By Nicole Garneau, PhD
I'm taking a detour from my intrigue with taste to jump into the
world of smell. We take our ability to smell for granted everyday
when we eat, and also in the way that it affects our memories and
emotions. But that's not what inspired this blog post today. Here
is what did: over 5.4 million Americans are living with Alzheimer's
and the disease leaves no survivors. "It destroys brain cells and
causes memory changes, erratic behaviors and loss of body
functions. It slowly and painfully takes away a person's identity,
ability to connect with others, think, eat, talk, walk and find his
or her way home." (From www.alz.org)
Pretty scary when you consider that there is no cure and no 100%
effective prevention or treatment, and the disease is predicted to
affect 13 million Americans by the year 2050. So what happens to
the brain, and how is smell a potential key?
Alzheimer's is a disease of the brain. In patients with the
disease the are two things that happen at the molecular level.
First, a by-product protein, called beta-amyloid, from a natural
process in the body, somehow builds up into clusters and can no
longer be readily cleared from in between brain cells. This is
especially the case in people who have a genetic mutation in a
protein called APOE, that normally helps clear the beta amyloid. A
loose analogy would be if you brain was like your neighborhood, and
you put out your trash (a by-product of natural processes in your
house). APOE is like the garbage truck which takes it away from
your curbside. Now imagine APOE is not working right, the trash
builds up and up and you can no longer leave your house, and
likewise nothing can get into your house. The result... you no
longer can access the things you need to survive. Scientists
believe this is how these amyloid clusters/plaques damage brain
cells and cause neurons to die.
Photo credit: www.alz.org
The second part of the molecular changes that can lead to
Alzheimer's Disease is due to a protein called tau (rhymes with
chow). Tau is like the structural king of the roadways in the brain
that get nutrients and supplies to neurons. When tau fails, the
roadways disintegrate and tangle into a mess (called tangles) and
brain cells die. Now combine the affect of tau failing and the
buildup of amyloid plaques and you have a lot of cell death. The
more cell death you have the more profound the stage of Alzheimer's
Take an interactive tour of the brain here to learn
more about tau and amyloid.
Enter the sense of smell and Dr. Claire Murphy of San Diego State
University. Dr. Murphy gave a presentation this morning on how
smell detection, through thresholds and recognition and naming, can
be used an early detection test for Alzheimer's Disease, and can
actually diagnose the disease long before symptoms arise because
the olfactory bulb is one of the first parts of the brain to be
affected by plaques and tangles before spreading to the rest of the
brain. She wowed the audience with her research which uses brain
imaging to look at the differences in how a healthy person
recognizes smells compared to someone with Alzheimer's
It was fascinating to see how detecting defects in olfaction may
help doctors recognize the disease earlier. While there is no cure
yet, there are drugs that slow the progression of the disease, and
there are links to nutrition, exercise and particularly to
education and life-long learning that may contribute to staving off
the pathologies related to tau tangles and amyloid clusters.
For more on preventative-based research, click here.
Dr. Murphy concluded her presentation by saying, "Chemosensory
function has a big clinical impact. If we can determine which tasks
[in olfaction detection] are informative, then olfaction may be an
important factor in this story." I couldn't agree more.
For now, off to some more talks. I'll be back to the topic of
taste for tomorrow and my final post. Hard to believe there is only
one more day of the conference!