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- κβ (NF- κβ ), 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- κβ 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.