Can coenzyme Q10 supplementation effectively reduce human tumour necrosis factor-α and interleukin-6 levels in chronic diseases? Protocol for a systematic review and meta-analysis of randomised controlled trials.

INTRODUCTION: Inflammation, as a critical factor, can cause numerous chronic diseases by creating various proinflammatory cytokines. Coenzyme Q10 (CoQ10) can potentially exert an anti-inflammatory agent; in turn, this agent can reduce the systemic inflammatory response. The aims of this study are to conduct a comprehensive systematic review and a meta-analysis for the determination of the CoQ10 efficacy on the changes in serum interleukin-6 (IL-6) and the tumour necrosis factor-α (TNF-α) levels in unhealthy subjects.

METHOD AND ANALYSIS: We will conduct an electronic search for articles published between January 1990 and January 2017 using a prespecified search strategy in MEDLINE, SCOPUS, EMBASE, CENTRAL and Web of Science.Our search will focus only on randomised controlled clinical trials in unhealthy subjects that employ either a parallel or a crossover design; this search will involve concurrent control groups. The primary outcomes of the literature are to determine the CoQ10 efficacy on the changes in the serum IL-6 and the TNF-α levels in unhealthy subjects. Secondary outcomes such as body mass index, serum adiponectin and high-sensitivity C-reactive protein levels, lipid profile and the heterogeneity assessment of the primary studies will be evaluated. The stages of screen articles, the extracts of relevant data and the assessment of study quality using the Cochrane risk of bias tool will be conducted independently by the two reviewers. Any disagreement will be resolved by discussion with a third person. If the number of eligible studies is sufficient, we will carry out a meta-analysis according to both outcomes.

ETHICS AND DISSEMINATION: This study is the protocol for a systematic review and no ethics approval is needed. The findings from the full systematic review will be published in a peer-reviewed journal, and they will also be exhibited at national/international academic and clinical conferences.

TRIAL REGISTRATION NUMBER: CRD42016052200.