Study On The Structure Of Gut Microbiota In Different Ethnic Groups By Pyrosequencing

A large number of studies have shown that the gut microbiota is closely related tohuman health and metabolism, in particular in metabolic diseases; therefor, the profiling ofhuman gut microbiota has become one of the research hot topics. In this study, we havestudied the effects of age, lifestyle and genotype on the gut microbiota of healthy Chinesepeople, meanwhile we have looked for the phenotypic characteristics that are responsible forthe differentiation between ethnic groups or lifestyles. Although the understanding of thehuman gut microbiota is of great interest due to recently accumulating evidence of its tightassociation with the human health, there is no evidence that a change in the composition ofthese microbes would impact on diseases. Oral probiotic strains and inulin could affectmicrobial environment of the gut microbiota, we conducted a meta-analysis of randomizedcontrolled trials that evaluated the effects of probiotics and inulin consumption on bloodlipids. The main results are described as follows：(1) We performed a structural survey of the gut microbiota of17healthy individuals (5infants,6young people, and6middle-aged people) by using deep454pyrosequencing of theV5-V6region of the16S ribosomal RNA gene. By combining an Unweighted Pair GroupMethod with Arithmetic Mean (UPGMA) and UniFrac principal component analysis (PCoA),we observed that the fecal microbial communities of the infant individuals were distinct fromthose of the other individuals (P>0.001). Multivariate analysis of variance showed that thedifference between the young and middle-aged individuals was not significant. The UniFracdistance metric indicated that the interpersonal variation was significantly greater among theinfants than among the young and middle-aged people (P>0.05). Firmicutes was identifiedas the predominant phylum in the young and middle-aged people, whereas Proteobacteriawas the most abundant in the infants (P>0.05). Contrasting to the findings of other studies,Klebsiella, rather than Bifidobacterium, was identified as the most abundant microbial genusin the infant samples. There were significant differences in the phylogenetic composition ofthe gut microbiota of the healthy Chinese infants and adults, but high similarities in thestructure of the gut microbiota of young and middle-aged people. Interpersonal variation wassignificantly greater among the infants than among the young or middle-aged people.(2) We compared the fecal microbiota of urban (N=15) and pastoral (N=28) residents inTibet. By using high-throughput16S rDNA sequencing and biochemical analyses, we foundthat although UPGMA and PCoA analysis both showed an overlapping of a few of thesamples,, the difference between the two groups was significant, as shown by Manovaanalysis (P <0.05). UniFrac distance metrics indicated that the interpersonal variation wassignificantly greater among the pastoral residents than the urban ones, meanwhile the meancommunity richness and diversity were higher in the pastoral residents. By Partial LeastSquare Discriminate Analysis (PLS-DA), we identified212OTUs as key phenotypes thatresponded to lifestyle, and more than a quarter of them were Blautia, Clostridium,Phascolarctobacterium, Roseburia and Subdoligranulum. By using Mann-Whitney test, wefound that the bacterial-derived short-chain fatty acids (SCFA) were enriched in urban residents as compared to the pastoral subjects. Thus, we could conclude that the gut microbialcommunities of the pastoral residents were distinct from that of the urban residents, and theirlifestyle had a significant effect on the gut community composition.(3) We compared the fecal microbiota of the Uygurs (N=28) and Kazakhs (N=15) livingin Urumqi. By using high-throughput16S rDNA sequencing and biochemical analyses, wefound that although UPGMA and PCoA analysis both showed an overlapping of a few of thesamples, the difference between the two groups was significant, as shown by Manova analysis(P <0.05). UniFrac distance metric indicated that the interpersonal variation was significantlygreater among the Kazakhs, meanwhile the mean community richness and diversity werehigher in the Uygurs. By PLS-DA Analysis, we identified69OTUs as key phenotypes thatresponded to genotype, and more than one third of them were Clostridium, Roseburia, Blautia,Subdoligranulum, Faecalibacterium, Bacteroides, and Dorea, By using Mann-Whitney test,we found that these bacterial short-chain fatty acids (SCFA) were enriched in the Uygurs.Thus, we could conclude that the gut microbial communities of the Kazakhs were distinctfrom that of the Uygurs, and genotype had a significant effect on the gut communitycomposition.(4) We collectively analyzed the gut microbiota in the92healthy young adults which hadbeen studied in part (1) to part (3). At the genus level, eleven taxa, which contained knownshort-chain fatty acids (SCFAs)-producing capacity, were universally present in all theindividuals. These included Phascolarctobacterium, Faecalibacterium, Blautia, Clostridium,and Ruminococcus. Canonical analysis of principal coordinates based on the unweightedUniFrac metric revealed that the volunteers clustered together mainly according to their ethnicbackground. A total of57OTUs were selected as the potential contributors to the ethnicbackground-driven structural variation. By the criterion that each selected OTU should bepresent in less than5%samples in at least one ethnic group but in more than67%samples inone or more of other groups, it appeared that the distinctiveness of the gut microbiotastructure in the Kazakh and Uygur ethnic groups was largely due to the absence of lineageswithin the genera Phascolarctobacterium, Bacteroides, and Roseburia. In addition, a differentset of OTUs was absent, including those within the genera Blautia and Prevotella.Interestingly, the Han and Tibetan showed a contrasting phenomenon. Thus, all92individualsshared a few common components, and any individual shared many components with a fewother individuals. However, very little was shared across all individuals.(5) Based on meta-analysis, we concluded that the consumption of oral probioticsexerted beneficial effects on the total cholesterol and LDL cholesterol for subjects with high,borderline high and normal cholesterol levels. Moreover, a diet rich in inulin was beneficial tothe plasma total and LDL cholesterol, as well as triglyceride concentration of hyperlipidemicsubjects, but had no effect on the plasma lipid in normolipidemic subjects.