Topical Area: Dietary Bioactive Components
Objectives : Plant secondary metabolites, such as polyphenols, are 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 colon cancer through modulating the antioxidant defense, which includes some of the major selenoproteins, e.g., thioredoxin reductases (TXNRD) and glutathione peroxidases (GPX). However, because such redox-active enzymes have been shown to be involved in both cancer prevention and promotion, the goal of our study is to assess the impact of high-polyphenol sorghum extracts on the expression of selenoproteins.
Human colon cancer cells (HT29, HCT116) were incubated with 1.25 mg high-polyphenol sorghum bran extract per mL medium for 48 h. RNA was extracted with Trizol/Chloroform, and reverse-transcribed to cDNA. mRNA expression of selenoproteins was quantitated using qPCR, normalized to GAPDH, and analyzed using GraphPad Prism. Protein lysates will be used for Western blotting and catalytic activity assays.
Results : Compared to solvent control, incubation of human colon cancer cells with high-polyphenol sorghum extracts for 48 h moderately impacted mRNA expression of investigated selenoproteins. One of the extracts resulted in a nearly doubled GPX1 mRNA expression in HCT116 cells (p=0.08), whereas preliminary results suggest that TXNRD1 expression may be lowered.
High-polyphenol varieties of sorghum may affect selenoprotein expression. Further investigations involving both shorter and longer-term incubation times, as well as effects on protein expression and activity will help elucidate the effects of these new sorghum varieties on selenoprotein expression important in prevention and promotion of colon cancer.
Funding Sources : Financial support was provided by Towson University’s Fisher College of Science and Mathematics (P. Tsuji) and the USDA (D. Smolensky).