The gut microbiome contains a complex community of microorganisms that influence digestion, immune activity, and metabolism.

Scientists are increasingly investigating whether these microbes also affect cardiovascular health, particularly through their interactions with the liver and the body's cholesterol-regulating systems.

How the Gut Microbiome May Influence Heart Health

The gut microbiome consists of bacteria and other microorganisms living throughout the digestive tract. Their activities produce metabolites, which are substances created during biological and chemical processes. Some metabolites enter circulation and influence how other tissues function.

The liver plays a central role in cholesterol production, processing, and removal from the bloodstream. Certain gut-derived substances may affect these processes, creating a biological connection between intestinal microbes and cardiovascular health.

Researchers investigating Bacteroides uniformis observed that this bacterial species was less abundant in samples from people with cardiovascular disease than in samples from healthier comparison groups. This observation suggested a potential relationship, although differences in bacterial abundance alone cannot establish whether a microorganism protects against disease or whether illness changes the gut environment.

What the Experiments Revealed

In the animal experiments, researchers administered live Bacteroides uniformis to mice that were fed a diet designed to promote plaque development. Compared with untreated animals, the mice receiving the bacterium developed substantially less arterial plaque. Measurements also showed improvements in circulating cholesterol levels and reductions in inflammatory immune cells within artery walls.

The researchers then investigated which substances produced by the bacterium might explain the results. Their analysis identified pentadecanoic acid, an odd-chain fatty acid also known as C15:0, as a key active compound.

When the researchers supplied the molecule directly, the plaque burden in the experimental mice fell by approximately 50%. This result suggested that the metabolite itself contributed to the protective effect rather than the entire bacterial community being solely responsible.

How Pentadecanoic Acid Affects Cholesterol

The research identified a mechanism involving HMG-CoA reductase, an enzyme that helps the liver produce cholesterol. Pentadecanoic acid inhibited this enzyme, reducing cholesterol synthesis and encouraging the liver to increase the availability of low-density lipoprotein receptors.

These receptors help remove LDL cholesterol from circulation by bringing it into liver cells for processing. Greater receptor activity can therefore improve the clearance of LDL cholesterol, which contributes to plaque formation when present at elevated levels over time.

This mechanism resembles the action of statins, a widely used class of cholesterol-lowering medications that also target HMG-CoA reductase. However, sharing a biological target does not mean pentadecanoic acid has the same effectiveness, dosage characteristics, or safety profile as prescribed medication.

The researchers also examined numerous bacterial strains and found that production of the compound was not limited to a single species. This finding suggests that several members of the gut microbiome may contribute to the body's supply of the molecule.

Dr. Ben Chen, a cardiovascular researcher and Senior Research Fellow at the Victorian Heart Institute at Monash University, highlighted the importance of the findings for understanding connections between intestinal microorganisms and vascular health. Commenting on the research, Chen described the study as providing: “valuable evidence that the gut microbiome can influence vascular health”

What the Human Evidence Still Needs to Establish

The researchers examined blood and stool samples from more than 200 human donors. People with abnormal blood lipid profiles had lower pentadecanoic acid concentrations, while samples from people with cardiovascular disease showed fewer bacterial genes associated with producing the compound.

These findings support further investigation, but they do not demonstrate that increasing pentadecanoic acid will reduce cardiovascular events in humans. Observational differences may reflect diet, underlying illness, medication use, or other influences.

The findings deepen scientific understanding of how the gut microbiome may influence cardiovascular health. However, carefully designed human trials must establish the effectiveness, appropriate dosage, and safety of any potential treatment. Until stronger clinical evidence becomes available, prescribed therapies and established cardiovascular prevention strategies remain essential for managing cholesterol and reducing long-term risk.