Various coding genes representing multiple functional categories are 
downregulated in blood mononuclear cells (BMC) of patients with sporadic 
Alzheimer disease (AD). Noncoding microRNAs (miRNA) regulate gene expression by 
degrading messages or inhibiting translation. Using BMC as a paradigm for the 
study of systemic alterations in AD, we investigated whether peripheral miRNA 
expression is altered in this condition. MicroRNA levels were assessed using the 
microRNA microarray (MMChip) containing 462 human miRNA, and the results 
validated by real time PCR. Sixteen AD patients and sixteen normal elderly 
controls (NEC) were matched for ethnicity, age, gender and education. The 
expression of several BMC miRNAs was found to increase in AD relative to NEC 
levels, and may differ between AD subjects bearing one or two APOE4 alleles. As 
compared to NEC, miRNAs significantly upregulated in AD subjects and confirmed 
by qPCR were miR-34a and 181b. Predicted target genes downregulated in Alzheimer 
BMC that correlated with the upregulated miRNAs were largely represented in the 
functional categories of Transcription/Translation and Synaptic Activity. 
Several miRNAs targeting the same genes were within the functional category of 
Injury response/Redox homeostasis. Taken together, induction of microRNA 
expression in BMC may contribute to the aberrant systemic decline in mRNA levels 
in sporadic AD.