2.5. Antioxidant and Redox Status 
Total antioxidant capacity was measured as the combined antioxidant activities of all serum constituents, including vitamins, proteins, lipids, glutathione, and uric acid. The assay relied on the ability of antioxidants in the sample to inhibit the oxidation of ABTS (2,2′-Azino-di-[3-ethylbenzthiazoline sulphonate]) to ABTS•+ by metmyoglobin and was quantified as Trolox, a water-soluble tocopherol analogue, equivalents. The decrease in ABTS oxidation was quantified colorimetrically at 734 nm using a Biotek Synergy H1 spectrophotometer (Agilent, Santa Clara, CA, USA). Reduced glutathione (GSH), oxidized glutathione (GSSG), and total glutathione in serum samples were quantified in duplicate using fluorometric GSH/GSSG ratio detection assay kit (Abcam, Cambridge, MA, USA) at the excitation/emission of 490/520 nm (Biotek Synergy H1). 