How intestinal bacteria can be linked to lupus

Women with lupus had higher amounts of a specific bacteria in their gut, as well as higher levels of antibodies directed against this bacteria.

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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, called microbiomes, play an important role in your health.

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

But when intestinal communities are unbalanced, they can 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 called lupus or SLE, is linked to the proliferation of certain bacteria in the intestines.

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

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

In this study, the researchers found that 61 women diagnosed with lupus had more intestinal bacteria known as Ruminococcus gnavus, compared to 17 healthy women.

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

"The results showed that the intestinal microbiome profiles of lupus patients were different from those of healthy individuals, and that these changes were correlated with the activity of the disease," said Jessy Alexander, PhD, Research Professor in the Department of Medicine at the University of Buffalo. l & # 39; study.

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

Most people with lupus have times when their illness is usually calm, known as remission. Between the two, the symptoms may increase, or "flares".

The study revealed that R. Gnavus Levels increased in the intestine during flares. Blood tests have also shown an increase in antibodies – immune proteins – that bind to the bacteria during these periods.

Alexander said "the antibodies generated by the patient against this bacteria were directly proportional to the severity of the disease."

The authors of the paper stress that their results can not indicate whether the proliferation of R. Gnavus causes or triggers lupus, or if disease outbreaks allow the bacteria to grow in the gut.

Dr. Martin Kriegel, PhD, assistant professor of immunobiology and rheumatology at the Yale School of Medicine, who did not participate in the study, said it was probably a "two-way street".

Alexander said the study reinforces the idea "that intestinal bacteria affect lupus, and opens the door to the development of prognostic tests revealing the pathological status of the patient with lupus nephritis".

"However, there is still a lot of work to be done," she added.

Kriegel's laboratory strives to identify specific bacteria that contribute to lupus.

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

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

Kriegel said that "the mere number of bacteria in the intestine makes it likely that not just one bacterium plays a role in lupus".

They do not all have the same impact on the disease.

"Some bacteria have overlapping effects," said Kriegel, "but most of the time, we've found that different bacteria induce different aspects of the disease."

Lupus is a complex disease causing many diseases. Even the "bad" bacteria involved in triggering the disease may be "good" in some people.

"There are certainly genetic and other factors involved," said Kriegel, "because the bacteria we found – L. reuteri – is actually quite innocuous. It's even considered a probiotic. "

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

One approach would be to modify the intestinal microbiome.

This could be done by eliminating bad bacteria, as with an antibiotic. However, antibiotics – described by Kriegel as "an atomic bomb for the microbiome" – can also kill good bacteria.

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

Another option would be to increase the good bacteria, as with probiotics – live bacteria ingested in tablet form. Or with fecal transplants, in which intestinal bacteria are transferred from the intestines of a healthy donor to a person with lupus.

Dietary changes can also alter the microbiome.

In the 2019 study, Kriegel's laboratory administered starch resistant to lupus-prone mice, after which their disease symptoms subsided.

"The diet shift we've given to mice has shifted the microbiome, so that good bacteria grow and produce factors that suppress bad bacteria," said Kriegel.

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

But all these treatments have been tested on mice and have not yet been tested or proven to work in humans.

Given the complex nature of lupus, treatment is unlikely to be unique. This points to a more personalized approach to lupus medicine.

"There will be subgroups of patients with a given disease who will benefit from the modulation of the microbiome in one way," said Kriegel, "and another subgroup of patients. who will benefit from a modification of the microbiome ".

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