Gut Bacteria Linked to the Buildup of Fatty Deposits in the Heart

Researchers in Sweden have uncovered a link between the levels of oral bacteria residing in the gut and the buildup of fatty cholesterol deposits in the heart’s blood vessels – a major cause of heart attacks. The study is published in Circulation.

Informing cardiovascular disease – the leading cause of death globally

Cardiovascular diseases are a major cause of death and disability worldwide and are responsible for approximately 17.9 million deaths per year.

The risk of developing cardiovascular disease is greatly increased by atherosclerosis – the buildup of fatty, cholesterol-rich deposits (plaques) in blood vessels – which can lead to clots and heart attacks.

The gut microbiome – the community of bacteria, viruses and fungi that reside in the gut – can influence the body’s health and metabolism. We also have an oral microbiome, which recent research has shown is connected to the gut microbiome through microbes that are transmitted from the mouth to the gut.

In previous studies, gut bacteria have been associated with symptomatic disease related to atherosclerosis – but it is unclear whether there are any links between non-symptomatic atherosclerosis and the gut microbiome.

To address this, researchers from Uppsala University and Lund University in Sweden analyzed the heart imaging and gut microbiome data of participants in the Swedish cardiopulmonary bioimage study (SCAPIS).

Links between gut bacteria and atherosclerosis

Technological advances have enabled bacterial communities from biological samples to be characterized in detail and at large scales through DNA sequencing, while advances in imaging techniques have enabled the detection and measurement of early atherosclerotic changes in the heart’s blood vessels.

Researchers used heart imaging and sequencing data from the stool samples of almost 9,000 participants in the SCAPIS study, one of the largest databases of its kind in the world. Participants were aged 50–65 years and had no 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. Species from the Streptococcus genus are common causes of pneumonia and infections of the throat, skin and heart valves. We now need to understand whether these bacteria are contributing to atherosclerosis development,” said Professor Tove Fall, co-senior author of the study and professor in molecular epidemiology at Uppsala University.

Some bacterial species linked to the buildup of fatty deposits in heart blood vessels were also linked to levels of the same species in the mouth, which Fall and colleagues measured using stool and saliva samples collected from the Malmö Offspring Study. These bacteria were associated with markers of inflammation in the blood, even after differences in diet and medication between the participants were accounted for.

“The large number of samples with high-quality data from cardiac imaging and gut flora allowed us to identify novel associations. Among our most significant findings, Streptococcus anginosus and S. oralis subsp. oralis were the two strongest ones,” said Dr. Sergi Sayols-Baixeras, lead author and postdoctoral researcher at Uppsala University.

“We have just started to understand how the human host and the bacterial community in the different compartments of the body affect each other. Our study shows worse cardiovascular health in carriers of streptococci in their gut. We now need to investigate if these bacteria are important players in atherosclerosis development,” said Professor Marju Orho-Melander, professor of genetic epidemiology at Lund University and co-senior author of the study.

Reference: Sayols-Baixeras S, Dekkers KF, Baldanzi G, et al. Streptococcus species abundance in the gut is linked to subclinical coronary atherosclerosis in 8,973 participants from the SCAPIS cohort. Circulation. 2023. doi: 10.1161/CIRCULATIONAHA.123.063914

This article is a rework of a press release issued by Uppsala University. Material has been edited for length and content.