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January 30, 2017

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An enzyme in saliva, which is also found in a popular Japanese dish, could treat celiac disease

Blue test tubes

By Amy Ratner, Beyond Celiac Medical and Science News Analyst

Fortunately for the Boston University researchers working on a new treatment for celiac disease, volunteers at the nearby Museum of Science did give a spit.

Visitors spit more than 800 samples of saliva into 5 milliliter tubes as part of a Living Laboratory program that brings scientists to the museum to share their work with the public. The volunteers gave researchers at the Henry M. Golden School of Dental Medicine enough bacteria from the saliva to isolate a new class of enzymes that has the potential to break down gluten.

Bacteria in our mouths

In a study published in the American Journal of Physiology-Gastrointestinal and Liver Physiology, scientists wrote they found “that exceptionally high gluten-degrading enzyme activities are naturally associated with bacteria” in the mouth. This led them to theorize that the enzyme from the saliva could be used as a treatment for celiac disease because it could break up the harmful parts of the protein that trigger intestinal damage.

The enzyme, though still in the early stages of study, could potentially be used in a supplement, as an ingredient in foods including yogurt or as an additive used during the processing of gluten-free foods where there is a risk of cross-contact. “We are looking at various ways of applying it,” said Eva Helmerhorst, Ph.D., senior study author and an associate professor in the dental school’s department of molecular and cell biology.

While the Rothia bacteria found in saliva contains only small amounts of the gluten-degrading enzyme, researchers noted that it belongs to the same class as a food-grade enzyme, B. subtilis, found in natto, a Japanese fermented soy bean dish.

“The enzyme from saliva is not yet available in large quantities, while natto is,” Helmerhorst said.

“The major point is now we have an enzyme that is effective, but different from the known enzymes that can degrade gluten,” said Detlef Schuppan, M.D., Ph.D., a study author and director of the Institute of Translational Immunology at the University Medical Center of the Johannes Gutenberg University in Mainz, Germany. “This study shows that enzymes of the subtilis class, interestingly enzymes that are already used in the food industry, have the ability to degrade the toxic gluten peptides.”

Though a lot of celiac disease research focuses on what occurs in the stomach and small intestine, the mouth is considered part of the digestive system so it’s not as unusual as it might seem that a dental school would be studying celiac disease, said Dr. Schuppan, also a professor of medicine and senior visiting scientist at the Beth Israel Deaconess Medical Center and Harvard Medical School.

“It’s not farfetched that you would look at enzymes produced by all the bacteria (in the digestive system), not just the bacteria in the small intestine,” he said, noting that to be used as treatment for celiac disease the enzyme would have to have a much higher concentration than it has in saliva. But because it lives naturally in the mouth, it’s likely to be safe if used in, for example, a supplement.

Additionally, the related B. subtilis is considered food safe and has been consumed for decades, something that might speed a path to Food and Drug Administration approval, Helmerhorst said.

Next step

Next, researchers will investigate how the enzyme works in the body instead of the culture dishes and test tubes where it’s been studied so far. They’ll examine how the enzymes behave as they move from the mouth through the small intestine, Helmerhorst explained. Initially, the studies will be done using mouse models and then move to human clinical trials if successful.

Future studies might also look at how the enzyme works when combined with others that also break down the harmful portions of the gluten protein.

“If you get two or three enzymes that are highly active you would get rigorous removal of gluten or degradation of gluten,” Dr. Schuppan said. But he noted that enzymes have to be extremely effective and quick and their speed of action and efficacy will determine how well they ultimately work as a treatment for celiac disease. “This is a hard job to do when gluten is in most foods, and it’s a hard job to do when you ingest foods that also contain many other constituents,” he said.

Researchers looking for new treatments for celiac disease are pursuing several approaches to prevent or reverse the damage caused by gluten. In addition to trying to detoxify or breakdown gluten in the gut using enzymes, these include altering the gluten in foods, binding the gluten in the gut so it is not absorbed, interrupting the immediate or delayed effects of gluten on the cells lining the intestine or interrupting the immune reactions that occur.

Meanwhile, the collection of saliva for the enzyme study resulted in some unexpected opportunities for Helmerhorst. She had the chance to spread the word about celiac disease while working with museum visitors. “We told them what we were going to do with the samples they gave us, and we educated them about the disease,” she said. “Plus, we showed them it is so easy to get involved in science.”

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