Bacteria that exist in our gut may affect how people respond to statins; medications used to control blood cholesterol levels. To date, doctors have not been able to properly explain why some patients on cholesterol-lowering medications respond well, while others don’t. Researchers have reported in the journal PLoS One that several bacterial-derived bile acids may be influencing how humans respond to statin treatment.

Statins, also known as HMG-CoA reductase inhibitors, are medications commonly prescribed to lower blood cholesterol levels. The drug blocks the action of an enzyme in the liver – HMG-CoA reductase – that is necessary for making cholesterol. Cholesterol is vital for normal cell and body function. However, excessive levels, specifically of LDL (low density lipoprotein, or “bad” cholesterol), can eventually lead to atherosclerosis, when cholesterol-containing plaques accumulate in the arteries and block the flow of blood. When statins reduce blood cholesterol levels, the patient has a lower risk of developing angina (chest pain), stroke or heart attack.

In this new study, researchers say how people respond may depend on their type of gut bacteria. These bacteria live in the human intestine and help break down food. They add that the impact of gut bacteria goes beyond digestion – they help our immune system, produce vitamins, influence our body weight, and also how we metabolize medications.

Study co-author, Rima Kaddurah-Daouk, from Duke University and team carried out a study with 100 individuals. They found that those whose LDL levels went down the most after taking Zocor (simvastatin), a statin medication, had higher levels of bacterial-derived bile acids from three specific gut bacteria – lithocholic acid (LCA), taurolithocholic acid (TLCA), and glycolithocholic acid (GLCA) – compared to those whose LDL levels did not drop as much.

Those that did not respond so well to Zocor had higher levels of five other bacterial-derived bile acids.

The authors suggest that the five bacterial-derived bile acids produced in the individuals who did not respond well to statins actually compete with the statin in binding to certain cells – they mimic the medication – they make it harder for the statin molecules to get to the liver cells where they would inhibit the production of HMG-CoA reductase.

Rima Kaddurah-Daouk said:

“We found that the benefit of statins could be partly related to the type of bacteria that lives in our guts. The reason we respond differently is not only our genetic makeup, but also our gut microbiome.”

The researchers say their findings may pave the way for tests which could determine which patients are likely to respond well to statins, and which won’t. A blood test could identify the bile acids which are likely to compete with certain statins. Patients with those compounds in their blood could be directed to other medications or different statins.

Consuming probiotics might also alter the intestinal flora so that the balance of bacteria in the gut is tilted towards bacteria that do not produce chemicals that neutralize the effects of statins.

The intestinal flora, also known as gut flora consists of microorganisms that exist in the digestive tract – it is the largest reservoir of human flora. Most of the intestinal flora is made up of bacteria. Between 300 and 1,000 different species live in the gut. Experts say about 99% of the bacteria in the gut probably come from just thirty or forty species.

Kaddurah-Daouk said:

“We’re at a very early stage of understanding this relationship, but [there’s] no doubt that metabolites from bacteria are playing an important role in regulating our systems.”

Written by Christian Nordqvist