Lecture Kiliaan Flashcards
mouse models for vascular factors in alzheimer’s disease
Are there treatments for AD?
There is no effective treatment yet
–> The focus lies on the early, asymptomatic phase, as treatment later on in the disease is not effective
What are the developmental stages of AD?
- Latent phase in which you have no cognitive decline yet and no neuropathology (amyloid), but a cerebrovascular imparement is alreadi visible
- Prodromal phase (ca. 5 years)
- disease (ca. 10 years)
What are the risk factors for cognitive decline and Alzheimer’s disease
- Age
- midlife hypertension
- Atherosclerosis
- Midlife obesity
- Stroke
- Hypercholesterolemia
- APOE4 allel
- Diabetes type II
- Atrial fibrillation
- Homocysteine
- Low education
Lifestyle:
- Smoking
- Diet
- Physical inactivity
What is the nutritional status of Alzheimer patients?
Already in a very early stage of AD:
- Less vitamin A, B12, C, D and E
- Less omega 3 fatty acids EPA DHA
- lowered selenium uridine
What is mediterranean-style diet associated with?
INVERSLY proportional to:
- Development of frailty in community dwelling older adults
- Incidence of hip fracture in prospective European study
What is a mediterranean-style diet?
HIGH intake of fruits, vegetables, legumes, UNSATURATED fatty acids from olive oil and Fish (DHA/EPA), whole grains, nuts, moderate wine
LOW intake of saturated fat, refined grains and red meat
Study in Spain: Mediterranean diet with extra-virgin olive oil or nuts to reduce incidence of major cardiovascular events in persons at high cardiovascular risk. What did it show?
People with Mediterranean diet people were less likely to die from cardiovascular diseases
New york city, study:
77 years of age
followed Mediterranean diet for 10 years.
Risk of developing MCI is lower in people adhering to mediterranean diet
Multi-ethnic community study in northern Manhattan New York 1393 cognitively normal participants (77 yrs), 275 developed MCI during follow-up of 4.5 yrs.
MCI : mild cognitive impairment
Nijmegen study research question and approach
Multi-factorial approach:
How does diet affect brain structure and function?
–> brain circulation (CBF) –> brain structure (white and grey matter) –> cognition
Alzheimer mice
induced Hypertension Obesity
induced stroke in mice
Multi-factorial way research
behavior
cognition
motor skills
muscle strength
animals are kept in digital ventilated cages (movement is measured in these cages)
MRI, PET scanning 11.7T:
- cerebral bloodflow
- neuroinflammation
- structural + functional connectivity
Postmortem analyses:
- biochemistry + immunohistochemistry lightssheet microscopy polarised light imaging
What were the investigated diets?
Fortasyn diet:
3.15% replaced by fish oil
DHA EPA
UMP
Choline
Phospholipids
B-vitamins
Antioxidants
Control diet:
5% fat
soy oil
coconut oil
corn oil
Dietary treatment in stroke
before:
- acclimatization (- 39)
- open field (-21)
- rotard
- grip test (-14)
- polar test
(-7) - Morris water maze
normal Mice (2-3 months old)
medial cerebral artery was occluded - transient ischemic stroke 30 min MCA occlusion
then:
stroke is performed
tMCAo Diet switch
Repeat:
- Open field
- MRI
- rotarod
- grip test
- pole test
- Ppi
- rotarod
- Open field ORT
- Grip test
- pole test
- MRI
Summary of measurements/experimental design for mice dietary treatment in stroke
- cognition + motor skill test
- Neuroimaging (PET, ASL, DTI, rsfMRI)
- Immunohistochemistry/ biochemistry
Cerebral bloodflow MRI Fortasyn vs control mice
day 7 and day 35 (even after one month there is very low blood flow in control diet), in mediterranean diet the cerebral bloodflow improved significantly after 7-35 days.
Diet restored CBF in right hippocampus at day 35 with mediterranean diet
Resting state fMRI functional connectivity
Control diet - less red squares, i.e. not so much connectivity)
Fortasyn diet - more red squares (more connectivity)
The mediterranean diet led to significantly more connectivity, especially between left and right motor cortex and more connectivity overall
(just one month of good diet!)
What are the results of the pole test?
Pole test: motor coordination
impact of diet on motor sklls after stroke
measure: rotation time –> fortasyn diet was significantly faster, i.e. mice on diet turn faster - improved motor coordination
uPET imaging of microglial activation
[18F]DPA-714 ligand for the 18 kDa translocatoprotein (TSPO), expressed by microglial cells & macrophages upon neuroinflammatory stimuli
-> VISUALIZE inflammation
control diet you see a lot of inflammation through activated microglia
in mediterranean diet you see less activated microglia, i.e. less inflammation
How can exercise impact be measured?
