Rice protein suppresses ROS generation and stimulates antioxidant gene expression via Nrf2 activation in adult rats.

To elucidate the effects of rice protein on the detoxification and antioxidant defense via the Nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, adult rats were fed casein and rice protein under cholesterol-free and -enriched dietary conditions. Nrf2 proteins and gene expressions were stimulated by rice proteins with respect to caseins accompanied by up-regulating the expression of gene encoding antioxidant and phase II detoxification in the rice protein groups. In the liver, compared with caseins, rice proteins significantly increased hepatic contents of reduced glutathione (GSH) and mRNA levels of glutamate cysteine ligase catalytic subunit (GCLC), glutamate cysteine ligase modulatory subunit (GCLM), glutathione S-transferase (GST), heme oxygenase 1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1), whereas hepatic accumulations of reactive oxygen species (ROS) and oxidized glutathione (GSSG) were markedly depressed in adult rats fed rice proteins. The present study demonstrates the endogenous antioxidant potential of rice proteins via mechanism through which Nrf2 activation plays an essential role in inducing Phase II antioxidants/detoxification enzymes and preventing ROS generation. This novel antioxidative function of rice protein is independent of dietary cholesterol during in adult rats.