All ETDs from UAB

Advisory Committee Chair

Wendy Demark-Wahnefried

Advisory Committee Members

Andrew Frugé

Brenda Bertrand

Stephen Barnes

Document Type

Thesis

Date of Award

2019

Degree Name by School

Master of Science (MS) School of Health Professions

Abstract

Breast cancer continues to be a very prevalent disease and impacts over 260,000 new patients per year in the United States. The gut microbiota composition may affect breast cancer risk by modulating various hormonal metabolites including endogenous estrogens. Dietary factors impact gut microbial ecology and influence the regulation of estrogen metabolism. Current evidence supports the potential role of dietary fiber in breast cancer prevention and its possible modulating influence on serum estrogen levels through the gut microbiota associated with β-glucuronidase activity. However, this mechanism is not clearly understood. In this study, we aimed to explore the associations between dietary fiber, the gut microbiota that are linked with β-glucuronidase activity, and circulating estrogen levels. We hypothesized that higher dietary fiber consumption will be associated with a lower abundance of intestinal microbiota that promotes β-glucuronidase enzyme activity and lower levels of circulating estrogen. This study included 29 newly-diagnosed (stage 0-II), post-menopausal breast cancer patients. For statistical analyses we integrated three data sets: 1) dietary recall data, 2) Illumina MiSeq generated microbiota relative abundance, and 3) HPLC-mass spectrometry-derived estradiol and estrone levels. We performed Spearman’s and partial correlations controlling for body mass index and age to assess potential associations. The results suggested the following: (1) total dietary fiber is inversely associated with Clostridium hathewayi (r= -0.419; p=0.024); (2) soluble fiber is inversely associated with Clostridium (r=-0.11; p=0.02); and (3) insoluble fiber is positively associated with Bacteroides uniformis sp. (r=0.382; p=0.041). Also, serum 17-estradiol and estrone levels are not correlated with species/genera or dietary fiber, though there is a trend toward an inverse association between soluble fiber and estradiol levels (r= -0.30; p=0.12). These results provide important insights about the underlying mechanisms of the interaction between fiber and estrogen metabolism regarding the breast cancer risk. Further studies are needed to better understand the complex dynamics between these factors.

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