Compared with the controls, probiotics significantly decreased serum creatinine (Scr) [WMD = −0.17 mg/dL; 95%CI = −0.29, −0.05; p = 0.004], blood urea nitrogen (BUN) [WMD = −1.36 mg/dL; 95%CI = −2.20, −0.52; p = 0.001], cystatin C (Cys C) [WMD = −29.50 ng/mL; 95%CI = −32.82, −26.18; p < 0.00001], urinary albumin/creatinine ratio (UACR) [WMD = −16.05 mg/g; 95%CI = −27.12, −4.99; p = 0.004] and natrium (Na) [WMD = −0.94 mmol/L; 95%CI = −1.82, −0.05; p = 0.04] in patients with DKD. The gene discussed is CST3; the disease is diabetic kidney disease.