Impact of 1 week voluntary exercise on stroke recovery in male mice.
Design:
- Occlusion of tMCA (30 min), leading to stroke
- tMCAO (transient middle cerebral artery occlusion) ß most common stroke in humans
- C57BL/6J mice
Animals put in cagen with or without running wheel and activity is monitored
After a week, animals are put in scanner (Neuroimaging (UHF 11.7 T) and immunohistochemistry
Beeficial effects on : cognition, neurogenesis, inflammation, infarct volumes
Just after one week of exercise
velocity, distance and time in running wheel is measured
Digital ventilated cages
24-7 monitoring of frequency, speed duration turning
WHat and when to measure activity in mice for impact of 1-week voluntary exercise on stroke?
ACTIVITY: They usually are active during the night, so focus on night.
LATERALITY: going to left or right
without RW: preference to go to the left
with RW: no preference
RW vs no RW CBF levels?
CBF increased in animals who had access to RW
1-week of RW resting state fMRI
Functional connectivity in significantly improved already after one week. Especially between right sensory cortex and left auditory cortex (p<0.02)
What is the cycle leading from hypertension until a problem and repair?
- Hypertension, artherosclerosis stroke influenced by lifestyle exercise medi/multinutrient diet
- impairment vasculature (occluded vessels/plaques)
- lower cerebral bloodflow + vascular plasticiy is lowered
- impaired energy metabolism mitochondria
- loss of white matter, less neurogenesis, less synapses
High fat diet then leads to neuronal dysfunction and cognitive impairment (Alzheimer’s disease)
- but with healthy lifestyle choises this can be reversed and a repair of the brain structure and function repair can take place.
High-fat diet (45% fat) on neurovascular function
functional hyperemia in rat brain compromised by high-fat diet (HFD)
4 weeks old rats 8 weeks HFD 45% fat or CD (control diet) 10% fat isocaloric
Stimulation of whisker (thick hair growing on face of mouse/cat etc.)
CBF % is measured and already after 8 weeks of high fat diet the % CBF is half of the CBF % increase in the control diet
Other study, high-fat high sugar diet and cognition
2 diets:
LFCC - low-fat, complex carbohydrate
HFS - saturated fat and sugar
Animals need much more time to find the platform
Spatial learning in rats on HFS diet significantly decreased after only 1/2 months of high fat diet
Impact of obesity and diet on the brain
LDLr ko mouse (cannot get rid of colesterol)
- got high fat diet HFD for 4 months.
- HFD + 5% Butyrate 2 months
What is butyrate?
Natural product of bacterial fermentation in the colon of undigested fibers (plant polysaccharides and resistant starch)
How does food influence gut bacteria, what is it good for?
Food/ ingested nutrients –> gut microbiota –> short-chain fatty acids
short-chain fatty acids –> food for epithelial cells, good for epithelium
short-chain fatty acids –> stimulated Enteroendocrine L cells in epithelial wall –> needed to create GLP-1 : hormones that go to hypothalamus and leads to lower hunger feeling
Ozempic GLP-1 : used for diabetes/obesity
Butyrate fiber fermentation
Actions of butyrate released by colonic microbial fermentation of fiber on host metabolism, inflammation and carcinogenesis
What is Butyrate good for
- Food for colonocytes
- Histone deacetylase inhibitor ( epigenetic regulation via acetylcholine-A, down reg of regulatory genes for inflammation, cell proliferation, apoptosis, and differentiation, suppress neoplastic transformation
- Immunomodulatory
GPCR binding, treg activation, +FOXP3 IL-10 expression, anti-inflammatory, apoptopic, cell cycle arrest, antiproliferative anti-neoplastic - mucosal defense
mucus production, thight jcts integrity
defensins, glucoronidase - counter-carcinogen oncogene suppression
What does butyrate do in mice?
Butyrate restores HFD induced increased body weight.
Body weight is increased in high-fat diet, but when butyrate is added, the weight of the animal goes back and goes towards Chow diet
How does butyrate influence CBF
Butyrate restores HFD decreased CBF in mid-adulthood.
In hippocampus CBF is restored when HFD is complemented with butyrate
How does butyrate influence connectivity?
