In Brief:
- Atherosclerosis causes coronary artery disease, the number one killer of both men and women in the United States.
- Viral atherosclerosis can occur in the absence of common risk factors, including high blood pressure, cigarette smoking, Type II Diabetes, and family history.
- Researchers study White Leghorn chickens because they develop high cholesterol levels similar to those found in humans.
Help! Sirens and bright lights engulf the driveway as an ambulance screeches to a halt. As his family watches desperately, Rich is pulled onto the stretcher and lifted inside. At the emergency room, doctors confirm he is having a heart attack caused by atherosclerosis.
Atherosclerosis is the build-up of cholesterol in arteries. It triggers coronary artery disease, the number one killer in the United States, in which accumulations of cholesterol called plaques form on artery walls (Mozaffarian, et al, 2015). When they rupture, material flows downstream, where it blocks smaller blood vessels, which can form a blood clot and eventually cause a heart attack. Scientists are studying White Leghorn chickens to understand atherosclerosis. Chickens are an excellent animal model because they have similar cholesterol levels to humans and are also hyperglycemic, a common risk factor for atherosclerosis (Ayala et al, 2005).
Because Rich maintained a healthy lifestyle and low levels of stress, he never imagined being at risk for coronary artery disease. However, researchers at the Washington Hospital Medical Center in Washington, D.C., explain that 50% of patients do not have common risk factors for atherosclerosis. They suggest that atherosclerosis could be caused by viral infections such as cytomegalovirus and herpesvirus (Fabricant, 1999).
Research
In pioneering studies with chickens in the 1960s, Dr. Catherine Fabricant of Cornell University’s College of Veterinary Medicine, discovered that the herpesvirus can lay the foundation for coronary artery disease. She separated the chickens into experimental groups and fed them diets with varying levels of cholesterol. Some were also injected with Marek’s disease virus (MDV), a herpesvirus found in chickens. In later studies, researchers noted that despite cholesterol or diet, unless the chickens were infected with the virus, no atherosclerotic plaques were seen (Epstein et al, 1999).
Researchers at the Robarts Research Institute in London, ON, Canada published a study on possible treatments for viral atherosclerosis. As in Fabricant’s study, the chickens were injected with MDV, and to increase the rate of formation of atherosclerotic plaques, they were fed high cholesterol diets. These scientists found drugs that could inhibit the the cell’s ability to produce cholesterol, lowering overall cholesterol levels (Lucas et al, 1998). After this treatment, the chickens had fewer atherosclerotic plaques (Gotto et al, 2006).
There are many patients, like Rich, who don’t realize they are at risk for coronary artery disease. The groundbreaking discovery in White Leghorn chickens that certain viruses can lead to heart disease gives researchers important information to use in the battle to overcome atherosclerosis.
Photo Credits:
Header: [“I love chickens! (White Leghorn Chickens)” by Holly Occhipinti, (Unedited). License: CC BY 2.0]