Sunday September 23, 2018

A study finds: What causes dementia?

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1 in 6 people over the age of 80 have dementia. Pixabay
1 in 6 people over the age of 80 have dementia. Pixabay
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Dementia results in a progressive and irreversible loss of nerve cells and brain functioning, causing loss of memory and cognitive impairments affecting the ability to learn. Currently, there is no cure.

Findings

  • The toxic build-up of urea, a compound created by the liver, in the brain has been found as the major reason that can cause brain damage and lead to Huntington’s Disease, one of seven major types of age-related dementia.
  • Urea level peaks in the brain even before dementia sets in. The discovery could one day help doctors diagnose and even treat dementia.
  • Urea is similarly linked to Alzheimer’s, suggesting that the toxic build-up of urea could be relevant to all types of age-related dementias.
44 million people worldwide suffer from dementia. Pixabay
44 million people worldwide suffer from dementia. Pixabay

“This study on Huntington’s Disease is the final piece of the jigsaw which leads us to conclude that high brain urea plays a pivotal role in dementia,” said Garth Cooper, Professor at The University of Manchester.

“Alzheimer’s and Huntington’s are at opposite ends of the dementia spectrum — so if this holds true for these types, then I believe it is highly likely it will hold true for all the major age-related dementias,” Cooper said, in the paper published in the Proceedings of the National Academy of Sciences.

Urea and ammonia in the brain are metabolic breakdown products of protein. If urea and ammonia build up in the body because the kidneys are unable to eliminate them, for example, serious symptoms can result, the researchers said.

“More research, however, is needed to discover the source of the elevated urea in Huntington’s Disease, particularly concerning the potential involvement of ammonia and a systemic metabolic defect,” Cooper noted.

For the study, the team used human brains, donated by families for medical research, as well as transgenic sheep in Australia.

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Scientists Discover A New Method To Fight Alzheimer’s, Dementia

Worldwide, about seven percent of people over 65 suffer from Alzheimer's or some form of dementia, a percentage that rises to 40 percent above the age of 85.

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Alzheimer's
One hemisphere of a healthy brain (L) is pictured next to one hemisphere of a brain of a person suffering from Alzheimer disease. VOA
Eliminating dead-but-toxic cells occurring naturally in the brains of mice designed to mimic Alzheimer’s slowed neuron damage and memory loss associated with the disease, according to a study published Wednesday that could open a new front in the fight against dementia.The accumulation in the body of “zombie cells” that can no longer divide but still cause harm to other healthy cells, a process called senescence, is common to all mammals.

Scientists have long known that these dead-beat cells gather in regions of the brain linked to old age diseases ranging from osteoarthritis and atherosclerosis to Parkinson’s and dementia.

Prior research had also shown that the elimination of senescent cells in ageing mice extended their healthy lifespan.

But the new results, published in Nature, are the first to demonstrate a cause-and-effect link with a specific disease, Alzheimer’s, the scientists said.

Alzheimer's
A lady suffering from Alzheimer’s. Flickr

But any treatments that might emerge from the research are many years down the road, they cautioned.

In experiments, a team led by Tyler Bussian of the Mayo Clinic in Rochester, Minnesota used mice genetically modified to produce the destructive, cobweb-like tangles of tau protein that form in the neurons of Alzheimer’s patients.

The mice were also programmed to allow for the elimination of “zombie” cells in the same region.

“When senescent cells were removed, we found that the diseased animals retained the ability to form memories, and eliminated signs of inflammation,” said senior author Darren Baker, also from the Mayo Clinic.

The mice likewise failed to develop Alzheimer’s signature protein “tangles”, and retained normal brain mass.

 

Alzheimer's
Alzheimer’s disease patient Isidora Tomaz, 82, sits in an armchair in her house in Lisbon, Portugal. It’s predicted that by 2050, 135 million Americans are going to suffer from mild cognitive impairment, a precursor of Alzheimer’s. VOA

Keeping zombies at bay

A closer look revealed that the “zombies” belonged to a class of cells in the brain and spinal cord, called glia, that provide crucial support and insulation to neurons.

“Preventing the build-up of senescent glia can block the cognitive decline and neuro-degeneration normally experienced by these mice,” Jay Penney and Li-Huei Tsai, both from MIT, wrote in a comment, also in Nature.

Bussian and his team duplicated the results with pharmaceuticals, suggesting that drugs could one day slow or block the emergence of Alzheimer’s by keeping these zombie cells at bay.

“There hasn’t been a new dementia drug in 15 years, so it’s exciting to see the results of this promising study in mice,” said James Pickett, head of research at Alzheimer’s Society in London.

 

Alzheimer's
The accumulation in the body of “zombie cells” that can no longer divide but still cause harm to other healthy cells, a process called senescence, is common to all mammals. IANS

For Lawrence Rajendran, deputy director of the Dementia Research Institute at King’s College London, the findings “open up new vistas for both diagnosis and therapy for neurodegenerative diseases, including Alzheimer’s.”

Up to now, dementia research has been mostly focused on the diseased neurons rather than their neighboring cells.

“It is increasingly becoming clear that other brains cells play a defining role,” Rajendran added.

Several barriers remain before the breakthrough can be translated into a “safe, effective treatment in people,” Pickett and other said.

The elderly often have lots of harmless brain cells that look like the dangerous senescent cells a drug would target, so the molecule would have to be good at telling the two apart.

Also Read: Common Painkillers Triple Harmful Side Effects in Dementia

Worldwide, about seven percent of people over 65 suffer from Alzheimer’s or some form of dementia, a percentage that rises to 40 percent above the age of 85.

The number afflicted is expected to triple by 2050 to 152 million, according to the World Health Organization, posing a huge challenge to healthcare systems. (VOA)