Correlation analysis revealed that Ileibacterium, Bifidobacterium, and Paramuribaculum enriched in the CTL group were positively correlated with ZO1, occludin, and claudin, but negatively correlated with Insulin, G6Pase, and PEPCK (Figure 6), which indicated that T2DM resulted in a decrease in the relative abundance of beneficial bacteria in the intestine. Here, OCLN is linked to type 2 diabetes mellitus.