Expression of many miRNAs altered in Alzheimer’s disease

Several microRNAs (miRNAs) are differentially expressed in the brain, cerebrospinal fluid and blood in Alzheimer’s disease (AD) and may help improve early detection of the disease, reports a recent meta-analysis.

Researchers retrieved 107 publications from the PubMed database, corresponding to 147 independent datasets. Majority of the miRNA expression data were collected from brain tissue (n=60), followed by blood (n=53) and cerebrospinal fluid (n=32) samples. Fifteen datasets reported findings for more than one tissue type.

A total of 260 meta-analyses were carried out on data from brain-derived specimens. Ten percent (n=25) showed study-wide differential expression that achieved statistical significance. Twelve miRNAs were upregulated, while the remaining 13 had their expression levels reduced. Nine miRNAs were classified as having strong evidence due to the consistency of effect across different studies.

Sixty-six meta-analyses were performed on miRNAs extracted from cerebrospinal fluid samples. Of these, five (8 percent) were differentially expressed in AD patients, each with consistent evidence across studies. All five miRNAs were found to be downregulated in patients vs controls.

Blood samples yielded the greatest number of putative miRNA biomarkers. Of the 135 meta-analyses, 24 percent (n=32) showed significantly different expression levels in AD patients; 19 were downregulated, while the rest were enriched. Twenty-one had strong supporting evidence.

Notably, five miRNAs were found to have significantly different expression levels in both brain-derived and blood samples, three of which were upregulated.