Recently, the involvement of ER stress in various diseases, such as diabetes, cancer, and ischemic cardiac disease, has been reported.27, 28, 29 With regard to neurodegenerative diseases, a series of reports have described the involvement of ER stress in Alzheimer's disease,28, 29 Parkinson's disease,30 and polyglutamine diseases.19 We have described the relationship between presenilin 1 and ER stress.31, 32 Given these findings, drugs that suppress ER stress may be valuable new targets in the treatment of these diseases. This evidence concerns the gene PSEN1 and diabetes mellitus.