Characteristic dysbiosis of gut microbiota of Chinese patients with diarrhea-predominant irritable bowel syndrome by an insight into the pan-microbiome

Background:Irritable bowel syndrome(IBS)is reported associated with the alteration of gut microbial composition termed as dysbiosis.However,the pathogenic mechanism of IBS remains unclear,while the studies of Chinese individuals are scarce.This study aimed to understand the concept of dysbiosis among patients with Chinese diarrhea-predominant IBS(IBS-D),as a degree of variance between the gut microbiomes of IBS-D population and that of a healthy population.Methods:The patients with IBS-D were recruited(assessed according to the Rome III criteria,by IBS symptom severity score)from the Outpatient Department of Gastroenterology of Peking University Third Hosp让al,and volunteers as healthy controls(HCs)were enrolled,during 2013.The 16S rRNA sequences were extracted from fecal samples.Ribosomal database project resources,basic local alignment search tool,and SparCC software were used to obtain the phylotype composition of samples and the internal interactions of the microbial community.Herein,the non-parametric test,Wilcoxon rank-sum test was carried out to find the statistical significance between HC and IBS-D groups.All the P values were adjusted to q values to decrease the error rate.Results:The study characterized the gut microbiomes of Chinese patients with IBS-D,and demonstrated that the dysbiosis could be characterized as directed alteration of the microbiome composition leading to greater disparity between relative abundance of two phyla,Bacteroidetes(Z=4.77,q=1.59×10^-5)and Firmicutes(Z=-3.87,q=5.83×10^-4).Moreover,it indicated that the IBS symptom features were associated with the dysbiosis of whole gut microbiome,instead of one or several certain genera even they were dominating.Two genera,Bacteroides and Lachnospiracea incertae sedis,were identified as the core genera,meanwhile,the non-core genera contribute to a larger pan-microbiome of the gut microbiome.Furthermore,the dysbiosis in patients with IBS-D was associated with a reduction of network complexity of the interacted microbial community(HC us.IBS-D:639 vs.154).The disordered metabolic functions of patients with IBS-D were identified as the potential influence of gut microbiome on the host(significant difference with q<0.01 between HC and IBS-D).Conclusions:This study supported the view of the potential influence of gut microbiome on the symptom of Chinese patients with IBS-D,and further characterized dysbiosis in Chinese patients with IBS-D,thus provided more pathological evidences for IBS-D with the further understanding of dysbiosis.

Relationship between Gut Microbiota and Phosphorus Metabolism in Hemodialysis Patients:A Preliminary Exploration

Background:Hyperphosphatemia is a risk factor associated with mortality in patients on maintenance hemodialysis.Gut absorption of phosphate is the major source.Recent studies indicated that the intestinal flora of uremic patients changed a lot compared with the healthy population,and phosphorus is an essential element of bacterial survival and reproduction.The purpose of this study was to explore the role of intestinal microbiota in phosphorus metabolism. Methods:A prospective self-control study was performed from October 2015 to January 2016.Microbial DNA was isolated from the stools of 20 healthy controls and 21 maintenance hemodialysis patients.Fourteen out of the 21 patients were treated with lanthanum carbonate for 12 weeks.Thus,stools were also collected before and after the treatment.The bacterial composition was analyzed based on 16S ribosomal RNA pyrosequencing.Bioinformatics tools,including sequence alignment,abundance profiling,and taxonomic diversity, were used in microbiome data analyses.Correlations between genera and the serum phosphorus were detected with Pearson's correlation. For visualization of the internal interactions and further measurement of the microbial community,SparCC was used to calculate the Spearman correlation coefficient with the corresponding P value between each two genera. Results:Thirteen genera closely correlated with serum phosphorus and the correlation coefficient was above 0.4(P <0.05).We also found that 58 bacterial operational taxonomic units (OTUs)were significantly different and more decreased OTUs were identified and seven genera (P <0.05)were obviously reduced after using the phosphate binder.Meanwhile,the microbial richness and diversity presented downward trend in hemodialysis patients compared with healthy controls and more downward trend after phosphorus reduction.The co-occurrence network of genera revealed that the network complexity of hemodialysis patients was significantly higher than that of controls,whereas treatment with lanthanum carbonate reduced the network complexity. Conclusions:Gut flora related to phosphorus metabolism in hemodialysis patients,and improving intestinal microbiota may regulate the absorption of phosphate in the intestine.The use of phosphate binder lanthanum carbonate leads to a tendency of decreasing microbial diversity and lower network complexity.

Clinical characteristic and fecal microbiota responses to probiotic or antidepressant in patients with diarrhea-predominant irritable bowel syndrome with depression comorbidity: a pilot study

To the Editor: Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder that presents as abdominal pain with altered bowel habits. The pathophysiologic mechanism of IBS is not well understood, although many hypotheses have been proposed, including visceral hypersensitivity, gastrointestinal dysmotility, lowgrade inflammation of the intestinal mucosa, and dysfunction of the brain-gut interaction. Dysfunction of the braingut interaction is thought to be involved in IBS because a considerable proportion of patients with IBS have some form of psychologic comorbidity, such as depression or anxiety. In addition, mental and psychologic problems increase the risk for IBS and the symptom severity of IBS. Recently, changes in the gut microbiota have also been suggested to contribute to both IBS and depression. Our previous study demonstrated significant altered gut microbiota profiles in patients with diarrhea-predominant IBS (IBS-D) and depression.