Gut bugs' byproduct may help predict heart attack, stroke risk

Scientists have found that a microbial byproduct of intestinal bacteria contributes to heart disease and can serve as an accurate screening tool for predicting future risks of heart attack and stroke.
In a previous study, Dr Stanley Hazen's, Vice Chair of Translational Research, Chair of the Department of Cellular and Molecular Medicine for the Lerner Research Institute, found that a chemical byproduct called trimethylamine N-oxide (TMAO) is produced when intestinal bacteria digest the nutrient phosphatidylcholine, commonly known as lecithin.
The prior research showed that TMAO levels in the blood were associated with heart disease.
Hazen, who is also section head of Preventive Cardiology & Rehabilitation in the Miller Family Heart and Vascular Institute at Cleveland Clinic, along with colleagues have now confirmed that gut flora are essential in forming TMAO in humans.

They also demonstrated a relationship between TMAO levels and future cardiac events like heart attack, stroke, and death - even in those with no prior evidence of cardiac disease risk.
To demonstrate the role of gut flora in forming TMAO, human subjects were asked to eat two hard-boiled eggs (a common dietary source of lecithin) and a capsule of labelled lecithin (as a tracer).

After ingestion, TMAO levels in the blood increased. However, when these same subjects were given a brief course of broad-spectrum antibiotics to suppress their gut flora, their TMAO levels were suppressed, and no additional TMAO was formed, even after ingesting lecithin.

These results demonstrated that the intestinal bacteria are essential for the formation of TMAO.
In the second phase of the study, the researchers measured TMAO levels in a large, independent, clinical cohort - consisting of more than 4,000 adults undergoing cardiac evaluation at Cleveland Clinic - over a three-year follow-up period.
They found that higher TMAO blood levels were associated with higher future risks of death and nonfatal heart attack or stroke over the ensuing three-year period, independent of other risk factors and blood test results.
"These studies show that measuring blood levels of TMAO could serve as a powerful tool for predicting future cardiovascular risk, even for those without known risk factors," Hazen said.

"Our goal is not to suggest dietary restrictions of entire food groups. Eggs, meat and other animal products are an integral part of most individuals' diets. Our work shows, however, that when digesting these foods, gut flora can generate a chemical mediator, TMAO, that may contribute to cardiovascular disease," Hazen said.
The study was published in The New England Journal of Medicine.