The Tau of Dementia

Dec. 27, 2013

By Medical Discovery News

The Tau of Dementia

All it takes is the instantaneous crash of an oncoming car. The heavy blow of a linebacker’s tackle. The explosion of a roadside bomb in Afghanistan. All these instances and more can cause traumatic brain injury (TBI). It used to be considered a one-time event, but its long-lasting impairments make it more of a chronic disease.

Sadly, there are no cures for TBI and each person experiences them in their own way. Just as each person is different, no two brain injuries are exactly alike. This makes it a very challenging condition to study and to treat. 

A silent injury, the damage of TBI is not outwardly visible, unlike a broken arm or an amputated leg. Some people have been accused of faking a brain injury, and some denied medical assistance because their injury is undetectable. Others think they are fine, but their reaction times are slower and they may have trouble with memory, focus, attention, and motor skills. Even a mild concussion can produce these effects. 

What’s more, someone with TBI is at a greater risk of developing dementia. Autopsies of the brains of athletes who had multiple concussions prove this connection. Their brains revealed that they had chronic traumatic encephalopathy (CTE), which has symptoms similar to Alzheimer’s disease. There isn’t a way to detect CTE and dementia other than through an autopsy, so it is difficult to know who has it for sure.

In the lab, CTE is recognizable through the detection of a protein called tau in certain areas of the brain. The presence of tau can impair normal cellular processes and result in trouble thinking or remembering. It seems like an easy fix – remove the tau and repair the dysfunctional brain cells. Unfortunately, it’s not that simple. Tau plays an important role in stabilizing the structure of brain cells, so removing all the tau from the brain would cause damage and dysfunction.

Too much tau is not good either. Then, individual units of tau protein accumulate and form structures of their own such as neurofibrillary tangles. These interfere with cells’ ability to communicate with each other. Aggregate tau can be toxic as well and is suspected to perpetuate the cell death processes that occur in the hours and weeks after an initial injury.

Researchers with the Sealy Center for Vaccine Development at UTMB have developed an antibody that detects this toxic form of tau protein without interrupting the processes of normal tau proteins. Using this antibody, they were able to find toxic tau tangles in animal brains after TBI. 

Next, they plan to use a similar antibody to inactivate the tau tangles with the hope of preventing further damage. This antibody appears to improve learning and memory in rodents with Alzheimer’s disease. In the future, it might be used as a therapeutic vaccine for many neurodegenerative disorders.  Right now though, researchers are working to ensure this therapy is safe and effective in animals before moving on to clinical trials with people.

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A Soldier’s Hidden Injury

By Medical Discovery News

March 17, 2012

A common story among soldiers coming home from Afghanistan is that outwardly they look fine. Yet soon, it’s apparent their memories aren’t as good as they used to be. They have headaches, can’t concentrate, and are irritable and often depressed. Soon, their symptoms put stress on their relationships and their lives begin to fall apart.

This is the picture of someone with traumatic brain injury or TBI, and it’s known as the signature injury of soldiers returning from Afghanistan and Iraq. But what’s even more troubling is that a new study shows these soldiers face over twice the risk of early on-set dementia and other diseases that attack the brain.

The study, led by Dr. Kristine Yaffe of the University of California San Francisco, analyzed the records of 281,540 veterans 55 or older. Of the vets who reported a TBI sometime between 1997 and 2000, 15 percent ended up with dementia seven years later. Compare that to just 6.8 percent of non-TBI vets who ended up with dementia.

The implications are enormous. According to the Pentagon, over 200,000 soldiers have suffered a brain injury over the past 10 years. Other sources put that number higher. In fact, consider the American public, of which 1.7 million suffer from some form of TBI each year.

Traumatic brain injury occurs when a sudden trauma causes damage to the brain. It happens when the head suddenly and violently hits an object, or when something pierces the skull and enters the brain. Soldiers are getting TBIs from roadside bombs and explosions, which account for 59 percent of injuries sustained in these attacks.

An increasing number of studies show head injuries are a risk factor for Alzheimer’s and other forms of dementia. For example, a single severe brain injury from a car accident or fall doubles the risk of Alzheimer’s. Within hours of the injury, a protein called amyloid-beta starts accumulating in the brain, creating a plaque characteristic of the disease. In autopsies of soldiers who suffered from their catastrophic brain injuries, one-third showed this build-up.

On the other hand, repeated, mild TBI leads to the build-up of a different protein called tau. This abnormal protein accumulates in nerve cells, clogging them up and eventually killing the cells. Over time, they destroy the brain’s ability to function normally, and this form of dementia is called chronic traumatic encephalopathy or CTE. Just recently, a star NFL football player who suffered from CTE committed suicide because of his symptoms.

In the latest study with vets, soldiers with TBI may be at risk for developing both types of dementia. Only in the past two years has the U.S. military become responsive to addressing and treating TBIs. Up until then, soldiers have shared stories of not being believed, and not getting the treatment they needed. Already, many with TBI are showing memory loss.

Yaffe’s study can spur scientists to investigate whether early treatment after a TBI can prevent the on-set of dementia in the future. They can also study why brain injuries prompt a build-up of damaging proteins. The study fills one other important purpose: creating more awareness of TBI so that returning soldiers don’t have to fight for the treatment they need.

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