Founction Evaluation And Mechanism Investigation Of Compound Probiotics On Alleviating Depression

Depression is a complex and multi-factorial mental disorder with the clinical symptoms including persistent low mood,loss appetite,anhedonia,sleep disturbance and et al.According to statistics from the WHO,there were more than 350 million depression patients around the world in 2017.Medical therapy is the main treatment method,which can produce good therapeutic effects for about 30% of patients.But current antidepressants are only used for treatment,not for prevention.Moreover,they exist obvious shortcomings,such as a lag period of 2 to 4 weeks and cause gastrointestinal discomfort.This will increase the negative concepts of patients.Therefore,adjuvant therapy products with preventive effects and alleviation capacity both on depression and gastrointestinal discomfort show great market value.The pivot role of “microbiota-gut-brain” has been recognized in the development of depression.Gut microbiota can not only alleviate gastrointestinal diseases,but also participate in the regulation of brain functions through the bioactive molecules it produced which can enter the circulatory system.Therefore,targeting gut microbiota is expected to become a new antidepressant adjuvant therapy.Psychobiotics are a type of probiotics that can participate in mood regulation,and it can be used to alleviate depression,anxiety,autism,chronic fatigue.In this study,through animal tests and clinical trial to evaluate the antidepressant effects of the compound probiotics.From the aspects of gut microbiota and short chain fatty acids(SCFA)to explore the potential mechanisms of compound probiotics to alleviate depression.Main research content and results are shown as follows:(1)Screening and clinical verification of the compound probiotics formula with excellent antidepressant effects: CUMS induced depression mice model was used to screen out the most excellent antidepressant compound probiotics from six multi-probiotics formula.Through PCA analysis of five behavioral indexes and four biochemical indexes,the best antidepressant formula M3(CCFM1025+CCFM687+CCFM6432)were screen out.After that,a random,placebo controlled clinical trial was performed to evaluate the antidepressant function of M3 on human body.The volunteers' blood and fecal sample(Placebo group,n=20;M3 group,n=17)were collected.Results indicated that one-month M3 treatment can significantly decrease the score of depression scales(Hamilton depression rating scale,Montgomery-asberg depression rating scale,Brief psychiatric rating scale).Additionally,M3 can decrease the score of Gastrointestinal symptom rating scale,and significantly alleviate constipation and diarrhea.In the serum depression biomarkers,only cortisol was reversed to normal level.So,M3 has similar antidepressant effects in depression mice and patients,and M3 also exhibit potential ability to alleviate intestinal dysfunction.(2)The specific relieving effect of compound probiotics M3 on depression: The classic pathological pathways of depression including HPA axis,level of 5-HT and BDNF in brain were explored.Results indicated that supplement of M3 can normalize the Glucocorticoid Receptor related gene(Nr3c1)expression to alleviate HPA axis hyperreactive and CNS inflammatory reaction.Besides,M3 improved the level of 5-HT in prefrontal cortex(PFC)and brain stem,whose potential reason includes two aspects:(a)M3 upregulated the level of LTryptophan(L-Trp)in colon and PFC,which can promote 5-HT synthesis in PFC;(b)M3decreased the 5-HT turnover(5-HIAA/5-HT)in PFC and brain stem.What's more,M3 upregulated the Phosphorylation level of c AMP-Response Element Binding Protein(CREB)and BDNF level,decreased the level of pro BDNF,thereby maintaining the balance of BDNF/pro BDNF.Additionally,M3 can decrease the symptoms of constipation(gastrointestinal transit rate,fecal water content,time to the first black stool detection).Those constipation phenotypes change may connect to the low expression of Slc6a4 gene by M3 which result in up-regulated colon 5-HT level.Hence,CUMS can induce mice generate depression and constipation at the same time.M3 intervention can alleviate HPA axis hyperreaction,upregulate level of 5-HT and BDNF in brain to relief depression.Additionally,M3 could alleviate constipation through increasing colon 5-HT level since 5-HT could improve gastrointestinal motility.(3)Exploration of M3 potential mechanisms in alleviating depression through gut microbiota and its metabolites: Through 16 S V3-V4 sequencing analysis and GC-MS detection,the change of gut microbiota and SCFA in depressed mice and depressed patients with M3 treatment were detected.Results indicated that M3 could improve gut microbiota diversity in depression mice,while no influence on depression patients' gut microbiota.However,M3 upregulated fecal acetate and butyrate levels in both depression patients and mice.Bifidobacterium and Faecalibaculum were positive correlate to acetate,while Alistipes is positive correlate to butyrate.To directly prove the influence of SCFAs on depression,four main SCFAs(acetate,propionate,butyrate and isobutyrate)-acylated starches were used to feed CUMS induced depression mice.It was found acetate,butyrate and isobutyrate could alleviate depression-and anxiety-like behavior,and decrease the hyperactive of HPA axis.Through correlation analysis,it was found acetate and butyrate are negative correlation with corticosterone,while positive correlation with colon 5-HT.Based on above results,we speculate the alleviation on depression and constipation by M3 may attribute to its capability in promoting gut microbiota to generate SCFAs,especially acetate and butyrate.