Antioxidant status of patients on peritoneal dialysis: associations with inflammation and glycoxidative stress.
BACKGROUND
Patients on peritoneal dialysis (PD) frequently exhibit oxidant-antioxidant imbalance, advanced glycation end-product overload, and subclinical inflammation but the interrelations between these pathophysiological changes have not been fully elucidated.


METHODS
To study possible associations, a cross-sectional study of antioxidant status, glycoxidative stress, and inflammation, using HPLC and ELISA methods, was undertaken in 37 PD patients and age- and sex-matched healthy controls.


RESULTS
Plasma ascorbate concentrations were low in patients not taking at least low-dose vitamin C supplements. In patients taking vitamin C supplements, there was a positive relation between ascorbate and pentosidine concentrations. Vitamin E and carotenoid concentrations were comparable between patients and controls, while lycopene and lutein/zeaxanthin concentrations were lower. Interleukin-6, C-reactive protein (CRP), and pentosidine concentrations were elevated in PD patients. beta-Cryptoxanthin, lycopene, and lutein/zeaxanthin concentrations were inversely related to interleukin-6 concentrations. beta-Cryptoxanthin concentrations were also inversely related to CRP concentrations. Pentosidine showed a low dialysate-to-plasma ratio, indicating low peritoneal clearance. Pentosidine concentrations increased with duration of PD therapy, while alpha- and beta-carotene concentrations decreased. Malondialdehyde concentrations were elevated compared to controls but remained within the normal range. Retinol concentrations decreased with PD therapy and were inversely related to interleukin-6 and CRP concentrations.


CONCLUSIONS
Low-dose vitamin C supplements and a carotenoid-rich diet should be recommended for PD patients to maintain normal antioxidant status and efficiently counteract the chronic inflammatory response, rather than high doses of vitamin C, which could play a role as a precursor of pentosidine.
Sundl
Isabella
I
Human Nutrition & Metabolism Research and Training Center Graz, Institute of Molecular Sciences, Karl-Franzens University, Graz, Austria.
Roob
Johannes M
JM
Meinitzer
Andreas
A
Tiran
Beate
B
Khoschsorur
Gholamali
G
Haditsch
Bernd
B
Holzer
Herwig
H
Winklhofer-Roob
Brigitte M
BM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000378:metabolism*; D001205:Ascorbic Acid / Q000008:administration & dosage; D002097:C-Reactive Protein / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005500:Follow-Up Studies; D006031:Glycosylation; D006801:Humans; D007249:Inflammation / Q000097:blood*; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D010530:Peritoneal Dialysis / Q000379:methods*; D011379:Prognosis; D014815:Vitamins / Q000008:administration & dosage
D000975:Antioxidants; D014815:Vitamins; D002097:C-Reactive Protein; D001205:Ascorbic Acid