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Improved antioxidant and fatty acid status of patients with cystic fibrosis after antioxidant supplementation is linked to improved lung function^1,2,3

¹ From the Discipline of Nutrition and Dietetics, Faculty of Health, University of Newcastle, Callaghan, Australia (LGW and MLG); the Department of Respiratory Medicine, Children’s Hospital at Westmead, Sydney, Australia (DAF); and the Department of Respiratory Medicine, New Children’s Hospital, Sydney, Australia (AKL).

Background: Oxidative stress, as measured by 8-iso-prostaglandin F₂ (8-iso-PGF₂), and depleted antioxidant defenses were shown in stable cystic fibrosis (CF) patients. The plasma fatty acid status of CF patients was linked to oxidative stress after respiratory exacerbations.

Objective: We examined changes in plasma 8-iso-PGF₂, antioxidant defenses, plasma fatty acid status, and clinical markers resulting from short-term antioxidant supplementation.

Design: Forty-six CF patients were randomly assigned to either group A [low dose of supplement (10 mg vitamin E and 500 µg vitamin A)] or group B [high dose of supplement (200 mg vitamin E, 300 mg vitamin C, 25 mg ß-carotene, 90 µg Se, and 500 µg vitamin A)]. Plasma concentrations of 8-iso-PGF₂, vitamins E and C, ß-carotene, zinc, selenium, and copper; plasma fatty acid composition; erythrocyte glutathione peroxidase (EC 1.11.1.9) and superoxide dismutase (EC 1.15.1.1) activities; lung function; and dietary intake were measured before and after 8 wk of supplementation.

Results: Antioxidant defenses in group B improved, whereas those in group A did not: in groups B and A, the mean (± SEM) changes () in vitamin E were 10.6 ± 1.5 and -1.9 ± 0.9 µmol/L, respectively (P < 0.001), ß-carotene were 0.1 ± 0.04 and -0.01 ± 0.02 µmol/L, respectively (P = 0.007), selenium were 0.51 ± 0.10 and -0.09 ± 0.04 µmol/L, respectively (P < 0.001), and glutathione peroxidase activity were 1.3 ± 0.3 and -0.3 ± 0.6 U/g hemoglobin, respectively (P = 0.016). There were no significant differences between the groups in 8-iso-PGF₂, vitamin C, fatty acid composition, superoxide dismutase activity, lung function, or white cell count. Within group B, ß-carotene correlated with percentage of forced vital capacity (r = 0.586, P = 0.005), selenium correlated with percentage of forced expiratory volume in 1 s (r = 0.440, P = 0.046), and plasma fatty acid concentrations correlated with percentage of forced expiratory volume in 1 s (r = 0.583, P = 0.006) and 8-iso-PGF₂ (r = 0.538, P = 0.010).

Conclusions: Whereas increased ß-carotene, selenium, and fatty acid concentrations are linked to improved lung function, increased plasma fatty acid concentrations are linked to oxidative stress. If oxidative stress is deemed to be important to the clinical outcome of CF patients, means of reducing oxidative stress while maintaining a high-fat, high-energy diet must be investigated.

Key Words: Cystic fibrosis • oxidative stress • antioxidant supplementation • isoprostanes • fatty acids • vitamin E • vitamin C • ß-carotene • glutathione peroxidase • superoxide dismutase

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