For the first time ever, researchers have found “unambiguous” signs of Alzheimer’s in a wild animal. It is hoped that this discovery could help push forward research into what leads to the devastating condition and, more crucially, how it might be prevented.
Only a few months ago the news broke that Alzheimer’s-like indications had been discovered in the brains of chimpanzees, marking the first time that they had ever been identified in a non-human animal. But the brains of the apes studied all came from individuals that had lived their lives in either zoos or sanctuaries, so what they could tell us about the potential existence of the disease in the wild was limited.
One of the most distinctive things about humans, unlike the vast majority of life on the planet, is the fact that both sexes live well beyond their reproductive years. The fertility of both men and women tends to start tailing off at around the age of 40, even though individuals can live to be 110. This gave researchers an avenue to explore: perhaps the development of Alzheimer’s is related to the ability to live long lives, even after fertility ends.
This led them to study the brains of dolphins, one of just a handful of other species that live long healthy lives after reproduction. In studying the brains of wild animals that died naturally and were then washed ashore on the Spanish coast, the researchers were able to identify two of the key markers for Alzheimer’s: beta-amyloid plaques and tau tangles.
The study, which has been published in the journal Alzheimer’s & Dementia, suggests that humans and dolphins (including the particularly long-lived orca) may be more susceptible to Alzheimer’s due to the way in which insulin works in these animals. Studies have found that extreme calorie restriction in some species can lead to an extension of life, and now the researchers suggest that the role insulin plays in regulating sugar in the blood may be having a comparable effect.
“We think that in humans, the insulin signalling has evolved to work in a way similar to that artificially produced by giving a mouse very few calories,” said study co-author Professor Simon Lovestone. “That has the effect of prolonging lifespan beyond the fertile years, but it also leaves us open to diabetes and Alzheimer’s disease.”
The team now thinks that the discovery of similar signatures to Alzheimer’s in dolphins could open up a new line of study for the disease. While it is difficult to know whether cetaceans in older age suffer from any of the same symptoms, such as memory loss or confusion, it will be a massive help to have another animal model for the condition.