Effects of short-chain fatty acids on gut microbiota and hippocampal TLR4/MyD88/NF-κB pathway proteins in depression model mice
Objective To investigate whether short chain fatty acid(SCFAs)intervention has an antidepressant effect by improving gut microbiota dysregulation and regulating the TLR4/MyD88/NF-κB in-flammatory pathway in depression model mice.Methods Totally 60 SPF grade male C57BL/6 J mice aged 6-8 weeks were randomly divided into three groups:control group,depression model group,and SCFAs group,with 20 mice in each group.The mice in depression model group and SCFAs group were given the chronic unpredictable mild stress(CUMS)stimulations for 8 weeks to establish the depression model.From the 6th week,SCFAs group mice were given a mixed solution of short chain fatty acid salts for drinking,until modeling was completed,meanwhile mice in the model group were given 0.78％NaCl solution for drinking.The depression-like behavior was assessed using the sucrose preference test(SPT)and forced swimming test(FST)following modeling,and the open field test(OFT)was employed to evaluate the anxiety-like behavior of mice.16S rRNA gene sequence was used to analyze the gut microbiota of mice.The activation of astrocytes and TLR4/MyD88/NF-κB inflammatory pathway in hippocampus was determined by immunofluorescence staining and Western blot.SPSS 26.0 was used for statistical analysis,one-way ANOVA was used for compar-ison among the three groups,and LSD-t test was used for further pairwise comparisons.Results There were statistically significant differences in the sugar water preference rate,the immobility time in FST,and the per-centage of activity time in OFT among the three groups(F=10.554,10.912,12.599,all P＜0.05).The the sugar water preference rate and the percentage of activity time in OFT of the depression model group were both lower than those of the control group(both P＜0.05),and the immobility time in FST was higher than that of the control group(P＜0.05).The sugar water preference rate in SCFAs group((84.7±3.5)％,(75.3±6.0)％)and the percentage of activity time in OFT((7.4±1.4)％,(3.2±0.9)％)were both higher than those in the depression model group(both P＜0.05),while the immobility time in FST was shorter than that in the depression model group((110.5±21.5)s,(148.0±20.1)s,P＜0.05).There was a statistical difference in the β diversity of gut microbiota among three groups(P=0.001).At the family level,compared with the depression model group,the relative abundance of Rikenellaceaee and Bacteroidaceae increased in the SCFAs group,while the relative abundance of Clostridia_UCG-014 decreased.At the genus level,the relative abundance of Clostridia_UCG-014 and Prevotella decreased,while the relative abundance of Alistipes in-creased(all P＜0.05).The immunofluorescence results showed that there was a statistically significant differ-ence in GFAP expression levels among the three groups of mice(F=16.565,P=0.004).The GFAP expres-sion in the depression model group was higher than that in the control group and SCFAs group(both P＜0.05).The Western blot results showed that there were statistically significant differences in the expression levels of TLR4,MYD88,and NF-κB ptoteins in the hippocampal tissue of the three groups(F=70.59,174.39,14.40,all P＜0.05).The protein levels of TLR4,MyD88,and NF-κB in the depression model group were all higher than those in the control group and SCFAs group(all P＜0.05).Conclusion SCFAs can a-meliorate the depressive-like behavior in depression model mice and reduce the activation of astrocytes in the hippocampus,which may be associated with the improvement of dysregulated gut microbiota and down-regula-tion of the TLR4/MyD88/NF-κB pathway protein.
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