Do mouth bacteria play a role in the development of arthritis?

The study key points

  • People at risk of developing rheumatoid arthritis (RA) and people with early RA (ERA) had higher levels of two bacteria species, Prevotella and Veillonella, in their saliva, according to a new study from the Netherlands.
  • Both groups had higher levels of Veillonella in their tongue’s bacterial coating.
  • Prevotella and Veillonella are potentially pro-inflammatory bacteria, and their prevalence indicates that oral microbes and RA may be related.
  • People with ERA, those at risk of developing RA, and those who have been diagnosed with RA have higher rates of periodontal disease and changes in their oral and intestinal microbiota, according to previous studies.
  • If confirmed, these results could shed light on how RA evolves and enhance RA and ERA preclinical research.

RA, an autoimmune disease that causes joint pain, swelling, and ultimately injury, affects an estimated 1.5 million people in the United States alone.

Researchers are still looking for new ways to diagnose RA, especially when it is in its early stages. That’s because the sooner a RA patient gets a correct diagnosis and treatment, the greater their chances of having a positive result, such as reducing joint injury and functional loss.

Researchers are still unsure what causes RA to grow, but it appears to be a combination of genetic and environmental factors.

Researchers have been looking into the connection between ERA, people at risk of RA, and changes in their oral and intestinal microbiota, or population of microbes, in recent years.

It appears that people with ERA and those at risk of developing RA have abnormally high levels of certain bacteria in the mucus lining their mouths and intestines. They also seem to have a higher risk of periodontal disease, or gum disease, than most people.

Furthermore, some research suggests that RA may start in the mouth.

That’s why a group of researchers from Amsterdam’s Academic Centre for Dentistry (ACTA) set out to compare the microbial populations and periodontal health of people with ERA, those at risk of RA, and a control group of people without these conditions.

Their findings were published in the journal Arthritis and Rheumatology.

RA and the oral microbiome

Researchers have long suspected that microorganisms stimulate or induce autoimmune diseases like RA.

Researchers have known for a long time that periodontal disease, changes in the oral and intestinal microbiota, and RA are related.

Oral microbes, especially anaerobic bacteria that do not require oxygen, appear to play a role in the production of RA, according to several studies.

Three forms of anaerobic bacteria found in the oral cavity have been identified in the joint fluid of people with RA, according to a 2009 report. Antibodies to some forms of anaerobic bacteria linked to periodontal disease have been linked to the production of RA in many studies.

Some researchers believe that these bacteria induce a RA-related immune response by generating proteins that cause anti-citrullinated protein antibodies to develop (ACPAs).

Different types of cells, including bone cells, tend to be stimulated by these chemicals, which appear to encourage inflammatory responses. According to some research, the response that ACPAs promote may be involved in the mediation of bone damage in RA patients’ joints.

For these and other factors, the detection of ACPAs in serum, the fluid portion of blood, is now considered the most specific biomarker for RA.

The presence of ACPAs in the blood appears to help predict the onset of RA several years before an individual develops clinical RA or experiences symptoms and is diagnosed with RA.

That’s why many research groups, including the current study’s team, have been looking into how changes in the composition and other components of the oral microbiome could be linked to the onset of RA.

Changes in the oral microbiota and the possibility of RA

Researchers looked at the oral microbiota and periodontal health of three classes of 50 people in the new report.

People in the first group had ERA, while those in the second group were at risk of developing RA (people with serum ACPAs or arthralgia). People in the third category didn’t have RA and weren’t at risk, didn’t have any autoimmune diseases, and were otherwise safe.

A dentist examined each participant to determine their periodontal condition. Dentists tested whether probing bled their gums, the inflamed gum surface region, and how deep dental tools could probe into the gum line.

They also looked at how many teeth each person had, how many were missing, decayed, or filled, and whether or not they wore a removable denture. They also inquired about the last time each participant brushed their teeth and their daily oral hygiene practises.

In addition, the researchers took samples of each participant’s tongue coating or film, saliva, and subgingival dental plaque (plaque found below the gum line).

They collected, analysed, and quantified the microbial communities inside the samples after using devices to amplify the DNA present in the samples. They then contrasted the three groups’ microbial differences.

There were no differences in periodontal conditions between the groups, according to the researchers. Dental plaque samples showed no differences as well.

However, there were variations in the oral saliva and tongue coating of people with ERA and those at risk of developing RA as compared to the control group.

In saliva samples from people with ERA and others at risk of RA, levels of bacteria from the genera Prevotella and Veillonella were higher than in the control group. The levels of Veillonella bacteria were also higher in the RA groups’ tongue coatings than in the control group’s.

These results, according to the authors, indicate that there may be a connection between the oral microbe and RA.

This suggests that bacteria from these two genera, as well as others previously implicated in the onset of RA, can help cause immune responses that influence the progression of the disease.

According to the writers, these results are consistent with previous research that found that people with new-onset RA and developed RA had higher levels of oral Prevotella bacteria. The findings back up previous studies that found higher levels of Prevotella bacteria in the gut microbiota of people with RA or ERA.

According to the scientists, certain strains of Prevotella can induce chronic inflammation, which can lead to the release of immune cells in the body. They go on to say that microbial dysbiosis, or microbial imbalances, can be partly resolved with RA treatment in some cases.

A broader perspective

Dr. Vanessa L. Kronzer, author of a recent review on the aetiology of RA, spoke with Medical News Today. She wrote, “

“This is an intriguing study that, in my opinion, accomplishes two objectives. For starters, it lends credence to the mucosal origin hypothesis for RA. Second, it appears that dysbiosis may occur prior to disease onset, suggesting that it can play a role in the pathogenesis of RA.”

This research, according to Dr. Kronzer, is “an significant step in a long road toward understanding the aetiology of this important disease.”

Johanna Kroese of ACTA, the study’s corresponding author, was also contacted by MNT. She went on to say:

“Our findings suggest that oral bacteria can play a role in the onset of RA. Through focusing on these bacteria, the risk of developing RA can be reduced. Future studies should concentrate on developing strategies to target these bacteria and improve oral health, which could ultimately lead to the development of RA disease prevention measures.”

Some drawbacks

While the research had many positive aspects, it also had some significant flaws.

People in the ERA group received RA medication, while those at risk of RA and those in the control group did not. The researchers also did not collect information on certain factors that may affect dental plaque, such as diet.

Future research, the authors conclude, would need to collect many datasets over longer periods of time, preferably using large numbers of people and reliable collection techniques, to validate their results.

Nonetheless, these results may have revealed yet another stepping stone in the RA creation phase, which is complex and elusive. This may be good news for the millions of people who suffer from RA, as well as the doctors and nurses who strive to diagnose and treat them.

While more research is required, “improving oral health is important for the entire population, and it wouldn’t hurt to pay attention to oral health in persons at risk of developing RA,” Johanna Kroese told MNT.

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