Stress linked to brain disease

A study by UC Irvine researchers could prove that stress is even more harmful to the human body than previously thought — specifically to the brain.

The researchers, led by Frank LaFerla, discovered a hormonal connection between stress and Alzheimer’s disease. The study shows that increased levels of stress increases acceleration of the disease through the brain.

UCI researchers Kim Green and Lauren Billings worked to solve the connection between stress and Alzheimer’s using a crew of genetically altered mice.

The first generation of mice were injected as embryos with genes related to brain dementia and Alzheimer’s. By altering breeding within that group, the team ensured that every following generation of mice was predisposed to the diseases.

By then injecting the later generations of mice with dexamethasone, a steroid-like substance similar to the hormones produced when a body is under stress, Green and Billings measured the acceleration of the disease through the brain.

What they found was unexpected.

When the mice were injected with a compound similar to stress hormones found in the human body, for seven days, plaque formed on the brain causing lesions.

Levels of the protein beta-amyloid rapidly increased by 60% when the dexamethasone was injected, creating lesions on the brain tissue.

“These hormones increase when a person is stressed,” Green said. “They tell you your body it is stressed.”

These same lesions were the type used as indicators of Alzheimer’s and dementia in brain tissue.

“When we made these mice, we were just interested in determining what acute affect the hormone had on them. Would it be good? Would it be bad?” LaFerla said. “We were surprised that it actually exacerbated the pathology over a very short period of time.”

The study’s findings mark another step in a line of research on the effects of stress on Alzheimer’s.

In 2005, the journal Neurology published a study that directly tied people who led stress-filled lives to increased cases of the debilitating brain diseases. Led by Robert Wilson, the study found that people with more stress in their lives were nearly 2 1/2 times more likely to develop Alzheimer’s than those less prone to stress.

Where Wilson’s study showed the connection, LaFerla and Green’s study approached the “why” behind the connection.

The duo’s study found that these hormones that act as a body’s response to stress trigger proteins in the body that accelerate the progression of the disease, Green said.

“With Alzheimer’s, these hormones are increased when a person is stressed,” he said. “Before no one knew what the cause was.”

To read more on the study, look for the journal Neuroscience or check the campus news section of UCI’s website, www.uci.edu.