5a,6a-Epoxyphytosterols and 5a,6a-Epoxycholesterol increase oxidative stress in rats on low-cholesterol diet

Abstract

Objective. Cholesterol oxidation products have an established proatherogenic and cytotoxic effect. An increased exposure to these substances may be associated with the development of atherosclerosis and cancers. Relatively little, though, is known about the effect of phytosterol oxidation products, although phytosterols are present in commonly available and industrial food products. Thus, the aim of the research was to assess the effect of 5a,6a-epoxyphytosterols, which are important phytosterol oxidation products, on redox state in rats. Material and Methods. The animals were divided into 3 groups and exposed to nutritional sterols by receiving feed containing 5a,6a-epoxyphytosterols (ES group) and 5a,6a-epoxycholesterol (Ech group) or sterol-free feed (C group). The levels of malondialdehyde (MDA), conjugated dienes (CD), and ferric reducing antioxidant potential (FRAP) were assayed in the plasma; anti-7-ketocholesterol antibodies and activity of paraoxonase-1 (PON1) were determined in serum, whereas the activity of catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), S-glutathione transferase (GST), and superoxide dismutase (SOD) were assayed in RBCs. Results. During the experiment, the levels of lipid peroxidation products increased, such as CD and anti-7-ketocholesterol antibodies. At the same time, the plasma levels of FRAP and serum activity of PON1 decreased alongside the reduced activity of GPx, GR, and SOD in RBCs. There was no effect of the studied compounds on the plasma MDA levels or on the activity of CAT and GST in RBCs. Conclusions. Both 5a,6a- epoxyphytosterols and 5a,6a-epoxycholesterols similarly dysregulate the redox state in experimental animal model and may significantly impact atherogenesis.