The present study showed that rats with CKD had elevated levels of CRE, BUN, NAG, IS, PCS, and LPS, decreased expression of colonic tight junction proteins claudin-1 and occludin, and significantly altered abundance of fecal species at the genus level of Bacteroides, Bifidobacterium, and Lactobacillus compared to the control group. Here, CLDN1 is linked to chronic kidney disease.