Next, to verify the altered SIRT3 gene expression, we examined mRNA expression in frontal cortex of AD and normal subjects using quantitative PCR analysis and found that SIRT3 mRNA is significantly decreased in patients with AD (n = 13) compared to normal subjects (n = 13) (P < 0.05) (Fig. 1B). This evidence concerns the gene SIRT3 and Alzheimer disease.