Enhanced resistance to oxidation of low density lipoproteins and decreased lipid peroxide formation during beta-carotene supplementation in cystic fibrosis.

We investigated the effect of correcting beta-carotene deficiency in cystic fibrosis (CF) patients on two parameters of lipid peroxidation. The resistance to oxidation of low density lipoprotein (LDL) was measured by the lag time preceding the onset of conjugated diene formation during exposure to copper(II) ions, and lipid peroxide formation was quantitated by malondialdehyde concentrations in plasma (TBA/HPLC method). Simultaneously, alpha-tocopherol and beta-carotene concentrations were determined in LDL and in plasma. Thirty-four CF patients were investigated before and after 3 months of oral beta-carotene supplementation. Beta-carotene concentrations increased (p < 0.0001) in plasma (mean +/- SD) (0.09 +/- 0.06 vs. 1.07 +/- 0.86 mumol/l) and in LDL (0.02 +/- 0.02 vs. 0.31 +/- 0.28 mol/mol), without significant changes in alpha-tocopherol, either in plasma (24.7 +/- 5.9 vs. 25.4 +/- 7.6) or in LDL (8.47 +/- 2.95 vs. 9.05 +/- 4.13). Lag times, being shorter (p < 0.05) in patients than in controls, increased from 48.5 +/- 21.3 to 69.1 +/- 27.9 min (p < 0.001) and plasma MDA concentrations, being greater (p < 0.0001) in patients than in controls, decreased from 0.95 +/- 0.32 to 0.61 +/- 0.15 mumol/l (p < 0.0001). At 3 months, lag times and MDA concentrations did not any longer differ between patients and controls. These data suggest that excess lipid peroxidation occurring in beta-carotene deficiency can be limited and normalized during efficient beta-carotene supplementation in CF patients.