| Background:Selective serotonin reuptake inhibitors(SSRIs)are widely used to treat depression.However,studies have showed that some depressed patients still not respond to SSRIs even if the blood concentration reached the standard after full treatment.In addition,ideal therapeutic effect could not be achieved for some other depressed patients no matter what kind of SSRIs used,which is called“SSRIs resistant”.For these patients,the clinical strategy is to increase the dosages of drugs,switch to another antidepressant,or continue with a combination of antidepressants.However,such a“trial and error”process often consumes a lot of time and economic costs,leading to the delay of depressed patients.What’s more,it can also lead to serious consequences such as self-harm and suicide.At present,clinicians mainly judge whether depression symptoms are relieved by patients’oral or self-measured scales,lacking of objective and effective evidence.In addition,most of studies on“SSRIs resistant”are clinical observations,while there are few basic studies.Therefore,the scientific connotation of“SSRIs resistant”needs to be further studied.Paroxetine,the most widely used SSRIs in clinic,has remarkable curative effects on depressed patients.However,merely 70%effective rate presents.Worse,Paroxetine has a number of side effects,including but not limited to,side effects on gastrointestinal tract system.Therefore,this study was conducted from the perspective of insufficient efficacy of antidepressants.Firstly,the chronic unpredictable mild stress(CUMS)model was applied.And then,the effects of Paroxetine on desperate-like behaviors of rats were tested by sucrose preference test,open field test,forced swimming test,and light-dark test.Meanwhile,factor analysis was performed.According to the results of factor analysis based on behavioral indicators,depressed rats received with Paroxetine were divided into Paroxetine responsive(PX-R)group and Paroxetine non-responsive(PX-N)group.On top of this,we applied microbiome and metabolomics,by 16S r RNA technology and nuclear magnetic resonance(~1H NMR),respectively,to demonstrate the differences in intestinal flora and metabolic profiles between PX-R and PX-N groups.The results of this study will provide research strategies for in-depth interpretation of the scientific connotation of"SSRIs resistant"and reveal its internal mechanism,lay a foundation for clinical rational drug use in depressed patients with"SSRIs resistant",and provide theoretical basis for clinical accurate diagnosis and treatment of patients with refractory depression.Objectives:1.To investigate the effects of Paroxetine on intestinal microflora in rats and the differences of intestinal microflora structure and composition between PX-R and PX-N groups.2.To investigate the effects of Paroxetine on fecal metabolism in depressed rats and the differences of fecal metabolic profile and metabolites between PX-R and PX-N groups.3.To explore the correlations among behavioral indicators,and different intestinal bacteria and metabolites of PX-R and PX-N groups.Methods:1.Firstly,the depressed model of rats was constructed.And then,the effects of Paroxetine on desperate-like behaviors of rats were tested by sucrose preference test,open field test,forced swimming test,and light-dark test.Meanwhile,factor analysis was performed.According to the results of factor analysis based on behavioral indicators,rats received with PX were divided into Paroxetine responsive(PX-R)group and Paroxetine non-responsive(PX-N)group.Finally,we quantitively characterize the effects of PX-R and PX-N groups for treating depression.2.We investigated the differences in structure,composition and functions of intestinal flora of rats between PX-R and PX-N groups based on 16S r RNA high-throughput sequencing technology.3.We investigated differences in fecal metabolic profiles,metabolites,and pathways of rats between PX-R and PX-N groups based on ~1H NMR metabolomics technology in combination with multivariate statistical analysis.4.We integrated the behavior indicators,intestinal flora,and differential metabolites related to responses to Paroxetine in terms of‘inner-and inter-layers’network based on Spearman correlation analysis.Results:1.The results of behavioral analysis showed that the depressed behaviors,anxiety behaviors,and autonomic ability of PX-R rats were significantly improved as compared with depressed rats.In PX-R group,the sucrose preferences rate,the number of total distance and rearings in open-field of rats were significantly increased,and the immobility time in forced swimming test of rats were prolonged.As compared with depressed rats,PX-N could not improve these behaviors of depressed rats.2.The results of intestinal flora analysis showed that Paroxetine significantly rebuilt disturbed intestinal flora induced by depression,improvedαdiversity andβdiversity.However,there was no significant change in PX-N group.After then,the functions of intestinal flora in PX-R group were changed,which was manifested in the relative abundance of Lactobacillus,Bacteroides,Prevotella and Oscillospira increased significantly,but not in PX-N group.Finally,we found that harmful bacteria such as Adlercreutzia,Alistipes and Aerococcus were enriched in PX-N group.3.The result of fecal metabolomics showed that fecal metabolic profiles were different between PX-R and PX-N groups.The relative abundances of propionate,lactate,isoleucine,citrulline were significantly increased,while that of glutamate and alpha-xylose were significantly decreased in PX-R group.There were no significant changes in PX-N group.PX-R group could significantly alleviate D-glutamine and D-glutamic acid metabolism,arginine and proline metabolism,whereas PX-N group could not.4.The results of Spearman analysis showed that indexes of different levels have significant correlations.The level of lactate was positively correlated with the relative abundances of Lactobacillus and Oscillospira.The sucrose preferences rates of rats were significantly correlated with the relative abundances of isoleucine,propionate,lactate,citrulline and glutamate.In the open field test,the number of total distance of rats were negatively correlated with the content changes of glutamate and alpha-xylose,and the time to escape from the central area was correlated with the content changes of differential metabolites.In the elevated maze test,the time spent in the opened arm was significantly correlated with the content changes of different metabolites.The immobility time of forced swim test was negatively correlated with the level of lactate,while positively correlated with the levels of glutamate and alpha-xylose.Conclusions:In this study,the differences of rats in Paroxetine responsive group and Paroxetine non-responsive group were demonstrated from behavioral indicators,microbiome and metabolome perspectives.The studies showed that Paroxetine could influence the composition of intestinal flora and fecal metabolites of depressed rats.The different efficacy of Paroxetine was related to the differences in intestinal flora and fecal metabolites.The current findings will not only improve the basic research on the underlying mechanisms of different effects of antidepressants,enrich the scientific connotation of the mechanism of action of antidepressants,contribute to the clinical search for biomarkers to reveal the effects of antidepressants,but also provide a new perspective for the development of alternative therapies for patients with refractory depression. |
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