Fructose Increases the Expression of Uric Acid-Induced Oxidative Stress Genes, NOX4 and FOXO3, in Cultured HepG2 Cells

Abstract

Abstract Objectives Uric acid is the final product of purine metabolism. The role of uric acid in oxidative stress is not clear. Studies have shown uric acid as antioxidant as well as pro-oxidant. High fructose sugar consumption increases uric acid levels by ATP depletion and the subsequent formation AMP which is a uric acid precursor. In our study, we investigated the effect of dose dependent treatments of fructose, uric acid, or a combination of both uric acid and fructose on expression of oxidative stress-related genes, mainly NADPH oxidase 4 (NOX4), superoxide dismutase 3 (SOD3), Forkhead Box O3 (FOXO3) and xanthine dehydrogenase (XDH) in cultured Hep G2 cells. Methods Human hepatocellular carcinoma [HEPG2] (ATCC HB8065) cells were treated with serum-free medium containing either 10 mM fructose, soluble uric acid (0.25 mM, 0.5 mM, or 0.75 mM), or a combination of fructose and uric acid. The cells were collected at the end of each incubation period (30 min, 2 and 24 hours) to extract total RNA. cDNA was synthesized from the extracted RNA. TaqMan assays were designed for use on real-rime PCR platform (QuantStudio 12 K Flex). TaqMan open array primers were custom-made by Thermo Fisher Scientific. Target quantification values were normalized against GAPDH levels and a combination of students’ t-test and ANOVA were applied. Results Soluble uric acid, either by itself or in conjunction with fructose, did not change the expression of the tested genes at 30 minutes or 2 hours. However, after 24 hours of incubation, uric acid increased the expression of NOX4 by 2 and FOXO3 by 1.5-fold (p < 0.05) whereas uric acid plus fructose-containing media increased the expression of NOX4 by 3.5 and FOXO3 by 2-fold (p < 0.05) after 24 hours of incubation as compared to control. No treatment differences were observed in the expression of SOD3. Conclusions These findings demonstrate that fructose increases the expression of uric acid-induced oxidative stress related genes. Funding Sources None.