Abstract: Objective To analyze the species, abundance and structure differences of intestinal flora between patients with type 2 diabetes mellitus (T2D) and healthy individuals and explore the correlation between intestinal flora changes and T2D. Methods We collected a total of 133 clinical fecal samples from 78 healthy individuals and 55 patients with T2D. Hiseq2500 was used for high-throughput sequencing of the V3+V4 regions of the 16S rRNA gene. Usearch and QIIME were used for data splicing and filtering, classification and species annotation. The Alpha diversity index and Beta diversity index of the samples were analyzed using R language data packets to compare the richness and diversity of the sample flora. The flora differences were compared between the two groups and the disease marker flora was screened after correction of the relevant factors. PICRUST software was used to predict the function of different flora. Results There was significant difference in the intestinal flora diversity between the two groups. Cluster analysis showed that Fimicutes and Bacteroidetes were the dominant species at the phylum level. LefSe analysis showed that significant differences in the relative abundance between the two groups in 2 phyla, 3 classes, 3 orders, 4 families and 10 genera. After correction for the influence of related factors, the markers of T2Drelated bacteria groups were identified, including Bifidobacterium, Bifidobacteriales, Bifidobacteriaceae, Actinobacteria, Bacilli, Lactobacillales, Lactobacillaceae and Lactobacillus. On this basis, analysis of KEGG metabolic pathways of the differential flora revealed significant differences in 36 KEGG metabolic pathways between the two groups, and the citric acid cycle, lipopolysaccharide biosynthesis and other metabolic pathways were all up-regulated in T2D group. Conclusion The composition and abundance of intestinal flora were different between T2D group and the normal group, and T2D group showed the characteristics of ecological imbalance.

Key words: type 2 diabetes mellitus; intestinal flora; 16S rRNA; metabolic pathways