“Humans are considered uniquely susceptible to Alzheimer’s disease, potentially due to genetic differences, changes in brain structure and function during evolution, and an increased lifespan. However, a new study provides the most extensive evidence of Alzheimer’s disease brain pathology in a primate species to date. Researchers found that the brains of aged chimpanzees, our closest living relatives, show pathology similar to the human Alzheimer’s disease brain.”
There is new research on the brain and Alzheimer’s from Kent State University that is quite eye opening and interesting. The study analyzed the brains of elderly chimpanzees our closest relatives whom we share about 98% of our DNA with. What they found was pathology in the chimp brains similar to what we see in humans suffering from the disease.
Estimates are that about 1/3 of people over age 65 suffer from some form of dementia in the USA and the most common cause of this dementia is Alzheimer’s. This disease is a progressive disease and it is irreversible. It results in impaired cognitive functioning and behavior changes including aggressiveness and combativeness in some patients. Genetic differences are attributed to explaining just why humans are so susceptible to the disease including changes in brain structure and functioning and researchers believe this is connected to our evolution and increased life span. However, this new research shows something similar also happens in the brains and functioning in elderly chimps!
There are a growing number of studies going on focusing on the evolutionary perspective of the disease with the focus being on identifying differences between humans and chimps and the hope is that these studies will help develop treatments for Alzheimer’s in humans. It’s thought that dysfunctional changes in two proteins (amyloid beta & tau) play a role in development of the disease. In Alzheimer’s amyhloid beta is overly produced which results in the forming of plaques between the brain cells (neurons). In healthy brains this protein is degraded and eliminated as we age but this doesn’t happen in the Alzheimer’s brain. Amyloid beta appears to initiate changes in the tau proteins and the result is that the brain cell’s structure is disrupted and destabilized. These alterations in the brain with Alzheimer’s leads to formation of neurofbrillary tangles and eventually death of the cell. Thus, the onset of dementia!
Analysis of elderly chimp brains began at Kent State back in 2013. The brains were from chimps who had died of natural causes in zoos and research centers. Most of the brains were collected by the Great Ape Aging Project. Examining these brains researchers were able to determine that all 20 elderly chimp brains were affected by amyloid beta plaques. As seen in humans with Alzheimer’s increasing large volumes of this protein were found in elderly chimps brains! The protein was found to be higher in blood vessels and this correlated with increased tau lesions. What this suggests is that the amyloid proteins buildup in the brain’s blood vessels precedes plaque formation in chimps and, perhaps, also in humans. But in humans with Alzheimer’s this protein buildup is mostly found in the form of plaques rather that in blood vessels! In humans the buildup of these plaques increases the risk of stroke and/or dementia. In the chimp brains Tau lesions were also found in the form of neurofibrilliary tangles and clusters along with pieces of dying neurons. We find these tangles in humans with the disease but the clusters appear specific to chimps. What this all indicates is that Alzheimer’s lesions are NOT specific to the human brain and this is contrary to general belief!!
Researchers are now going to be attempting to determine if these pathology’s play any key role in age-related cognitive decline in chimps. The Great Ape Aging Project began 20 years ago and what has been noticed is that chimps show similar behavior as they age to aging humans!
So for the first time we’ve found signs of Alzheimer’s or something similar in chimps. This is some very interesting and revealing research in my mind as what we are finding in our closest evolutionary relative (chimps) is in some ways similar to what happens in human brains with Alzheimer’s but in other ways a bit different. I’m happy that this kind of research is being done because it may help us to eventually find some sort of cure to this debilitating disease or, at least, aid us in finding better ways to manage the disease.
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