Guest post by Ingrid R. Niesman, MS PhD
With better nutrition and rapid advancements in veterinary care, our cats are aging in our households in record numbers. Geriatric cats share many of the same clinical pathologies as humans; including increased diabetes, osteoarthritis, chronic kidney disease, high blood pressure and vision/hearing loss.
Simply old age or disease?
One of the most striking similarities to aged humans is the newly recognized prevalence of cognitive dysfunction syndrome (CDS) in cats. Feline CDS shares many typical symptomatic traits with Alzheimer’s disease. In humans, Alzheimer’s is frequently diagnosed in early phases by changes in smells and taste that can affect eating, disorientation and bouts of wandering, impaired inter-personal relationships and poor monetary judgement. We can extrapolate these to feline characteristics: cats will become disoriented in familiar spaces, alter their eating habits, or withdraw from their basic routines. Some cats may become more affectionate and needy over time, neglect their toilet training and increase inappropriate nighttime “talking”.
CDS has been a recognized syndrome in dogs for many years, but unlike felines, dogs do not display a human-like pathology. Cats are the only widely studied species to date that have senile (amyloid) plaques clogging brain communication, and tangles of a protein called tau building up in neurons, representing the best clinical model we have to mimic human neurodegenerative diseases.
The most recent documentation of this concept was published June 27, 2019 in The Journal of Comparative Neurology by a group of Alzheimer’s disease researchers. They used archived aged feline brain sections representing known Alzheimer’s clinical brain areas and stained their tissues using the same antibodies pathologists use to assess human Alzheimer’s. They found Alzheimer’s-like amyloid staining in about 85% of their samples, and four cats had human-like hyper-phosphorylated tau tangles.
A diagnosis of feline CDS is basically a category of exclusion rather than a firm diagnosis of a known disease. Our ability to ask cats probing detailed questions to assess their cognitive function is, of course, nonexistent. Other possible clinical pathologies need to be eliminated before CDS is determined. Sadly, there is no current effective treatment for human Alzheimer’s or feline CDS. What we need for therapies to be developed is an animal model where we can pinpoint some of the very earliest behavioral, biochemical and neurological changes that occur during development of full-blown neurodegenerative disease.
Can any old cat serve as a therapy surrogate?
Can cats, specifically Siamese and Siamese-derived breeds, fill this void? Science says yes, this may be possible. In my previous posting, I outlined how the signature Siamese mutation in the gene tyrosinase may be responsible for some of the described quirky Siamese-specific behaviors, by causing an imbalance in the neurotransmitter dopamine. To take this concept one step further, when Siamese mutant tyrosinase is expressed in neurons, it may not take normal shape and may form clumps, termed aggregates by scientists. One popular theory for the initial trigger of Alzheimer’s is the accumulation of these types of misfolded proteins in neurons, which can lead to cell death. If mutant tyrosinase indeed misfolds as predicted, we have an opportunity to treat both felines and humans by screening for effective compounds, dietary supplements or even environmental enrichment protocols that can interfere with this process early on clinically.
Calling on citizen scientists
What can you as a cat owner do to help move this field forward? Watch your aging cats closely for any subtle behavioral changes. In her seminal 2011 review, leading CDS researcher Dr. Danielle Gunn-Moore finds that almost a third of pet cats over 11 years old show at least one CDS-like trait. The prevalence increases to half by the time animals get to 15 years old.
Take your aging cats to the vet for frequent health checks and report all unusual patterns. The earlier we can spot potential neurodegenerative changes, the earlier scientists and doctors can develop clinical diagnostic tests and then possibly find an elusive Alzheimer’s/CDS therapy.
Do you have an aging Siamese cat?
For my own work, I am interested in hearing all anecdotal stories about aging Siamese cats. I would like to get a non-scientific perspective on how often owners have experienced aging Siamese that might fit the CDS clinical criteria. What age did you first notice changes, how quickly did they progress, was your cat in distress at any point? This is a new and developing field of feline health. Who knows what we will learn from our association with our pets that will benefit humans and cats.
If you’d like to help me and ultimately help all of us further understand all feline aging changes at a molecular level, please like and share this post across your social networks.
Ingrid R. Niesman MS PhD is the Director of the SDSU Electron Microscope Imaging Facility at San Diego State University.
Beta-amyloid and Tau pathology in the aging feline brain. Flock KL, Smith JD, Crary JF, Hefti MM. JCompNeurology-Research in Systems Neuroscience. 2019 June epub doi: 10.1002/cne.24741.