High-fibre diets, such as those including broccoli sprouts or other cruciferous vegetables, may reduce illness symptoms and improve quality of life in mice with inflammatory bowel disease (IBD), a study said.
The findings were reported in mSystems, an American Society for Microbiology journal.
The researchers investigated the interactions between mice and their immune systems, as well as the broccoli sprout diet, microbes within the Crohn’s-afflicted gut, and how those microbes would use an inactive compound in the broccoli sprouts to make an anti-inflammatory compound in the gut in the study.
They also sought to see if, and how much, a diet rich in broccoli sprouts reduces Crohn’s symptoms, given the anti-inflammatory metabolites found in the sprouts.
In the study, the researchers used four groups of IL-10-KO mice. In the first round, scientists enlisted 4-week-old mice who ate regular mouse chow the entire time, as well as mice who ate mouse chow with raw broccoli sprouts mixed in. They used the same two diet groups in the second round, but the mice were 7 weeks old.
The researchers were particularly interested in understanding the development of IBDs in early life, which is why they studied the Crohn’s mouse models at the juvenile stage (4-6 weeks old) and at the adolescence stage (7-9 weeks old) with hopes to better understand how host-diet-microbial community interactions and disease severity differ by age.
The mice were fed for 7 days to acclimate to their respective diets before the researchers triggered symptoms, and the mice stayed on their diets for the following 2 weeks while the disease progressed.
To trigger symptoms, new healthy mice that host more microbes were added to the cage. Since the IL-10-KO mice in the study can’t produce IL-10, their immune systems have trouble tolerating gut microbiota, and the new microbes in the cage triggered colitis and Crohn’s symptoms. For the next 15-16 days after infection, the researchers regularly weighed the mice and collected faecal samples to assess for signs of colitis development.
At the end of the study, the researchers examined the gut tissues of the euthanized mice and microbial communities present throughout their intestines, as well as the presence of certain markers of inflammation and broccoli metabolites in the blood. The researchers wanted to know what types of microbes were living in particular parts of the gut.
In other words, they wanted to understand how the broccoli sprout diet affected microbial biogeography in the Crohn’s models since they cannot study this in humans.
DNA was extracted from the intestinal tissue samples collected from the mice and sent for sequencing to identify the bacteria present. Once the sequencing data was returned, the researchers used bioinformatics software and human ingenuity to study the gut microbial ecology of our mouse models.
“We found many exciting results from this study. First, we show that the mice that ate the broccoli sprout diet had a greater concentration of an anti-inflammatory metabolite called sulforaphane in their blood. Even though our mice were immunocompromised and had colitis, this increase in sulforaphane protected them from severe disease symptoms like weight loss, faecal blood and diarrhoea,” said Lola Holcomb, lead author and a PhD. Candidate in the Graduate School of Biomedical Sciences and Engineering at the University of Maine.
Lola is a member of a lab led by Suzanne Ishaq, Ph.D., a corresponding study author and assistant professor of animal and veterinary sciences at the University of Maine, School of Food and Agriculture, Orono, Maine.
Interestingly, the researchers found that the younger group of mice, the juveniles, responded better to the broccoli sprout diet than their adolescent counterparts did. The younger mice had milder disease symptoms and richer gut microbial communities. Furthermore, the younger mice showed stronger bacterial community similarity to each other (aka, stronger beta-diversity), and stronger adherence to location-specific community composition throughout different parts of the gut.
“Simply put, we found that of the 4 groups we studied, the younger mice fed a broccoli sprout diet had the mildest disease symptoms and the most robust gut microbiota,” Holcomb said.
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