AD Other Lecturer Flashcards
The healthy brain
Healthy neurones, synapses, glial cells, vascular system
AD stages
Brain changes start decades before symptoms show (up to 15 years)
Amnestic MCI: memory problems, cognitive ok, brain compensates for changes
Cognitive decline accelerated after AD diagnosis (few years)
Total loss of independent function
Pathological hallmarks of AD
Extracellular:
amyloid plaques (blood vessel walls, cerebral amyloid angiopathology) AB
Intracellular:
Neurofibrillary tangles TAU
What is happening during MCI and early AD
Lag of 15 years before prevalence of AD (observation)
Extensive synapse loss in early AD - 44% dentate gyrus
55% CA1
(highly correlated with cognitive impairment)
Hypothetical time course of AD events
Amyloid-beta accumulation
Synaptic dysfunction
Tau mediated neuronal injury (but could this be before synaptic dysfunction)
Brain structure loss
Cognition loss
Clinical function loss
Amyloids
Proteins that can misfold, aggregate and may be insoluble
How are amyloids formed
Processing of amyloid precursor protein - Function in body unknown
APP beta cleavage, transmembrane protein (AB), gamma secretase cuts within plasma membrane leaving just AB and AICD fragment
APP alpha cleavage, cleaves in between AB so prevents AB formation
Could gamma secratase be a target for therapeutics?
Yes
If prevent from working then the formation of AB prevented as cannot separate to for AB and AICD
Presenilins (PS1) mutations (part of gamma secratase complex) found in AD disease
How can targeting alpha cleavage be used for therapeutics in AD
(ADD EXTRA READING)
Increase alpha cleavage
Genetic components of AD
Mutations found in APP and PS1 resulting in increased [AB] in brain (will get AD)
Initial focus on plaques but now on soluble forms of AB
> 50 mutations in APP gene that lead to early onset AD and related to beta cleavage and gamma cleavage (correlation)
Higher prevalence of AD in people with Down syndrome
Copy of chromosome 21
APP found in chromosome 21
Bigger dose of APP so increased AB formation
Woman with partial chromosome 21 copy - did not develop AD and lived til 78 because did not have part of chromosome that holds APP
Mutation in APP protecting against AD and age related cognitive decline
APP mutation A637T
1795 sample - 1 in 100 had the mutation
>80% with mutation protected from cognitive decline
Hek cells transferred with different variants of APP gene, critical comparison - A673T had significantly less AB (causation)
What percentage of cases of AD do not have clear genetic cause?
> 95%
Alzheimer’s disease risk factors
Age
Lifestyle (diet, cardiovascular health, social factors)
Clinical (high blood pressure, diabetes, depression, Down syndrome)
Genetic (APOE variants)
Mutations (APP in familial AD)
preclinical trajectory in AD
Teens and 20s - pre- MCI so preventative action
MCI - modifying
AD - symptomatic
Using MMSE score
Active immunotherapy against AB
Vaccination with AN-1792
Given to moderate to advanced AD
Stopped due to brain inflammation
Research on post mortem brains - plaques were cleared in some but they continued to decline in cognitive ability
Passive immunotherapy
Aducanumab
Given to mild to moderate AD
Slow cognitive decline and dose dependent amyloid removal but not as good as active immunisation