A recent report has shown that Sirt1 is upregulated in mouse models for Alzheimer's disease and amyotrophic lateral sclerosis protecting against neurodegeneration [35], whereas another report showed that Sirt1 increasingly expressed in neurons by excitotoxic injury induces NAD depletion enhancing neuronal death [9]. The gene discussed is SIRT1; the disease is early-onset autosomal dominant Alzheimer disease.