The impact of curcumin supplementation on systemic lupus erythematosus and lupus nephritis: A systematic review

Objective Curcumin is the active ingredient in the curry spice turmeric. It has anti-inflammatory properties due to the inhibition of transcription factors and inflammatory mediators such as nuclear factor-kappa beta (NF-kappa beta), cyclooxygenase-2 (COX2), lipoxygenase (LOX), tumor necrosis factoralpha (TNF-alpha), and interleukin-1 (IL-1) and 6 (IL-6). This review examines the literature regarding the efficacy of curcumin on systemic lupus erythematosus disease activity. Methods A search was conducted following guidelines in the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) using the PubMed, Google Scholar, Scopus, and MEDLINE electronic databases to retrieve relevant studies assessing the impact of curcumin supplementation on SLE. Results The initial search yielded three double-blind, placebo-controlled, randomized clinical trials, three human in vitro studies, and seven mouse-model studies. In human trials, curcumin decreased 24-h and spot proteinuria, but the trials were small, ranging from 14 to 39 patients, with varied curcumin doses and different study durations ranging from 4 to 12 weeks. There was no change in C3, dsDNA, or the Systemic Lupus Erythematosus Disease Activity (SLEDAI) scores even in the longer trials. The mouse-model trials yielded more data. NF-kappa beta activation was suppressed along with inducible nitric oxide synthase (NOS) species expression when 1 mg/kg/day of curcumin was administered for 14 weeks, leading to significant decreases in dsDNA, proteinuria, renal inflammation, and IgG subclasses. Another study suggested that curcumin reduced B cell-activating factor (BAFF) when used for up to 8 weeks at 50 mg/kg/day. A reduction in pro-inflammatory Th1 and Th17 percentages, IL-6 and anti-nuclear antibody (ANA) levels were reported. The doses used in the murine models were much higher than those used in human trials, with 12.5 mg-200 mg/kg/day used for over 16 weeks; highlighting that the optimal time for an immunological effect to be observed may require 12-16 weeks of curcumin use. Conclusion Despite the wide use of curcumin in everyday life, its molecular and anti-inflammatory use has only been partially explored. Current data show a potential benefit on disease activity. Still, no uniform dose can be advised because long-duration, large-scale randomized trials using defined dosing are needed in different subsets of SLE, including lupus nephritis patients.