| IBD is a common digestive disease characterized by chronic,relapsing gastrointestinal tract inflammatory reactions.Although its exact etiology and mechanism are still unclear,researchers have found that the incidence of IBD varies greatly by types of host diets.The consumption of high-fat and high-meat diets may exacerbate the deterioration of IBD.While a vegetarian diet may significantly ameliorate IBD onset and activity.Research has shown that diets can regulate the structure and composition of intestinal microbiota and even genes and functions of certain strains.In addition to host diets,with the in-depth study of host-gut microbial interactions,researches have shown that gut microbiota can affect the occurrence and development of IBD.Especially some specific probiotics,such as Lactobacillus,which is great potential in the prevention and adjuvant treatment of IBD.Based on the above conclusions,this study proposes a hypothesis: whether the dietary structure can achieve the alleviation of IBD by regulating the structure and composition of Lactobacillus and even its genes and functions.Therefore,this study collected fecal samples from different diets,and analyzed the effects of different diets on the growth and colonization of Lactobacillus fermentum by Illumina high-throughput sequencing.Also,the different impacts on DSS-induced colitis in mice by Lactobacillus fermentum from different diets were also discussed.What's more,based on comparing genomes and in vitro experiments,the relationship between the effects of Lactobacillus fermentum towards colitis and host diets was initially explored.The main research contents are as follows:Lactobacillus community of human stool samples from different dietary sources was performed by Illumina high-throughput sequencing technology.First,153 healthy human stool samples were collected from all over China by volunteer recruitment,including 51 vegetarian samples,56 omnivorous samples and 46 high-meat samples.High-throughput sequencing results showed that the richness,homogeneity and total species richness of Lactobacillus community were significantly higher in the vegetarian group than in the omnivorous and high-meat groups.In addition,the relative abundance of Lactobacillus fermentum was 5.34% in the vegetarian group,2.74% in the omnivorous group,and only1.34% in the high-meat group,indicating that different diets had an effect on the growth and colonization of Lactobacillus fermentum,and therefore Lactobacillus fermentum was selected for the subsequent evaluation of probiotic function for IBD alleviation.Isolation and screening Lactobacillus fermentum from different dietary sources of human fecal samples,resulted in 17 strains of vegetarian-source,14 strains of omnivorous sources,and 11 strains of high-meat sources.And DSS was used to establish a mice colitis model to evaluate the probiotic function of IBD.At first,10 strains were randomly selected from each diet group to carry out the mixed bacteria group experiment.The results showed that compared with the omnivorous group and the high-meat group,Lactobacillus fermentum from vegetarian diet had better anti-inflammatory effects and significantly improved the inflammatory reaction,the results showed that the DAI of inflammatory mice decreased significantly,the inflammatory infiltration and mucosal bleeding of colon tissue decreased significantly,and the transcription levels of inflammatory cytokines and gut barrier improved significantly,and a return to the normal intestinal flora.At the same time,determination of short-chain fatty acid in mice faeces showed that the vegetarian-source Lactobacillus fermentum could significantly increase the concentration of short-chain fatty acids in the intestines,especially the concentration of acetic acid increased by 66% compared with the omnivorous group and 82% compared with the carnivorous group.Then,a single strain of Lactobacillus fermentum was randomly selected from each diet group and the results were similar to those of mixed culture group.The ability of vegetarian single strain to alleviate IBD was better than that of omnivorous and high-meat single strain.Based on the analysis method of comparative genome,this study further explored the internal mechanism of different dietary sources of Lactobacillus fermentum to improve IBD.Then annotated its genome information through the KEGG database.Vegetarian-source Lactobacillus fermentum is enriched with more genes related to carbohydrate metabolism,while meat-derived Lactobacillus fermentum is enriched with more amino acid metabolism.Analysis of its carbohydrate-active enzyme genes also showed similar results.Vegetarian-derived Lactobacillus fermentum contains more genes encoding glycoside hydrolase family.After further analysis of its functional genes,it was found that the copy number of gene ME2 in vegetarian-source Lactobacillus fermentum was significantly higher than that of omnivorous and high-meat sources.ME2 is closely related to the metabolism and synthesis of pyruvate,which is an important precursor substance of short-chain fatty acids.Therefore,this article speculates that Lactobacillus fermentum is affected by the type of host diet,and the copy number of its functional gene ME2 has changed,leading to differences in the ability of strains to produce short-chain fatty acids between different dietary sources.Finally,the ability to produce short-chain fatty acids in vitro was tested to further verify that the vegetarian-source Lactobacillus fermentum has the strongest ability to produce short-chain fatty acids.The acetic acid content per milliliter of bacterial liquid is 1.2 times that of omnivorous sources and 1.3 times that of meat sources.In summary,this study proved that the type of diets can relieve IBD by adjusting the abundance and function of specific probiotics in the intestine,such as Lactobacillus fermentum.This study further explored the relationship between diet,gut microbiota and IBD,and directed screening of Lactobacillus fermentum with the ability to alleviate IBD through different dietary patterns,which is conducive to the further exploration of Lactobacillus fermentum with excellent probiotic functions. |
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