Peripheral inflammatory biomarkers in Alzheimer's disease and mild cognitive impairment: a systematic review and meta-analysis.

Abstract

In the past few decades, it has been demonstrated with animal models and clinical studies that a chronic inflammatory process significantly contributes to Alzheimer's disease (AD) pathogenesis. We systematically searched on PubMed and Web of Science for studies associated with peripheral inflammatory biomarkers in AD and mild cognitive impairment (MCI) before July 2018. Meta-analysis was conducted to summarise results of studies relative to peripheral cytokines and chemokines in AD and MCI. Mean (± SD) concentrations of peripheral inflammatory biomarkers for AD, MCI and healthy controls were extracted from these studies. Our meta-analysis revealed consistently elevated concentrations of inflammatory biomarkers such as C-reactive protein, interleukin-1β (IL-1β), IL-2, IL-6, IL-12, IL-18, monocyte chemotactic protein-1 (MCP-1), MCP-3, IL-8 and interferon-γ-inducible protein 10 in AD patients, whereas no consistent results were obtained for elevated concentrations of cytokines or chemokines except MCP-1 in MCI patients. In conclusion, these results provided evidence to support that systematic inflammation might be a biomarker for AD diagnosis, whereas it might be a later event during AD disease progression.