Gene expression as peripheral biomarkers for sporadic Alzheimer's disease.

Alzheimer's disease (AD), the most common cause of dementia, is a progressive neurodegenerative disease. At present, diagnosis of AD is rather late in the disease. Therefore, we attempted to find peripheral biomarkers for the early diagnosis of AD. We investigated the profiles of 33 genes, previously found by our group to have altered expression in postmortem brains of AD. The gene profiles were studied via quantitative-real-time-reverse-transcription-polymerase-chain-reaction, in whole blood samples (collected with the PAXgene blood RNA system) isolated from a population clinically diagnosed with AD and healthy controls (1-year period/ up to 4 samples). Five genes showed significant correlation to the dementia score, Mini-Mental State Examination (MMSE). Focusing on the two genes with the smallest p-value, H3-histone and cannabinoid-receptor-2, notable increases in these genes were found in peripheral blood mRNA in subjects with lower MMSE scores. Seasonal variations in gene expression were not significant due to sample size, but did seem to vary due to time of sample withdrawal. In conclusion, gene expression profiling might be a promising method to investigating a large population with the aim of developing an early diagnosis of AD.