This gut bug may help lower LDL cholesterol like statins: Scientists find how

For years, the fight against cholesterol has taken place largely in the liver, where drugs quietly block an enzyme responsible for making LDL or bad cholesterol and help clear it from the bloodstream. Now, scientists have found an unexpected player in the human body that does the same job as the drug: a bacterium living in the human gut.

The bacterium, Bacteroides uniformis, appears to manufacture a small molecule that can interfere with the body’s cholesterol-making machinery. In mice, that molecule lowered cholesterol and helped shrink the fatty plaques that accumulate inside arteries.

The finding offers more than hope. Perhaps some of the microbes living inside us are not merely passengers — or even partners in digestion — but tiny chemical factories capable of making substances that protect us from disease. The discovery, published in Nature, is still far from becoming a treatment. The experiments that produced the most striking results were performed in mice, and researchers have not yet shown that the same process lowers cholesterol or reverses arterial plaque in people.

But the study raises a question that would have seemed almost fanciful not long ago: Could the next generation of cholesterol-lowering medicine come, at least in part, from the microbes already living inside our bodies?

A clue in the gut

The human intestine is home to trillions of microorganisms, which produce chemicals that can enter the bloodstream and influence metabolism, inflammation and other processes throughout the body. Researchers began by comparing the gut microbiomes of people with and without cardiovascular disease. One bacterium caught their attention: people with cardiovascular disease tended to have lower levels of B. uniformis.

That finding was only a clue. It could not prove that the bacterium protects against heart disease. People with cardiovascular disease also differ in diet, medication, lifestyle and many other factors that can alter the microbiome. So, the researchers moved to experiments in mice.

They used mice prone to developing atherosclerosis, the gradual buildup of fatty plaques inside arteries. When the mice were given live B. uniformis, they developed considerably less plaque than untreated animals. Their blood also contained lower levels of cholesterol and other fats, while inflammation inside their artery walls was reduced. The researchers then looked into what the bacterium was producing that might explain the effect. The answer appeared to be pentadecanoic acid, or C15:0.

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A molecule that resembles a drug

C15:0 is not a newly discovered substance. But the new research found how it functioned. It suppressed an enzyme that plays a central role in the liver’s production of cholesterol. This is the same major enzyme targeted by the cholesterol-lowering drugs we know as statins.

When the enzyme is inhibited, the liver increases the number of LDL or bad cholesterol receptors on its cells. These receptors pull LDL cholesterol out of the bloodstream, lowering the amount circulating in the blood.

In the mouse experiments, the effects went beyond cholesterol. Treatment with B. uniformis reduced arterial plaque by roughly one-third. Experiments with the isolated molecule produced an even larger reduction under the study conditions.

The findings suggest that a gut bacterium may be acting like a tiny biological factory, manufacturing a molecule that influences one of the body’s central cholesterol pathways.

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What about humans?

The researchers examined blood and stool samples from more than 200 human participants. People with abnormal blood lipid levels tended to have lower concentrations of C15:0, while people with cardiovascular disease had fewer bacterial genes associated with producing the molecule.

Can we increase the bacterium ourselves?

The discovery naturally raises another question: if B. uniformis may be beneficial, can we encourage more of it to grow in our gut? Human research has found that a fermentable dietary fibre found naturally in foods such as onions, garlic, leeks and chicory root, can increase B. uniformis in some people. Other research has found changes in the bacterium associated with β-glucan, a type of fibre found in foods such as oats and barley.

But researchers have not yet demonstrated the complete chain in humans: eating a particular fibre, increasing B. uniformis, increasing C15:0, lowering LDL and ultimately reducing arterial plaque. So, it would be premature to recommend a B. uniformis probiotic as a cholesterol treatment.

For now, the sensible approach remains the familiar one: eat a varied, fibre-rich diet containing vegetables, fruits, beans, whole grains, nuts and seeds. Such foods support a diverse gut microbiome, even though we do not yet know whether deliberately increasing B. uniformis will reduce cardiovascular risk.

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A glimpse of a different kind of medicine

Scientists are beginning to view the gut microbiome as something resembling a biochemical organ. The microbes living inside us consume components of our food and produce molecules that can influence our own biology. That raises the possibility of a new kind of medicine: rather than simply giving someone a drug, perhaps doctors could one day encourage particular microbes to manufacture therapeutic molecules inside the body. Some of the answers we are seeking may already be living inside us.