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Could probiotics help treat irritable bowel disease? Andrew Brookes/Getty Images
  • A “leaky” gut wall can cause inflammation in people with inflammatory bowel disease.
  • In a study involving human cell cultures and mice, scientists found that a particular strain of the bacterium Lactobacillus acidophilus may restore the integrity of the gut wall and reduce inflammation.
  • The researchers speculate that probiotics containing this strain of L. acidophilus could help treat inflammatory bowel disease and other conditions that involve gut inflammation.

In inflammatory bowel disease (IBD), inflammation of the digestive tract can cause abdominal pain, diarrhea, fatigue, and weight loss, among other symptoms.

Crohn’s disease and ulcerative colitis are the two main types of IBD.

The Centers for Disease Control and Prevention (CDC) estimates that around 3 million adults in the United States have IBD.

One of the characteristics of the disease is increased permeability of the walls of the intestine — sometimes known as a leaky gut — which can provoke inflammation of the gut lining.

Protein complexes called “tight junctions” (TJs) act similarly to rivets to bind together adjacent cells in the gut’s lining to prevent microorganisms and other contents from seeping out.

The intestine’s TJ barrier is defective in IBD and other inflammatory conditions of the gut, including celiac disease and necrotizing enterocolitis.

Currently, there are no effective treatments to “tighten” the TJ barrier and reduce the permeability of the gut.

However, several studies have found that “friendly” bacteria in the gut help strengthen the intestinal barrier.

Scientists know that people with IBD have an imbalance in their gut bacteria, with reduced overall diversity of species and larger numbers of bacteria that provoke inflammation.

Researchers have tried to identify particular species of probiotic bacteria that enhance the TJ barrier and that could make effective treatments for IBD, but with inconclusive results.

However, in a new study, scientists have discovered a strain of Lactobacillus acidophilus that strengthens the TJ barrier in human cell cultures.

The strain, known as LA1, also reduced colitis, or inflammation of the inner lining of the colon, in a mouse model of IBD.

“Our data indicate that LA1 is able to prevent colonic inflammation formation and promote colitis healing,” says lead investigator Dr. Thomas Ma, Ph.D., of Penn State College of Medicine, Hershey Medical Center, in Hershey.

He says the findings suggest that the strain could have applications in a wide range of disorders involving chronic inflammation associated with a leaky gut, in addition to IBD.

These conditions include celiac disease, an autoimmune reaction to gluten in food, and necrotizing enterocolitis, where bacteria invade the intestine wall of premature infants.

The results of the study appear in The American Journal of Pathology.

The researchers screened more than 20 different probiotic species for their ability to tighten the TJ barrier.

They tested the bacteria in cultures of a human cell line called Caco-2, which scientists often use to model the intestinal epithelium.

Only LA1 caused a rapid, strong tightening of the TJ barrier.

The bacteria appeared to achieve this by activating a protein in the membrane of the cells, called a Toll-like receptor.

Toll-like receptors, part of the body’s immune defenses, recognize patterns on the surface of microbes.

Similar to ringing an intruder alarm, when the bacterium bound to the receptors, it triggered a train of events inside the cells that tightened the TJ barrier.

To test whether LA1 would have the same effect in a live animal, the researchers administered it orally to mice.

LA1 rapidly enhanced the TJ barrier in the animals, which then protected them against chemically induced colitis.

The bacterium also promoted healing of the intestinal barrier in mice with colitis.

In mice, the same Toll-like receptors mediated these enhancements of the TJ barrier.

Food manufacturers include L. acidophilus in a range of commercial brands of probiotic yogurt.

Medical News Today asked Dr. Ma whether any of these products contain the specific bacterial strain, LA1, that appears to protect the gut lining from inflammation.

“Unfortunately, most probiotic companies do not list the specific strains contained in their probiotic product,” Dr. Ma explained.

“The Lactobacillus acidophilus strain that we referred to as LA1 is available in some of the commercial products, but it is not clear which do and do not,” he said.

He added that the amount of probiotic bacteria in a product is also crucial to their biological effect, with quantities in excess of 1 billion colony-forming units per dose working best.

Dr. Ma went on to say that L. acidophilus is a component of healthy adults’ gut flora, but not necessarily LA1.

Because the bacterium undergoes constant genetic change, every individual will have different and often unique strains of the bacterium.

A person’s diet helps determine the makeup of their gut microbiota, as recent research reported by MNT discovered.

The principal limitation of the current lab-based study was that its findings might not apply to people with inflammatory bowel conditions.

However, Dr. Ma and his colleagues hope to extend their investigation to include human volunteers, with possible clinical trials on the horizon.

“The future direction of research in our laboratory is to test this in humans to see if [the bacteria] tighten the intestinal barrier and prevent or treat diseases associated with a leaky gut,” said Dr. Ma.