Until recently, scientists believed that only humans could develop the protein plaques that indicate Alzheimer’s. That changed in August, when a study showed that chimpanzees who died from natural causes at zoos and research centers can also develop beta-amyloid plaques and tau tangles, though they don’t show symptoms as far as scientists can observe. A new study from Oxford University shows that dolphins, too, develop Alzheimer’s—the first known wild animal to do so.
Oxford University scientist Simon Lovestone studied the brains of dolphins who died naturally and washed up on the Spanish coast. What he and other researchers found was an accumulation of beta-amyloid and tau tangles.
The team has a theory that animals like humans and dolphins are uniquely susceptible to Alzheimer’s because they live so far past their reproductive years. Dolphins can live 25 to 40 years after reproductivity drops off; humans can live anywhere from 40 to 60 years after their reproductivity dwindles after 40. The scientists who studied the dolphins have made the connection between the similar ways humans and dolphins process insulin, the blood sugar regulator. Insulin triggers a chemical process throughout the body known as insulin signaling. Changes in this signaling can cause diabetes. At the same time, scientists believe insulin signaling is what allows humans to live so long. In studies on mice and fruit flies, mimicking insulin signaling of humans by extreme calorie restriction increased lifespan by up to three times.
‘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,” said Lovestone in a statement. “That has the effect of prolonging lifespan beyond the fertile years, but it also leaves us open to diabetes and Alzheimer’s disease.”
While this study gives us a much better animal model to study Alzheimer’s, scientists don’t know whether the protein accumulation leads to the same symptoms humans experience with dementia.
Read the full study in the journal Alzheimer’s and Dementia.