‘Good’ gut bacteria may actually lower heart disease risk linked to eating red meat

COLUMBUS, Ohio — In 2018, a landmark study showed that gut bacteria plays an important role in red meat’s contribution to heart disease. Now, researchers from The Ohio State University say some gut bacteria may actually prevent heart disease, rather than promote it.

Gut bacteria synthesizes a molecule called trimethylamine (TMA) when they digest molecules in the foods people eat, like red meat. The human liver then converts that molecule to TMAO, the culprit with a connection to heart disease. Researchers recently discovered that one species of gut bacteria, called Eubacterium limosum, actually digests these molecules in a different way that prevents TMA formation. Scientists are already calling this species a “good” bacteria status because it calms down gut inflammation.

“Over the last decade, it has become apparent that bacteria in the human gut influence our health in many ways. The organism we studied affects health by preventing a problematic compound from becoming a worse one,” says lead researcher and professor of microbiology Joseph Krzycki in a university release

Preventing a bad nutrient from getting worse

Krzycki and his colleagues discovered the beneficial effects of E. limosum by feeding the bacteria several different compounds, including L-carnitine. L-carnitine is a chemical compound in red meat and fish which can be metabolized into TMA by gut bacteria. However, E. limosum metabolizes it in a way that prevents its conversion to TMA.

The key is the protein MtcB. This enzyme cuts specific molecules called methyl groups (a carbon atom surrounded by three hydrogen atoms) off of compounds to help gut bacteria survive. When it cuts the methyl group off of L-carnitine, it can no longer be transformed into TMA. This is the first time researchers have observed a species of gut bacteria converting L-carnitine into a neutral form, rather than a harmful one. 

In the gut, different species of bacteria compete for nutrients. If the balance in the competition for L-carnitine is tipped away from the “bad” bacteria and toward the beneficial E. limosum, this could help support heart health in people. Krzycki is careful to caution that scientists don’t know enough about E. limosum and MtcB yet to say for sure whether the bacteria could help prevent heart disease or not.

“It’s too soon to say whether this bacterium could have therapeutic value. But that’s what we’re working toward,” the study author concludes.

These findings are published in the Journal of Biological Chemistry.