heart attacks circadian rhythms

Why intense light can protect cardiovascular health

The light boosts a critical gene that strengthens blood vessels

August 8, 2019

Science Daily/University of Colorado Anschutz Medical Campus

Researchers at the University of Colorado Anschutz Medical Campus have found that intense light amplifies a specific gene that bolsters blood vessels and offers protection against heart attacks.

 

"We already knew that intense light can protect against heart attacks, but now we have found the mechanism behind it," said the study's senior author Tobias Eckle, MD, PhD, professor of anesthesiology at the University of Colorado School of Medicine.

 

The study was published recently in the journal Cell Reports.

 

The scientists discovered that housing mice under intense light conditions for one week `robustly enhances cardio protection', which resulted in a dramatic reduction of cardiac tissue damage after a heart attack. They also found that humans could potentially benefit from a similar light exposure strategy.

 

In an effort to find out why, they developed a strategy to protect the heart using intense light to target and manipulate the function of the PER2 gene which is expressed in a circadian pattern in the part of the brain that controls circadian rhythms.

 

By amplifying this gene through light, they found that it protected cardiovascular tissues against low oxygen conditions like myocardial ischemia, caused by reduced oxygen flow to the heart.

 

They also discovered that the light increased cardiac adenosine, a chemical that plays a role in blood flow regulation.

 

Mice that were blind, however, enjoyed no cardio protection indicating a need for visual light perception.

 

Next, they investigated whether intense light had similar effects on healthy human volunteers. The subjects were exposed to 30 minutes of intense light measured in lumens. In this case, volunteers were exposed to 10,000 LUX, or lumens, on five consecutive days. Researchers also did serial blood draws.

 

The light therapy increased PER2 levels as it did in mice. Plasma triglycerides, a surrogate for insulin sensitivity and carbohydrate metabolism, significantly decreased. Overall, the therapy improved metabolism.

 

Eckle has long known that light plays a critical role in cardiovascular health and regulating biological processes. He pointed out that past studies have shown an increase in myocardial infarctions during darker winter months in all U.S. states, including sunnier places like Arizona, Hawaii and California. The duration of the light isn't as important as the intensity, he said.

 

"The most dramatic event in the history of earth was the arrival of sunlight," Eckle said. "Sunlight caused the great oxygen event. With sunlight, trillions of algae could now make oxygen, transforming the entire planet."

 

Eckle said the study shows, on a molecular level, that intensive light therapy offers a promising strategy in treating or preventing low oxygen conditions like myocardial ischemia.

 

He said if the therapy is given before high risk cardiac and non-cardiac surgery it could offer protection against injury to the heart muscle which can be fatal.

 

"Giving patients light therapy for a week before surgery could increase cardio protection," he said. "Drugs could also be developed that offer similar protections based on these findings. However, future studies in humans will be necessary to understand the impact of intense light therapy and its potential for cardio protection."

https://www.sciencedaily.com/releases/2019/08/190808115052.htm

Why heart failure patients suffer depression, impaired thinking

April 5, 2019

Science Daily/University of Guelph

A new study explains why heart failure patients often have trouble with thinking and depression, pointing to ways to prevent and treat both heart and brain maladies through the emerging field of circadian medicine.

 

Heart failure patients often have trouble with thinking and depression.

 

A new study by University of Guelph researchers explains why and points to ways to prevent and treat both heart and brain maladies through the emerging field of circadian medicine.

 

Published recently in Nature's Scientific Reports, the study is the first to reveal how cognition and mood in mice are regulated by the body clock and how pertinent brain regions are impaired in heart failure, said Tami Martino, a professor in U of G's Department of Biomedical Sciences and director of the Centre for Cardiovascular Investigations.

 

"Neurosurgeons always look in the brain; cardiologists always look in the heart. This new study looked at both," said Martino, whose work in the emerging field of circadian medicine is supported by funding from the Canadian Institutes of Health Research. She recently received a Mid-Career Investigator Award from the Heart and Stroke Foundation of Canada.

 

Coronary heart disease, the most common cause of heart failure, causes one in three deaths in Canada, according to the Heart and Stroke Foundation.

 

Human patients with heart failure often have neurological conditions such as cognitive impairment and depression, said Martino. She worked on the study with master's student Austin Duong and PhD student Cristine Reitz -- both co-first authors -- and neuroscientists including U of G psychology professor Boyer Winters and biomedical sciences professor Craig Bailey.

 

Martino suspected the heart-brain connection involved the circadian mechanism molecule, called "clock."

 

Circadian rhythms in humans and other organisms follow Earth's 24-hour cycle of light and darkness, signalling when to sleep and when to be awake.

 

Martino's earlier research showed how disrupting circadian rhythms -- as with shift workers, jet-lagged travellers and patients disturbed in intensive-care units -- can trigger changes that worsen heart disease and impair overall health and well-being.

 

For this new study, the researchers compared normal mice with mice carrying a mutation in their circadian mechanism (called "clock mice"). They found that the mutation affected the structure of neurons in brain areas important for cognition and mood.

 

Working with University of Toronto colleagues, the team also found differences in clock regulation of blood vessels in the brains of the clock mice.

 

After inducing heart failure in mice to simulate human heart failure, they used microarray profiling to identify key genes in the brain that were altered in neural growth, stress and metabolism pathways.

 

The results show that the circadian mechanism influences neural effects of heart failure, said Martino. Pointing out that no cure exists for the heart condition, she said understanding how the circadian mechanism works in the brain may lead to new strategies to improve patients' quality of life.

 

Patients recovering from heart attacks often experience disturbed circadian rhythms from light, noise and interactions with hospital staff at night. "Maintaining circadian rhythms especially for patients with heart disease could lead to better health outcomes."

 

More generally, the findings point to potential health benefits for people in general. Avoiding shift work for people with underlying heart conditions or sleep disorders, reducing light at night or avoiding social jet lag (going to bed late and waking up later than usual on weekends) could all help reduce neurobiological impairments.

 

Those problems -- and potential solutions -- involve not just hearts but brains, she said. "If we're not yet able to cure heart failure, we should at least be focusing on how we can improve quality of life for patients."

https://www.sciencedaily.com/releases/2019/04/190405124313.htm

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