Stranded dolphins show signs of Alzheimer’s disease in their brains: ScienceAlert

Stranded dolphins show signs of Alzheimer’s disease in their brains: ScienceAlert

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Scientists have found markers of Alzheimer’s disease in the brains of three different species of dolphins found dead washed ashore.

Proof for mass exodus of cetaceans exists since before our own recorded historybut why dolphins and whales beach in groups is an eternal mystery.

Although a direct link has been found between naval sonar and some beaked whalesand some individual animals washed ashore are clearly unwell, some with a belly full of plastic wastemost mass blocks provide little or no clues.

Toothed whales (Odontocetes) share a number deal with peopleincluding (in at least five species that we know of) menopause. Their ability to live well past their reproductive years means they have the potential to be susceptible to late-onset diseases as well.

Alzheimer’s disease is the most common cause of disability in aging people, gradually impairing memory, learning and communication. Now it appears that similar suffering may also affect our water-dwelling mammalian relatives.

“I’ve always been interested in answering the question: do only humans get dementia? says neuroscientist Frank Gunn-Moore of the University of St. Andrews in Scotland.

“Our findings answer this question because they show that the potential pathology associated with dementia is indeed not seen only in patients.”

Leiden University biologist Marissa Wascher and colleagues examined the brains of 22 stranded dolphins to look for biochemical markers present in humans with Alzheimer’s. These include amyloid-beta plaques, which until it is no longer considered a direct cause of the disease are still present in increased numbers in those who have it; and clusters of tau proteins with hyperphosphorylation – when phosphate groups have been added to all possible binding sites of the protein molecule.

They found accumulations of amyloid-beta plaques and hyperphosphorylated tau in three dolphins, each from a different species: the fin whale (Globicephala melas), the white-beaked dolphin (Lagenorhynchus albirostris) and the common bottlenose dolphin (Tursiops abbreviated). These individuals also had signs of old age such as worn or lost teeth and an increase in the ratio of white to gray matter in the brain tissues.

What’s more, the locations of brain lesions found in the dolphins matched equivalent areas seen in humans with Alzheimer’s.

Although it was not possible for the researchers to confirm a diagnosis of Alzheimer’s because they could not test the levels of cognitive impairment in the deceased animals, there was no evidence of accumulations of the two proteins in people without the disease.

“We were fascinated to see brain changes in aging dolphins similar to those seen in human aging and Alzheimer’s disease,” says University of Edinburgh neuroscientist Tara Spiers-Jones.

What are the dolphins highly social animals, it is possible that they will help their colleagues who are beginning to struggle with their brains. That means there’s a chance they’ll survive longer, allowing further disease progression, than in solitary species, the researchers noted.

Dolphin stranding is common in one of the species studied, G. melassupporting “sick driver‘ theory for this mysterious, fatal behavior.

“In humans, the first symptoms of cognitive decline associated with AD include confusion of time and place and a poor sense of direction,” Vacher and colleagues explain in their paper.

“If the leader of a group of G. melas suffers from similar neurodegenerative-related cognitive decline, which can lead to disorientation leading to the pod being driven into shallow water and subsequent stranding.”

However, “whether these pathological changes contribute to the stalling of these animals is an interesting and important question for future work,” Spiers-Jones concludes.

This research was published in European Journal of Neuroscience.

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