Odd But True: Intense Light Protects Cardiovascular Health

American researchers have uncovered the mechanism that allows intense light to protect people against heart attacks.

Intense light amplifies a specific gene -- called PER2-- that bolsters blood vessels and offers protection against heart attacks, according to a study by a team from the University of Colorado Anschutz Medical Campus. The study was recently published in the journal, Cell Reports.

In the study, the scientists discovered that having mice under intense light conditions for one week “robustly enhances cardio protection.” This action also resulted in a dramatic reduction of cardiac tissue damage after a heart attack.

Researchers also found humans can potentially benefit from a similar light exposure strategy.

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

To find out why this is so, researchers developed a strategy to protect the heart. They used intense light to target and manipulate the function of the PER2 gene. This specific gene is expressed in a circadian pattern in the part of the brain controlling our circadian, or sleep-wake, rhythms.

By amplifying this gene through light, they found it protected cardiovascular tissues against low oxygen conditions like myocardial ischemia that is caused by reduced oxygen flow to the heart. They also discovered the light increased cardiac adenosine, a chemical that plays a role in blood flow regulation.

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

Researchers then investigated if intense light had similar effects on healthy human participants. They exposed participants to 30 minutes of intense light. In this case, they were exposed to 10,000 LUX or lumens on five consecutive days. Serial blood draws were also done.

The light therapy increased PER2 levels. On the other hand, plasma triglyceride (a surrogate for insulin sensitivity and carbohydrate metabolism) showed significant decrease. Overall, metabolism improved due to the therapy.

Dr. Eckle has long known light plays a critical role in cardiovascular health and regulating biological processes. He said past studies have shown an increase in myocardial infarctions during darker winter months in all U.S. states. The duration of the light isn't as important as the intensity, however.

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

The study showed intensive light therapy on a molecular level offers a promising strategy in treating or preventing low oxygen conditions such as myocardial ischemia. It might also offer protection against injury to the heart muscle that can be fatal if the therapy is given before high risk cardiac and non-cardiac surgery, he added.