For years, scientists have wondered if there was a connection between the type of bacteria in our bodies, particularly our guts, and the development of RA. Could tiny micro-organisms predict who is most susceptible to developing RA and who might be more resistant to the disease? A recent study shows some strong connections between the type of bacteria in our guts and certain genes that may predict RA development

A team of researchers from the Mayo Clinic in Rochester, Minn., and the University of Illinois at Urbana published a study in the peer-reviewed journal Public Library of Science One in April 2012 showing that the types of bacteria lurking in the guts of mice may predict which animals are more susceptible to developing RA and collagen-induced arthritis (CIA), and which mice may be more resistant to the disease. In addition, another set of scientists at the University of Illinois at Urbana have completed a study of humans to examine how consuming different types and amounts of dietary fiber could change their gut bacteria, shifting the mix toward more bacteria with potentially anti-inflammatory properties. Their study was to be published in the Journal of Nutrition in the summer of 2012.

For years, Veena Tareja, PhD, worked with RA patients at the Mayo Clinic and listened to their observations about the connection between diet and inflammation. “They would say, ‘I eat this and my arthritis gets worse.’ I always had the feeling that the gut had something to do with arthritis, because it takes most of the body’s abuse,” says Tareja, the institution’s lead researcher on the new study.

Genes and Bugs

Tareja and her colleagues knew that there were already strong correlations between mice that carry genes with particular genetic variations called alleles and the susceptibility to develop – or resist developing – RA. Mice with the gene HLA-DRB1*0401 are more susceptible to developing RA and CIA, while mice with the gene HLA-DRB1*0402 are more resistant. In addition, they knew the 0401 allele’s presence in people with arthritis was also strongly correlated to gender; three females to one male carrying that gene develop arthritis.

They suspected that the different genes must trigger different reactions in the guts of the mice that tipped the susceptibility scale one way or the other. Several recent studies, including a paper published in Arthritis & Rheumatism in 2010 by rheumatologist Jose Scher, MD, and his colleagues at the Arthritis Clinic of New York University Hospital for Joint Diseases, also established a connection between the presence of certain bacteria in the body, namely inflamed gums, and RA. 

Dr. Scher urges that finding particular bacteria in the gums of people with RA does not necessarily mean those bugs trigger RA, but is merely one step on the road to understanding possible connections. “This remains an association and causality will be difficult to prove,” he says.

Taneja and her colleagues felt that there might be some connection to the gut bacteria found in mice with the particular HLA genes. “We thought, ‘There’s got to be something this gene is doing. Our genes affect what these bugs are doing. The genes and the bugs are related somehow,’” she says. 

She also says that the gut microbiome, or the type of bacteria that are in a person’s digestive system, are affected by various factors, including diet, and more likely, our genes. “We all walk around with millions of bugs inside us, but the balance of bugs makes the difference, along with genes. Until now, nobody took it seriously, but now with new technology, we can see these bugs.” 

Scientists once had to examine bacteria in a Petri dish, says Dr. Scher, but now, they can sequence the bacteria’s DNA and analyze the bugs more accurately.