alzheimer's and iron homeostasis
TRANSCRIPT
Developing Diagnostic Tools for Alzheimer’s Disease Using Iron Biomarkers
By Shayan WasehMasters in Public Health
Thomas Jefferson University
Dr. Michael Garrick, Lin Zhao, Dr. Zohi Sternberg, Daniel Sternberg
Background Information
Alzheimer’s Disease: A Big Problem1
• More than five million elderly Americans have Alzheimer’s disease
• The population of America with Alzheimer’s disease is larger than the entire population of Norway
• The estimated economic cost of Alzheimer’s disease for the United States is over 200 billion dollars a year
• The estimated cost of Alzheimer’s disease in the United States is more than the gross domestic product of Ukraine and Cuba combined
How Do We Cure Alzheimer’s Disease?• First we need to be able to diagnose it:
• Currently, physicians cannot definitively diagnose Alzheimer’s disease until a patient dies and they look at his or her brain
• This is too late to be helpful for the patient. Even if we had a cure, we need to know who actually has Alzheimer’s disease to use it effectively
• Once Alzheimer’s disease damages the brain, nothing will restore function. Even a cure would only prevent more damage, not repair it
• It is clear that we need a way to diagnose Alzheimer’s disease early on
Healthy | Alzheimer’s
We may be able to use the body’s iron homeostasis to help diagnose Alzheimer’s
disease early on
1. Long before Alzheimer’s disease damages the brain, there is
inflammation
2. Inflammation is often caused by infection, so the body reacts as if it is
being invaded by microbes
The body responds by hiding much of its iron
inside body cells, where microbes cannot easily
reach the iron and use it to grow
3. Even though the inflammation in early
Alzheimer’s disease is not caused by microbes, the body responds as if it is. Therefore,
we can test blood proteins and hormones to see if this
response is occurring.
It may mean that the patient has early Alzheimer’s disease
Introduction to the Body’s Iron
Homeostasis
Introduction to the Body’s Iron Homeostasis #2
Here is a brief and simplified overview of exactly how the body responds to inflammation by storing iron inside body cells2
Fe
1. Iron in cells is stored by binding with a protein called ferritin while iron in the circulation is bound with a protein called transferrin.
2. Iron enters the cell through transferrin receptors and leaves the cell through ferroportin
3. When there is inflammation, the body uses a hormone called hepcidin to stop iron from leaving the cell through ferroportin
4. This means that iron is entering cells but not leaving them – resulting in storage inside cells
So What Does This Have To Do With Alzheimer’s Disease?• There is neuroinflammation in the brain, even decades before
Alzheimer’s disease begins to impair daily function
• Since there is neuroinflammation, we should be able to look at the patient’s blood to see if the iron-storing reaction is occurring
• If a patient has their blood tested over several years and this process is chronically occurring with no acute cause, then it may point towards early Alzheimer’s disease as the cause
Research Methods
Origination of Samples and Patient Data• Blood samples and longitudinal clinical data were collected from a
Layton Aging & Alzheimer’s Research Center patient cohort• 57 samples from 44 Alzheimer’s patients • 31 samples from 21 control patients
• Clinical data included socioeconomic status, age of death, diagnosis, and mini-mental state exam (MMSE) score• The MMSE tracks cognitive decline. It is scored out of thirty points, and asks
thirty questions and actions such as “what is the year?” or name three objects. As mental ability deteriorates, MMSE score also declines.
Our Experimental Data from Patient Samples• Blood samples were thawed at room temperature and then
centrifuged to separate the plasma which was pipetted into 96-well plates. The plasma is where the iron-related biomarkers reside.
• We used quantitative colorimetric determination to measure iron levels and unbound iron-binding capacity• Ferrozine Stanbio kit with neocuproine to prevent copper interference,
hydroxylamine to reduce iron to its ferrous form, and hydrochloric acid to release iron so that it can be measured.• BioTek EL808 absorbance reader
The clear plasma sample changes colors depending on how much iron is in the sample – more iron, more color
The absorbance reader measures color intensity, so we can calculate biomarker levels
• We were able to experimentally measure iron levels and unbound iron-binding capacity.• Samples with sufficient volume were tested twice to ensure reliability of
measurements
• Those measurements allowed us to calculate total iron-binding capacity (TIBC), which is an indirect measure of transferrin.• Total iron-binding capacity = serum iron + unbound iron-binding capacity
• We combined these biomarker measurements and calculations with serum hepcidin and ferritin values from another lab and with the longitudinal patient data we gathered.
• Once all of this data was gathered together, we performed exploratory statistics to better understand how Alzheimer’s disease impacts iron homeostasis and the body’s iron-storing response to inflammation
Data and Results
Result #1 – Serum Iron Levels DropsAs MMSE scores drop
(Alzheimer’s disease and cognition worsen), serum
iron levels drop
This makes sense since inflammation is
worsening, causing more iron storage in cells
Result #2 – More Transferrin in Alzheimer’s
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Alzheimer'sControl
Tran
sfer
rin C
once
ntra
tion
(ug/
mL)
Patients with Alzheimer’s disease had higher levels of
transferrin compared to controls (344 ug/mL vs. 288 mg/uL)
This makes sense since iron binds transferrin in the blood
stream, allowing it to enter cells through transferrin receptors
Ferritin (TIBC)
Result #3 – More Ferritin in Alzheimer’s
Patients with Alzheimer’s disease had more ferritin
compared to controls. Additionally, the ratio of
serum iron to ferritin was lower (3.17 vs 8.03)
This makes sense since iron in the cells is stored with ferritin, so more ferritin means more
storage is occurring
Result #4 – Hepcidin Is Higher in Alzheimer’s
To tie it all together, we found that patients with Alzheimer’s disease have
higher hepcidin levels. These hepcidin levels
increase as MMSE score decreases.
This is likely why we see all the iron storing effects
in Alzheimer’s disease
Discussion and Conclusion
Model for Our Results1
Patients with Alzheimer’s disease have mild inflammation,
which gets worse as there is more and more damage and
loss of brain function
2More and more hepcidin is released as brain damage
continues
3This increases transferrin in the
blood and ferritin in the cells
The transferrin allows iron to enter the cells, while the ferritin keeps
the iron in cellular storage
4Overall cellular storage of iron
What Does This Mean For Alzheimer’s Patients?• While differences in hepcidin, ferritin, and transferrin between
healthy people and people that will develop Alzheimer’s disease are small in the early stages, they slowly become more different.
• This may allow us to use these differences to predict if someone will develop Alzheimer’s disease or not
• This research may serve as a foundation for developing future diagnostic tools
Acknowledgements and Citations
Acknowledgements• I would like to thank Dr. Michael Garrick and Lin Zhao for their
support and guidance throughout my research project• This research was made possible through the Center for
Undergraduate Research and Creative Activities (CURCA) Undergraduate Research Grant from the State University of New York at Buffalo• I would also like to thank my family and loved ones for their support,
particularly Nooshin Asadpour, as well as my parents Mandana and Shahdad Waseh
Citations1. "Latest Alzheimer's Facts and Figures." Latest Facts & Figures
Report. Alzheimer's Association, 29 Mar. 2016. Web. 22 Feb. 2017.
2. Garrick, Michael D., and Laura M. Garrick. "Cellular iron transport." Biochimica et Biophysica Acta (BBA)-General Subjects 1790.5 (2009): 309-325.
Thank You!