Intestinal bacteria, that is. Rheumatoid arthritis has long been a medical mystery – an autoimmune disease that’s triggered by who-knows-what, but that suddenly starts attacking the joints and causing chronic pain and fatigue. Well, Laboratory Equipment says some NYU researchers might just have found the culprit lurking in patients’ digestive tracts:
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.
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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.
“Studies in rodent models have clearly shown that the intestinal microbiota contribute significantly to the causation of systemic autoimmune diseases,” says Dan Littman, the Helen L. and Martin S. Kimmel Professor of Pathology and Microbiology and a Howard Hughes Medical Institute investigator.
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“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,” says Randy Longman, a post-doctoral fellow in Littman’s laboratory and a gastroenterologist at Weill-Cornell, and an author on the new study. Exactly how this expansion relates to disease remains unclear even in animal models, he says.
Why P. copri growth seems to take off in newly diagnosed patients with rheumatoid arthritis is also unclear, the researchers say. Both environmental influences, such as diet and genetic factors can shift bacterial populations within the gut, which may set off a systemic autoimmune attack. Adding to the mystery, P. copri extracted from stool samples of newly diagnosed patients appears genetically distinct from P. copri found in healthy individuals, the researchers found.
The germ might not *cause* the chronic disease… but it seems to be involved *somehow*.