Dolphins and humans have many similarities, such as their ability to form social relationships and to communicate using their own language (among other things), and now a new study has added dementia as one of the things we humans share in common with these marine mammals. (Related: New study examines complexity of dolphin culture; researchers determine that brain size correlates with “human-like” behaviors and societies.)
An international team of researchers examined the dead bodies of beached dolphins on the Spanish coast, which revealed to them the telltale signs of Alzheimer's disease, particularly the beta-amyloid protein plaques and “tangles” of tau proteins. According to the team, this is likely associated with insulin function.
Insulin regulates sugar levels in the blood, and triggers what’s known as “insulin signaling.” Changes in insulin signaling in humans and other mammals can cause diabetes.
Studies have found that changing insulin signaling in smaller animals such as mice and fruit flies by extreme calorie restriction could extend their lifespans, but the findings of this new study suggests that the same process could cause other animals to be more prone to dementia.
“We think that in humans, the insulin signaling has evolved to work in a way similar to that artificially produced by giving a mouse very few calories,” according to Professor Simon Lovestone, an old age psychiatrist from Oxford Health NHS Foundation Trust. “That has the effect of prolonging lifespan beyond the fertile years, but it also leaves us open to diabetes and Alzheimer’s disease."
This suggests that dolphins and killer whales (orcas), which have long post-fertility life spans similar to humans, have an insulin signaling system that makes them an interesting model of diabetes. Furthermore, the study reveals signs that dolphin brains exhibit symptoms of dementia identical to those seen in humans.
“It is very rare to find signs of full-blown Alzheimer’s disease in non-human brains,” according to Professor Lovestone. “This is the first time anyone has found such clear evidence of the protein plaques and tangles associated with Alzheimer’s disease in the brain of a wild animal.”
The researchers see this as a breakthrough for developing better approaches to treating the disease, paving the way for a new avenue for testing Alzheimer's drugs. This is the first evidence of the disease being detected in a wild animal.
This poses some challenges in finding new “targets” for curing the disease, according to Professor Lovestone. However, he thinks that if altered insulin signaling can make an animal more susceptible to Alzheimer’s disease, this might present possibilities of being able produce mice that are a true model of the disease, which then can be tested to find new treatments.
Read more about the symptoms and causes of dementia at Alzheimers.news.
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