Antidepressant-like Effects And The Substances Of Cistanche Tubulosa Stems Based On The "Gut-Brain" Axis And Gastrointestinal Metabolism Analysis

Cistanches Herba is officially recorded as the dried succulent stems of Cistanche deserticola Y.C.Ma and C.tubulosa(Schrenk)R.Wight used for the treatment of kidney deficiency,impotence,female infertility,morbid leucorrhea,profuse metrorrhagia,and senile constipation.Pharmacological investigations have indicated that Cistanches Herba possess a broad range of biological activities including anti oxidative,neuroprotective,and cardioactive effects.Recently,Cistanches Herba has been identified for its anti-depressive effect,however,its substancial bases and pharmacological mechanism were not clearly elucidated.In this study,the gastrointestinal metabolism of the Cistanches Herba in vivo and in vitro were comprehensively investigated.Additionally,efficacy and material basis of antidepressant-like effect of C.tubulosa extract(CTE)was screened and evaluated,and the gastrointestinal metabolism of CTE in normal and depressive rats were also studied.Finally,the pharmacological mechanism of antidepressant-like effects of C.tubulosa through restore homeostasis of gut microbiota and targeting the "gut-brain"axis disorders in rats was discussed1.Gastrointestinal metabolism of active components from Cistanches HerbaThe gastrointestinal metabolic profile of echinacoside,verbascoside,isoverbascoside,and 2'-acetylverbascoside were firstly anayzed.These four single compounds of PhGs in simulated gastric and intestinal juice were stable.The degraded metabolites hydroxytyrosol(HT)and 3-hydroxyphenylpropionic(3-HPP)were transformed from echinacoside,verbascoside,isoverbascoside,and 2'-acetylverbascoside by human intestinal bacteria and demonstrated similar bioactivities to their precursors.The gastrointestinal metabolism of the Cistanches Herba,including C.deserticola(CD)and C.tubulosa(CT)water extract were then investigated.PhGs were easily biotransformed to their aglycone and caffeic acid derivatives through deglycosylation and decaffeoyl in gastric juice,intestinal juice,human intestinal bacteria,and human intestinal microsomes phase I metabolism.Iridoid glycosides were easily transformed to their aglycones in human intestinal bacteria.Furthermore,the prototype components and metabolites of CD and CT water extract in rat urine,feces,and serum were then rapidly screened.Results of this study indicated that PhGs were mainly metabolized into degradation products HT and caffeic acid(CA)in the gastrointestinal tract of rats.2.Evaluation and screening of antidepressant-like effect of C.tubulosa extractIn this study,C.tubulosa was selected for evaluating its antidepressant-like effects due to its higher content of PhGs compared to C.deserticola,behavioral despair model in mice was used for screening antidepressant-like effect of CTE(consisted of 48.6%PhGs,6.9%iridoid glycosides,and 20.0%total saccharides).In addition,chronic unpredictable stress(CUS)rats was used for screening antidepressant-like effect of CTE.As a result,CTE showed excellent antidepressant effect on mice,CTE can significantly improve depression-like behaviors of the CUS rats.In addition,Fr.2(iridoid glycosides)can significantly decrease the immobility time in the tail suspension test and forced swimming test in mice,but showed weaker antidepressive effect than CTE.3.Antidepressant-like effective substances of C.tubulosa based on gastrointestinal metabolismBased on the metabolic profile of Cistanches Herba,metabolites of CTE by normal and CUS rat intestinal bacteria in vitro were identified.PhGs and iridoid glycosides were metabolized to their aglycones which possess the same bioactivities as the precursors by normal and CUS rat intestinal bacteria.The differences between metabolism of CTE by normal and CUS rat intestinal bacteria were attributed to the process of metabolism,the capacity of deglycosylation and isomerization reaction by CUS rat intestinal bacteria was obviously weaker than normal rat.The disordered intestinal bacteria in CUS rat might led to the weakening of metabolic capacity.After oral administration of CTE in normal and CUS rats,metabolites from rat urine were aglycones of PhGs and iridoid glycosides,and their further phase ? metabolites of HT and CA.Compared with the normal group,the prototype constituents of iridoid glycosides,and aglycones of PhGs were detected in CUS rats,while more phase ? metabolites were found in normal rats,which indicated the metabolic capacity of CUS rats were reduced.4.Pharmacological mechanism of antidepressant-like effect of CTE based on "gut-brain" axisAfter 4 weeks treatment of CTE on CUS rats,levels of 5-HT and brain-derived neurotrophic factor(BDNF)in rat hippocampus were significantly increased compared with CUS rats,levels of 5-HT in rat colon were significantly increased as well.Additionally,CTE can significant increase the relative abundance of Bacteroides,Parabacteroides,Butyricimonas,and Weissella compared with the CUS group,and significant decrease the abundance of Ruminococcus,Deinococcus,Trichococcus,and Brachybacterium.In addition,CTE administration had a significant effect on fecal short-chain fatty acids(SCFAs)including acetate,and hexanoic acid.Pearson's correlation analysis demonstrated that 4 weeks treatment of CTE on CUS rats changed the composition of the gut microbiota,improved hippocampus 5-HT and BDNF,colon 5-HT,and SCFAs production,then substantially altered depressive pathology.In conclution,CTE showed excellent antidepressant-like effect,and the effective substances of CTE were its gastrointestinal metabolites,through restoring homeostasis of gut microbiota for microbiota-gut-brain axis disorders.