Characteristics of Gut Microbiota in Diarrhea-predominant Irritable Bowel Syndrome of Han Nationality in Southwest China

Backgroud To study of gut microbiota in IBS-D of Han nationality in Southwest China, explore its relationship with environmental factors and differential expression function of gut microbiota in patients. Methods 120 cases of IBS-D group and 63 cases of HCs group were recruited, baseline data such as age, height, weight, monthly income, work intensity, eating habits and exercise were collected. HAMA and HAMD scores were performed on the two groups. IBS-D group was scored with IBS-SSS and IBS-QOL, and the differences in gastrointestinal symptoms, mental and psychological status and quality of life were compared. The laboratory tests were performed such as blood routine and liver function. Fresh feces of the two groups were collected for 16S rDNA sequencing. Then analyze the differences of gut microbiota between the two groups, and look for typical biomarkers of each. According to the dominant species and differentially expressed species at different classification levels, FAPROTAX was used to predict the functional differences of gut microbiota between the two groups. Taking the above scores and laboratory tests as environmental factors, spearman correlation analysis was conducted at the phylum level to explore the impact of environmental factors on the occurrence and development of gut microbiota and IBS-D. Results IBS-D patients are mostly concentrated in low-medium income people with medium-high labor intensity. The sleep time, exercise time, intake of vegetables and fruits of IBS-D are significantly lower than those of HCs, and the proportion of IBS-D who like to eat pepper is significantly higher than those of HCs. The scores of HAMA and HAMD, Urea nitrogen, AST, ALT , GGT in IBS-D were significantly higher than those in HCs.The richness of gut microbiota in IBS-D was significantly lower than that in HCs, but not diversity and eveness. The beta diversity index of gut microbiota community was significantly different between the two groups. The biomarkers of IBS-D were Prevotella, Clostridiales and Roseburia, the biomarkers of HCs were Veillonellaceae, Bacteroides-coprocola, Bifidobacteriales, Bifidobacteriumde, etc. The functions of gut microbiota in IBS-D were significantly up-regulated in cellulolysi, xylanolysis, and significantly down-regulated in fermentation, methanogenesis, nitrite_ammonification, nitrate_reduction. Correlation analysis showed that multiple intestinal microorganisms were closely related to HAMA, IBS-SSS, IBS-QOL, inflammatory indexes and liver enzymes. Conclusion There are significant differences in richness of gut microbiota, flora structure and flora function between IBS-D and HCs in Southwest China. These differences may be closely related to environmental factors such as eating habits, living habits and mental and psychological factors.The trial was registered and approved in China Clinical Trial Registry (Registration No.ChiCTR2100045751)