Boffins have identified a blood protein myeloperoxidase (MPO) secreted by white blood cells, that both signals inflammation and releases a bleach-like substance that damages the cardiovascular system, which might be a clue to why apparently healthy persons could be at high risk of heart attacks.
The study was conducted by a team of researchers led by Matthijs Boekholdt at the Academic Medical Center in Amsterdam, the Netherlands.
Earlier studies in patients with chest pain and heart disease have linked elevated levels of MPO with those at highest risk for a heart attack.
As part of the study, to examine the relationship of MPO to cardiovascular risk in apparently healthy individuals, researchers recruited healthy people living in Norfolk, United Kingdom, between 1993 and 1997, as part of a larger community-based research program known as the European Prospective Investigation Into Cancer and Nutrition (EPIC) and took their baseline blood samples and froze it for future analysis.
After an average of eight years, 1,138 EPIC-Norfolk participants had been admitted to the hospital or died from the effects of coronary artery disease (CAD), including heart attack.
The researchers matched these patients with study participants who remained healthy throughout the follow-up period, selecting those of the same gender and similar ages and enrolment times.
Researchers found that the average blood levels of MPO were significantly higher in those who developed heart disease than in those who remained healthy.
The study suggested that although MPO is intended to kill harmful bacteria, it might instead inflame the body's arteries and cripple protective substances in the blood.
Elevated MPO levels signalled increased risk even in those with acceptable levels of LDL cholesterol, HDL cholesterol or C-reactive protein, a widely acknowledged marker of inflammation.
The study noted that MPO changes low-density-lipoprotein (LDL) cholesterol into a harmful oxidized form that cause atherosclerosis and the 'bleach' produced by MPO damages the arteries directly, causing cell death and erosion of the arterial lining, a process that can create unstable plaques.
MPO also hampers the protective effects of high-density-lipoprotein (HDL) cholesterol and reduces the availability of nitric oxide, a natural chemical that relaxes the blood vessels.
"MPO levels help to identify individuals at increased risk for CAD when traditional risk screening fails," Dr. Boekholdt said.
The findings of the study were published in the July issue of the Journal of the American College of Cardiology (JACC).