Dynamic thiol/disulfide homeostasis in patients with age-related macular degeneration

Purpose: We evaluated dynamic thiol/disulfide homeostasis (TDH), malondialdehyde (MDA) levels, and catalase (CAT) activity in patients with age-related macular degeneration (AMD). All analyzes were conducted on plasma samples. Methods: Thirty-two patients with AMD and 38 age-matched healthy controls were included. Native thiol, total thiol, and disulfide levels and TDH status were determined using a novel, automated assay. MDA levels and CAT activity were determined. Percentages were compared using the chi-squared test. The Student's t-test and Mann-Whitney U-test were used to compare quantitative variables. Results: Native thiol levels were significantly lower (p=0.004) in patients with AMD (272.02 +/- 52.41 mu mol/l) than in healthy individuals (307.82 +/- 47.18 mu mol/l), whereas disulfide levels were significantly higher (p<0.001) in patients with AMD than in controls (21.64 +/- 5.59 vs. 14.48 +/- 5.37 mu mol/L). Dynamic TDH was also significantly lower (p<0.001) in patients with AMD than in controls (13.41 +/- 4.3 vs. 25.41 +/- 14.52 mu mol/l). No significant differences were evident in total thiol or MDA levels. Mean CAT activity was significantly higher (p=0.043) in patients with AMD compared with controls (0.035 vs. 0.018 k/ml). Conclusions: The antioxidant/oxidant balance demonstrated by dynamic TDH is shifted to the oxidative side in patients with AMD.