Topical Area: Dietary Bioactive Components
Objectives : Polyphenols are plant secondary metabolites found in many fruits, grains, and vegetables, and are thus a part of normal human diet. One such food is sorghum (Sorghum bicolor), a cereal grain that contains varying concentrations of polyphenols. Many polyphenols have been implicated in the regulation of bioactivating (phase 1) and bioinactivating (phase 2) enzymes. The goal of this study is to assess the impact of sorghum polyphenol extracts on the expression of xenobiotic-activating and -inactivating enzymes important in cancer prevention and promotion.
Methods : Polyphenols were extracted from two types of sorghum bran. Human colon cancer cells (HT29, HCT116) were incubated with 1.25 mg extract per mL medium for 48 hours. RNA was extracted with Trizol/Chloroform, and reverse-transcribed to cDNA. mRNA expression of carcinogen-activating and -inactivating enzymes are quantitated using qPCR, normalized to GAPDH as internal control, and analyzed using GraphPad Prism. Protein extracts will be used for Western blotting to assess impact on protein expression and enzymatic activity.
Results : Compared to solvent control, mRNA expression of the arylhydrocarbon receptor (AHR) nuclear transferase (ARNT) increased in HT29 cells exposed to a novel high-polyphenol abstract (N=4, p=0.0017), whereas expression of AHR itself remained unaffected. Preliminary data suggest that expression of carcinogen-metabolizing enzymes, such as CYP1A1, may also increase in colon cancer cells upon exposure to the novel high-polyphenol extract.
Conclusions : The balance of xenobiotic-bioactivating and –inactivating enzymes is important to consider, as we investigate carcinogenesis and its prevention using dietary micronutrients. We continue to elucidate the expression and activity of such phase I and II enzymes in colon cancer cell models exposed to polyphenolic extracts.
Funding Sources :
Financial support was provided by Towson University’s Fisher College of Science and Mathematics (P. Tsuji), and the USDA (D. Smolensky).