PARAMETERS OF THE ANTIOXIDANT PROTECTIVE SYSTEM IN PATIENTS WITH CYSTIC FIBROSIS (CF)

Abstract

Selenium (Se) dependent glutathione peroxidase (GPH-Px) and α-tocopherol (α-T), as part of the antioxidative system, synergistically protect membrane lipids from free radical damage. GPH-Px activity has been shown to be a more reliable indicator of Se bioavailability than blood Se levels. In CF patients, vitamin E deficiency is well known; in contrast, there are only a few data on impaired GPH-Px activity in these patients.

Patients and methods: In 41 CF patients aged 0.8-27.6 yrs, GPH-Px activity and α-T in red blood cell (RBC) membranes, plasma α-T and plasma α-T/cholesterol ratio were determined. Correlations with parameters of nutritional status (NS), nutrient intake, fat absorption and liver disease (LD) were studied.

Results: GPH-Px activity was decreased in 34 patients, ranging from 3% to 79% (x=44.12, SEM=3.49) below the lower limit of the normal range. In 17 patients, RBC α-T was 2% to 82% (x=29.12, SEM= 5.67) below the cut-off point, in spite of oral α-T supplements (100-300 mg/d). In addition, only 4 patients had normal values both for GPH-Px and RBC α-T, and 14 were deficient for both. Severe GPH-Px deficiency tended to be associated with worse NS. In patients with LD (n=7), α-T levels were lower than in the others. No correlation with the other parameters studied was found.

Conclusions: The combined deficiency of both GPH-Px and α-T in 34% of CF patients may be particularly deleterious due to their synergism in preventing lipid peroxidation. α-T supplementation has been recommended for GPH-Px deficiency; yet, in our CF patients, high dose oral α-T was not always effective in correcting vitamin E deficiency and will therefore obviously not compensate for the lack of antioxidative capacity due to GPH-Px deficiency.

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