Gut bacteria may play role in onset of rheumatoid arthritis

A new study has suggested that bacterial disturbances in the gut may play a role in autoimmune attacks on the joints.

Researchers have linked a species of intestinal bacteria known as Prevotella copri to the onset of rheumatoid arthritis, the first demonstration in humans that the chronic inflammatory joint disease may be mediated in part by specific intestinal bacteria.

The new findings by laboratory scientists and clinical researchers in rheumatology at NYU School of Medicine add to the growing evidence that the trillions of microbes in our body play an important role in regulating our health.

Using sophisticated DNA analysis to compare gut bacteria from fecal samples of patients with rheumatoid arthritis and healthy individuals, the researchers found that P. copri was more abundant in patients newly diagnosed with rheumatoid arthritis than in healthy individuals or patients with chronic, treated rheumatoid arthritis.

Moreover, the overgrowth of P. copri was associated with fewer beneficial gut bacteria belonging to the genera Bacteroides.

Randy S. Longman, MD, PhD, a post-doctoral fellow in Dr. Littman's laboratory and a gastroenterologist at Weill-Cornell, and an author on the new study, said that expansion of P. copri in the intestinal microbiota exacerbates colonic inflammation in mouse models and may offer insight into the systemic autoimmune response seen in rheumatoid arthritis.

The researchers said that why P. copri growth seems to take off in newly diagnosed patients with rheumatoid arthritis is also unclear.

To determine if particular bacterial species correlate with rheumatoid arthritis, the researchers sequenced the so-called 16S gene on 44 fecal DNA samples from newly diagnosed patients with rheumatoid arthritis prior to immune-suppressive treatment; 26 samples from patients with chronic, treated rheumatoid arthritis; 16 samples from patients with psoriatic arthritis (characterized by red, flaky skin in conjunction with joint inflammation); and 28 samples from healthy individuals.

Seventy-five percent of stool samples from patients newly diagnosed with rheumatoid arthritis carried P. copri compared to 21.4 percent of samples from healthy individuals; 11.5 percent from chronic, treated patients; and 37.5 percent from patients with psoriatic arthritis.

The study has been published in the open-access journal eLife.