Consistent with this view, more than 80% of patients suffering from AD develop diabetes or glucose intolerance [21], and postmortem analysis of brain from AD patients has detected a significant decreased expression and activation of IR, insulin-like growth factor 1 (IGF-1) and insulin receptor substrate-1 (IRS-1) [22], with a pattern resembling that observed during age-related changes [23]. Here, IRS1 is linked to diabetes mellitus.