Restoring amyloid-β42 and γ-secretase function in Alzheimer's disease

Area of Science:

• Neuroscience
• Neurology
• Biochemistry

Background:

• Traditional Alzheimer's disease (AD) models implicate increased gamma-secretase activity and amyloid-beta 42 (Aβ42) overproduction.
• Emerging data challenges this, showing reduced cerebrospinal fluid Aβ42 levels in AD patients, particularly those with genetic mutations or Down syndrome.

Purpose of the Study:

• To re-evaluate the role of gamma-secretase activity and Aβ42 levels in Alzheimer's disease pathophysiology.
• To explore the potential of restoring Aβ42 levels as a therapeutic strategy.

Main Methods:

• Analysis of existing evidence linking gamma-secretase function, Aβ42 levels, and AD progression.
• Review of findings from genetic studies (APP, PSEN1, PSEN2 mutations) and Down syndrome.
• Examination of the effects of anti-amyloid therapies and the potential neuropeptide function of Aβ42.

Main Results:

• Approximately 90% of pathogenic PSEN1 mutations decrease gamma-secretase activity and Aβ42 production.
• Lower gamma-secretase activity and soluble Aβ42 levels correlate with earlier dementia onset, poorer cognition, and faster progression.
• Higher soluble Aβ42 levels are associated with preserved cognition and delayed dementia in some AD forms.

Conclusions:

• Alzheimer's disease pathophysiology may involve reduced, not increased, gamma-secretase activity and Aβ42 levels.
• Restoring Aβ42 levels above a compensatory threshold could offer disease-modifying benefits.
• Repurposing drugs that increase soluble Aβ42 warrants investigation for slowing AD progression.