Effect of Curcumin on Diabetic Kidney Disease: A Systematic Review and Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Clinical Trials

Background. Curcumin, a polyphenolic constituent from Curcuma longa, possesses antioxidant, hypolipidemic, and antidiabetic properties and has been reported to protect against diabetic kidney disease (DKD); however, the effect is inconsistent. Objective. This systematic review and meta-analysis aimed to investigate the effect of curcumin supplementation on renal function, lipid profile, blood pressure, and glycemic control in DKD. Methods. A systematic and comprehensive literature search of interrelated randomized controlled trials (RCTs) was conducted in PubMed, Embase, Cochrane Library, Web of Science, Scopus, and ClinicalTrials.gov from inception to July 30, 2021. Two investigators independently extracted data and assessed the risk of bias. Weighted mean differences (WM Ds) with 95% confidence intervals (CIs) were calculated to describe the effect sizes using a fixed-effect model. Statistical analysis was performed using STATA 14.0 and RevMan 5.3. Results. Five RCTs involving 290 participants with DKD were included. Curcumin supplementation significantly improved the serum creatinine (WMD: -0.16 mg/dl., 95% CI: -0.3 to -0.02, P =0.029, I-2 = 0%, moderate certainty), total cholesterol (WMD: -10.13 mg,/dL, 95% CI: -17.84 to -2.14, P = 0.01, I-2 = 0%, moderate certainty), systolic blood pressure (WMD: 3.94 mmHg, 95% CI: 1.86 to 6.01, P < 0.01, I-2 = 33.5%, moderate certainty), and fasting blood glucose (WMD: -8.29 mg/dL, 95% CI: -15.19 to -1.39, P=0.019, I-2 = 43/%, moderate certainty) levels; however, it had no significant effects on blood urea nitrogen, proteinuria, triglyceride, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, and diastolic blood pressure levels. Conclusions. Curcumin may provide great potential effects against DKD. More large-scale and high-quality RCTs are required to confirm these findings.