Preliminary Study On The Effect And Mechanism Of Phenylethanoid Glycosides On Functional Dyspepsia In Rats

Houpo,the cortex of Magnolia officinalis Rehd.et Wils.or Magnolia officinalis Rehd.et Wils.var.biloba Rehd.et Wils.,has been used as a traditional Chinese medicine.In clinics,Houpo has often been used in combination with other traditional Chinese medicines for the treatment of digestive tract diseases,especially functional dyspepsia(FD).As Houpo has always been used as an aqueous decoction,in our early studies,phenylethanol glycosides(PhGs),kinds of the water-soluble compounds,were isolated from Houpo and they showed anti-spasmodic activity on isolated colon of rats.Howerer,few study about the effect of PhGs on rats in vivo was reported.Therefore,in this paper,for the first time,the effects of phenylethanoid glycosides extract(PGE)and magnoloside A(MA)on normal rats and on FD rats that were resulting from the combination of iodoacetamide(IA)irritation on neonatus and alternate-day fasting(ADF)on adult were studied,and then the possible mechanism was discussed.1 The preparation of MA and quantitative analysis of the main components of PGEAbout 2.54 g of MA was isolated and purified by gel chromatography and reverse phase chromatography.At the same time,an HPLC method for the determination of MA and magnoloside B in PGE was established,and the contents of MA and magnoloside B in PGE were tested to be 10.49%and 15.91%,respectively.2 The effect of PGE and MA on normal ratsEffects of PGE and MA on normal rats were investigated by continuous intragastric administration for 8 days.The results showed that there was no statistically significant difference(P>0.05)on body weight,gastric emptying rate or intestinal ink pushing rate of the PGE and MA groups,compared with those of the normal group.3 The effect of PGE and MA on FD rats and its possible mechanismThe rats were divided into control group,model group,high dose MA group(MA-H,20 mg/Kg),medium dose MA group(MA-M,10 mg/Kg),low dose MA group(MA-L,5 mg/Kg),PGE group(PGE,40 mg/Kg)and positive control group(Dom).3.1 Histological examination of stomach and the effect on the intestinal absorption of FD ratsThe result of histological examination suggested that there was no morphological change in the stomach of FD rats compared with those of the control group.The content of serum D-xylose showed that there was no significant difference between any two groups,which suggested that the ability of intestinal absorption of all groups was good.3.2 The effect on gastric emptying of FD ratsCompared with the control group,the decrease of gastric emptying rate of the model group was statistically significant(P<0.05).Compared with those in the model group,the gastric emptying rates of rats in the MA-H,MA-L and PGE group were significantly increased.The results showed that MA and PGE could improve the delayed gastric emptying of FD rats.3.3 The effect on brain-gut peptides(BGPs)and inflammatory factors of FD ratsLevels of gastrin(GAS),motilin(MTL),somatostatin(SS),calcitonin gene related protein(CGRP),vasoactive intestinal peptide(VIP),5-hydroxytryptamine(5-HT),interferon-y(IFN-y)and interleukin-4(IL-4)in serum or tissues were measured by using enzyme linked immunosorbent assay(ELISA);levels of nitric oxide synthase(NOS),lactic acid(LD)and amylase(AMS)in serum were measured by using colorimetry.The result showed that,compared with the control group,levels of GAS,MTL and AMS were significantly decreased,and levels of 5-HT,CGRP,VIP,NOS,LD and IL-4 were significantly increased in the model group(P<0.05)Compared with the model group,levels of GAS,MTL and AMS were increased in the PGE and MA groups,while levels of 5-HT,CGRP,VIP,LD and IL-4 were decreased,and all of these changes were statistically significant(P<0.05).Moreover,dose-response effects of MA were found in the cases of MTL,SS,5-HT,CGRP,IL-4,LD and AMS.In addition,the synergistic effect of PhGs was suggested by comparing the data between the MA-L and PGE group.Effects on intestinal bacteria of FD ratsIntestinal bacteria in feces of experimental rats were analyzed by 16S rRNA gene sequencing.Compared with the control group,the total relative abundance of Firmicutes and Bacteroidetes was increased,while the ACE index was significantly decreased in the model group(P<0.05).Compared with the model group,the total relative abundance of Firmicutes and Bacteroidetes was decreased and the ACE index was increased after being administrated by PGE and MA for 2 weeks.The result showed that the PhGs of Houpo could improve the richness of intestinal bacteria.By using LEfSe,14 differential bacteria were screened out from the annotation information of OTUs,and 19 metabolism-related differential pathways were screened out from the function prediction results by Tax4fun.Thus,the above 14 differential bacteria and 19 metabolism-related differential pathways were speculated to be the potential targets of PGE and MA.3.4 Effects on concentrations of short-chain fatty acids(SCFAs)of FD ratsConcentrations of 8 SCFAs in the feces of rats were determined by GC/MS.The result showed that though there was no statistical difference between any two groups on the contents of 8 SCFAs and total SCFA,some upward trends on the concentrations of total SCFA,acetic acid and propionic acid were observed in the model group,compared with the control group,while some downward trends were observed after PGE and MA administration.It was suggested that contents of SCFAs could be affected by PGE and MA,and SCFAs might be potential targets of PGE and MA.3.5 Preliminary study on the mechanismWith double variable spearman correlation analysis,the association between 14 differential bacteria and 19 differential pathways and level of 5-HT,LD,IFN-?,IL-4,AMS,GAS,MTL,NOS,SS,CGRP,VIP,and concentrations of 8 SCFAs were studied,respectively.It was found that 14 differential bacteria and 19 differential pathways were significantly correlated with BGPs and other physiological indicators,while few significantly correlated with SCFAs.At the same time,associations between levels of 5-HT,LD,IFN-?,IL-4,AMS,GAS,MTL,NOS,SS,CGRP,VIP and concentrations of 8 SCFAs were also studied,and SCFAs were found to be significantly correlated with 5-HT,AMS,LD,NOS and CGRP.In conclusion,PhGs could statistically improve the gastric emptying rate of FD rats,increase levels of GAS and MTL,and reduce levels of 5-HT,CGRP and VIP(with dose-dependence relationship),which suggested that PhGs were beneficial to the gastric motor and visceral hypersensitivity.PhGs could also adjust the structure of intestinal bacteria,reduce the total relative abundance of Firmicutes and Bacteroidetes and increase the species richness;change the functional pathways of the intestinal bacteria;regulate concentrations of SCFAs and indirectly regulate the secretion of gastrointestinal hormones.