Psoriatic arthritis (PsA) is a type of chronic inflammatory arthritis (joint disease) that is associated with psoriasis. In past decades, researchers have identified several risk factors for PsA, such as genetic and lifestyle factors, and more recently, changes within the microbiome. Certain bacteria in the gut may be linked to the autoimmune response that leads to joint inflammation.
The gut microbiome, or gut flora, includes the microorganisms (bacteria, fungi, and viruses) that we harbor in our intestines. The intestines alone house more than 100 trillion microorganisms, some of which may be “good” or “bad” — helpful or harmful to your health. Microorganisms can also exist on the skin and other surfaces throughout the body.
The healthy gut microbiome has several functions:
The gut microbiome begins its evolution starting at birth. Researchers have found that the mode of delivery of a newborn (vaginally or cesarean section) and whether the newborn was breastfed largely plays a role in their overall gut health. Other factors that affect gut health include:
When there is an imbalance of microorganisms (good vs. bad bacteria) within the gut, this state is called gut dysbiosis. Gut dysbiosis is associated with different autoimmune diseases, including PsA.
This imbalance of gut microbiota leads to dysregulation and dysfunction of the microorganisms. It’s believed that disruption of the gut’s functions may ultimately lead to the development of PsA and other autoimmune diseases. A study published in 2014 found that people with psoriatic arthritis had significantly lower levels of gut bacteria and a less diverse gut microbiome than people without PsA. Also, researchers found the microbiomes of people with PsA were almost identical to the microbiomes of those with inflammatory bowel disease (IBD), which may explain why people with PsA are 6.5 times more likely to develop Crohn’s disease, a type of IBD.
Why does gut dysbiosis happen? In animal models of arthritis, mice that were exposed to specific gut bacterial species were at a higher risk of developing PsA compared to mice that were raised in a “germ-free” environment. This finding shows that exposure to specific microbes may be enough to induce joint inflammation.
Overusing antibiotics or having a poor diet can also cause gut dysbiosis. Researchers have also found that certain medications — such as immunosuppressive medications, biologics, and nonsteroidal anti-inflammatory drugs (NSAIDs) — can destroy gut bacteria, change the gut microbiome diversity, and lead to gut barrier dysfunction, more commonly called “leaky gut syndrome.”
Inside the intestines, a layer of cells (the epithelial barrier) builds the mucosal barrier that helps the intestines absorb nutrients and block large molecules and other microorganisms from entering. If the epithelial barrier becomes more permeable, bacteria, toxins, and other substances can enter the bloodstream. The term “leaky gut syndrome” refers to a condition known as increased intestinal permeability.
This change in permeability can lead to inflammation and affect the digestive tract’s naturally occurring bacteria. Permeability can have significant impacts on the gastrointestinal (GI) tract and the body as a whole. Although leaky gut syndrome is not recognized as its own disease, changes in intestinal permeability have been linked to several chronic diseases, including type 1 diabetes, celiac disease, and IBD. Some studies have suggested that the condition may also play a role in psoriasis and PsA.
In some people, PsA is genetically predisposed (more likely) — particularly in those with a family member who has PsA. Researchers believe that in people with a higher risk of PsA, having a leaky gut may allow substances that can trigger or worsen PsA to enter the bloodstream. This idea also supports the theory that PsA does not begin at the joint but rather in the gut.
However, some scientists believe that environmental factors are responsible for triggering the development of PsA. Research has found that disease-causing bacteria can lead to a leaky gut and trigger the symptoms of autoimmune diseases. In addition, similar to gut dysbiosis, certain medications may play a role in mucosal barrier damage. Some studies have found that people with long-term use of NSAIDs had an increased risk of leaky gut syndrome, increasing their risk of moving bacteria and yeasts into the bloodstream and toward the joints.
For these reasons, some GI researchers have suggested that the traditional understanding that environmental and genetic factors alone lead to autoimmune disorders is incomplete. Instead, some experts believe that genetics, immune system dysfunction, and environmental triggers — combined with a weaker intestinal barrier and disruption of the gut microbiome — may play a role in the development of some autoimmune disorders. Overall, the exact cause-and-effect relationship between the microbiome and PsA needs to be further explored.
Diet and lifestyle approaches may help you optimize your gut health.
An animal study found that mice that were fed a diet high in fat and sugar (as the Western diet is) became more susceptible to skin and joint inflammation. However, when the mice were fed a diet low in fat and sugar, their susceptibility decreased and reversed the proinflammatory effects of the high-fat, high-sugar diet.
Other studies have also found that changing your diet can alter your gut microbiome and possibly change the course of PsA or slow down its development. Adopting a low-fat, low-sugar, or plant-based diet may be beneficial for some people with PsA. A plant-based diet that is high in fiber includes foods such as whole grains, brown rice, fruits, vegetables, legumes, beans, nuts, and seeds. If you are considering changing your diet, speak with your doctor first to discuss the best options for you.
Learn more about anti-inflammatory diets for psoriasis and PsA.
Some lifestyle changes have been found to increase the diversity of the microbiome. Adopting healthy lifestyle habits such as daily exercise, good sleep habits, stress management, and avoiding smoking can be beneficial for your gut health.
MyPsoriasisTeam is the social network for people with psoriatic disease. Here, more than 100,000 members from around the world come together to ask questions, offer support and advice, and meet others who understand life with psoriatic arthritis and psoriasis.
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