Alzheimer’s may start in blood and move to the brain, study finds

Alzheimer’s disease, the terminal brain affliction that leads to confusion, memory loss and eventually death, may actually begin in the blood and larger bodily tissues before progressing into the brain, a new study from the University of British Columbia and Third Military Medical University found.

The study, led by psychiatry professor Weihong Song in Vancouver and neurology professor Yan-Jiang Wang in Chongqing, China and published in the journal Molecular Psychiatry, found that the proteins that contribute to the development of Alzheimer’s disease may actually begin in the body and migrate into the brain later.

The protein is called amyloid-beta, was first identified in 1984 as a probable culprit in Alzheimer’s disease, according to the Alzheimer’s Association. Amyloid is created naturally in the blood and muscles, but in Alzheimer’s patients it appears to build up in the brain and create “sticky” plaques that clump up and kill brain cells, the researchers wrote in a press release.

In their study, the researchers surgically attached two mice together in a process called parabiosis – meaning they shared the same blood supply. One of the mice had been genetically modified with a mutant gene that produced high levels of amyloid.

After a year, the normal mice appeared to “contract” Alzheimers just from receiving the blood of their partners, the researchers found. “Not only did the normal mice develop plaques, but also a pathology similar to “tangles”– twisted protein strands that form inside brain cells, disrupting their function and eventually killing them from the inside-out,” the university wrote in the press release.

In fact, the mice began to experience brain impairments after only a few months, the researchers said. Song wrote that this study could help explain how Alzheimer’s progresses, and why it appears to strike older people more often.

“The blood-brain barrier weakens as we age,” Song wrote in the release. “That might allow more amyloid beta to infiltrate the brain, supplementing what is produced by the brain itself and accelerating the deterioration.”

The news could lead to more treatments that focus on targeting the plaques early on, before they begin affecting the brain. Roughly 5 million Americans are living with the disease, and 1 in 3 seniors will eventually die from it or another form of dementia, according to the Alzheimer’s Association.

Alzheimer’s disease is usually caused by genetic factors and, possibly, certain lifestyle choices that result in a slow build-up of the plaque, according to the National Institutes of Health. It is not known to be transferable through the blood in normal circumstances (the mouse study, where two animals shared the same blood supply for months, was not a normal circumstance), and a 1999 study concluded there was no increased incidence of the disease among those who received blood transfusions.

This story was originally published November 1, 2017 at 9:17 AM with the headline "Alzheimer’s may start in blood and move to the brain, study finds."