CXCL12 and diabetes mellitus: As we speculated, saxagliptin might protect podocytes by inhibiting DPP-4 enzyme activity and preventing SDF-1α cleavage; therefore, we determined the DPP-4 enzyme activity in both serum and renal tissue and found that saxagliptin obviously inhibited the diabetes-enhanced DPP-4 enzyme activity in diabetic rats (Figures 4A,B).