miRNAs as Epigenetic Biomarkers in the Study of the Bidirectional Relationship between Type 2 Diabetes Mellitus and Periodontitis: A Systematic Review.

The objective of this study is to analyze the miRNA expression of oral fluids such as gingival crevicular fluid (GCF) in patients with periodontitis and Type 2 diabetes mellitus, and how these epigenetic biomarkers can influence the bidirectional relationship of these two inflammatory diseases. This review was conducted following the PRISMA criteria. PubMed, Scopus, Cochrane Library, Embase, and Web of Science databases were searched for clinical studies conducted on humans investigating, through GCF miRNA expression, the relationship between periodontal diseases and type 2 diabetes mellitus. In addition, the etiopathogenic pathways of the studied miRNAs were analyzed using the DIANA MIR path tool. A total of 1436 references were identified in the initial literature search, and seven articles were finally included in this review. Most of the articles included in this review were case-control studies and examined the expression of miRNAs in patients with periodontitis with or without diabetes. Due to their characteristics, miRNAs appear to be the ideal biomarkers for improving the understanding and knowledge of the etiopathogenic pathways that link both diseases. Among all the studied miRNAs, miR-146a, miR-155, miR-200b, miR-223, and miR-203 showed strong involvement in inflammatory and metabolic pathways, making them potential good diagnostic and prognostic biomarkers.