Trillions of microbes call our bodies home, and the ones that live in the gut can have a powerful impact on human health and disease. Some of the microbes in the human gut microbiome and the molecules they create can be very beneficial. Reporting in the Journal of Biological Chemistry, researchers have now found that one type of gut microbe may reduce the risk of heart attacks by reducing the production of an artery-clogging molecule. The molecule is made in the gut and released into the bloodstream. It then moves to the liver where it's converted into a harmful form. The microbe is called Eubacterium limosum, and it's already been shown to reduce 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," said the senior study author Joseph Krzycki, a professor of microbiology at Ohio State. "It's too soon to say whether this bacterium could have therapeutic value. But that's what we're working toward."
Clogged arteries are a symptom of atherosclerosis, an arterial disease that can lead to a heart attack. Trimethylamine (TMA) is generated when some microbes in the intestine interact with chemicals like L-carnitine that are produced during the breakdown of food in the gut. In this study, the researchers found that E. limosum has a different effect, and its interaction with L-carnitine does not lead to the production of more TMA.
The scientists suggested that a bacterial enzyme called MtcB is responsible for this effect by removing a methyl chemical group from larger compounds, which helps bacteria survive.
"The bacterium does this for its own benefit, but it has the downstream effect of reducing the toxicity of TMA," Krzycki said. "Up until now, the only known gut microbial reactions with L-carnitine involved converting it into its bad form. We've discovered that a bacterium known to be beneficial could remove a methyl group and send the resulting product down another pathway without making any other harmful compounds in the process."
IN this work, the researches exposed E. limosum cultures to various molecules including L-carnitine. The bacteria began to generate MtcB only in the presence of L-carnitine, which demethylated the L-carnitine, enabling the microbe to consume the nutrient.
"MtcB is part of a family of proteins with thousands of representatives that may use different compounds and change what nutrients bacteria consume in the gut," Krzycki said. "These proteins may behave very similarly chemically, but using different compounds obviously can create big changes as far as biology goes."