International Business Department           Liu Bojia           April 3, 2023

  There are countless gut bacteria living in our intestines, and different groups of bacteria interact and compete with each other. Different dietary habits and medication use also contribute to the growth of certain types of bacteria, resulting in individuals having unique gut flora characteristics, which also contribute to differences in the risk of developing many diseases among individuals.

  According to previous studies, changes in gut flora have been associated with the development of a number of diseases, including obesity, diabetes, and NAFLD. In addition, cohort studies have shown that patients with atherosclerosis and acute coronary syndromes have changes in the diversity and population composition of gut bacteria, suggesting that these microbes far away from the gut can also affect our heart health.

  In new research published today in Cell, scientists from the Boulder Institute and Massachusetts General Hospital have jointly found that gut bacteria can indeed influence the risk of cardiovascular disease and have identified a class of cholesterol-metabolising bacteria that prefer to metabolise cholesterol, which may help individuals to reduce the accumulation of cholesterol and reduce the burden on the cardiovascular system.

  For the study, the authors analysed data from more than 1,400 volunteers in a decades-long project, the Framingham Heart Study, which focused on numerous risk factors that may influence cardiovascular disease, including blood metabolites and faecal microbes.

  The new study re-examined the comprehensive genomic analysis of faecal samples from the project, from which they revealed more than 16,000 associations between microbes and metabolic markers, with one group of gut bacteria called Oscillibacter catching their attention because the more of these bacteria were present in the faecal samples, the lower the cholesterol levels of the volunteers were. In addition, Oscillibacter levels were significantly linked to cholesterol and derivatives in the faeces.

  According to the data analysed from the samples, the abundance of Oscillibacter bacteria was also very high, with typically 1 Oscillibacter bacteria present in every 100 bacteria. This also suggests to the authors that they have a pivotal role in the absorption and breakdown of cholesterol in the gut.

  In laboratory experiments with cultured Oscillibacter bacteria, the researchers found that after absorbing cholesterol, they metabolise it into a variety of intermediary metabolites, including cholesterol in the form of cholesterol enolone and hydroxycholesterol, which are then continued to be broken down by other species of microbes, and ultimately excreted out of the body in the faeces.

  Back in 2020, the team also discovered another type of bacteria that can lower cholesterol levels, Eubacterium coprostanoligenes, which encodes an enzyme that also converts cholesterol into cholesterol-enriched ketones. The authors believe that this type of bacteria and the newly discoveredOscillibacterbacteria are likely to play a synergistic role and work together to help metabolise cholesterol in the body.

  Nowadays, cardiovascular disease has become a major cause of human death, and high cholesterol will elevate the risk of atherosclerosis and ischaemic cardiovascular disease. Therefore, scientifically lowering cholesterol is one of the most important strategies to combat cardiovascular diseases. The researchers point out that the findings of the new study suggest that intestinal bacteria have an important role in the cholesterol metabolism pathway, and pinpointing such bacteria and increasing their levels by means of faecal transplants may be a new cholesterol-lowering strategy to reduce people's risk of cardiovascular disease.