Butyrate restores HFD induced connectivity decrease in mid-adulthoof
HFD reduced FC within the somatosensory cortex and hippocampus and butyrate restores connectivity
How does butyrate affect spatial learning and memory impairment in mid-adult obesogenic mice
Butyrate restores HFD induced spatial learning & memory impairment in mid-adult obesogenic mice
Mice spent more time in the area with platform
How does butyrate affect adipocytes size in HFD fed mice?
Butyrate restores adipocyte size in HFD fed mice
Adipokines in white adipose tissue
link between obesity, vascular factors and dementia.
fat surrounding the organs there is a lot of inflammatori factors (interleukins SAA MCP-1) growth factors (NGF, HGF but also those for
thrombosis/hypertension/atherosclerosis
Hypertension
long term medical condition with elevated arterial blood pressure
Leptin
increased in HFD: enhance arterial thrombosis angiogenesis, impair arterial distensibility and satiety hormone
Hypotension
low blood pressure. Cardiovascular condition characterized by abnormally reduced blood pressure
SAA
pro-inflammatory cytokine, macrophage infiltration adipose tissue. systemic SAA promotes artherosclerosis
HFD affects plasma adipokine concentrations which is inhibited by butyrate
How does butyrate and HFD influence microbiota composition in mid adulthood
There is a correlationn between fecal microbiota genus and neuroinflammation. The abundance of Dorea is higher in HFD (correlation with neuroinflammation) compared to HFDB while Bacteroidales is higher in HFDB (anti-neuroinflammation, butyrate producing bacteria)
Summary
- Obesity and HFD may affect the brain via vascular system and/or via WAT (white adipose tissue)
- butyrate supplementation or fibre rich diets may serve as potential preventative for obesity and obesity-related disease, and in the long-run as preventative for dementia
Alzheimer’s disease
- AD affects over 55 million people worldwide
- age is th emajor risk factor for AD (47% of people older than 85 years affected
- 139 million affected in 2050
first case of AD
August D(eter) 1850-1906
Alois Alzheimer (1864-1915)
got access to brain and Bielschowsky stained tissue sections from auguste D
Plaques AD
beta Amyloid production from Precurser proteine (APP)
APP- transmenbrane proteine amyloid is cut free from APP through beta-Secrase and gamma-Secrase. Then, beta amyloide is stored in plaques
Different mutations (genetic)
when mutation is in the middle of beta amyloid (Dutch-Q; Italian-K; Arctic-G) causes severe CAA (cerebral amyloid angiopathy
Amyloid is mostly deposited in vessel holes
CAA - cerebral amyloid angiopathy
immunofluorescent staining for beta amyloid ( you can see it attached to the vessels and wholes ) vessels.
Vessel walls become weak
1991 discovery mutations in APP on chromosome 21 (Down’s syndrome), chromosome 14 and 1 (presenilin 1,2) > early onset AD
First Mouse models for AD in 90’s
put human mutation in mouse
Transgenic mouse models for AD
APPswe/PS1 dE9
- transfection of genome fragments including promotor and exon – starts with production of beta Amyloid
-
What types of models for AD
95% are sAD heterogenous pathogenesis linked to >20 genes, greatest influence ApoE4, TREM2
no/little mice models (non-humane primates)
<1% are EOAD linked to APP, PSEN1 or PSEN2 mutations
transgenic rats and transgenic mice
not very good as most people have the sAD
The onset and progression of synaptic impairment, memory loss and beta amyloid and tau pathology in Tg mouse models
APP (one mutation in the APP)
- problems with mechanisms in hippocampus, but short term memory and beta amyloid pathology etc, only start quite late (9 months ca)
APP/PS1
- problems already start around month 3
3 x Tg
Aged: takes very long (very expensive)
EOAD based IPSCs – trangenic mice major examples
3xTg
TgSwDI
other
Research tools: mouse models transgenic mice (e.g. ALzheimer’s disease, APP/PS1)
We can measure:
- behavior
- cognition
- motor skills
blood pressure
MRI
- Brain structure (DTI, rsfMRI)
- Brain perfusion (ASL)
- Metabolism (MRS)
APP/PS1 - blood pressure
Systolic blood pressure AD vs WT mice:
SBP is very hightened in AD vs WT, but SBP in AD mice at 16-month decreases over time
Bloodflow and vasoactivity 18 month WT vs APP/PS1
Cerebral vasoreactivity difference betwee normal and vasoconstriction is significant in WT and not or in less brain regions significant for AbetaPP/PS1, i.e. vessels are not reacting anymore
Where and when can beta amyloid be seen?
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