Abstract: Described is a targeted gene therapy for use in the delay or treatment of a symptomatic stage of aging and/or age-related disease in a subject, in particular to maintain or restore endoplasmic reticulum proteostasis. The gene therapy comprises the administration of a therapeutically effective amount of a pharmaceutically acceptable composition comprising X-box binding protein 1 (XBP1) or an agent that stimulates neuronal expression of XBP1 in the brain of the subject.