Intestines and heart
How Good Gut Bacteria Help Reduce the Risk of Cardiovascular Disease
Anna Yudina, "Scientific Russia"
Scientists have discovered that one of the beneficial bacteria found in the human intestine has an advantage that has not yet been recognized: it can reduce the risk of heart disease, according to a press release from Ohio State University How good gut bacteria help reduce the risk for heart disease.
Article by Kountz et al. MtcB, a member of the MttB superfamily from the human gut acetogen Eubacterium limosum, is a cobalamin-dependent carnitine demethylase published in The Journal of Biological Chemistry – VM.
The activity of bacteria in the intestine reduces the production of a chemical associated with the development of arterial blockage. After production in the intestine, the chemical enters the bloodstream and into the liver, where it passes into the most harmful form.
Researchers from Ohio State University have traced the behavior of bacteria that can improve human health. In fact, these microbes compete with harmful bacteria for access to the same nutrients in the intestine – and if good bacteria win, they can prevent health problems that arise as a result of improper digestion of food.
There is still a lot of work ahead, but scientists see the potential for using this microbe, Eubacterium limosum, for therapeutic purposes in the future. Previous studies have already shown that the bacterium is "good" because it calms inflammation in the intestine.
"Over the past decade, it has become obvious that bacteria in the human gut largely affect our health. The microbe we studied affects health by preventing the problematic compound from getting worse," said Joseph Krzycki, a professor of microbiology at Ohio State. – It is too early to say whether this bacterium may have therapeutic value. But that's what we're aiming for."
The chemical associated with arterial blockage that characterizes atherosclerosis is called trimethylamine, or TMA. It is formed during the metabolic process when some intestinal microbes – usually bacteria considered useless to humans – interact with certain nutrients from food. Among these nutrients is L–Carnitine, a chemical compound found in meat and fish, which is also used as a dietary supplement to improve recovery after exercise.
Krzycki and his colleagues found that E.limosum interacts with L-carnitine in the intestine in a different way, and this interaction excludes the role of L-carnitine in the production of TMA (other nutrients are also involved in the production of TMA in the intestine).
Researchers link the beneficial behavior of bacteria to a protein called MtcB, an enzyme that cuts off certain molecules from compounds to help bacteria generate energy and survive. The process is called demethylation and involves removing one methyl group– a carbon atom surrounded by three hydrogen atoms –to change the structure or function of the compound.
"The bacterium does this for its own benefit, but has the side effect of reducing the toxicity of TMA," Krzycki said. – To date, the only known microbial reactions in the gut with L-carnitine have involved turning it into a bad form. We found that a bacterium that is known to be beneficial can remove the methyl group and send the resulting product along a different pathway to avoid harmful compounds in the process."
In these interactions, L-carnitine functions as a substrate for growth – a compound consumed by the body for life and growth, as well as a target for enzymatic activity. During the study, the scientists fed E. limosum cultures with an assortment of potential substrates, including L-carnitine. It was only when L-carnitine was proposed that the microbe synthesized the MtcB protein specifically to cleave off the methyl group of L-carnitine – in fact, MtcB is part of the natural way bacteria consume nutrients.
Krzycki said the discovery of this significant health benefit in a single type of gut bacteria suggests that there is still much to learn about how gut bacteria can affect processes related to human metabolism.
"MtcB is part of a family of proteins with thousands of representatives that can use different compounds and alter the nutrients that bacteria consume in the gut," he said. "These proteins can behave very similar chemically, but using different compounds can obviously lead to big changes in biology."
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