Abstract
Colorectal cancer (CRC) is the third leading cause of cancer death for both men and women in the United States, yet it is treatable and preventable. African Americans have higher incidence of CRC than other racial/ethnic groups, however, it is unclear whether this disparity is primarily due to environmental or biological factors. Short chain fatty acids (SCFAs) are metabolites produced by bacteria in the colon and are known to be inversely related to CRC progression. The aim of this study is to investigate how stool SCFA levels, markers of inflammation in stool and dietary intake relate to colonoscopy findings in a diverse patient population. Stool samples from forty-eight participants were analyzed for SCFA levels and inflammatory markers (lysozyme, secretory IgA, lactoferrin). Additionally, participants completed the National Cancer Institute’s Diet History Questionnaire II (DHQ II) to report dietary intake over the past year. Subsequently, the majority of participants underwent screening colonoscopy. Our results showed that African Americans had higher total levels of SCFAs in stool than other racial/ethnic groups, significantly lower intake of non-starchy vegetables and similar inflammatory marker expression and colonoscopy outcomes, compared to others. This work is an initial exploration into the biological and clinical factors that may ultimately inform personalized screening approaches and clinical decision-making to improve colorectal cancer disparities for African Americans.
Highlights
Colorectal cancer (CRC) is the third leading cause of cancer death overall in the United States [1].CRC incidence and death rates vary by race/ethnicity; African Americans (AA) suffer the greatestGenes 2018, 9, 119; doi:10.3390/genes9030119 www.mdpi.com/journal/genesGenes 2018, 9, 119 incidence and mortality rate and are diagnosed at later stages than other racial/ethnic groups in the US, despite comparable screening rates [2,3]
Though environmental and biological factors, including diet, gut microbiota and intestinal inflammation have been linked to progression and prevention of CRC, it is unclear whether these factors play a role in CRC outcome disparities between AA and others
Our study found that AAs had higher stool levels of Short chain fatty acids (SCFAs) than others but were not significantly different in their likelihood of having abnormal colonoscopies
Summary
Colorectal cancer (CRC) is the third leading cause of cancer death overall in the United States [1].CRC incidence and death rates vary by race/ethnicity; African Americans (AA) suffer the greatestGenes 2018, 9, 119; doi:10.3390/genes9030119 www.mdpi.com/journal/genesGenes 2018, 9, 119 incidence and mortality rate and are diagnosed at later stages than other racial/ethnic groups in the US, despite comparable screening rates [2,3]. CRC incidence and death rates vary by race/ethnicity; African Americans (AA) suffer the greatest. The gut microbiota, the more than 1 trillion bacteria inhabiting the intestinal tract, and the metabolites they produce, including short chain fatty acids (SCFAs), may be important modifiable factors related to CRC risk. That individuals diagnosed with CRC have modified bacterial profiles and different levels of bacterial metabolites such as SCFAs as compared to healthy controls [4,5,6,7,8,9,10,11,12,13]. In a small pilot study with average risk adults (5 AA, 5 Hispanic, 5 Native American and 5 White participants), we previously showed AAs to have significantly lower stool acetate, butyrate and total SCFA levels than other racial/ethnic groups and to have a significantly higher Firmicutes/Bacteroidetes ratio [14]. One recent study found higher SCFAs in the stool of AAs with adenomatous polyps than in the stool of healthy AAs [15]
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