The Mechanism By Which Sea Red Rice Outer Layer Fraction Improved Depression-like Behaviors And Pathological Changes Induced By Chronic Unpredictable Mild Stress In Mice

With the gradual increase in the pressure of life in modern society,the incidence of depression is increased.At the present,the etiology and mechanism of depression are still unclear,while there is no effective treatments.In order to explore the pathogenesis of depression,the hypotheses of macrophages/T cell inflammation and neurotrophic factor deficiency in were extensively studied in the past several decades.Recent studies had found that "microbe-gut-brain" axis disorders play an important role in the pathogenesis of depression.However,whether the change of intestinal microbes plays an antidepressant effect through its metabolite short-chain fatty acids(SCFAs),and whether SCFAs changes are correlated to depression-like behavior are unknown.As the regulation of intestinal flora imbalance has become a new treatment direction,sea red rice outer layer fraction(SRROLF)is rich in high fiber,flavonoids,ferulic acid,?-aminobutyric acid and other active substances,so it has the functions of regulating the composition of intestinal microbes,enhancing anti-stress response,and anti-inflammatory.This present study comprehensively evaluated the antidepressant effect of SRROLF on a mice model of depression induced by chronic unpredictable mild stress(CUMS).The study was from gut microbes to short-chain fatty acids,then to neuroinflammation,neurotrophin and neurotransmitters to reveal the mechanism of SRROLF in the treatment of depression.Methods:1.In this study used CUMS to establish a depression-like animal model.Chronic stress lasts for 9 weeks while were fed a 5% SRROLF.2.Sucrose preference test(SPT),elevated plus maze(EPM),tail suspension test(TST)were used to investigate the depressive-related behavior.3.Real-time fluorescent quantitative PCR to determine the population of mouse intestinal Lactobacillus,Bifidobacterium,Clostridium and Escherichia coli.4.The content of valeric acid,acetic acid,butyric acidand propionic acid in the colon were detected by GC-MS.5.The concentration of Norepinephrine(NE),5-Hydroxytryptamine(5-HT),Dopamine(DA)and its metabolites 3-methoxy-4-hydroxyphenylglycol(MHPG),5-Hydroxyindoleacetic acid(5-HIAA),3,4-dihydroxyphenylacetic acid(DOPAC)were measured by high-performance liquid chromatography.6.The expression of microglia M1 phenotype(Iba-1)and inflammatory factors(Interferon gamma(IFN)-?,Interleukin(IL)-4,IL-10,Transforming growth factor(TFG)-?)in mouse hippocampus was detected by ELISA kit.7.Real-time fluorescent quantitative PCR was used to detect the expression of M1 Iba-1 and M2 CD206,neurotrophic factor and its receptors(Glial fibrillary acidic protein(GFAP),Brain derived neurotrophic factor(BDNF),and Tyrosine Kinase B(Trk B))in hippocampus,and Western Blot method was used to detect the expression of CD206,GFAP,BDNF protein and its receptors Trk B and p75 Neurotrophin Receptor(p75)in hippocampus.8.Used Graph Pad Prism 6 software to analyze the correlation between the lack of anhedonia and desperate abandonment behavior in mice and the content of short-chain fatty acids in the colon.Result:1.Compared to controls,CUMS significantly down-regulated sucrose intake,but significantly increased the immobility time in TST and the anxiety in EPM.However,these behavioral changes were improved by SRROLF;.2.CUMS significantly reduced the population of Lactobacillus and Bifidobacterium in the intestines,and significantly increases the population of Clostridium.CUMS also significantly reduced the content of acetic acid,propionic acid,butyric acid and valeric acid in the colon.These results were significantly reversed by SRROLF;3.After CUMS exposure,the contents of DOPAC,5-HT,NE and their metabolites in the mouse prefrontal cortex were significantly reduced,which were attenuated by SRROLF;4.The results of real-time fluorescent quantitative PCR and Western Blot showed that CUMS significantly reduced the expression of CD206,GFAP,BDNF,and Trk B protein in the hippocampus,but significantly increased the expression of p75 protein.Again,SRROLF could significantly attenuate these changes;5.ELISA results showed that CUMS significantly decreased the concentration of IL-4,IL-10 and TFG-?,while significantly increased the concentration of Iba-1 and IFN-?,which were significantly attenuated by SRROLF;6.Through the correlation analysis of Graph Pad Prism 6 software,it was found that the lack of anhedonia and increased desperate or abandonment behavior were related to decreased short-chain fatty acids in the colon of CUMS mice.Conclusion:(1)CUMS could induce depressive and anxiety-like behaviors in mice,which lead to intestinal flora imbalance,neuro-inflammation,decreased the content of SCFAs and decreased in neurotrophion and neurotransmitters.(2)Sea red rice peel could improve the depression-like behavior of mice induced by chronic stress.Its mechanism may be related to regulating the imbalance of intestinal flora,increasing the content of short-chain fatty acids,reducing inflammation,and regulating neurotransmitter and neurotrophic factors are related.(3)For the first time,it was found that the lack of anhedonia and desperate abandonment behavior in mice were related to short-chain fatty acids,which provides a very important direction for the treatment of depression.