Triclosan may be linked to gastrointestinal disease

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Triclosan, an antimicrobial agent found in toothpaste and other oral care products, may be associated with a type of gut inflammation that induces chronic digestive diseases, according to a study published on January 10 in Nature Communications.

In the study, researchers found that microbial enzymes induced colitis, a type of irritable bowel disease (IBD), in mice by reactivating triclosan (TCS) in the gastrointestinal tract.

"The safety of TCS and related compounds should be reconsidered given their potential for intestinal damage," wrote the group, co-led by several authors, including Jianan Zhang, PhD, from the department of food science at the University of Massachusetts Amherst.

In 2015, an estimated 3 million adults in the U.S. were diagnosed with irritable bowel disease. That represents a 50% increase from 1999, when approximately 2 million were diagnosed with IBD. Patients with IBD are at greater risk of developing colorectal cancer, Zhang and colleagues noted.

The increase in cases of IBD has been associated with exposure to environmental chemicals; however, the mechanisms are unclear. Triclosan, an antimicrobial agent that the U.S. Food and Drug Administration (FDA) removed from over-the-counter soaps in 2016, can still be found in more than 2,000 industrial and consumer products, including mouthwash, shaving cream, and toys. Triclosan has been associated with increased antibiotic resistance, hormone disruption, and osteoporosis, and in the U.S., it is detected in approximately 75% of urine samples.

Furthermore, a recent study showed that exposure to triclosan increased the severity of colitis and exaggerated the development of colitis-associated colorectal cancer in mouse models, according to the authors. These results supported the hypothesis that triclosan may be a risk factor for IBD and related conditions, they noted.

What connects the gut microbiota and triclosan toxicity remains unknown, so the researchers sought to identify such gut microbial factors. To do so, Zhang and colleagues fed mice a diet that contained triclosan for four weeks, and then the collected tissues were analyzed using liquid chromatography-tandem mass spectrometry.

The group found that microbial beta-glucuronidase (GUS) enzymes played a major role in activating triclosan and inflaming the gut and inducing digestive disease.

"Our results define a mechanism by which intestinal microbes contribute to the metabolic activation and gut toxicity of TCS, and highlight the importance of considering the contributions of the gut microbiota in evaluating the toxic potential of environmental chemicals," the authors concluded.

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