Healthy Blood Vessels May Help Prevent Alzheimer’s Disease

AD affects an estimated 5.4 million Americans and this number is projected to continue to increase with the oncoming Silver Tsunami because currently there is no cure, as such Alzheimer’s disease is considered to be one of the greatest health challenges of the century. 

Healthy blood vessels are suspected to be key to brain health, especially in older age. USC researchers have shown that damaged brain capillaries rather than plaques and tangles of abnormal proteins may prime the brain for Alzheimer’s disease decades before symptoms appear. 

“The fact that we’re seeing the blood vessels leaking, independent of tau and independent of amyloid, when people have cognitive impairment on a mild level, suggests it could be a totally separate process or a very early process,” said Berislav Zlokovic, director of the Zilkha Neurogenetic Institute at the Keck School of Medicine of USC.

Cells that form the walls of capillaries fit together tightly in healthy brains to form a barrier that keeps stray cells, metals, pathogens, and other unhealthy substances from reaching brain tissue. This is called the blood brain barrier, but in some aging brains the seams between cells will loosen, blood vessels become permeable and neurons begin to die. 

“We’ve also learned that pericytes, a type of cell in the blood-brain barrier, not only help push blood through the brain but also secrete a substance that protects neurons,” Zlokovic said.

“Brain imaging is integral to studying Alzheimer’s disease. In visualizing the blood-brain barrier in people, we actually can see and measure changes where the barrier breaks down,” says Arthur Toga director of the USC Mary and Mark Stevens Neuroimaging and Informatics Institute at the Keck School of Medicines. “We’ve been able to correlate greater leakage with increased cognitive decline.”

Brain imaging allowed the team to detect changes which potentially may be indicative of disease in the spaces around blood vessels in the brain; these perivascular spaces help drain fluid and metabolic waste from the brain. 

Senior research associate Diana Younan is studying the link between air pollution and dementia as the exact mechanism is not fully understood, such as does fine particle pollution penetrate the BBB and infiltrate brain tissue, could it be a matter of pollution triggering inflammation?

When exploring the protective effects of higher levels of education, physical activity and challenging work that contribute to resilience in brain function the team studied participants exposed to fine particle pollution and found that higher levels of cognitive reserve appear to protect against dementia.

“Here in Los Angeles, you can’t really avoid air pollution,” Younan said. “So, if people are staying involved in mentally stimulating activities, it could decrease the risk of memory problems later on.”

Assistant Professor of Psychology Daniel Nation found that those with untreated diabetes developed signs of Alzheimer’s disease at a rate of 1.6 times faster than those who did not have diabetes. This may be due to diabetes treatment helping to keep blood vessels in the brain healthy, which may stave off dementia. 

“It’s clear that the medicines for treating diabetes make a difference in the progression of dementia,” Nation said. “But it’s unclear how exactly those medications slow or prevent the onset of Alzheimer’s disease, so that is something we need to investigate.”

Along with other University of Southern California Alzheimer’s scientist findings, these studies will be presented and on display at the Alzheimer’s Association International Conference July 2019 in Los Angeles.