high relapse rate and only provide good treatment outcomes for about 30% of patients with depression.The various adverse reactions that occur during treatment further reduce patients’ drug dependence.Additionally,these drugs cannot be used for preventive treatment of depression.Therefore,there is a need for the development of auxiliary treatments for depression that have preventive effects and weak adverse reactions.In recent years,the inflammatory pathogenesis of depression and the important role of gut microbiota in the pathological mechanism of depression have received increasing attention.The regulation of gut microbiota to prevent or alleviate depression symptoms has broad application prospects.As a medicinal and edible herb,goji berry is widely recognized for its safety and nourishing effects.Lycium barbarum polysaccharide(LBP)is the main active ingredient in goji berries,and its anti-inflammatory properties and neuroprotective effects make it a promising candidate for the prevention and treatment of depression.Therefore,this study aims to explore the anti-depressive function and potential molecular mechanisms of LBP through the regulation of gut microbiota and short-chain fatty acids(SCFAs),providing a research basis for the development of safe and effective preventive and therapeutic measures for depression.Methods1.Establish a lipopolysaccharide(LPS)depression animal model and evaluate the depressive state of mice through behavioral experiments such as sucrose preference test(SPT)and tail suspension test(TST),and detect the level of inflammatory factors in the hippocampus of mice using real-time fluorescent quantitative PCR to verify the effectiveness of the model.2.Analyze and detect the characteristics of the microbiota in the colon contents of LPS-induced depressed mice using 16 S r RNA gene sequencing,explore the effect of the LPS depression model on the gut microbiota of mice,and identify key microbial populations.3.Establish an LPS depression animal model and administer LBP as a preventive treatment to the model mice,with fluoxetine as a positive control drug.Evaluate the anti-depressive effect of LBP by conducting behavioral experiments and measuring the level of inflammatory factors in the hippocampus of mice using real-time fluorescent quantitative PCR.4.Analyze and detect the characteristics of the microbiota in the colon contents of mice treated with LBP using 16 S r RNA gene sequencing,explore the effect of LBP treatment on the gut microbiota of depressed mice,identify key microbial populations that change during the treatment process,and compare them with the fluoxetine treatment group.5.Use gas chromatography-mass spectrometry(GC-MS)to measure the level of short-chain fatty acids(SCFAs)in the colon contents of mice treated with LBP,and compare it with the fluoxetine treatment group.Combined with the results of microbiome sequencing,explore the function of LBP in improving the gut microbiota of mice and exerting an anti-depressive effect.Results1.Depression model of mice was successfully established through intraperitoneal injection of LPS,which resulted in a lack of pleasure and despair-like behavior,and induced neuroinflammation in mice.The results of behavioral tests showed that compared with the control group,the SPT value of mice in the LPS group was significantly decreased(P<0.001),and the TST value was significantly increased(P<0.01).Real-time fluorescent quantitative PCR showed that the expression levels of IL-β(P<0.01)and TNF-α(P<0.001)in the hippocampus of mice in the LPS group were significantly increased.2.LPS significantly altered the gut microbiota of mice.Compared with the contro l group,the abundance of phylum Bacteroidetes was upregulated,and the ratio of Firm icutes to Bacteroidetes was decreased in the gut of LPS mice.The abundance of Strept ococcaceae was significantly decreased,while the abundance of Lactobacillaceae was abnormally increased.At the species level,the abundance levels of uncultured＿bacteri um＿g＿Dubosiella,Lactobacillus＿acidophilus,and Bifidobacterium＿animalis were dec reased in the LPS group,while the levels of Lactobacillus＿reuteri,Lactobacillus＿muri nus,Lacobaillus＿johnsonii,and Lacobacilus＿intestinalis were significantly higher.3.LBP preventive treatment can alleviate the depressive state of LPS model mice.Compared with the LPS group,the SPT values of mice in the LBP(40mg/kg)and LB P(80mg/kg)groups were significantly increased(P<0.05,P=0.12),and the TST value s were significantly decreased(P<0.01,P<0.05).LBP treatment also reduced the expre ssion levels of IL-β and TNF-α in the hippocampus of mice(P<0.01,P<0.001)(P<0.01,P<0.0001).At the same time,LBP restored the expression levels of TLR4,IIKKα,a nd p65 in the hippocampus(P<0.05,P<0.01)(P<0.01,P=0.05)(P<0.05,P<0.01).4.LBP treatment significantly altered the gut microbiota composition of mice.Co mpared with the LPS model group and the fluoxetine treatment group,the beta-diversi ty of the gut microbiota in the LBP treatment group was closer to that of the control gr oup.At the community level,the abundance of Streptococcaceae was significantly inc reased,while the abundance of Lactobacillaceae was decreased in the gut of LBP mic e.At the species level,LBP treatment restored the abundance levels of unultured＿bate rim＿g＿Dubosila,Lactobacillus＿murinus,Lactobacillus＿reuteri,and Bifidobacterium＿animalis in the gut of mice,making them closer to the levels in the control group.5.LBP treatment can alleviate the decrease in SCFAs levels induced by LPS.Under the induction of LPS,the levels of butyric acid(P=0.0889),isovaleric acid,and hexan oic acid in the mouse gut showed a decreasing trend compared with the control group.After LBP treatment,the levels of butyric acid,isobutyric acid,valeric acid,isovaleric acid,hexanoic acid,and isohexanoic acid showed varying degrees of upregulation.C ompared with the LPS model group,the levels of butyric acid(P<0.05),isobutyric aci d(P<0.01),and valeric acid(P<0.05)in the gut of mice in the LBP(80mg/kg)group w ere significantly increased,and the level of isobutyric acid(P<0.05)was significantly increased in the LBP(40mg/kg)group.However,after fluoxetine treatment,the levels of acetic acid and butyric acid in the mouse gut were further consumed,and the levels of acetic acid(P<0.001)and butyric acid(P<0.05)were significantly decreased comp ared with the control group.Conclusions1.The construction of an LPS depression model can effectively induce depressiv e-like symptoms in mice and trigger neuroinflammation in them.2.The LPS depression model can significantly alter the microbial structure of the mouse gut,disrupting the stability of the gut microbiota while inducing neuroinflamm ation in mice with depressive symptoms.3.Prophylactic treatment with LBP can effectively alleviate LPS-induced depress ive-like behavior in mice and improve the level of inflammatory factors in the hippoca mpus,providing a basis for the use of goji polysaccharides as a natural remedy for dep ression.4.LBP treatment can improve the gut microbiota structure in mice with depressio n,restoring the composition of the gut microbiota to a level closer to that of the blank control group.Fluoxetine treatment cannot restore the structure of the gut microbiota i n mice.5.After acting on the gut microbiota,LBP may regulate the metabolism of gut mi crobiota and increase the level of SCFAs in the gut.Unlike fluoxetine,which exhibits sustained consumption of SCFAs in the gut,LBP exhibits a restorative effect that is m ore conducive to building a healthy gut environment.