Researchers in Cleveland have found a second bacteria in the human digestive system that converts meat into substances that block arteries.
The two discoveries by the same team of researchers hold out hope that the formation of these harmful substances can be blocked.
The Cleveland Clinic researchers first discovered that microbes in the human digestive tract turn L-carnitine, a nutrient abundant in red meat, into trimethylamine-N-oxide (TMAO), a metabolite that promotes hardening of the arteries.
Now, they have identified a second metabolite, called gamma-butyrobetaine, that they say is generated to an even greater extent by gut bacteria after L-carnitine is ingested, and it too contributes to atherosclerosis.
The new findings, published in the journal Cell Metabolism, show gamma-butyrobetaine can itself be converted into TMAO.
The researchers also discovered the bacteria that produce gamma-butyrobetaine from L-carnitine are different from the bacterial species that produce trimethylamine from L-carnitine.
The discovery that metabolism of L-carnitine involves two different gut microbial pathways, as well as different types of bacteria, could lead to new strategies for preventing atherosclerosis, the researchers said.
For example, therapies could be developed to inhibit various bacterial enzymes or to shift gut bacterial composition with probiotics and other treatments.
"While this is into the future, the present studies may help us to develop an intervention that allows one to 'have their steak and eat it too' with less concern for developing heart disease," said Dr. Stanley Hazen, of Lerner Research Institute and the Miller Family Heart and Vascular Institute at Cleveland Clinic, who led the research.