Abstract
Whey protein concentrate (WPC), which contains α-lactalbumin and β-lactoglobulin, is utilized widely in the food industry. The Maillard reaction is a complex reaction that produces Maillard reaction products (MRPs), which are associated with the formation of antioxidant compounds. In this study, the hepatoprotection activity of MRPs of WPC against oxidative stress through the Nrf2-dependent antioxidant pathway in HepG2 cells was examined. Glucose-whey protein concentrate conjugate (Glc-WPC) was obtained from Maillard reaction between whey protein concentrate and glucose. The fluorescence intensity of Glc-WPC increased after 7 d compared to native WPC, and resulted in loss of 48% of the free amino groups of WPC. The SDS-PAGE patterns of Glc-WPC showed the presence of a high-molecular-weight portion. Treatment of HepG2 cells with Glc-WPC increased cell viability in the presence of oxidative stress, inhibited the generation of intracellular reactive oxygen species by t-BHP, and increased the glutathione level. Nrf2 translocation and Nrf2, NOQ1, HO-1, GCLM and GCLC mRNA levels were increased by Glc-WPC. Also, Glc-WPC increased the phosphorylation of ERK 1/2 and JNK. The results of this study demonstrate that Glc-WPC activates the Nrf2-dependent pathway through the phosphorylation of ERK 1/2 and JNK in HepG2 cells, and induces production of antioxidant enzymes and phase II enzymes.
