By Sharon Begley
NEW YORK (Reuters) - Thousands of heart attack victims every year have none of the notorious risk factors before their crisis - not high cholesterol, not unhealthy triglycerides. Now the search for the mystery culprits has turned up some surprising suspects: the trillions of bacteria and other microbes living in the human gut.
In a study released on Wednesday, scientists discovered that some of the bugs turn lecithin - a nutrient in egg yolks, liver, beef, pork and wheat germ - into an artery-clogging compound called TMAO. They also found that blood levels of TMAO predict heart attack, stroke or death, and do so "independent of other risk factors," said Dr Stanley Hazen, chairman of cellular and molecular medicine at the Cleveland Clinic's Lerner Research Institute, who led the study.
That suggests a TMAO test could enter the arsenal of blood tests that signal possible cardiovascular problems ahead. "TMAO might identify people who are at risk (for heart attacks and strokes) despite having no other risk factors," Hazen said.
The discovery also suggests a new approach to preventing these cardiovascular events: altering gut bacteria so they churn out less TMAO.
The study joins a growing list of findings that link human "microbiota" - microbes in the gut, nose and genital tract, and on the skin - to health and disease. Research has shown that certain species of gut bacteria protect against asthma, for instance, while others affect the risk of obesity. Last week scientists reported that circumcision alters bacteria in the penis, and that this change (not only the anatomical one) helps protect men from HIV/AIDS, probably by reducing the number of bacteria that live in oxygen-free environments such as under the foreskin.
"It's very strong work," Dr Martin Blaser of New York University Langone Medical Center, a pioneer in studies of the microbiota, said of the TMAO study. "They show clearly that human microbiota play a key role in producing TMAO, suggesting new approaches to prevention and treatment" of cardiovascular disease.
NORMAL CHOLESTEROL, FATAL HEART ATTACK
The new study builds on a 2011 discovery by the Cleveland Clinic team that, in lab mice, gut bacteria turn lecithin in food into TMAO, or trimethylamine-N-oxide, causing heart disease. In addition, they found, people with high levels of TMAO are more likely to have heart disease.
But that research left two questions hanging: Do human gut bacteria trigger the lecithin-to-TMAO alchemy, like those in mice? And do high levels of TMAO predict heart attacks and stroke in people many years out, not simply mark the presence of cardiovascular disease at the time of the blood test?
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Gut bugs are implicated in heart attacks and stroke