You share your body with trillions of microbes – many of them beneficial bacteria living in your intestinal tract. Collectively called the microbiome, these bugs influence health and disease through complex interactions with your immune system. Often, their role is protective, guarding against pathogens and inflammation. But increasingly strong evidence suggests that disruptions in the microbial ecosystem may cause or contribute to many chronic diseases, including rheumatoid arthritis (RA).
Jose Scher, MD, a rheumatologist at New York University Langone Medical Center, studies the connection between intestinal bugs and arthritis. He thinks the overgrowth of normally benign bacteria called Prevotella – which are far more abundant in people with untreated RA – may trigger an inflammatory response that targets the joints. It’s also possible Prevotella crowds out beneficial bacteria that keep inflammation in check. Either way, Scher is confident there’s a connection between the microbiome and arthritis.
Whether gut bacteria actually cause arthritis remains a matter of debate. But it’s clear they affect the way certain arthritis drugs work in the body. Microbes can activate some medicines – making them more toxic – and inactivate others, so they’re less effective. Peter Turnbaugh, a microbiologist and microbiome researcher at the University of California, San Francisco, says although the idea that the microbiome influences drug metabolism has been around for decades, scientists are just now starting to understand specific interactions.
For instance, gut microbes that produce a compound called p-cresol increase the toxicity of the pain killer acetaminophen. And a bacteria-produced enzyme seems to be responsible for gastrointestinal bleeding and ulcers in people taking nonsteroidal anti-inflammatory drugs (NSAIDs). A 2012 mouse study published in The Journal of Pharmacology and Experimental Therapeutics found that inhibiting the enzyme – glucuronidase – reduced intestinal damage from a number of different NSAIDs.
Can Your Gut Heal Your Joints?
One of the hottest questions right now is whether it will be possible to treat arthritis and other diseases by adjusting the microbiome. A growing number of scientists think so.
Writing in a review article published in the March 2016 issue of Current Opinion in Rheumatology, researchers from the University of Glasgow in the UK noted that “interventions targeting the microbiota may become therapeutically viable for some types of inflammatory arthritis.”
That idea is echoed by Martin Blaser, MD, a microbiologist at New York University Langone Medical Center and a widely respected microbiome expert.
“This is a fertile area for research because we know that particular microbes talk to human physiology in different ways with different vocabularies. As our understanding of this relationship grows, we may use it to regulate disease,” he says.
Although there are few human studies, animal models have demonstrated some intriguing findings. A 2013 study published in the Journal of Interferon & Cytokine Research looked at the effect of two common bacterial strains on arthritis in rats. Results showed that bacteria commonly found in yogurt, Lactobacillus casei and Lactobacillus acidophilus, reduced joint inflammation more effectively than the NSAID indomethacin.
Still, the most enthusiastic researchers say you probably won’t be taking probiotics (supplements containing beneficial bacteria) to treat arthritis anytime soon. One major stumbling block is that researchers aren’t sure what a healthy microbiome looks like. Which bacteria will ease aching joints? No one really knows. But Dr. Blaser foresees a time when probiotics “that have been verified and clinically tested in rigorous clinical trials” may be an effective arthritis treatment.
Dr. Scher thinks the best way to modify the microbiome is through diet. He points to studies showing that people with RA have benefitted from adopting a Mediterranean diet high in fish, olive oil and vegetables. Other studies have found that a vegan diet profoundly changes the gut microbiome and improves arthritis symptoms.
Both Dr. Scher and Dr. Blaser are optimistic about the future of microbiome research. “These are very early days,” Dr. Blaser says, “but the field is moving ahead. This is the scientific frontier.”
Author: Linda Rath for the Arthritis Foundation