Scientists find signs of Alzheimer's in the brains of three different dolphin species

sarahjay1 (69)memberin Popular STEM • last year

(Wikimedia Commons https://bit.ly/3IFrAjh)

Researchers from the University of Glasgow found biomarkers for Alzheimer's disease in cetaceans near the coast of Scotland.

The team led by Mark Dagleish found aggregates of hyperphosphorylated tau protein and beta-amyloid plaques in the brains of three individuals: a pilot whale, a white-faced dolphin and a bottlenose dolphin.

Alzheimer's disease is the main cause of dementia.

Patients deteriorate memory, cognitive and communication skills, and in the end they can not do the simplest household chores.

It is still not possible to reliably establish the causes of the development of the disease.

However, its characteristic neuronal signs are known - the accumulation of beta-amyloid plaques and hyperphosphorylated tau protein in the brain.

OTHER ANIMALS
Alzheimer's disease is believed to affect only humans.

It is possible to artificially induce such a pathology in laboratory animals, but this will not exactly repeat the development of the disease in humans.

However, some similar pathological changes are found in the brains of other animals.

Thus, beta-amyloids and neurofibrillary tangles from tau protein have already been found in the brains of chimpanzees who died in old age.

Bottlenose dolphins found dead off the coast of Florida and Massachusetts also had beta-amyloids in their brains.

One of the reasons why some cetaceans can develop Alzheimer's-like pathologies is their long lifespan: dolphins, for example, live an average of 20 to 30 years.

However, in addition to the benefits, longevity brings with it an increased risk of various diseases, including dementia.

Also, many cetaceans care for their sick counterparts - and they live even longer, because of which the disease can progress.

THE STUDY
Dagleish team studied the brains of eighteen representatives of five different species of toothed whales that were found dead off the coast of Scotland:

2 gray dolphins (Grampus griseus)
5 common pilot whales (Globicephala melas)
5 white-faced dolphins (Lagenorhynchus albirostris)
5 porpoises (Phocoena phocoena)
1 bottlenose dolphin (Tursiops truncatus)

Scientists took brain samples from the Scottish Biobank, which stores tissues found on the coast of cetaceans, pinnipeds and sea turtles.

The researchers selected samples based on signs of aging: worn teeth, white matter over gray matter, and estimated age.

Using immunohistochemistry, scientists found beta-amyloid plaques in the brains of all individuals.

Three dolphins of different species (bottlenose dolphin, white-nosed dolphin and pilot whale) had both beta-amyloid plaques around neurons and aggregates of hyperphosphorylated tau protein inside neurons.

(Dagleish et al / European Journal of Neuroscience, 2022 https://bit.ly/3VMMBLs)

Another pilot whale had tau aggregates but no amyloid plaques.

The simultaneous accumulation of beta-amyloid and tau in the cetacean brain suggests that these 3 species spontaneously develop Alzheimer's-like neuropathology.

It is not known whether they exhibit cognitive impairment characteristic of the disease, and how the pathology affects their health in general.

However, the authors suggest that this neuropathology may explain why groups of healthy dolphins sometimes swim in shallow water or wash ashore: the animals can follow their sick leader.

The Dagleish team also noted that toothed whales could be a good model for studying Alzheimer's disease.

This is because non-human primates and other animals do not spontaneously develop the disease.

In the future, we could study more different species, individuals and age groups of toothed whales, including those that live in captivity.

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