Identification of potential blood biomarkers for early diagnosis of Alzheimer’s disease through RNA sequencing analysis

• Published in: Alzheimer's research & therapy Vol. 12; no. 1; pp. 87 - 12
• Main Authors: Shigemizu, Daichi, Mori, Taiki, Akiyama, Shintaro, Higaki, Sayuri, Watanabe, Hiroshi, Sakurai, Takashi, Niida, Shumpei, Ozaki, Kouichi
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 16.07.2020; BioMed Central; BMC
• Subjects: Adult; Advertising executives; Alzheimer Disease - diagnosis; Alzheimer Disease - genetics; Alzheimer's disease; Biobanks; Biological markers; Biomarkers; Biomarkers for early diagnosis; Blood tests; Cognitive ability; Cognitive Dysfunction - diagnosis; Cognitive Dysfunction - genetics; Data analysis; Dementia; Development and progression; Diagnosis; Early Diagnosis; Genes; Genomes; Geriatrics; Humans; Library collections; Lymphocytes; Medical diagnosis; Memory; Neutrophils; Older people; Ontology; Prospective Studies; RNA; RNA sequencing; Sequence Analysis, RNA; RNA sequencing; Alzheimer’s disease; Biomarkers for early diagnosis
• ISSN: 1758-9193; 1758-9193
• DOI: 10.1186/s13195-020-00654-x

With demographic shifts toward older populations, the number of people with dementia is steadily increasing. Alzheimer's disease (AD) is the most common cause of dementia, and no curative treatment is available. The current best strategy is to delay disease progression and to practice early intervention to reduce the number of patients that ultimately develop AD. Therefore, promising novel biomarkers for early diagnosis are urgently required. To identify blood-based biomarkers for early diagnosis of AD, we performed RNA sequencing (RNA-seq) analysis of 610 blood samples, representing 271 patients with AD, 91 cognitively normal (CN) adults, and 248 subjects with mild cognitive impairment (MCI). We first estimated cell-type proportions among AD, MCI, and CN samples from the bulk RNA-seq data using CIBERSORT and then examined the differentially expressed genes (DEGs) between AD and CN samples. To gain further insight into the biological functions of the DEGs, we performed gene set enrichment analysis (GSEA) and network-based meta-analysis. In the cell-type distribution analysis, we found a significant association between the proportion of neutrophils and AD prognosis at a false discovery rate (FDR) < 0.05. Furthermore, a similar trend emerged in the results of routine blood tests from a large number of samples (n = 3,099: AD, 1,605; MCI, 994; CN, 500). In addition, GSEA and network-based meta-analysis based on DEGs between AD and CN samples revealed functional modules and important hub genes associated with the pathogenesis of AD. The risk prediction model constructed by using the proportion of neutrophils and the most important hub genes (EEF2 and RPL7) achieved a high AUC of 0.878 in a validation cohort; when further applied to a prospective cohort, the model achieved a high accuracy of 0.727. Our model was demonstrated to be effective in prospective AD risk prediction. These findings indicate the discovery of potential biomarkers for early diagnosis of AD, and their further improvement may lead to future practical clinical use.