Date of Award

Spring 5-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Microbiology

First Committee Advisor

Suzanne Ishaq

Second Committee Member

Edward Bernard

Third Committee Member

Yanyan Li

Additional Committee Members

Benjamin King

Abstract

Globally, millions of people have been diagnosed with a type of inflammatory bowel disease (IBD). These diseases cause dysfunction of the gastrointestinal (GI) tract, resulting in a wide range of symptoms that create disruption in overall health. Research has suggested that diet and the microbial community composition of the gut microbiome play a significant role in regulating gastrointestinal inflammation. Specifically, studies have shown that diets high in cruciferous vegetables, such as broccoli, are associated with a reduction in gastrointestinal inflammation. Glucoraphanin is a compound present in broccoli that can be metabolized by gut bacteria to become an anti-inflammatory compound known as sulforaphane. Our initial research showed that the administration of a broccoli sprout diet to mouse models for Crohn’s disease and ulcerative colitis, two major types of IBD, yields inflammation reduction and symptom resolution. For these trials, fecal samples obtained from different sections of the mouse bowel were tested for presence of glucoraphanin-metabolizing genes present in a common gut bacterium, Bacteroides thetaiotaomicron (B. theta). Glucoraphanin conversion is higher and more reliable in mice than in people, however mouse models are not perfect representatives of humans. Hoping to understand the impacts of broccoli sprouts on the human gut microbiome, fecal samples were obtained from healthy individuals who consumed broccoli sprouts for 28 consecutive days, as long-term diet interventions are needed to meaningfully change gut microbial communities. In a separate trial conducted by the scientists at Brassica Protections Product, fecal samples were collected from people who were administered a single dietary supplement containing a high dose of glucoraphanin with and without plant-sourced myrosinase, as a means of evaluating the effectiveness of glucoraphanin conversation which was or was not reliant on gut microbiota, respectively. These samples were analyzed for glucoraphanin-metabolizing genes from B. theta and other commensal gut bacteria. Data collected from these human trial experiments aided in understanding the impacts of a whole food broccoli sprout diet and supplementation of glucoraphanin on the bacterial community composition of the gut microbiota. Additionally, this work will help grow and strengthen the current knowledge on broccoli as an anti-inflammatory and the variabilities present in the gut microbiomes of humans.

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