Effects of long-term zinc supplementation on plasma thiol metabolites and redox status in patients with age-related macular degeneration.
OBJECTIVE
To determine the effects of zinc supplementation on plasma thiol metabolites and their redox status in a cohort of patients with age-related macular degeneration (AMD).


METHODS
Randomized clinical trial that evaluated the effects of high doses of zinc and antioxidants on plasma biomarkers of oxidative stress.


METHODS
This was an ancillary study of the Age-Related Eye Disease Study (AREDS). Subjects with AMD were randomized to one of four treatment groups: (1) antioxidants (vitamin C, 500 mg; vitamin E, 400 IU; and beta carotene, 15 mg), (2) zinc (80 mg zinc oxide, 2 mg cupric oxide), (3) antioxidants plus zinc, or (4) placebo. At 20 and 80 months after randomization, blood specimens were collected and analyzed for glutathione (GSH), oxidized glutathione (GSSG), cysteine (Cys), and cystine (CySS).


RESULTS
Although zinc supplementation had no apparent effect on plasma thiol/disulfide redox status at the first blood draw, the group of patients receiving zinc supplementation at the second blood draw had significantly less CySS compared with those not receiving zinc (54.9 vs 64.1 microM; P = .01). There was a time-dependent oxidation of the plasma GHS pool and was not affected by zinc supplementation.


CONCLUSIONS
Because increased CySS level is associated with aging, oxidative stress, and age-related diseases, the apparent prevention of increased CySS by zinc supplementation warrants additional investigation.
Moriarty-Craige
Siobhan E
SE
Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA.
Ha
Khoi-Nguyen
KN
Sternberg
Paul
P
Lynn
Michael
M
Bressler
Susan
S
Gensler
Gary
G
Jones
Dean P
DP
D000368:Aged; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000097:blood*; D003553:Cystine / Q000097:blood*; D019587:Dietary Supplements; D005260:Female; D005978:Glutathione / Q000097:blood*; D019803:Glutathione Disulfide / Q000097:blood*; D006801:Humans; D008268:Macular Degeneration / Q000097:blood* / Q000188:drug therapy; D008297:Male; D010084:Oxidation-Reduction; D015034:Zinc Oxide / Q000008:administration & dosage*
D003553:Cystine; D005978:Glutathione; D003545:Cysteine; D015034:Zinc Oxide; D019803:Glutathione Disulfide