Expression of Toll-Like receptors in metabolic syndrome: A systematic review

Introduction: Toll-Like Receptors (TLRs) of innate immune system have documented roles in the pathogenesis of metabolic disorders. This study aims to systematically review the expression of TLRs on metabolic syndrome (MetS). Materials and methods: We systematically searched PubMed/Medline, ISI web of Science, Scopus, Google Scholar, EMBASE, and OVID databases until February 2017. The terms ‘‘Metabolic Syndrome’’ OR ‘‘Mets’’ AND ‘‘Toll like receptor’’ OR ‘‘Toll like’’ OR ‘‘TLRs’’ OR ‘‘TLR’’ were used. “Expression” advertently was not used in our search and was considered in the selection process. Three steps for selecting the articles and then their qualification were conducted. Results: First, 1373 articles were found in the international databases. After removing duplicates, 963 papers remained and after two steps of selection, this number reached 410 and then 27, respectively. After full text screening and qualifying processes, we finally included 13 articles consisting of five animal and eight human studies. All human studies reported overexpression of TLRs (types 2, 4, 5, 9) in MetS, and most animal studies documented an increased TLRs expression. Conclusion: This systematic review provides evidence for the relation of innate immune system with MetS. Its findings regarding overexpression of special TLRs (e.g. types 2, 4, 5, 9) in MetS and their basic mechanisms and clinical implications might be investigated in further studies.