2.8. Measurement of Glutathione Peroxidase 1 (GPx1) and Superoxide Dismutase (SOD) Serum Activity

As a measure of antioxidant potential, the serum activity of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured before and after respective diet protocol using previously established methods by our research group [22,24,25]. GPx activity was determined indirectly by measuring the rate of nicotinamide adenine dinucleotide phosphate (NADPH) oxidation to NADP+, accompanied by a decrease in absorbance at 340 nm over 5 min. Total SOD activity was measured as the degree of inhibition of reduction of cytochrome C by a superoxide radical. Enzyme activity assays were performed using a Lambda 25UV-Vis spectrophotometer equipped with UV WinLab 6.0 software package (PerkinElmer For the Better, Waltham, MA, USA). Measured activities of all investigated enzymes were expressed as U (mg protein)-1.