The effect of antioxidants supplementation on oxidative stress and proinflammatory biomarkers in patients with chronic kidney disease: a systematic review and meta-analysis.

Abstract

This systematic review and meta-analysis aimed to address the effect of antioxidant supplementation on oxidative stress and proinflammatory biomarkers in patients with Chronic Kidney Disease (CKD). Systematic literature searches from the date of inception up to September 16th, 2022, were performed on PubMed, SCOPUS, and the Cochrane Central Register of Controlled Trials using relevant keywords, i.e., "Chronic Kidney Disease" and "antioxidants", and "supplementation". All studies relevant to the selection criteria were included in the analysis, focusing on any type of oxidative stress and proinflammatory biomarkers. A meta-analysis of included literature was conducted if sufficient data was obtained. This systematic review involved 32 published studies, with most having a Jadad score of ≥ 3 (65.6%). Only studies on antioxidants, i.e., polyphenols (n=5) and vitamin E (n=6) in curcumin/turmeric, were sufficient to be included in a meta-analysis. Curcumin/turmeric supplementation was found to significantly reduce the serum c-reative protein (CRP) [standardized mean difference (SMD) -0.5238 (95% CI: -1.0495, 0.0019); p = 0.05; I2 = 78%; p = 0.001]. Similarly, vitamin E supplementation was found to significantly reduce the serum CRP [SMD -0.37 (95% CI: -0.711, -0.029); p = 0.03; I2= 53%; p = 0.06] , but not serum interleukin-6 (IL-6) [SMD -0.26 (95% CI: -0.68, 0.16); p = 0.22; I2 = 43%; p = 0.17] and malondialdehyde (MDA) content [SMD -0.94 (95% CI: -1.92, 0.04); p = 0.06; I2= 87%; p = 0.0005]. Our review suggests that curcumin/turmeric and vitamin E supplements effectively lower serum CRP levels in CKD patients, particularly those undergoing chronic dialysis (CKD-5D). Higher scales of randomized controlled trials (RCTs) are still needed for other antioxidants due to inconclusive and contradicting results.