Heart health: The role played by gut bacteria

• Certain bacteria in the gut, especially some species of strep normally found in the mouth and digestive tract, may affect heart health.
• In particular, researchers say, gut bacteria may be linked to a build-up of plaque that can lead to clogged arteries.
• Experts say the new findings build on previous research that indicates a link between gut bacteria and cardiovascular health.

Some heart problems may begin in the mouth and gut, a new study suggests.

Atherosclerotic plaques — commonly known as clogged arteries — are deposits of fat, cholesterol, and other substances that are a major cause of heart attacks.

A higher occurrence of these plaques is associated with the presence of certain oral bacteria in the gut — particularly Streptococcus bacteria — according to Swedish researchers.

The study, led by researchers at Uppsala and Lund University and published in the journal Circulation, was based on an analysis of gut bacteria and cardiac imaging of 8,973 people aged 50 to 65 who did not have any previously known heart disease.

“We found that oral bacteria, especially species from the Streptococcus genus, are associated with increased occurrence of atherosclerotic plaques in the small arteries of the heart when present in the gut flora,” said Dr. Tove Fall, a study author and a professor of molecular epidemiology in the department of medical sciences and the SciLifeLab at Uppsala University, in a press statement.

Details from the study on gut bacteria and heart health

Researchers used advanced imaging technology to detect early buildup of plaque in the heart’s blood vessels.

They combined the information with genetic sequencing data on a wide range of bacteria that inhabit the gut (including the mouth and throat).

In addition to the association between atherosclerotic plaque and Streptococcus anginosus, researchers also reported that Streptococcus oralis appeared to be related to plaque buildup.

Fatty deposits in the arteries were linked to levels of some species of Streptococcus in the mouth as well as in the gut, the researchers wrote.

“We have just started to understand how the human host and the bacterial community in the different compartments of the body affect each other,” said Dr. Marju Orho-Melander, a senior author of the study and a professor of genetic epidemiology at Lund University.

“Our study shows [altered] cardiovascular health in carriers of streptococci in their gut. We now need to investigate if these bacteria are important players in atherosclerosis development,” she said in a press statement.

How heart health is affected by gut bacteria

“Emerging evidence suggests that alterations in the composition and function of the gut microbiota, often referred to as dysbiosis, may contribute to various health conditions, including cardiovascular diseases,” said Dr. Kezia Joy, an advisor for United Kingdom-based online healthcare provider Welzo who was not involved in the study.

“Studies have shown that certain gut bacteria can produce metabolites, such as trimethylamine N-oxide (TMAO), which have been implicated in the development and progression of atherosclerosis,” Joy told Medical News Today. “TMAO has been associated with increased inflammation, oxidative stress, and the formation of atherosclerotic plaques. Furthermore, the gut microbiota can influence various physiological processes, including lipid metabolism, inflammation, and immune responses, which are key factors in the development of cardiovascular diseases.”

“The strength of this study is that it’s a large cohort [of participants], the researchers have done a very careful analysis of them at an early stage of cardiovascular disease, and the use of biomarkers” to identify specific gut bacteria that may play a role in plaque formation, said Dr. Bina Joe, chair of the physiology and pharmacology department at the University of Toledo in Ohio and founding director of the school’s Center for Hypertension and Precision Medicine who was also not involved the study.

The importance of gut bacteria research

Joe, who has led previous research into associations between gut bacteria and high blood pressure, said the Swedish study is an important step forward in a field of research where more is suspected than proven about the relationship between bacteria and cardiovascular disease.

For example, dentists now advise flossing as a way to limit the accumulation of oral bacteria that seem to increase the risk of heart disease.

“We don’t know why, but it works,” Joe told Medical News Today.

Questions for future research include drilling down further on which specific bacteria affect cardiovascular illness and conducting longitudinal studies that could establish a causal link rather than an an association between gut flora and heart health, Joe said.

For example, she said, while strains of Streptococcus bacteria exist in both the mouth and gut, it’s unlikely that a single strain is responsible for plaque buildup, since bacteria that live in an oxygenated environment can’t survive in an anaerobic environment like the gut, and vice-versa.

“It’s not clear which species of Streptococcus [the researchers] are talking about,” said Joe. “In the end, it may not be a particular bacteria, but a whole population involved.”

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