Changes Of Gut Microbiota Before And After Treatment Of Methimazole In Graves Disease Patients

Objective: The pathogenesis of Graves' disease(GD)is not yet completely clear.But it can be determined that,on the basis of genetic susceptibility,the immune function disorder caused by environmental factors has been proved to be an important component,environmental factors and the composition of gut microbiota are closely related to the structure.The purpose of this study was to analyze the Changes of gut microbiota before and after treatment of Methimazole in patients with GD and to explore the correlation between the changes of specific flora and correlation of thyroid associated antibodies.Methods: The newly diagnosed GD patients(UGD group,n=18)were selected from the Endocrinology Department of Zunyi Medical University affiliated Hospital.The thyroid function returned to the normal level after treatment of Methimazole(TGD group,n=10).In addition,the healthy population in the physical examination center of the affiliated Hospital of Zunyi Medical University at the same time was collected as the normal control group(NC group,n=11).Collect the medical history data,human parameters,thyroid function,blood routine,liver and kidney function,glucose and lipid metabolism and other related biochemical indicators.The stool samples were collected,the DNA of the gut microbiota was extracted,the 16 S rRNA gene was amplified,and the Illumina platform was sequenced.The relative abundance of Bifidobacterium in NC group and UGD group was correlated with TRAb,TgAb and TPOAb by Spearman rank test.Results:(1)Through sequencing,a total of 1562445 high-quality sequences were obtained,of which 477940 was from the NC group;722725 were from the UGD group;361780 were from the TGD group;each sample has an average of(40063±6355)valid sequences.The quantity of common and unique OTUs in the 3 groups was graphically presented through a Venn diagram.The NC group had 409 unique OTUs,the UGD group had 525 unique OTUs,and the TGD group had 191 unique OTU.Moreover,a total of 2177 OTUs in 3 groups overlapped each other.There were no differences in Chao1 index,ACE index,Shannon index and Simpson index between the three groups(P>0.05),but the diversity of gut microbiota in GD group was lower than that in NC group.Beta diversity analyses based on Nonmetric Multidimensional Scaling(NMDS)could discriminate the NC samples from UGD and TGD samples.(2)Firmicutes,Bacteroidetes,Actinobacteria and Proteobacteria constituted the four dominant phyla in all samples,accounting for more than 99% of the total number of bacteria.Relative abundance of Actinobacteria and Cyanobacteria was significantly higher and Firmicutes was significantly lower in UGD samples than that in NC samples(P<0.05),TM7 and [Thermi] were significantly different between UGD and NC group as well as between TGD and NC group(P<0.05).(3)A total of 19 genera with proportions above 1% were detected and Bacteroides accounted for the largest proportion in all samples.Relative abundance of Bifidobacterium and Collinsella was higher and Roseburia and Dialister was lower in UGD samples than that in NC samples(P<0.05);Relative abundance of Bacteroides was higher and Prevotella and Dialister was lower in TGD samples than that in NC samples(P<0.05);Prevotella and Collinsella were higher in UGD group than in TGD group(P<0.05).(4)Linear discriminant analysis(LDA)results showed the dominant abundance distribution of Bifidobacteriaceae,Clostridiaceae,Carnobacteriaceae in the UGD group than that in the NC group,while the dominant abundance distribution of Porphyromonadaceae,Rikenellacaeae,Veillonellaceae,etc was found in NC group.Xanthomonadates,Xanthomonadaceae,_Chromatiaceae_and Alteromonadales were enriched in the TGD group,while Leuconostocaceae was mainly enriched in the UGD group(LDA value>2,P<0.05).(5)Correlation analysis of Relative abundance of Bifidobacterium with TRAb,TgAb and TPOAb between the NC and UGD groups by using Spearman rank test.The abundance of Bifidobacterium showed a significant positive association with hyperthyroidism include TRAb(r=0.588,P=0.002),TgAb(r=0.463,P=0.023),TPOAb(r=0.578,P=0.002).Conclusion: Intestinal biodiversity was decreased in GD patients.There were some differences in gut microbiota between normal people and Methimazole before and after treatment.It was mainly the change of the abundance of some pathogenic bacteria such as Collinsella and the beneficial bacteria(Roseburia)producing SCFAs.But The change of the abundance of Bifidobacterium was positively correlated with TRAb,TgAb amd TPOAb,suggesting that it may be related to the immune mechanism of GD.Therefore,we hypothesized that gut microbiota disorder may be one of the pathogenesis of GD.