Comparison Of Enteric Prebiotic Function Between Pectin And Inulin

The gut tract of mammals harbours a complex and dynamic microbiota population that plays a vital role in maintaining host immune and metabolic homeostasis and protecting against pathogens.There is a growing recognition on the role of diet in modulating the composition and metabolic activity of gut microbiota,which in turn can impact health.The supplementation of dietary polysaccharides is considered as the best way of maintaining a healthy gut microbiota population.Dietary polysaccharides can escape from the degradation of host digestive enzymes,and fermented by the gut microbiota which selectively alters its taxonomic composition and metabolic activity,therby confer health benefits to the host.Different dietary polysaccharides will have different effects on the host due to structural differences.Pectin and inulin are two common dietary polysaccharides.The difference in the probiotic effects of pectin and inulin has not been reported.In this study,healthy Wistar rats were fed with AIN-93 M standard diet,pectin diet and inulin diet for 30 days,then the differences in cecum microbiota,mucosal microbiota,short chain fatty acids levels,metabolites composition and MUC2 levels in the colon contents were compared.Then we used starch,pectin and inulin as the sole carbon source to ferment the cecum contents in vitro: The bacterial composition,short chain fatty acids levels and metabolites composition of the fermentation broth were analyzed.The LS174 T cells were treated with fermentation broth to compare the effects of different polysaccharides before and after fermentation on LS174 T cell MUC2 secretion.The results showed that:(1)In terms of microbiota regulation,pectin and inulin promoted the growth of potential beneficial bacteria and reduced the abundance of pathogenic bacteria.Compared with standard diet,in cecum,higher abundance of Christensenellaceae?R-7?group and Lachnospira in pectin diet and inulin diet were found(p<0.05),and pectin promoted the growth of Lactobacillus more than inulin(p<0.05)while there was no significant difference between other beneficial bacteria(such as Bifidobacteria and Akkermansia).In mucus layer,the abundance of Helicobacter and Escherichia-Shigella in pectin diet decreased(p<0.05).Although the abundance of Escherichia-Shigella in inulin diet decreased(p<0.05),high abundance of Helicobacter in inulin diet were found.In fermentation broth,the abundance Lactobacillus in pectin broth and inulin broth increased(p<0.05).In addition,pectin increased the abundance of Bifidobacteria(p<0.05).(2)In terms of metabolites regulation,pectin and inulin promoted the production of acetic acid both in vivo and in vitro experiments.In cecum,the content of acetic acid was significantly correlated to four genera in cecum content,including Christensenellaceae?R-7?group(r = 0.53),Coprococcus?2(r =-0.47),Anaerotruncus(r =-0.55)and Ruminococcus?1(r =-0.60),while no significant correlation between acetic acid and mucosal microbiota was found.In fermentation broth,acetic acid significantly correlated to four genera of Veillonella(r = 0.61),Bifidobacterium(r = 0.68),Lactobacillus(r = 0.65)and Allobaculum(r = 0.68).Inulin also showed the effect of promoting the production of butyric acid in cecum,and butyric acid content was significantly correlated with Ruminococcaceae?UCG-014(r = 0.53),but no increase in butyric acid content in inulin broth was observed.Pectin and inulin also changed the composition of other metabolites.In cecum,it was found that pectin reduced the level of 3-methylindole and lithocholic acid,and inulin reduced the level of p-cresol.The decrease of these metabolites may be beneficial to the host health.(3)In terms of promoting MUC2 secretion,both pectin and inulin raised the content of colonic MUC2(p<0.05).Pearson correlation analysis between MUC2,gut microbiota and gut metabolites showed that MUC2 content was significantly correlated with Anaerotruncus(r =-0.62),Ruminococcus?1(r =-0.52),acetic acid(r = 0.80),Lucyoside Q(r = 0.57),Soyasapogenol B 24-O-b-D-glucoside(r = 0.59),25-Acetylvulgaroside(r =-0.66),3?-Androstanediol glucuronide(r =-0.55)and Corosolic acid(r =-0.48).There was no significantly correlation between MUC2 and mucosal microbiota.In simulated fermentation in vitro,comparing to unfermented medium and starch fermentation broth,pectin and inulin fermentation broth stimulated LS174 T cells to secrete more MUC2(p<0.05).We also found high level of acetic acid in pectin and inulin fermentation broth,but no significant changes in the content of other metabolites that were significantly related to MUC2 were observed.Conclusion: Both pectin and inulin positively regulated the composition of microbiota and metabolites,including promoting the growth of potential beneficial bacteria,reducing the abundance of pathogenic bacteria,promoting the production of short chain fatty acids,and reducing the content of potential harmful metabolites.But the kands of microbiota and metabolites regulated by pectin and inulin were not completely consistent.Compared with the inulin,the abundance of Lactobacillus in the cecum and fermentation broth of the pectin intervention is higher,and the abundance of Helicobacter in the mucus layer is lower,so pectin may shape a healthier intestinal microbiota than inulin.Pectin and inulin have a similar effect on increasing MUC2 secretion,which may be related to the increase of acetic acid.