A joint study by Philadelphia’s Monell Chemical Sense Center
and the U.S. Department of Agriculture (USDA) suggests the possibility of
detecting early stages of Alzheimer’s disease from the odor signature of urine.
Although the study was done on mice and a lot of work needs to be done,
researchers are hopeful the findings will lead to a non-invasive urine test
that diagnoses the neurodegenerative disease before it finds time to do too
much damage to the brain.
Dr. Bruce Kimball, an author of the study, and a chemical
ecologist with the USDA NWRC, said before this study they focused mostly on alterations
in body smell caused by elements that derive outside the body, for example
viruses and vaccines.
Dr. Kimball said the findings may be useful for other
neurologic diseases as well, since they now know that odor signatures of the
urine can be changed by alterations in the brain typical of Alzheimer’s.
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Alzheimer’s has been recently ranked as the third leading cause of death in the United States. An estimated 5.3 million Americans have Alzheimer’s.
Around 800,000 people in the UK are affected by Alzheimer’s disease.
Although, the exact cause of the disease is not known, AlFuois Alzheimer, the German psychiatrist who described the disease, identified two hallmarks of the disease – abnormal quantities of protein (amyloid plaques) and fibers (tau tangles) in the brain.
While there is no way to reverse or stop the progression of this
dreaded disease yet, an early and accurate diagnosis would provide patients and
their caregivers time to plan and the healthcare professionals time to discover
a treatment to ease the symptoms.
For their study, the researchers worked with mice that
artificially developed amyloid plaques in their brains same as the ones found
in the brains of Alzheimer’s patients. For the breeding process, scientists
inserted human genes into the genomes of the mice then used drugs to activate
them. The mutations in the genes cause the brain cells of the mice to produce excessive
amyloid precursor protein.
These types of mice are known as APP (amyloid precursor
protein transgenic) mice. These mice similar behavioral symptoms of mental
deterioration.
In the modified mice brain, the amyloid plaques clog the
brain in a similar way that is observed in humans with Alzheimer’s disease.
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The researchers used three different strains of APP mice.
After using behavioral and chemical analysis, the team discovered that each
strain of these APP mice had specific urine smell signatures that were noticeably
different from those mice in the control group.
The odor changes were not the result of new compounds being
created in the body, but instead were changes in concentrations of normal
urinary compounds.
The odor differences between control mice and those with
Alzheimer's predated detectable quantities of plaque accumulation in the APP
mice brains. Further studies revealed that the definite odor profiles could be
used to pinpoint APP mice against control mice.
Coauthor of the study Dr. Daniel Wesson, of Case Western
Reserve University in Cleveland, said while this study is at the proof-of-concept
stage, biomarkers to identify early-stage Alzheimer’s may someday be
pinpointed by identifying distinctive odor signatures.
The findings were published in the journal Scientific Reports.
