As stated in section 1.2.1, a decrease in the number of bacteria that produce HSDH in the intestinal tract of DKD patients prevents the isomerization of stone cholic acid and reduces the production of stone cholic acid derivatives, thus suppressing Treg differentiation and the inhibition of Th17 differentiation, disrupting the immune balance of Treg/Th17 cells, and exacerbating the disorder of the immune environment in DKD patients (Figure 2). Here, SDS is linked to diabetic kidney disease.