PER1 and rheumatoid arthritis: Our data revealed that Nrf2 and HO-1 protein expressions decreased in SD-CIA control group; however, dietary OL and Per-OL treatments could restore Nrf2 and HO-1 expressions conferring a remarkable role of Nrf2/HO-1 signaling pathway in the beneficial effects of OL and Per-OL-enriched-diets in CIA model of RA.