AChemS 2012 Day 3: Sensing Brain Disease

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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

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.

Early _stage

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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 disease.

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 Disease.

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!

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