Women with lupus had higher amounts of a specific bacterium in their gut, along with increased levels of an antibody to that bacterium.

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Experts are learning how the gut microbiome affects people with lupus. Getty Images

Bacteria and other microorganisms living in your gut, known as the microbiome, play a big role in keeping you healthy.

They help you digest food, provide essential vitamins and other nutrients, and help control your immune system.

But when the intestinal communities are out of balance, they may contribute to health problems, including autoimmune diseases such as inflammatory bowel disease, type 1 diabetes, multiple sclerosis, and rheumatoid arthritis.

A new study in women now suggests that systemic lupus erythematosus, also known as lupus or SLE, is linked to the overgrowth of certain bacteria in the intestines.

Lupus is a chronic disease that results in inflammation in many parts of the body, including the kidneys, heart, and brain. This disease, which is more common in women, is potentially life-threatening.

Like other autoimmune diseases, lupus is caused by the immune system mistakenly attacking a person’s own tissues, rather than foreign germs.

In the study, researchers found that 61 women diagnosed with lupus had higher amounts of a gut bacterium known as Ruminococcus gnavus, compared to 17 healthy women.

The bacterium was also present in healthy women, but at much lower levels.

“The results showed that lupus patients have gut microbiome patterns different from healthy individuals, and these changes correlated with disease activity,” said Jessy Alexander, PhD, a research professor in the department of medicine at the University at Buffalo, who was not involved in the study.

The paper was published February 19 in the Annals of the Rheumatic Diseases.

Most people with lupus have times when their disease is mostly quiet, known as a remission. In between, symptoms can increase, or “flare.”

The study found that R. gnavus levels increased in the gut during flares. Blood tests also showed a rise in antibodies — immune proteins — that bind to the bacterium during these times.

Alexander said “the antibodies generated by the patient against this bacteria was directly proportional to the severity of the disease.”

The authors of the paper caution that their results can’t show whether the overgrowth of R. gnavus causes or triggers lupus, or if disease flares allow the bacterium to thrive in the gut.

Dr. Martin Kriegel, PhD, an assistant professor of immunobiology and rheumatology at Yale School of Medicine, who was not involved in the study, said it’s likely a “two-way street.”

Alexander said the study strengthens the idea “that gut bacteria affect the disease lupus, and opens the door to developing prognostic tests that reveal the disease status of the lupus nephritis patient.”

“However, a lot more work remains to be done,” she added.

Kriegel’s lab works on identifying specific bacteria that contribute to lupus.

In a study published last month in Cell Host & Microbe, Kriegel and his colleagues found that a certain gut bacterium worsened the disease in lupus-prone mice.

This bacterium, Lactobacillus reuteri, is not the same as the one identified in women with lupus by the authors of the recent study.

Kriegel said the “sheer number of bacteria in the gut makes it likely that not just one bacterium plays a role in lupus.”

Nor do they all have the same impact on the disease.

“There are some overlapping effects of certain bacteria,” said Kriegel, “but for the most part we found that different bacteria induce different aspects of the disease.”

Lupus is a complex disease with a lot driving it. Even the “bad” bacteria involved in triggering the disease can be “good” in some people.

“There are definitely genetic and other factors involved,” said Kriegel, “because the bacterium that we found — L. reuteri — is actually quite innocuous. It’s even promoted as a probiotic.”

Preliminary studies with animal models point to possible treatments for lupus and other autoimmune diseases.

One approach would be to alter the gut microbiome.

This could be done by eliminating bad bacteria, such as with an antibiotic. However, antibiotics — which Kriegel described as “an atomic bomb to the microbiome” — can also kill good bacteria.

In a study published last year in , Kriegel and his team developed a vaccine against a bacterium involved in lupus in mice. The vaccine primes the immune system to attack one specific bacterium while leaving other bacteria alone.

Another option would be to increase the good bacteria, such as with probiotics — live bacteria ingested in pill form. Or with fecal transplants, in which gut bacteria are transferred from the gut of a healthy donor to a person with lupus.

Dietary changes can also shift the microbiome.

In the 2019 study, Kriegel’s lab gave resistant starch to lupus-prone mice, after which their disease symptoms lessened.

“The diet change that we gave to the mice shifted the microbiome, so that good bacteria grew and produced factors that suppressed the bad bacteria,” said Kriegel.

Resistant starch is a carbohydrate found in foods like green bananas, whole-grain oats, lentils, and cooked and cooled rice. It is fermented in the large intestine, where it feeds good bacteria in the gut.

But all of these treatments were tested in mice and have yet to be tested or proven to work in people.

Given the complex nature of lupus, it’s unlikely that treatment will be one-size-fits-all. This points toward a more personalized medicine approach to lupus.

“There will be subgroups of patients with a certain disease that will benefit from modulating the microbiome in one way,” said Kriegel, “and another subset of patients that will benefit from altering it in another way.”